To see the other types of publications on this topic, follow the link: IRES – Internal Ribosome Entry Site.
Journal articles on the topic 'IRES – Internal Ribosome Entry Site'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 journal articles for your research on the topic 'IRES – Internal Ribosome Entry Site.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
Au, Hilda H., Gabriel Cornilescu, Kathryn D. Mouzakis, Qian Ren, Jordan E. Burke, Seonghoon Lee, Samuel E. Butcher, and Eric Jan. "Global shape mimicry of tRNA within a viral internal ribosome entry site mediates translational reading frame selection." Proceedings of the National Academy of Sciences 112, no. 47 (November 9, 2015): E6446—E6455. http://dx.doi.org/10.1073/pnas.1512088112.
Full textAbstract:
The dicistrovirus intergenic region internal ribosome entry site (IRES) adopts a triple-pseudoknotted RNA structure and occupies the core ribosomal E, P, and A sites to directly recruit the ribosome and initiate translation at a non-AUG codon. A subset of dicistrovirus IRESs directs translation in the 0 and +1 frames to produce the viral structural proteins and a +1 overlapping open reading frame called ORFx, respectively. Here we show that specific mutations of two unpaired adenosines located at the core of the three-helical junction of the honey bee dicistrovirusIsraeli acute paralysis virus(IAPV) IRES PKI domain can uncouple 0 and +1 frame translation, suggesting that the structure adopts distinct conformations that contribute to 0 or +1 frame translation. Using a reconstituted translation system, we show that ribosomes assembled on mutant IRESs that direct exclusive 0 or +1 frame translation lack reading frame fidelity. Finally, a nuclear magnetic resonance/small-angle X-ray scattering hybrid approach reveals that the PKI domain of the IAPV IRES adopts an RNA structure that resembles a complete tRNA. The tRNA shape-mimicry enables the viral IRES to gain access to the ribosome tRNA-binding sites and form intermolecular contacts with the ribosome that are necessary for initiating IRES translation in a specific reading frame.
2
Terenin, Ilya M., Sergei E. Dmitriev, Dmitri E. Andreev, Elizabeth Royall, Graham J. Belsham, Lisa O. Roberts, and Ivan N. Shatsky. "A Cross-Kingdom Internal Ribosome Entry Site Reveals a Simplified Mode of Internal Ribosome Entry." Molecular and Cellular Biology 25, no. 17 (September 1, 2005): 7879–88. http://dx.doi.org/10.1128/mcb.25.17.7879-7888.2005.
Full textAbstract:
ABSTRACT Rhopalosiphum padi virus (RhPV) is an insect virus of the Dicistroviridae family. Recently, the 579-nucleotide-long 5′ untranslated region (UTR) of RhPV has been shown to contain an internal ribosome entry site (IRES) that functions efficiently in mammalian, plant, and insect in vitro translation systems. Here, the mechanism of action of the RhPV IRES has been characterized by reconstitution of mammalian 48S initiation complexes on the IRES from purified components combined with the toeprint assay. There is an absolute requirement for the initiation factors eIF2 and eIF3 and the scanning factor eIF1 to form 48S complexes on the IRES. In addition, eIF1A, eIF4F (or the C-terminal fragment of eIF4G), and eIF4A strongly stimulated the assembly of this complex, whereas eIF4B had no effect. Although the eIF4-dependent pathway is dominant in the RhPV IRES-directed cell-free translation, omission of either eIF4G or eIF4A or both still allowed the assembly of 48S complexes from purified components with ∼23% of maximum efficiency. Deletions of up to 100 nucleotides throughout the 5′-UTR sequence produced at most a marginal effect on the IRES activity, suggesting the absence of specific binding sites for initiation factors. Only deletion of the U-rich unstructured 380-nucleotide region proximal to the initiation codon resulted in a complete loss of the IRES activity. We suggest that the single-stranded nature of the RhPV IRES accounts for its strong but less selective potential to bind key mRNA recruiting components of the translation initiation apparatus from diverse origins.
3
Beales, Lucy P., Andreas Holzenburg, and David J. Rowlands. "Viral Internal Ribosome Entry Site Structures Segregate into Two Distinct Morphologies." Journal of Virology 77, no. 11 (June 1, 2003): 6574–79. http://dx.doi.org/10.1128/jvi.77.11.6574-6579.2003.
Full textAbstract:
ABSTRACT An increasing number of viruses have been shown to initiate protein synthesis by a cap-independent mechanism involving internal ribosome entry sites (IRESs). Predictions of the folding patterns of these RNA motifs have been based primarily on sequence and biochemical analyses. Biophysical confirmation of the models has been achieved only for the IRES of hepatitis C virus (HCV), which adopts an open structure consisting of two major stems. We have conducted an extensive comparison of flavivirus and picornavirus IRES elements by negative stain transmission electron microscopy. All of the flavivirus IRESs we examined (those of GB virus-B, GB virus-C, and classical swine fever virus) fold to give a structure similar to that of the HCV IRES, as does an IRES recently found on mRNA encoded by human herpesvirus 8. The larger picornavirus IRESs (those of foot-and-mouth disease virus, rhinovirus, encephalomyocarditis virus, and hepatitis A virus) are morphologically similar, comprising a backbone with two protruding stems, and distinct from the flavivirus IRESs.
4
Ochs, Kerstin, Lanja Saleh, Gergis Bassili, Volker H. Sonntag, Amandus Zeller, and Michael Niepmann. "Interaction of Translation Initiation Factor eIF4B with the Poliovirus Internal Ribosome Entry Site." Journal of Virology 76, no. 5 (March 1, 2002): 2113–22. http://dx.doi.org/10.1128/jvi.76.5.2113-2122.2002.
Full textAbstract:
ABSTRACT Poliovirus translation is initiated at the internal ribosome entry site (IRES). Most likely involving the action of standard initiation factors, this highly structured cis element in the 5" noncoding region of the viral RNA guides the ribosome to an internal silent AUG. The actual start codon for viral protein synthesis further downstream is then reached by ribosomal scanning. In this study we show that two of the secondary structure elements of the poliovirus IRES, domain V and, to a minor extent, domain VI, are the determinants for binding of the eukaryotic initiation factor eIF4B. Several mutations in domain V which are known to greatly affect poliovirus growth also seriously impair the binding of eIF4B. The interaction of eIF4B with the IRES is not dependent on the presence of the polypyrimidine tract-binding protein, which also binds to the poliovirus IRES. In contrast to its weak interaction with cellular mRNAs, eIF4B remains tightly associated with the poliovirus IRES during the formation of complete 80S ribosomes. Binding of eIF4B to the IRES is energy dependent, and binding of the small ribosomal subunit to the IRES requires the previous energy-dependent association of initiation factors with the IRES. These results indicate that the interaction of eIF4B with the 3" region of the poliovirus IRES may be directly involved in translation initiation.
5
Oumard, A., M. Hennecke, H. Hauser, and M. Nourbakhsh. "Translation of NRF mRNA Is Mediated by Highly Efficient Internal Ribosome Entry." Molecular and Cellular Biology 20, no. 8 (April 15, 2000): 2755–59. http://dx.doi.org/10.1128/mcb.20.8.2755-2759.2000.
Full textAbstract:
ABSTRACT The ubiquitous transcription factor NRF (NF-κB repressing factor) is a constitutive transcriptional silencer of the multifunctional cytokine interferon-β. NRF mRNA contains a long 5′ untranslated region (5′UTR) predicted to fold into a strong secondary structure. The presence of stable hairpins is known to be incompatible with efficient translation by ribosomal scanning. Using dicistronic reporter gene constructs, we show that the NRF 5′UTR acts as an internal ribosome entry site (IRES) which directs ribosomes to the downstream start codon by a cap-independent mechanism. The relative activity of this IRES in various cell lines is at least 30-fold higher than that of picornaviral IRESs. The NRF 5′UTR also functions as a translational enhancer in the context of monocistronic mRNAs. Our results indicate that the NRF 5′UTR contains a highly potent IRES, which may allow for an alternate mode of translation under physiological conditions in which cap-dependent translation is inhibited.
6
Spriggs, Keith A., Laura C. Cobbold, Catherine L. Jopling, Rebecca E. Cooper, Lindsay A. Wilson, Mark Stoneley, Mark J. Coldwell, et al. "Canonical Initiation Factor Requirements of the Myc Family of Internal Ribosome Entry Segments." Molecular and Cellular Biology 29, no. 6 (January 5, 2009): 1565–74. http://dx.doi.org/10.1128/mcb.01283-08.
Full textAbstract:
ABSTRACT Initiation of protein synthesis in eukaryotes requires recruitment of the ribosome to the mRNA and its translocation to the start codon. There are at least two distinct mechanisms by which this process can be achieved; the ribosome can be recruited either to the cap structure at the 5′ end of the message or to an internal ribosome entry segment (IRES), a complex RNA structural element located in the 5′ untranslated region (5′-UTR) of the mRNA. However, it is not well understood how cellular IRESs function to recruit the ribosome or how the 40S ribosomal subunits translocate from the initial recruitment site on the mRNA to the AUG initiation codon. We have investigated the canonical factors that are required by the IRESs found in the 5′-UTRs of c-, L-, and N-myc, using specific inhibitors and a tissue culture-based assay system, and have shown that they differ considerably in their requirements. The L-myc IRES requires the eIF4F complex and the association of PABP and eIF3 with eIF4G for activity. The minimum requirements of the N- and c-myc IRESs are the C-terminal domain of eIF4G to which eIF4A is bound and eIF3, although interestingly this protein does not appear to be recruited to the IRES RNA via eIF4G. Finally, our data show that all three IRESs require a ternary complex, although in contrast to c- and L-myc IRESs, the N-myc IRES has a lesser requirement for a ternary complex.
7
Ochs, Kerstin, RenéC Rust, and Michael Niepmann. "Translation Initiation Factor eIF4B Interacts with a Picornavirus Internal Ribosome Entry Site in both 48S and 80S Initiation Complexes Independently of Initiator AUG Location." Journal of Virology 73, no. 9 (September 1, 1999): 7505–14. http://dx.doi.org/10.1128/jvi.73.9.7505-7514.1999.
