Journal articles: 'NX11'

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Li, Ying, Yeou-cherng Bor, Mark P. Fitzgerald, Kevin S. Lee, David Rekosh, and Marie-Louise Hammarskjold. "AnNXF1mRNA with a retained intron is expressed in hippocampal and neocortical neurons and is translated into a protein that functions as an Nxf1 cofactor." Molecular Biology of the Cell 27, no. 24 (December 2016): 3903–12. http://dx.doi.org/10.1091/mbc.e16-07-0515.

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The Nxf1 protein is a major nuclear export receptor for the transport of mRNA, and it also is essential for export of retroviral mRNAs with retained introns. In the latter case, it binds to RNA elements known as constitutive transport elements (CTEs) and functions in conjunction with a cofactor known as Nxt1. The NXF1 gene also regulates expression of its own intron-containing RNA through the use of a functional CTE within intron 10. mRNA containing this intron is exported to the cytoplasm, where it can be translated into the 356–amino acid short Nxf1(sNxf1) protein, despite the fact that it is a prime candidate for nonsense-mediated decay (NMD). Here we demonstrate that sNxf1 is highly expressed in nuclei and dendrites of hippocampal and neocortical neurons in rodent brain. Additionally, we show that sNxf1 localizes in RNA granules in neurites of differentiated N2a mouse neuroblastoma cells, where it shows partial colocalization with Staufen2 isoform SS, a protein known to play a role in dendritic mRNA trafficking. We also show that sNxf1 forms heterodimers in conjunction with the full-length Nxf1 and that sNxf1 can replace Nxt1 to enhance the expression of CTE-containing mRNA and promote its association with polyribosomes.

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Gales, Jón Pol, Julie Kubina, Angèle Geldreich, and Maria Dimitrova. "Strength in Diversity: Nuclear Export of Viral RNAs." Viruses 12, no. 9 (September 11, 2020): 1014. http://dx.doi.org/10.3390/v12091014.

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The nuclear export of cellular mRNAs is a complex process that requires the orchestrated participation of many proteins that are recruited during the early steps of mRNA synthesis and processing. This strategy allows the cell to guarantee the conformity of the messengers accessing the cytoplasm and the translation machinery. Most transcripts are exported by the exportin dimer Nuclear RNA export factor 1 (NXF1)–NTF2-related export protein 1 (NXT1) and the transcription–export complex 1 (TREX1). Some mRNAs that do not possess all the common messenger characteristics use either variants of the NXF1–NXT1 pathway or CRM1, a different exportin. Viruses whose mRNAs are synthesized in the nucleus (retroviruses, the vast majority of DNA viruses, and influenza viruses) exploit both these cellular export pathways. Viral mRNAs hijack the cellular export machinery via complex secondary structures recognized by cellular export factors and/or viral adapter proteins. This way, the viral transcripts succeed in escaping the host surveillance system and are efficiently exported for translation, allowing the infectious cycle to proceed. This review gives an overview of the cellular mRNA nuclear export mechanisms and presents detailed insights into the most important strategies that viruses use to export the different forms of their RNAs from the nucleus to the cytoplasm.

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Aibara, Shintaro, Eugene Valkov, Meindert H. Lamers, Lyudmila Dimitrova, Ed Hurt, and Murray Stewart. "Structural characterization of the principal mRNA-export factor Mex67–Mtr2 fromChaetomium thermophilum." Acta Crystallographica Section F Structural Biology Communications 71, no. 7 (June 27, 2015): 876–88. http://dx.doi.org/10.1107/s2053230x15008766.

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Members of the Mex67–Mtr2/NXF–NXT1 family are the principal mediators of the nuclear export of mRNA. Mex67/NXF1 has a modular structure based on four domains (RRM, LRR, NTF2-like and UBA) that are thought to be present across species, although the level of sequence conservation between organisms, especially in lower eukaryotes, is low. Here, the crystal structures of these domains from the thermophilic fungusChaetomium thermophilumare presented together with small-angle X-ray scattering (SAXS) andin vitroRNA-binding data that indicate that, not withstanding the limited sequence conservation between different NXF family members, the molecules retain similar structural and RNA-binding properties. Moreover, the resolution of crystal structures obtained with theC. thermophilumdomains was often higher than that obtained previously and, when combined with solution and biochemical studies, provided insight into the structural organization, self-association and RNA-binding properties of Mex67–Mtr2 that facilitate mRNA nuclear export.

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Talhouarne, Gaëlle J. S., and Joseph G. Gall. "Lariat intronic RNAs in the cytoplasm of vertebrate cells." Proceedings of the National Academy of Sciences 115, no. 34 (August 6, 2018): E7970—E7977. http://dx.doi.org/10.1073/pnas.1808816115.

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Most intronic RNAs are degraded within seconds or minutes after their excision from newly formed transcripts. However, stable intronic sequence RNAs (sisRNAs) have been described from oocytes of the frog Xenopus, from Drosophila embryos, and from human cell lines. In Xenopus oocytes, sisRNAs are abundant in both the nucleus and cytoplasm, they occur in the form of lariats, and they are stable for days. In this study we demonstrate that cytoplasmic sisRNAs are also found in human, mouse, chicken, and zebrafish cells. They exist as circular (lariat) molecules, mostly 100–500 nucleotides in length, and are derived from many housekeeping genes. They tend to have an unusual cytosine branchpoint (with the exception of those from the frog). Stable lariats are exported from the nucleus to the cytoplasm by the NXF1/NXT1 system, demonstrating that their presence in the cytoplasm is not due to passive diffusion. Lariats in the cytoplasm are not associated with transcripts of the genes from which they are derived. The biological significance of cytoplasmic sisRNAs remains obscure.