Full textAbstract:
ABSTRACT Most eukaryotic initiation factors (eIFs) are required for internal translation initiation at the internal ribosome entry site (IRES) of picornaviruses. eIF4B is incorporated into ribosomal 48S initiation complexes with the IRES RNA of foot-and-mouth disease virus (FMDV). In contrast to the weak interaction of eIF4B with capped cellular mRNAs and its release upon entry of the ribosomal 60S subunit, eIF4B remains tightly associated with the FMDV IRES during formation of complete 80S ribosomes. Binding of eIF4B to the IRES is energy dependent, and binding of the small ribosomal subunit to the IRES requires the previous energy-dependent association of initiation factors with the IRES. The interaction of eIF4B with the IRES in 48S and 80S complexes is independent of the location of the initiator AUG and thus independent of the mechanism by which the small ribosomal subunit is placed at the actual start codon, either by direct internal ribosomal entry or by scanning. eIF4B does not greatly rearrange its binding to the IRES upon entry of the ribosomal subunits, and the interaction of eIF4B with the IRES is independent of the polypyrimidine tract-binding protein, which enhances FMDV translation.
8
Camerini, Valentina, Didier Decimo, Laurent Balvay, Mauro Pistello, Mauro Bendinelli, Jean-Luc Darlix, and Théophile Ohlmann. "A Dormant Internal Ribosome Entry Site Controls Translation of Feline Immunodeficiency Virus." Journal of Virology 82, no. 7 (January 30, 2008): 3574–83. http://dx.doi.org/10.1128/jvi.02038-07.
Full textAbstract:
ABSTRACT The characterization of internal ribosome entry sites (IRESs) in virtually all lentiviruses prompted us to investigate the mechanism used by the feline immunodeficiency virus (FIV) to produce viral proteins. Various in vitro translation assays with mono- and bicistronic constructs revealed that translation of the FIV genomic RNA occurred both by a cap-dependent mechanism and by weak internal entry of the ribosomes. This weak IRES activity was confirmed in feline cells expressing bicistronic RNAs containing the FIV 5′ untranslated region (UTR). Surprisingly, infection of feline cells with FIV, but not human immunodeficiency virus type 1, resulted in a great increase in FIV translation. Moreover, a change in the cellular physiological condition provoked by heat stress resulted in the specific stimulation of expression driven by the FIV 5′ UTR while cap-dependent initiation was severely repressed. These results reveal the presence of a “dormant” IRES that becomes activated by viral infection and cellular stress.
9
Murray, Kenneth E., Benjamin P. Steil, Allan W. Roberts, and David J. Barton. "Replication of Poliovirus RNA with Complete Internal Ribosome Entry Site Deletions." Journal of Virology 78, no. 3 (February 1, 2004): 1393–402. http://dx.doi.org/10.1128/jvi.78.3.1393-1402.2004.
Full textAbstract:
ABSTRACT cis-acting RNA sequences and structures in the 5′ and 3′ nontranslated regions of poliovirus RNA interact with host translation machinery and viral replication proteins to coordinately regulate the sequential translation and replication of poliovirus RNA. The poliovirus internal ribosome entry site (IRES) in the 5′ nontranslated region (NTR) has been implicated as a cis-active RNA required for both viral mRNA translation and viral RNA replication. To evaluate the role of the IRES in poliovirus RNA replication, we exploited the advantages of cell-free translation-replication reactions and preinitiation RNA replication complexes. Genetic complementation with helper mRNAs allowed us to create preinitiation RNA replication complexes containing RNA templates with defined deletions in the viral open reading frame and the IRES. A series of deletions revealed that no RNA elements of either the viral open reading frame or the IRES were required in cis for negative-strand RNA synthesis. The IRES was dispensable for both negative- and positive-strand RNA syntheses. Intriguingly, although small viral RNAs lacking the IRES replicated efficiently, the replication of genome length viral RNAs was stimulated by the presence of the IRES. These results suggest that RNA replication is not directly dependent on a template RNA first functioning as an mRNA. These results further suggest that poliovirus RNA replication is not absolutely dependent on any protein-RNA interactions involving the IRES.
10
Rijnbrand, René, Geoffrey Abell, and Stanley M. Lemon. "Mutational Analysis of the GB Virus B Internal Ribosome Entry Site." Journal of Virology 74, no. 2 (January 15, 2000): 773–83. http://dx.doi.org/10.1128/jvi.74.2.773-783.2000.
Full textAbstract:
ABSTRACT GB virus B (GBV-B) is a recently discovered hepatotropic flavivirus that is distantly related to hepatitis C virus (HCV). We show here that translation of its polyprotein is initiated by internal entry of ribosomes on GBV-B RNA. We analyzed the translational activity of dicistronic RNA transcripts containing wild-type or mutated 5′ nontranslated GBV-B RNA (5′NTR) segments, placed between the coding sequences of two reporter proteins, in vitro in rabbit reticulocyte lysate and in vivo in transfected BT7-H cells. We related these results to a previously proposed model of the secondary structure of the GBV-B 5′NTR (M. Honda, et al. RNA 2:955–968, 1996). We identified an internal ribosome entry site (IRES) bounded at its 5′ end by structural domain II, a location analogous to the 5′ limit of the IRES in both the HCV and pestivirus 5′NTRs. Mutational analysis confirmed the structure proposed for domain II of GBV-B RNA, and demonstrated that optimal IRES-mediated translation is dependent on each of the putative RNA hairpins in this domain, including two stem-loops not present in the HCV or pestivirus structures. IRES activity was also absolutely dependent on (i) phylogenetically conserved, adenosine-containing bulge loops in domain III and (ii) the primary nucleotide sequence of stem-loop IIIe. IRES-directed translation was inhibited by a series of point mutations predicted to stabilize stem-loop IV, which contains the initiator AUG codon in its loop segment. A reporter gene was translated most efficiently when fused directly to the initiator AUG codon, with no intervening downstream GBV-B sequence. This finding indicates that the 3′ limit of the GBV-B IRES is at the initiator AUG and that it does not require downstream polyprotein-coding sequence as suggested for the HCV IRES. These results show that the GBV-B IRES, while sharing a common general structure, differs both structurally and functionally from other flavivirus IRES elements.
11
Lytle, J. Robin, Lily Wu, and Hugh D. Robertson. "The Ribosome Binding Site of Hepatitis C Virus mRNA." Journal of Virology 75, no. 16 (August 15, 2001): 7629–36. http://dx.doi.org/10.1128/jvi.75.16.7629-7636.2001.
Full textAbstract:
ABSTRACT Hepatitis C virus (HCV) infects an estimated 170 million people worldwide, the majority of whom develop a chronic infection which can lead to severe liver disease, and for which no generally effective treatment yet exists. A promising target for treatment is the internal ribosome entry site (IRES) of HCV, a highly conserved domain within a highly variable RNA. Never before have the ribosome binding sites of any IRES domains, cellular or viral, been directly characterized. Here, we reveal that the HCV IRES sequences most closely associated with 80S ribosomes during protein synthesis initiation are a series of discontinuous domains together comprising by far the largest ribosome binding site yet discovered.
12
Fuchs, Gabriele, Alexey N. Petrov, Caleb D. Marceau, Lauren M. Popov, Jin Chen, Seán E. O’Leary, Richard Wang, Jan E. Carette, Peter Sarnow, and Joseph D. Puglisi. "Kinetic pathway of 40S ribosomal subunit recruitment to hepatitis C virus internal ribosome entry site." Proceedings of the National Academy of Sciences 112, no. 2 (December 16, 2014): 319–25. http://dx.doi.org/10.1073/pnas.1421328111.
Full textAbstract:
Translation initiation can occur by multiple pathways. To delineate these pathways by single-molecule methods, fluorescently labeled ribosomal subunits are required. Here, we labeled human 40S ribosomal subunits with a fluorescent SNAP-tag at ribosomal protein eS25 (RPS25). The resulting ribosomal subunits could be specifically labeled in living cells and in vitro. Using single-molecule Förster resonance energy transfer (FRET) between RPS25 and domain II of the hepatitis C virus (HCV) internal ribosome entry site (IRES), we measured the rates of 40S subunit arrival to the HCV IRES. Our data support a single-step model of HCV IRES recruitment to 40S subunits, irreversible on the initiation time scale. We furthermore demonstrated that after binding, the 40S:HCV IRES complex is conformationally dynamic, undergoing slow large-scale rearrangements. Addition of translation extracts suppresses these fluctuations, funneling the complex into a single conformation on the 80S assembly pathway. These findings show that 40S:HCV IRES complex formation is accompanied by dynamic conformational rearrangements that may be modulated by initiation factors.
13
Costa-Mattioli, Mauro, Yuri Svitkin, and Nahum Sonenberg. "La Autoantigen Is Necessary for Optimal Function of the Poliovirus and Hepatitis C Virus Internal Ribosome Entry Site In Vivo and In Vitro." Molecular and Cellular Biology 24, no. 15 (August 1, 2004): 6861–70. http://dx.doi.org/10.1128/mcb.24.15.6861-6870.2004.
Full textAbstract:
ABSTRACT Translation of poliovirus and hepatitis C virus (HCV) RNAs is initiated by recruitment of 40S ribosomes to an internal ribosome entry site (IRES) in the mRNA 5′ untranslated region. Translation initiation of these RNAs is stimulated by noncanonical initiation factors called IRES trans-activating factors (ITAFs). The La autoantigen is such an ITAF, but functional evidence for the role of La in poliovirus and HCV translation in vivo is lacking. Here, by two methods using small interfering RNA and a dominant-negative mutant of La, we demonstrate that depletion of La causes a dramatic reduction in poliovirus IRES function in vivo. We also show that 40S ribosomal subunit binding to HCV and poliovirus IRESs in vitro is inhibited by a dominant-negative form of La. These results provide strong evidence for a function of the La autoantigen in IRES-dependent translation and define the step of translation which is stimulated by La.
14
Venkatesan, Arun, and Asim Dasgupta. "Novel Fluorescence-Based Screen To Identify Small Synthetic Internal Ribosome Entry Site Elements." Molecular and Cellular Biology 21, no. 8 (April 15, 2001): 2826–37. http://dx.doi.org/10.1128/mcb.21.8.2826-2837.2001.
Full textAbstract:
ABSTRACT We report here a novel fluorescent protein-based screen to identify small, synthetic internal ribosome entry site (IRES) elements in vivo. A library of bicistronic plasmids encoding the enhanced blue and green fluorescent proteins (EBFP and EGFP) separated by randomized 50-nucleotide-long sequences was amplified in bacteria and delivered into mammalian cells via protoplast fusion. Cells that received functional IRES elements were isolated using the EBFP and EGFP reporters and fluorescence-activated cell sorting, and several small IRES elements were identified. Two of these elements were subsequently shown to possess IRES activity comparable to that of a variant of the encephalomyocarditis virus IRES element in a context-independent manner both in vitro and in vivo, and these elements functioned in multiple cell types. Although no sequence or structural homology was apparent between the synthetic IRES elements and known viral and cellular IRES elements, the two synthetic IRES elements specifically blocked poliovirus (PV) IRES-mediated translation in vitro. Competitive protein-binding experiments suggested that these IRES elements compete with PV IRES-mediated translation by utilizing some of the same factors as the PV IRES to direct translation. The utility of this fluorescent protein-based screen in identifying IRES elements with improved activity as well as in probing the mechanism of IRES-mediated translation is discussed.
15
Shaw-Jackson, Chloë, and Thomas Michiels. "Absence of Internal Ribosome Entry Site-Mediated Tissue Specificity in the Translation of a Bicistronic Transgene." Journal of Virology 73, no. 4 (April 1, 1999): 2729–38. http://dx.doi.org/10.1128/jvi.73.4.2729-2738.1999.
Full textAbstract:
ABSTRACT The 5′ noncoding regions of the genomes of picornaviruses form a complex structure that directs cap-independent initiation of translation. This structure has been termed the internal ribosome entry site (IRES). The efficiency of translation initiation was shown, in vitro, to be influenced by the binding of cellular factors to the IRES. Hence, we hypothesized that the IRES might control picornavirus tropism. In order to test this possibility, we made a bicistronic construct in which translation of the luciferase gene is controlled by the IRES of Theiler’s murine encephalomyelitis virus. In vitro, we observed that the IRES functions in various cell types and in macrophages, irrespective of their activation state. In vivo, we observed that the IRES is functional in different tissues of transgenic mice. Thus, it seems that the IRES is not an essential determinant of Theiler’s virus tropism. On the other hand, the age of the mouse could be critical for IRES function. Indeed, the IRES was found to be more efficient in young mice. Picornavirus IRESs are becoming popular tools in transgenesis technology, since they allow the expression of two genes from the same transcription unit. Our results show that the Theiler’s virus IRES is functional in cells of different origins and that it is thus a broad-spectrum tool. The possible age dependency of the IRES function, however, could be a drawback for gene expression in adult mice.
16
Martineau, Yvan, Christine Le Bec, Laurent Monbrun, Valérie Allo, Ing-Ming Chiu, Olivier Danos, Hervé Moine, Hervé Prats, and Anne-Catherine Prats. "Internal Ribosome Entry Site Structural Motifs Conserved among Mammalian Fibroblast Growth Factor 1 Alternatively Spliced mRNAs." Molecular and Cellular Biology 24, no. 17 (September 1, 2004): 7622–35. http://dx.doi.org/10.1128/mcb.24.17.7622-7635.2004.
Full textAbstract:
ABSTRACT Fibroblast growth factor 1 (FGF-1) is a powerful angiogenic factor whose gene structure contains four promoters, giving rise to a process of alternative splicing resulting in four mRNAs with alternative 5′ untranslated regions (5′ UTRs). Here we have identified, by using double luciferase bicistronic vectors, the presence of internal ribosome entry sites (IRESs) in the human FGF-1 5′ UTRs, particularly in leaders A and C, with distinct activities in mammalian cells. DNA electrotransfer in mouse muscle revealed that the IRES present in the FGF-1 leader A has a high activity in vivo. We have developed a new regulatable TET OFF bicistronic system, which allowed us to rule out the possibility of any cryptic promoter in the FGF-1 leaders. FGF-1 IRESs A and C, which were mapped in fragments of 118 and 103 nucleotides, respectively, are flexible in regard to the position of the initiation codon, making them interesting from a biotechnological point of view. Furthermore, we show that FGF-1 IRESs A of murine and human origins show similar IRES activity profiles. Enzymatic and chemical probing of the FGF-1 IRES A RNA revealed a structural domain conserved among mammals at both the nucleotide sequence and RNA structure levels. The functional role of this structural motif has been demonstrated by point mutagenesis, including compensatory mutations. These data favor an important role of IRESs in the control of FGF-1 expression and provide a new IRES structural motif that could help IRES prediction in 5′ UTR databases.
17
Buck, Christopher B., Xuefei Shen, Michael A. Egan, Theodore C. Pierson, Christopher M. Walker, and Robert F. Siliciano. "The Human Immunodeficiency Virus Type 1gag Gene Encodes an Internal Ribosome Entry Site." Journal of Virology 75, no. 1 (January 1, 2001): 181–91. http://dx.doi.org/10.1128/jvi.75.1.181-191.2001.
Full textAbstract:
ABSTRACT Several retroviruses have recently been shown to promote translation of their gag gene products by internal ribosome entry. In this report, we show that mRNAs containing the human immunodeficiency virus type 1 (HIV-1) gag open reading frame (ORF) exhibit internal ribosome entry site (IRES) activity that can promote translational initiation of Pr55 gag . Remarkably, this IRES activity is driven by sequences within the gag ORF itself and is not dependent on the native gag 5′-untranslated region (UTR). This cap-independent mechanism for Pr55 gag translation may help explain the high levels of translation of this protein in the face of major RNA structural barriers to scanning ribosomes found in the gag 5′ UTR. The gag IRES activity described here also drives translation of a novel 40-kDa Gag isoform through translational initiation at an internal AUG codon found near the amino terminus of the Pr55 gag capsid domain. Our findings suggest that this low-abundance Gag isoform may be important for wild-type replication of HIV-1 in cultured cells. The activities of the HIV-1 gag IRES may be an important feature of the HIV-1 life cycle and could serve as a novel target for antiretroviral therapeutic strategies.
18
Lozano, Gloria, Rosario Francisco-Velilla, and Encarnacion Martinez-Salas. "Deconstructing internal ribosome entry site elements: an update of structural motifs and functional divergences." Open Biology 8, no. 11 (November 2018): 180155. http://dx.doi.org/10.1098/rsob.180155.
Full textAbstract:
Beyond the general cap-dependent translation initiation, eukaryotic organisms use alternative mechanisms to initiate protein synthesis. Internal ribosome entry site (IRES) elements are cis -acting RNA regions that promote internal initiation of translation using a cap-independent mechanism. However, their lack of primary sequence and secondary RNA structure conservation, as well as the diversity of host factor requirement to recruit the ribosomal subunits, suggest distinct types of IRES elements. In spite of this heterogeneity, conserved motifs preserve sequences impacting on RNA structure and RNA–protein interactions important for IRES-driven translation. This conservation brings the question of whether IRES elements could consist of basic building blocks, which upon evolutionary selection result in functional elements with different properties. Although RNA-binding proteins (RBPs) perform a crucial role in the assembly of ribonucleoprotein complexes, the versatility and plasticity of RNA molecules, together with their high flexibility and dynamism, determines formation of macromolecular complexes in response to different signals. These properties rely on the presence of short RNA motifs, which operate as modular entities, and suggest that decomposition of IRES elements in short modules could help to understand the different mechanisms driven by these regulatory elements. Here we will review evidence suggesting that model IRES elements consist of the combination of short modules, providing sites of interaction for ribosome subunits, eIFs and RBPs, with implications for definition of criteria to identify novel IRES-like elements genome wide.
19
Wang, Xinying, Marli Vlok, Stephane Flibotte, and Eric Jan. "Resurrection of a Viral Internal Ribosome Entry Site from a 700 Year Old Ancient Northwest Territories Cripavirus." Viruses 13, no. 3 (March 17, 2021): 493. http://dx.doi.org/10.3390/v13030493.
Full textAbstract:
The dicistrovirus intergenic region internal ribosome entry site (IGR IRES) uses an unprecedented, streamlined mechanism whereby the IRES adopts a triple-pseudoknot (PK) structure to directly bind to the conserved core of the ribosome and drive translation from a non-AUG codon. The origin of this IRES mechanism is not known. Previously, a partial fragment of a divergent dicistrovirus RNA genome, named ancient Northwest territories cripavirus (aNCV), was extracted from 700-year-old caribou feces trapped in a subarctic ice patch. The aNCV IGR sequence adopts a secondary structure similar to contemporary IGR IRES structures, however, there are subtle differences including 105 nucleotides upstream of the IRES of unknown function. Using filter binding assays, we showed that the aNCV IRES could bind to purified ribosomes, and toeprinting analysis pinpointed the start site at a GCU alanine codon adjacent to PKI. Using a bicistronic reporter RNA, the aNCV IGR can direct translation in vitro in a PKI-dependent manner. Lastly, a chimeric infectious clone swapping in the aNCV IRES supported translation and virus infection. The characterization and resurrection of a functional IGR IRES from a divergent 700-year-old virus provides a historical framework for the importance of this viral translational mechanism.
20
Shibuya, Norihiro, and Nobuhiko Nakashima. "Characterization of the 5′ internal ribosome entry site of Plautia stali intestine virus." Journal of General Virology 87, no. 12 (December 1, 2006): 3679–86. http://dx.doi.org/10.1099/vir.0.82193-0.
Full textAbstract:
The RNA genome of Plautia stali intestine virus (PSIV; Cripavirus, Dicistroviridae) contains two open reading frames, the first of which is preceded by a 570 nt untranslated region (5′ UTR). The 5′ UTR was confirmed to be an internal ribosome entry site (IRES) using an insect cell lysate translation system: translation of a second cistron increased 14-fold in the presence of the 5′ UTR and a cap analogue did not inhibit translation of the second cistron. Deletion analysis showed that 349 bases corresponding to nt 225–573 in the PSIV genome were necessary for internal initiation. The PSIV 5′ IRES did not function in rabbit reticulocyte lysate or wheatgerm translation systems; however, the intergenic IRES for capsid translation of PSIV was functional in both systems, indicating that the 5′ IRES and the intergenic IRES have distinct requirements for their activities. Chemical and enzymic analyses of the 5′ IRES of PSIV indicate that its structure is distinct from that of Rhopalosiphum padi virus. Because 5′ IRES elements in some dicistroviruses have been reported to be active in plant and mammalian cell-free translation systems, there appears to be variation among dicistroviruses in the mechanism of translation initiation mediated by 5′ IRES elements.
21
Huez, Isabelle, Laurent Créancier, Sylvie Audigier, Marie-Claire Gensac, Anne-Catherine Prats, and Hervé Prats. "Two Independent Internal Ribosome Entry Sites Are Involved in Translation Initiation of Vascular Endothelial Growth Factor mRNA." Molecular and Cellular Biology 18, no. 11 (November 1, 1998): 6178–90. http://dx.doi.org/10.1128/mcb.18.11.6178.
Full textAbstract:
ABSTRACT The mRNA of vascular endothelial growth factor (VEGF), the major angiogenic growth factor, contains an unusually long (1,038 nucleotides) and structured 5′ untranslated region (UTR). According to the classical translation initiation model of ribosome scanning, such a 5′ UTR is expected to be a strong translation inhibitor. In vitro and bicistronic strategies were used to show that the VEGF mRNA translation was cap independent and occurred by an internal ribosome entry process. For the first time, we demonstrate that two independent internal ribosome entry sites (IRESs) are present in this 5′ UTR. IRES A is located within the 300 nucleotides upstream from the AUG start codon. RNA secondary structure prediction and site-directed mutagenesis allowed the identification of a 49-nucleotide structural domain (D4) essential to IRES A activity. UV cross-linking experiments revealed that IRES A activity was correlated with binding of a 100-kDa protein to the D4 domain. IRES B is located in the first half of the 5′ UTR. An element between nucleotides 379 and 483 is required for its activity. Immunoprecipitation experiments demonstrated that a main IRES B-bound protein was the polypyrimidine tract binding protein (PTB), a well-known regulator of picornavirus IRESs. However, we showed that binding of the PTB on IRES B does not seem to be correlated with its activity. Evidence is provided of an original cumulative effect of two IRESs, probably controlled by different factors, to promote an efficient initiation of translation at the same AUG codon.
22
Masek, Tomas, Vaclav Vopalensky, Ondrej Horvath, Lucie Vortelova, Zuzana Feketova, and Martin Pospisek. "Hepatitis C virus internal ribosome entry site initiates protein synthesis at the authentic initiation codon in yeast." Journal of General Virology 88, no. 7 (July 1, 2007): 1992–2002. http://dx.doi.org/10.1099/vir.0.82782-0.
Full textAbstract:
Hepatitis C virus (HCV) is an important pathogen causing both acute and chronic infections in humans. The HCV polyprotein is synthesized by cap-independent translation initiation after ribosome binding to the highly structured internal ribosome entry site (IRES). The HCV IRES has been shown to have a low requirement for translation initiation factors and the ability to bind directly to the 40S ribosomal subunit. A novel yeast bicistronic reporter system, suitable for sensitive and accurate analysis of IRES activity, has been developed. It employs signal amplification based on the Gal4p transcription factor-mediated activation of a variety of secondary reporter genes. The system has a broad dynamic range and, depending on the nature of the particular secondary reporter, can be used both for precise measurements of IRES activity and for selection and screening for novel IRES variants and IRES trans-acting factors. By using this novel bicistronic system, it was shown that the HCV IRES is functional in yeast cells. Mutational analysis of the IRES loop IV and the adjacent region revealed that, in yeast, as in mammalian cells, translation initiates preferentially at the authentic 342AUG codon and that disruption of the HCV IRES loop IV abrogates its function, whilst minor positional changes or substitutions of the initiation codon within loop IV are largely tolerated. These findings bring more general insights to translation initiation, but also open the door for utilization of yeast and its sophisticated genetics for searching for new antiviral drugs and HCV IRES trans-acting proteins.
23
Marschalek, Adriane, Stefan Finke, Martin Schwemmle, Daniel Mayer, Bernd Heimrich, Lothar Stitz, and Karl-Klaus Conzelmann. "Attenuation of Rabies Virus Replication and Virulence by Picornavirus Internal Ribosome Entry Site Elements." Journal of Virology 83, no. 4 (December 10, 2008): 1911–19. http://dx.doi.org/10.1128/jvi.02055-08.
Full textAbstract:
ABSTRACT Gene expression of nonsegmented negative-strand RNA viruses is regulated at the transcriptional level and relies on the canonical 5′-end-dependent translation of capped viral mRNAs. Here, we have used internal ribosome entry sites (IRES) from picornaviruses to control the expression level of the phosphoprotein P of the neurotropic rabies virus (RV; Rhabdoviridae), which is critically required for both viral replication and escape from the host interferon response. In a dual luciferase reporter RV, the IRES elements of poliovirus (PV) and human rhinovirus type 2 (HRV2) were active in a variety of cell lines from different host species. While a generally lower activity of the HRV2 IRES was apparent compared to the PV IRES, specific deficits of the HRV2 IRES in neuronal cell lines were not observed. Recombinant RVs expressing P exclusively from a bicistronic nucleoprotein (N)-IRES-P mRNA showed IRES-specific reduction of replication in cell culture and in neurons of organotypic brain slice cultures, an increased activation of the beta interferon (IFN-β) promoter, and increased sensitivity to IFN. Intracerebral infection revealed a complete loss of virulence of both PV- and HRV2 IRES-controlled RV for wild-type mice and for transgenic mice lacking a functional IFN-α receptor (IFNAR−/−). The virulence of HRV2 IRES-controlled RV was most severely attenuated and could be demonstrated only in newborn IFNAR−/− mice. Translational control of individual genes is a promising strategy to attenuate replication and virulence of live nonsegmented negative-strand RNA viruses and vectors and to study the function of IRES elements in detail.
24
Kaminski, Ann, Tuija A. A. Pöyry, Peter J. Skene, and Richard J. Jackson. "Mechanism of Initiation Site Selection Promoted by the Human Rhinovirus 2 Internal Ribosome Entry Site." Journal of Virology 84, no. 13 (April 28, 2010): 6578–89. http://dx.doi.org/10.1128/jvi.00123-10.
Full textAbstract:
ABSTRACT Translation initiation site usage on the human rhinovirus 2 internal ribosome entry site (IRES) has been examined in a mixed reticulocyte lysate/HeLa cell extract system. There are two relevant AUG triplets, both in a base-paired hairpin structure (domain VI), with one on the 5′ side at nucleotide (nt) 576, base paired with the other at nt 611, which is the initiation site for polyprotein synthesis. A single residue was inserted in the apical loop to put AUG-576 in frame with AUG-611, and in addition another in-frame AUG was introduced at nt 593. When most of the IRES was deleted to generate a monocistronic mRNA, the use of these AUGs conformed to the scanning ribosome model: improving the AUG-576 context increased initiation at this site and decreased initiation at downstream sites, whereas the converse was seen when AUG-576 was mutated to GUA; and AUG-593, when present, took complete precedence over AUG-611. Under IRES-dependent conditions, by contrast, much less initiation occurred at AUG-576 than in a monocistronic mRNA with the same AUG-576 context, mutation of AUG-576 decreased initiation at downstream sites by ∼70%, and introduction of AUG-593 did not completely abrogate initiation at AUG-611, unless the apical base pairing in domain VI was destroyed by point mutations. These results indicate that ribosomes first bind at the AUG-576 site, but instead of initiating there, most of them are transferred to AUG-611, the majority by strictly linear scanning and a substantial minority by direct transfer, which is possibly facilitated by the occasional persistence of base pairing in the apical part of the domain VI stem.
25
Gallego, J., and G. Varani. "The hepatitis C virus internal ribosome-entry site: a new target for antiviral research." Biochemical Society Transactions 30, no. 2 (April 1, 2002): 140–45. http://dx.doi.org/10.1042/bst0300140.
Full textAbstract:
The hepatitis C virus (HCV) is the main causative agent of non-A, non-B hepatitis in humans and a major cause of mortality and morbidity in the world. Currently there is no effective treatment available for the infection caused by this virus, whose replication depends on an unusual translation-initiation mechanism. The viral RNA contains an internal ribosome-entry site (IRES) that is recognized specifically by the small ribosomal subunit and by eukaryotic initiation factor 3, and these interactions allow cap (7-methylguanine nucleotide)-independent initiation of viral protein synthesis. In this article, we review the structure and mechanism of translation initiation of the HCV IRES, and its potential as a target for novel antivirals.
26
Cevallos, Randal C., and Peter Sarnow. "Factor-Independent Assembly of Elongation-Competent Ribosomes by an Internal Ribosome Entry Site Located in an RNA Virus That Infects Penaeid Shrimp." Journal of Virology 79, no. 2 (January 15, 2005): 677–83. http://dx.doi.org/10.1128/jvi.79.2.677-683.2005.
Full textAbstract:
ABSTRACT The Taura syndrome virus (TSV), a member of the Dicistroviridae family of viruses, is a single-stranded positive-sense RNA virus which contains two nonoverlapping reading frames separated by a 230-nucleotide intergenic region. This intergenic region contains an internal ribosome entry site (IRES) which directs the synthesis of the TSV capsid proteins. Unlike other dicistroviruses, the TSV IRES contains an AUG codon that is in frame with the capsid region, suggesting that the IRES initiates translation at this AUG codon by using initiator tRNAmet. We show here that the TSV IRES does not use this or any other AUG codon to initiate translation. Like the IRES in cricket paralysis virus (CrPV), the TSV IRES can assemble 80S ribosomes in the absence of initiation factors and can direct protein synthesis in a reconstituted system that contains only purified ribosomal subunits, eukaryotic elongation factors 1A and 2, and aminoacylated tRNAs. The functional conservation of the CrPV-like IRES elements in viruses that can infect different invertebrate hosts suggests that initiation at non-AUG codons by an initiation factor-independent mechanism may be more prevalent.
27
Kaku, Yoshihiro, Louisa S. Chard, Toru Inoue, and Graham J. Belsham. "Unique Characteristics of a Picornavirus Internal Ribosome Entry Site from the Porcine Teschovirus-1 Talfan." Journal of Virology 76, no. 22 (November 15, 2002): 11721–28. http://dx.doi.org/10.1128/jvi.76.22.11721-11728.2002.
Full textAbstract:
ABSTRACT The teschoviruses constitute a recently defined picornavirus genus. Most of the genome sequence of the porcine teschovirus-1 (PTV) Talfan and several other strains is known. We now demonstrate that initiation of protein synthesis occurs at nucleotide (nt) 412 on the PTV Talfan RNA and that nt 1 to 405 contains an internal ribosome entry site (IRES) that functions efficiently in vitro and within mammalian cells. In comparison with other picornavirus IRES elements, the PTV IRES is relatively short and lacks a significant polypyrimidine tract near the 3′ end. Expression of an enterovirus 2A protease, which induces cleavage of eIF4G within the translation initiation complex eIF4F, has little effect on the PTV IRES activity within BHK cells. The PTV IRES has a unique set of properties and represents a new class of picornavirus IRES element.
28
Han, Baoguang, and Jian-Ting Zhang. "Regulation of Gene Expression by Internal Ribosome Entry Sites or Cryptic Promoters: the eIF4G Story." Molecular and Cellular Biology 22, no. 21 (November 1, 2002): 7372–84. http://dx.doi.org/10.1128/mcb.22.21.7372-7384.2002.
Full textAbstract:
ABSTRACT As an alternative to the scanning mechanism of initiation, the direct-internal-initiation mechanism postulates that the translational machinery assembles at the AUG start codon without traversing the entire 5′ untranslated region (5′-UTR) of the mRNA. Although the existence of internal ribosome entry sites (IRESs) in viral mRNAs is considered to be well established, the existence of IRESs in cellular mRNAs has recently been challenged, in part because when testing is carried out using a conventional dicistronic vector, Northern blot analyses might not be sensitive enough to detect low levels of monocistronic transcripts derived via a cryptic promoter or splice site. To address this concern, we created a new promoterless dicistronic vector to test the putative IRES derived from the 5′-UTR of an mRNA that encodes the translation initiation factor eIF4G. Our analysis of this 5′-UTR sequence unexpectedly revealed a strong promoter. The activity of the internal promoter relies on the integrity of a polypyrimidine tract (PPT) sequence that had been identified as an essential component of the IRES. The PPT sequence overlaps with a binding site for transcription factor C/EBPβ. Two other transcription factors, Sp1 and Ets, were also found to bind to and mediate expression from the promoter in the 5′-UTR of eIF4G mRNA. The biological significance of the internal promoter in the eIF4G mRNA might lie in the production of an N-terminally truncated form of the protein. Consistent with the idea that the cryptic promoter we identified underlies the previously reported IRES activity, we found no evidence of IRES function when a dicistronic mRNA containing the eIF4G sequence was translated in vitro or in vivo. Using the promoterless dicistronic vector, we also found promoter activities in the long 5′-UTRs of human Sno and mouse Bad mRNAs although monocistronic transcripts were not detectable on Northern blot analyses. The promoterless dicistronic vector might therefore prove useful in future studies to examine more rigorously the claim that there is IRES activity in cellular mRNAs.
29
Hahm, Bumsuk, Yoon Ki Kim, Jong Heon Kim, Tae Yoon Kim, and Sung Key Jang. "Heterogeneous Nuclear Ribonucleoprotein L Interacts with the 3′ Border of the Internal Ribosomal Entry Site of Hepatitis C Virus." Journal of Virology 72, no. 11 (November 1, 1998): 8782–88. http://dx.doi.org/10.1128/jvi.72.11.8782-8788.1998.
Full textAbstract:
ABSTRACT Translation initiation of hepatitis C virus (HCV) RNA occurs by internal entry of a ribosome into the 5′ nontranslated region in a cap-independent manner. The HCV RNA sequence from about nucleotide 40 up to the N terminus of the coding sequence of the core protein is required for efficient internal initiation of translation, though the precise border of the HCV internal ribosomal entry site (IRES) has yet to be determined. Several cellular proteins have been proposed to direct HCV IRES-dependent translation by binding to the HCV IRES. Here we report on a novel cellular protein that specifically interacts with the 3′ border of the HCV IRES in the core-coding sequence. This protein with an apparent molecular mass of 68 kDa turned out to be heterogeneous nuclear ribonucleoprotein L (hnRNP L). The binding of hnRNP L to the HCV IRES correlates with the translational efficiencies of corresponding mRNAs. This finding suggests that hnRNP L may play an important role in the translation of HCV mRNA through the IRES element.
30
Bakhshesh, Mehran, Elisabetta Groppelli, Margaret M. Willcocks, Elizabeth Royall, Graham J. Belsham, and Lisa O. Roberts. "The Picornavirus Avian Encephalomyelitis Virus Possesses a Hepatitis C Virus-Like Internal Ribosome Entry Site Element." Journal of Virology 82, no. 4 (December 12, 2007): 1993–2003. http://dx.doi.org/10.1128/jvi.01957-07.
Full textAbstract:
ABSTRACT Avian encephalomyelitis virus (AEV) is a picornavirus that causes disease in poultry worldwide, and flocks must be vaccinated for protection. AEV is currently classified within the hepatovirus genus, since its proteins are most closely related to those of hepatitis A virus (HAV). We now provide evidence that the 494-nucleotide-long 5′ untranslated region of the AEV genome contains an internal ribosome entry site (IRES) element that functions efficiently in vitro and in mammalian cells. Unlike the HAV IRES, the AEV IRES is relatively short and functions in the presence of cleaved eIF4G and it is also resistant to an inhibitor of eIF4A. These properties are reminiscent of the recently discovered class of IRES elements within certain other picornaviruses, such as porcine teschovirus 1 (PTV-1). Like the PTV-1 IRES, the AEV IRES shows significant similarity to the hepatitis C virus (HCV) IRES in sequence, function, and predicted secondary structure. Furthermore, mutational analysis of the predicted pseudoknot structure at the 3′ end of the AEV IRES lends support to the secondary structure we present. AEV is therefore another example of a picornavirus harboring an HCV-like IRES element within its genome, and thus, its classification within the hepatovirus genus may need to be reassessed in light of these findings.
31
Pisarev, Andrey V., Louisa S. Chard, Yoshihiro Kaku, Helen L. Johns, Ivan N. Shatsky, and Graham J. Belsham. "Functional and Structural Similarities between the Internal Ribosome Entry Sites of Hepatitis C Virus and Porcine Teschovirus, a Picornavirus." Journal of Virology 78, no. 9 (May 1, 2004): 4487–97. http://dx.doi.org/10.1128/jvi.78.9.4487-4497.2004.
Full textAbstract:
ABSTRACT Initiation of protein synthesis on picornavirus RNA requires an internal ribosome entry site (IRES). Typically, picornavirus IRES elements contain about 450 nucleotides (nt) and use most of the cellular translation initiation factors. However, it is now shown that just 280 nt of the porcine teschovirus type 1 Talfan (PTV-1) 5′ untranslated region direct the efficient internal initiation of translation in vitro and within cells. In toeprinting assays, assembly of 48S preinitiation complexes from purified components on the PTV-1 IRES was achieved with just 40S ribosomal subunits plus eIF2 and Met-tRNAi Met. Indeed, a binary complex between 40S subunits and the PTV-1 IRES is formed. Thus, the PTV-1 IRES has properties that are entirely different from other picornavirus IRES elements but highly reminiscent of the hepatitis C virus (HCV) IRES. Comparison between the PTV-1 IRES and HCV IRES elements revealed islands of high sequence identity that occur in regions critical for the interactions of the HCV IRES with the 40S ribosomal subunit and eIF3. Thus, there is significant functional and structural similarity between the IRES elements from the picornavirus PTV-1 and HCV, a flavivirus.
32
Dobrikova, Elena Y., Rachel N. Grisham, Constanze Kaiser, Jennifer Lin, and Matthias Gromeier. "Competitive Translation Efficiency at the Picornavirus Type 1 Internal Ribosome Entry Site Facilitated by Viral cis and trans Factors." Journal of Virology 80, no. 7 (April 1, 2006): 3310–21. http://dx.doi.org/10.1128/jvi.80.7.3310-3321.2006.
Full textAbstract:
ABSTRACT Enteroviruses (EVs) overcome their host cells by usurping the translation machinery to benefit viral gene expression. This is accomplished through alternative translation initiation in a cap-independent manner at the viral internal ribosomal entry site (IRES). We have investigated the role of cis- and trans-acting viral factors in EV IRES translation in living cells. We observed that considerable portions of the viral genome, including the 5′-proximal open reading frame and the 3′ untranslated region, contribute to stimulation of IRES-mediated translation. With the IRES in proper context, translation via internal initiation in uninfected cells is as efficient as at capped messages with short, unstructured 5′ untranslated regions. IRES function is enhanced in cells infected with the EV coxsackievirus B3, but the related poliovirus has no significant stimulatory activity. This differential is due to the inherent properties of their 2A protease and is not coupled to 2A-mediated proteolytic degradation of the eukaryotic initiation factor 4G. Our results suggest that the efficiency of alternative translation initiation at EV IRESs depends on a properly configured template rather than on targeted alterations of the host cell translation machinery.
33
Romero-López, Cristina, Raquel Díaz-González, Alicia Barroso-delJesus, and Alfredo Berzal-Herranz. "Inhibition of hepatitis C virus replication and internal ribosome entry site-dependent translation by an RNA molecule." Journal of General Virology 90, no. 7 (July 1, 2009): 1659–69. http://dx.doi.org/10.1099/vir.0.008821-0.
Full textAbstract:
Hepatitis C virus (HCV) protein synthesis is mediated by a highly conserved internal ribosome entry site (IRES), mostly located at the 5′ untranslatable region (UTR) of the viral genome. The translation mechanism is different from that used by cellular cap-mRNAs, making IRESs an attractive target site for new antiviral drugs. The present work characterizes a chimeric RNA molecule (HH363-50) composed of two inhibitors: a hammerhead ribozyme targeting position 363 of the HCV genome and an aptamer directed towards the essential stem–loop structure in domain IV of the IRES region (which contains the translation start codon). The inhibitor RNA interferes with the formation of a translationally active complex, stalling its progression at the level of 80S particle formation. This action is likely related to the effective and specific blocking of HCV IRES-dependent translation achieved in Huh-7 cells. The inhibitor HH363-50 also reduces HCV RNA levels in a subgenomic replicon system. The present findings suggest that HH363-50 could be an effective anti-HCV compound and highlight the possibilities of antiviral agents based on RNA molecules.
34
Kolupaeva, Victoria G., Ivan B. Lomakin, Tatyana V. Pestova, and Christopher U. T. Hellen. "Eukaryotic Initiation Factors 4G and 4A Mediate Conformational Changes Downstream of the Initiation Codon of the Encephalomyocarditis Virus Internal Ribosomal Entry Site." Molecular and Cellular Biology 23, no. 2 (January 15, 2003): 687–98. http://dx.doi.org/10.1128/mcb.23.2.687-698.2003.
Full textAbstract:
ABSTRACT Initiation of translation of encephalomyocarditis virus mRNA is mediated by an internal ribosome entry site (IRES) comprising structural domains H, I, J-K, and L immediately upstream of the initiation codon AUG at nucleotide 834 (AUG834). Assembly of 48S ribosomal complexes on the IRES requires eukaryotic initiation factor 2 (eIF2), eIF3, eIF4A, and the central domain of eIF4G to which eIF4A binds. Footprinting experiments confirmed that eIF4G binds a three-way helical junction in the J-K domain and showed that it interacts extensively with RNA duplexes in the J-K and L domains. Deletion of apical hairpins in the J and K domains synergistically impaired the binding of eIF4G and IRES function. Directed hydroxyl radical probing, done by using Fe(II) tethered to surface residues in eIF4G's central domain, indicated that it is oriented with its N terminus towards the base of domain J and its C terminus towards the apex. eIF4G recruits eIF4A to a defined location on the IRES, and the eIF4G/eIF4A complex caused localized ATP-independent conformational changes in the eIF4G-binding region of the IRES. This complex also induced more extensive conformational rearrangements at the 3′ border of the ribosome binding site that required ATP and active eIF4A. We propose that these conformational changes prepare the region flanking AUG834 for productive binding of the ribosome.
35
Yu, Yongjun, and James C. Alwine. "19S Late mRNAs of Simian Virus 40 Have an Internal Ribosome Entry Site Upstream of the Virion Structural Protein 3 Coding Sequence." Journal of Virology 80, no. 13 (July 1, 2006): 6553–58. http://dx.doi.org/10.1128/jvi.00517-06.
Full textAbstract:
ABSTRACT The late mRNAs of simian virus 40 (SV40) are polycistronic. The 19S mRNAs encode primarily the virion structural proteins VP2 and VP3. The VP2 and VP3 coding sequences are located in the same reading frame, and the VP3 AUG is an internal AUG for VP2. We tested whether an internal ribosome entry site (IRES) might be located upstream of the VP3 AUG that would facilitate its utilization, especially late in infection when cap-dependent translation is reduced (19). Using dicistronic reporter systems for IRES detection, we detected IRES activity within SV40 nucleotides (nts) 565 to 916, the region between the VP2 and VP3 AUGs. Nuclease protection analysis and primer extension analysis indicate no aberrant transcription or splicing that could account for false prediction of an IRES. Deletion analysis of the region indicates the presence of two functional IRESs, one within nts 661 to 830 and the other within nts 771 to 915. These two regions, each containing one IRES, have essentially the same IRES activity as the entire region spanning nts 616 to 915, which contains both IRESs. This suggests that potential secondary structures in the overlapping regions spanning nts 661 to 830 and nts 771 to 915 may be in dynamic equilibrium, such that there is only one functional IRES at any one time. These data strongly suggest that an IRES can be utilized for VP3 translation from the SV40 19S late mRNAs.
36
Saleh, Lanja, René C. Rust, Ralf Füllkrug, Ewald Beck, Gergis Bassili, Kerstin Ochs, and Michael Niepmann. "Functional interaction of translation initiation factor eIF4G with the foot-and-mouth disease virus internal ribosome entry site." Journal of General Virology 82, no. 4 (April 1, 2001): 757–63. http://dx.doi.org/10.1099/0022-1317-82-4-757.
Full textAbstract:
In the life-cycle of picornaviruses, the synthesis of the viral polyprotein is initiated cap-independently at the internal ribosome entry site (IRES) far downstream from the 5′ end of the viral plus-strand RNA. The cis-acting IRES RNA elements serve as binding sites for translation initiation factors that guide the ribosomes to an internal site of the viral RNA. In this study, we show that the eukaryotic translation initiation factor eIF4G interacts directly with the IRES of foot-and-mouth disease virus (FMDV). eIF4G binds mainly to the large Y-shaped stem–loop 4 RNA structure in the 3′ region of the FMDV IRES element, whereas stem–loop 5 contributes only slightly to eIF4G binding. Two subdomains of stem–loop 4 are absolutely essential for eIF4G binding, whereas another subdomain contributes to a lesser extent to binding of eIF4G. At the functional level, the translational activity of stem–loop 4 subdomain mutants correlates with the efficiency of binding of eIF4G in the UV cross-link assay. This indicates that the interaction of eIF4G with the IRES is crucial for the initiation of FMDV translation. A model for the interaction of initiation factors with the IRES element is discussed.
37
Sasaki, Jun, and Nobuhiko Nakashima. "Translation Initiation at the CUU Codon Is Mediated by the Internal Ribosome Entry Site of an Insect Picorna-Like Virus In Vitro." Journal of Virology 73, no. 2 (February 1, 1999): 1219–26. http://dx.doi.org/10.1128/jvi.73.2.1219-1226.1999.
Full textAbstract:
ABSTRACT AUG-unrelated translation initiation was found in an insect picorna-like virus, Plautia stali intestine virus (PSIV). The positive-strand RNA genome of the virus contains two nonoverlapping open reading frames (ORFs). The capsid protein gene is located in the 3′-proximal ORF and lacks an AUG initiation codon. We examined the translation mechanism and the initiation codon of the capsid protein gene by using various dicistronic and monocistronic RNAs in vitro. The capsid protein gene was translated cap independently in the presence of the upstream cistron, indicating that the gene is translated by internal ribosome entry. Deletion analysis showed that the internal ribosome entry site (IRES) consisted of approximately 250 bases and that its 3′ boundary extended slightly into the capsid-coding region. The initiation codon for the IRES-mediated translation was identified as the CUU codon, which is located just upstream of the 5′ terminus of the capsid-coding region by site-directed mutagenesis. In vitro translation assays of monocistronic RNAs lacking the 5′ part of the IRES showed that this CUU codon was not recognized by scanning ribosomes. This suggests that the PSIV IRES can effectively direct translation initiation without stable codon-anticodon pairing between the initiation codon and the initiator methionyl-tRNA.
38
Martínez-Salas, Encarnación, Almudena Pacheco, Paula Serrano, and Noemi Fernandez. "New insights into internal ribosome entry site elements relevant for viral gene expression." Journal of General Virology 89, no. 3 (March 1, 2008): 611–26. http://dx.doi.org/10.1099/vir.0.83426-0.
Full textAbstract:
A distinctive feature of positive-strand RNA viruses is the presence of high-order structural elements at the untranslated regions (UTR) of the genome that are essential for viral RNA replication. The RNA of all members of the family Picornaviridae initiate translation internally, via an internal ribosome entry site (IRES) element present in the 5′ UTR. IRES elements consist of cis-acting RNA structures that usually require specific RNA-binding proteins for translational machinery recruitment. This specialized mechanism of translation initiation is shared with other viral RNAs, e.g. from hepatitis C virus and pestivirus, and represents an alternative to the cap-dependent mechanism. In cells infected with many picornaviruses, proteolysis or changes in phosphorylation of key host factors induces shut off of cellular protein synthesis. This event occurs simultaneously with the synthesis of viral gene products since IRES activity is resistant to the modifications of the host factors. Viral gene expression and RNA replication in positive-strand viruses is further stimulated by viral RNA circularization, involving direct RNA–RNA contacts between the 5′ and 3′ ends as well as RNA-binding protein bridges. In this review, we discuss novel insights into the mechanisms that control picornavirus gene expression and compare them to those operating in other positive-strand RNA viruses.
39
Krüger, Martin, Carmela Beger, Peter J. Welch, Jack R. Barber, Michael P. Manns, and Flossie Wong-Staal. "Involvement of Proteasome α-Subunit PSMA7 in Hepatitis C Virus Internal Ribosome Entry Site-Mediated Translation." Molecular and Cellular Biology 21, no. 24 (December 15, 2001): 8357–64. http://dx.doi.org/10.1128/mcb.21.24.8357-8364.2001.
Full textAbstract:
ABSTRACT Ribozymes are small catalytic RNA molecules that can be engineered to enzymatically cleave RNA transcripts in a sequence-specific fashion and thereby inhibit expression and function of the corresponding gene product. With their simple structures and site-specific cleavage activity, they have been exploited as potential therapeutic agents in a variety of human disorders, including hepatitis C virus (HCV) infection. We have designed a hairpin ribozyme (Rz3′X) targeting the HCV minus-strand replication intermediate at position 40 within the 3′X tail. Surprisingly, Rz3′X was found to induce ganciclovir (GCV)-resistant colonies in a bicistronic cellular reporter system with HCV internal ribosome entry site (IRES)-dependent translation of herpes simplex virus thymidine kinase (TK). Rz3′X-transduced GCV-resistant HeLa reporter cells showed substantially reduced IRES-mediated HCV core protein translation compared with control vector-transduced cells. Since these reporter systems do not contain the HCV 3′X tail sequences, the results indicate that Rz3′X probably exerted an inhibitory effect on HCV IRES activity fortuitously through another gene target. A novel technique of ribozyme cleavage-based target gene identification (cleavage-specific amplification of cDNA ends) (M. Krüger, C. Beger, P. J. Welch, J. R. Barber, and F. Wong-Staal, Nucleic Acids Res. 29:e94, 2001) revealed that human 20S proteasome α-subunit PSMA7 mRNA was a target RNA recognized and cleaved by Rz3′X. We then showed that additional ribozymes directed against PSMA7 RNA inhibited HCV IRES activity in two assay systems: GCV resistance in the HeLa IRES TK reporter cell system and a transient transfection assay performed with a bicistronicRenilla-HCV IRES-firefly luciferase reporter in Huh7 cells. In contrast, ribozymes were inactive against IRES of encephalomyocarditis virus and human rhinovirus. Additionally, proteasome inhibitor MG132 exerted a dose-dependent inhibitory effect on HCV IRES-mediated translation but not on cap-dependent translation. These data suggest a principal role for PSMA7 in regulating HCV IRES activity, a function essential for HCV replication.
40
Merrill, Melinda K., Elena Y. Dobrikova, and Matthias Gromeier. "Cell-Type-Specific Repression of Internal Ribosome Entry Site Activity by Double-Stranded RNA-Binding Protein 76." Journal of Virology 80, no. 7 (April 1, 2006): 3147–56. http://dx.doi.org/10.1128/jvi.80.7.3147-3156.2006.
Full textAbstract:
ABSTRACT Translation of picornavirus plus-strand RNA genomes occurs via internal ribosomal entry at highly structured 5′ untranslated regions. In addition to canonical translation factors, translation rate is likely influenced by supplementary host and viral trans-acting factors. We previously reported that insertion of a heterologous human rhinovirus type 2 internal ribosomal entry site (IRES) into the poliovirus (PV) genome, generating the chimeric virus PV-RIPO, selectively abrogates viral translation and propagation in neurons, which eliminate poliovirus's signature neuropathogenicity. While severely deficient in cells of neuronal lineage, the rhinovirus IRES promotes efficient propagation of PV-RIPO in cancer cells. Tumor-specific IRES function can be therapeutically exploited to direct viral cytotoxicity to cancer cells. Neuron-glioma heterokaryon analysis implicates neuronal trans-dominant inhibition in this effect, suggesting that host trans-acting factors repress IRES function in a cell-type-specific manner. We identified a set of proteins from neuronal cells with affinity for the rhinovirus IRES, including double-stranded RNA-binding protein 76 (DRBP76). DRBP76 associates with the IRES in neuronal but not in malignant glioma cells. Moreover, DRBP76 depletion in neuronal cells enhances rhinovirus IRES-driven translation and virus propagation. Our observations suggest that cell-type-specific association of DRBP76 with the rhinovirus IRES represses PV-RIPO translation and propagation in neuronal cells.
41
Paek, Ki Young, Chon Saeng Kim, Sung Mi Park, Jong Heon Kim, and Sung Key Jang. "RNA-Binding Protein hnRNP D Modulates Internal Ribosome Entry Site-Dependent Translation of Hepatitis C Virus RNA." Journal of Virology 82, no. 24 (October 8, 2008): 12082–93. http://dx.doi.org/10.1128/jvi.01405-08.
Full textAbstract:
ABSTRACT Hepatitis C virus (HCV) is one of the major causative agents of virus-related hepatitis, liver cirrhosis, and hepatocellular carcinoma in humans. Translation of the HCV polyprotein is mediated by an internal ribosomal entry site (IRES) in the 5′ nontranslated region of the genome. Here, we report that a cellular protein, hnRNP D, interacts with the 5′ border of HCV IRES (stem-loop II) and promotes translation of HCV mRNA. Overexpression of hnRNP D in mammalian cells enhances HCV IRES-dependent translation, whereas knockdown of hnRNP D with small interfering RNAs (siRNAs) inhibits translation. In addition, sequestration of hnRNP D with an interacting DNA oligomer inhibits the translation of HCV mRNA in an in vitro system. Ribosome profiling experiments reveal that HCV RNA is redistributed from heavy to light polysome fractions upon suppression of the hnRNP D level using specific siRNA. These results collectively suggest that hnRNP D plays an important role in the translation of HCV mRNA through interactions with the IRES. Moreover, knockdown of hnRNP D with siRNA significantly hampers infection by HCV. A potential role of hnRNP D in HCV proliferation is discussed.
42
Lu, Jie, Yuanyang Hu, Liu Hu, Shan Zong, Dawei Cai, Junping Wang, Haiyang Yu, and Jiamin Zhang. "Ectropis obliqua picorna-like virus IRES-driven internal initiation of translation in cell systems derived from different origins." Journal of General Virology 88, no. 10 (October 1, 2007): 2834–38. http://dx.doi.org/10.1099/vir.0.83201-0.
Full textAbstract:
Ectropis obliqua picorna-like virus (EoPV) is an insect RNA virus that causes a lethal granulosis infection of larvae of the tea looper (Ectropis obliqua). An internal ribosome entry site (IRES) mediates translation initiation of EoPV RNA. Here, bicistronic constructs were used to examine the 5′ untranslated region (UTR) of EoPV for IRES activity. The capacities of the EoPV 5′ UTR IRES and another insect virus IRES, the cricket paralysis virus intergenic region IRES, to mediate internal translation initiation in a variety of translation systems were also compared. The results demonstrated that the EoPV IRES functioned efficiently not only in mammalian cell-derived systems, but also in an insect cell-derived translation system. However, it functioned inefficiently in a plant cell-derived translation system. This study reveals the host preferences of the EoPV IRES and important differences in IRES function between the EoPV IRES and other characterized picorna-like insect viral IRESs.
43
Chard, Louisa S., Marie-Eve Bordeleau, Jerry Pelletier, Junichi Tanaka, and Graham J. Belsham. "Hepatitis C virus-related internal ribosome entry sites are found in multiple genera of the family Picornaviridae." Journal of General Virology 87, no. 4 (April 1, 2006): 927–36. http://dx.doi.org/10.1099/vir.0.81546-0.
Full textAbstract:
The internal ribosome entry site (IRES) elements from porcine enterovirus 8 and simian virus 2, two members of a proposed new genus within the family Picornaviridae, were characterized. These IRES elements, in common with the porcine teschovirus 1 IRES, were found to be related functionally and structurally to the IRES element from Hepatitis C virus, a member of the family Flaviviridae. Partial secondary structure predictions were derived and functional assays demonstrated that these IRES elements continued to be active when eIF4G was cleaved and when the activity of eIF4A was blocked.
44
Zheng, Qingyun, Xueyan Zhang, Hua Yang, Jinyan Xie, Yilin Xie, Jinzhong Chen, Chenghui Yu, and Chen Zhong. "Internal Ribosome Entry Site Dramatically Reduces Transgene Expression in Hematopoietic Cells in a Position-Dependent Manner." Viruses 11, no. 10 (October 8, 2019): 920. http://dx.doi.org/10.3390/v11100920.
Full textAbstract:
Bicistronic transgene expression mediated by internal ribosome entry site (IRES) elements has been widely used. It co-expresses heterologous transgene products from a message RNA driven by a single promoter. Hematologic gene delivery is a promising treatment for both inherited and acquired diseases. A combined strategy was recently documented for potential genome editing in hematopoietic cells. A transduction efficiency exceeding ~90% can be achieved by capsid-optimized recombinant adeno-associated virus serotype 6 (rAAV6) vectors. In this study, to deliver an encephalomyocarditis virus (EMCV) IRES-containing rAAV6 genome into hematopoietic cells, we observed that EMCV IRES almost completely shut down the transgene expression during the process of mRNA–protein transition. In addition, position-dependent behavior was observed, in which only the EMCV IRES element located between a promoter and the transgenes had an inhibitory effect. Although further studies are warranted to evaluate the involvement of cellular translation machinery, our results propose the use of specific IRES elements or an alternative strategy, such as the 2A system, to achieve bicistronic transgene expression in hematopoietic cells.
45
Tahiri-Alaoui, Abdessamad, Lorraine P. Smith, Suzan Baigent, Lydia Kgosana, Lawrence J. Petherbridge, Luke S. Lambeth, William James, and Venugopal Nair. "Identification of an Intercistronic Internal Ribosome Entry Site in a Marek's Disease Virus Immediate-Early Gene." Journal of Virology 83, no. 11 (March 18, 2009): 5846–53. http://dx.doi.org/10.1128/jvi.02602-08.
Full textAbstract:
ABSTRACT In this study, we have identified an internal ribosome entry site (IRES) from the highly infectious herpesvirus Marek's disease virus (MDV). The IRES was mapped to the intercistronic region (ICR) of a bicistronic mRNA that we cloned from the MDV-transformed CD4+ T-cell line MSB-1. The transcript is a member of a family of mRNAs expressed as immediate-early genes with two open reading frames (ORF). The first ORF encodes a 14-kDa polypeptide with two N-terminal splice variants, whereas the second ORF is contained entirely within a single exon and encodes a 12-kDa protein also known as RLORF9. We have shown that the ICR that separates the two ORFs functions as an IRES that controls the translation of RLORF9 when cap-dependent translation is inhibited. Deletion analysis revealed that there are two potential IRES elements within the ICR. Reverse genetic experiments with the oncogenic strain of MDV type 1 indicated that deletion of IRES-controlled RLORF9 does not significantly affect viral replication or MDV-induced mortality.
46
Fernández-Miragall, Olga, and Encarnación Martínez-Salas. "In vivo footprint of a picornavirus internal ribosome entry site reveals differences in accessibility to specific RNA structural elements." Journal of General Virology 88, no. 11 (November 1, 2007): 3053–62. http://dx.doi.org/10.1099/vir.0.83218-0.
Full textAbstract:
Internal ribosome entry site (IRES) elements were described in picornaviruses as an essential region of the viral RNA. Understanding of IRES function requires a detailed knowledge of each step involved in the internal initiation process, from RNA folding and IRES–protein interaction to ribosome recruitment. Thus, deciphering IRES accessibility to external agents due to RNA structural features, as well as RNA–protein protection within living cells, is of primary importance. In this study, two chemical reagents, dimethylsulfate (DMS) and aminomethylpsoralen, have been used to footprint the entire IRES of foot-and-mouth disease virus (FMDV) in living cells; these reagents enter the cell membrane and interact with nucleic acids in a structure-dependent manner. For FMDV, as in other picornaviruses, viral infection is dependent on the correct function of the IRES; therefore, the IRES region itself constitutes a useful target of antiviral drugs. Here, the in vivo footprint of a picornavirus IRES element in the context of a biologically active mRNA is shown for the first time. The accessibility of unpaired adenosine and cytosine nucleotides in the entire FMDV IRES was first obtained in vitro by DMS probing; subsequently, this information was used to interpret the footprint data obtained in vivo for the mRNA encompassing the IRES element in the intercistronic space. The results of DMS accessibility and UV–psoralen cross-linking studies in the competitive cellular environment provided evidence for differences in RNA structure from data obtained in vitro, and provided essential information to identify appropriate targets within the FMDV IRES aimed at combating this important pathogen.
47
Arhab, Yani, Alexander G. Bulakhov, Tatyana V. Pestova, and Christopher U. T. Hellen. "Dissemination of Internal Ribosomal Entry Sites (IRES) Between Viruses by Horizontal Gene Transfer." Viruses 12, no. 6 (June 4, 2020): 612. http://dx.doi.org/10.3390/v12060612.
Full textAbstract:
Members of Picornaviridae and of the Hepacivirus, Pegivirus and Pestivirus genera of Flaviviridae all contain an internal ribosomal entry site (IRES) in the 5′-untranslated region (5′UTR) of their genomes. Each class of IRES has a conserved structure and promotes 5′-end-independent initiation of translation by a different mechanism. Picornavirus 5′UTRs, including the IRES, evolve independently of other parts of the genome and can move between genomes, most commonly by intratypic recombination. We review accumulating evidence that IRESs are genetic entities that can also move between members of different genera and even between families. Type IV IRESs, first identified in the Hepacivirus genus, have subsequently been identified in over 25 genera of Picornaviridae, juxtaposed against diverse coding sequences. In several genera, members have either type IV IRES or an IRES of type I, II or III. Similarly, in the genus Pegivirus, members contain either a type IV IRES or an unrelated type; both classes of IRES also occur in members of the genus Hepacivirus. IRESs utilize different mechanisms, have different factor requirements and contain determinants of viral growth, pathogenesis and cell type specificity. Their dissemination between viruses by horizontal gene transfer has unexpectedly emerged as an important facet of viral evolution.
48
Pudi, Renuka, Sudhamani S. Ramamurthy, and Saumitra Das. "A Peptide Derived from RNA Recognition Motif 2 of Human La Protein Binds to Hepatitis C Virus Internal Ribosome Entry Site, Prevents Ribosomal Assembly, and Inhibits Internal Initiation of Translation." Journal of Virology 79, no. 15 (August 1, 2005): 9842–53. http://dx.doi.org/10.1128/jvi.79.15.9842-9853.2005.
Full textAbstract:
ABSTRACT Human La protein is known to interact with hepatitis C virus (HCV) internal ribosome entry site (IRES) and stimulate translation. Previously, we demonstrated that mutations within HCV SL IV lead to reduced binding to La-RNA recognition motif 2 (RRM2) and drastically affect HCV IRES-mediated translation. Also, the binding of La protein to SL IV of HCV IRES was shown to impart conformational alterations within the RNA so as to facilitate the formation of functional initiation complex. Here, we report that a synthetic peptide, LaR2C, derived from the C terminus of La-RRM2 competes with the binding of cellular La protein to the HCV IRES and acts as a dominant negative inhibitor of internal initiation of translation of HCV RNA. The peptide binds to the HCV IRES and inhibits the functional initiation complex formation. An Huh7 cell line constitutively expressing a bicistronic RNA in which both cap-dependent and HCV IRES-mediated translation can be easily assayed has been developed. The addition of purified TAT-LaR2C recombinant polypeptide that allows direct delivery of the peptide into the cells showed reduced expression of HCV IRES activity in this cell line. The study reveals valuable insights into the role of La protein in ribosome assembly at the HCV IRES and also provides the basis for targeting ribosome-HCV IRES interaction to design potent antiviral therapy.
49
Rahmagiarti, Cintera, Silvia Tri Widyaningtyas, and Budiman Bela. "Konstruksi Plasmid Rekombinan untuk Inisiasi Translasi Enhance Green Fluorescent Protein oleh Internal Ribosomal Entry Site HIV-1." Media Penelitian dan Pengembangan Kesehatan 28, no. 2 (October 17, 2018): 67–72. http://dx.doi.org/10.22435/mpk.v28i2.181.
Full textAbstract:
Human immunodeficiency virus (HIV) is a virus that causes acquired immunodeficiency virus syndrome (AIDS). The HIV genome has a cap structure at 5’ and polyadenylation at 3’ on mRNA resulting in a translation initiation through scanning at 5'untranslated region (UTR). The Vpr protein produced during viral replication causes the 5'cap scanning to be inhibited so HIV-1 can directly recruit the ribosome at the start codon via internal ribosomal entry site (IRES). IRES activity is high at G2/M phase and highest expression in monocyte cell line (THP-1) and lymphocyte (HPB-ALL). The role of HIV IRES however, is not yet known in infection of nondividing cells by HIV-1. HIV-1 IRES and egfp from pcDNA5FRT/TO were amplified with PCR. The insert DNA (HIV-1 IRES_egfp) and pcDNA3.1(+) were digested with EcoRI and ApaI and then ligated. The verification was performed with PCR colonies, restriction verification, and sequencing. The size of insert DNA is 1067 bp while the vector is 5379 bp. E. coli transformed with DNA ligation produces 70 colonies, control of ligation produces 5 colonies, and negative control didn’t grow. 19 colonies contain recombinant DNA, restriction verification was of the appropriate size, and the sequence verification didn’t find any mutation. Therefore, the subcloning process pcDNA3.1_IRES HIV-1_egfp was successfully performed.
Abstrak
Human immunodeficiency virus (HIV) merupakan virus penyebab acquired immunodeficiency virus syndrome (AIDS). Genom HIV memiliki struktur cap di 5’ dan poliadenilasi di 3’ mRNA sehingga proses inisiasi translasi melalui pemindaian 5’cap pada struktur untranslated region (UTR) di 5’ mRNA HIV. Protein Vpr yang dihasilkan selama replikasi virus menyebabkan pemindaian melalui 5’cap terhambat sehingga HIV-1 dapat langsung merekrut ribosom pada kodon awal translasi melalui struktur internal ribosomal entry site (IRES). Aktivitas IRES tinggi pada fase G2/M dan ekspresi gen tinggi pada sel line monosit (THP-1) dan limfosit (HPB-ALL). Namun, peran IRES HIV-1 belum diketahui pada sel tidak membelah yang merupakan sel target pada infeksi HIV-1. DNA sekuen IRES HIV-1 dan egfp dari pcDNA5FRT/TO diamplifikasi dengan PCR. DNA sisipan (IRES HIV-1_egfp) dan pcDNA3.1(+) dipotong dengan EcoRI dan ApaI lalu DNA sisipan diligasi dengan pcDNA3.1(+). Verifikasi hasil klona dilakukan dengan PCR koloni, verifikasi restriksi, dan sekuensing. Restriksi DNA sisipan menghasilkan pita berukuran 1067 pb. Restriksi vektor plasmid menghasilkan pita berukuran 5379 pb. E.coli yang ditransformasi DNA ligasi menghasilkan 70 koloni, kontrol ligasi 5 koloni, dan kontrol negatif tidak tumbuh. 19 koloni terverifikasi mengandung DNA rekombinan, verifikasi restriksi memiliki ukuran sesuai, dan verifikasi sekuensing tidak terdapat perubahan basa. Oleh karena itu, proses subkloning pcDNA3.1_IRES HIV-1_egfp berhasil dilakukan.
50
Guest, Stephen, Evgeny Pilipenko, Kamal Sharma, Konstantin Chumakov, and Raymond P. Roos. "Molecular Mechanisms of Attenuation of the Sabin Strain of Poliovirus Type 3." Journal of Virology 78, no. 20 (October 15, 2004): 11097–107. http://dx.doi.org/10.1128/jvi.78.20.11097-11107.2004.
Full textAbstract:
ABSTRACT Mutations critical for the central nervous system (CNS) attenuation of the Sabin vaccine strains of poliovirus (PV) are located within the viral internal ribosome entry site (IRES). We examined the interaction of the IRESs of PV type 3 (PV3) and Sabin type 3 (Sabin3) with polypyrimidine tract-binding protein (PTB) and a neural cell-specific homologue, nPTB. PTB and nPTB were found to bind to a site directly adjacent to the attenuating mutation, and binding at this site was less efficient on the Sabin3 IRES than on the PV3 IRES. Translation mediated by the PV3 and Sabin3 IRESs in neurons of the chicken embryo spinal cord demonstrated a translation deficit for the Sabin3 IRES that could be rescued by increasing PTB expression in the CNS. These data suggest that the low levels of PTB available in the CNS, coupled to a reduced binding of PTB on the Sabin3 IRES, leads to its CNS-specific attenuation. This study also demonstrates the use of the chicken embryo to easily investigate translation of RNA within a neuron in the CNS of an intact living organism.