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Aibara, Shintaro, Jun Katahira, Eugene Valkov, and Murray Stewart. "The principal mRNA nuclear export factor NXF1:NXT1 forms a symmetric binding platform that facilitates export of retroviral CTE-RNA." Nucleic Acids Research 43, no. 3 (January 27, 2015): 1883–93. http://dx.doi.org/10.1093/nar/gkv032.

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Zhang, Zi Chao, Neal Satterly, Beatriz M. A. Fontoura, and Yuh Min Chook. "Evolutionary development of redundant nuclear localization signals in the mRNA export factor NXF1." Molecular Biology of the Cell 22, no. 23 (December 2011): 4657–68. http://dx.doi.org/10.1091/mbc.e11-03-0222.

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In human cells, the mRNA export factor NXF1 resides in the nucleoplasm and at nuclear pore complexes. Karyopherin β2 or transportin recognizes a proline–tyrosine nuclear localization signal (PY-NLS) in the N-terminal tail of NXF1 and imports it into the nucleus. Here biochemical and cellular studies to understand the energetic organization of the NXF1 PY-NLS reveal unexpected redundancy in the nuclear import pathways used by NXF1. Human NXF1 can be imported via importin β, karyopherin β2, importin 4, importin 11, and importin α. Two NLS epitopes within the N-terminal tail, an N-terminal basic segment and a C-terminal R-X2-5-P-Y motif, provide the majority of binding energy for all five karyopherins. Mutation of both NLS epitopes abolishes binding to the karyopherins, mislocalized NXF1 to the cytoplasm, and significantly compromised its mRNA export function. The understanding of how different karyopherins recognize human NXF1, the examination of NXF1 sequences from divergent eukaryotes, and the interactions of NXF1 homologues with various karyopherins reveals the evolutionary development of redundant NLSs in NXF1 of higher eukaryotes. Redundancy of nuclear import pathways for NXF1 increases progressively from fungi to nematodes and insects to chordates, potentially paralleling the increasing complexity in mRNA export regulation and the evolution of new nuclear functions for NXF1.

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Wendt, Lisa, Janine Brandt, Bianca S. Bodmer, Sven Reiche, Marie Luisa Schmidt, Shelby Traeger, and Thomas Hoenen. "The Ebola Virus Nucleoprotein Recruits the Nuclear RNA Export Factor NXF1 into Inclusion Bodies to Facilitate Viral Protein Expression." Cells 9, no. 1 (January 11, 2020): 187. http://dx.doi.org/10.3390/cells9010187.

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Ebola virus (EBOV) causes severe outbreaks of viral hemorrhagic fever in humans. While virus-host interactions are promising targets for antivirals, there is only limited knowledge regarding the interactions of EBOV with cellular host factors. Recently, we performed a genome-wide siRNA screen that identified the nuclear RNA export factor 1 (NXF1) as an important host factor for the EBOV life cycle. NXF1 is a major component of the nuclear mRNA export pathway that is usurped by many viruses whose life cycles include nuclear stages. However, the role of NXF1 in the life cycle of EBOV, a virus replicating in cytoplasmic inclusion bodies, remains unknown. In order to better understand the role of NXF1 in the EBOV life cycle, we performed a combination of co-immunoprecipitation and double immunofluorescence assays to characterize the interactions of NXF1 with viral proteins and RNAs. Additionally, using siRNA-mediated knockdown of NXF1 together with functional assays, we analyzed the role of NXF1 in individual aspects of the virus life cycle. With this approach we identified the EBOV nucleoprotein (NP) as a viral interaction partner of NXF1. Further studies revealed that NP interacts with the RNA-binding domain of NXF1 and competes with RNA for this interaction. Co-localization studies showed that RNA binding-deficient, but not wildtype NXF1, accumulates in NP-derived inclusion bodies, and knockdown experiments demonstrated that NXF1 is necessary for viral protein expression, but not for viral RNA synthesis. Finally, our results showed that NXF1 interacts with viral mRNAs, but not with viral genomic RNAs. Based on these results we suggest a model whereby NXF1 is recruited into inclusion bodies to promote the export of viral mRNA:NXF1 complexes from these sites. This would represent a novel function for NXF1 in the life cycle of cytoplasmically replicating viruses, and may provide a basis for new therapeutic approaches against EBOV, and possibly other emerging viruses.

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Chappaz, Stéphane, Charity W. Law, Mark R. Dowling, Kirstyn T. Carey, Rachael M. Lane, Linh H. Ngo, Vihandha O. Wickramasinghe, Gordon K. Smyth, Matthew E. Ritchie, and Benjamin T. Kile. "Germline heterozygous mutations in Nxf1 perturb RNA metabolism and trigger thrombocytopenia and lymphopenia in mice." Blood Advances 4, no. 7 (April 1, 2020): 1270–83. http://dx.doi.org/10.1182/bloodadvances.2019001323.

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Abstract In eukaryotic cells, messenger RNA (mRNA) molecules are exported from the nucleus to the cytoplasm, where they are translated. The highly conserved protein nuclear RNA export factor1 (Nxf1) is an important mediator of this process. Although studies in yeast and in human cell lines have shed light on the biochemical mechanisms of Nxf1 function, its contribution to mammalian physiology is less clear. Several groups have identified recurrent NXF1 mutations in chronic lymphocytic leukemia (CLL), placing it alongside several RNA-metabolism factors (including SF3B1, XPO, RPS15) whose dysregulation is thought to contribute to CLL pathogenesis. We report here an allelic series of germline point mutations in murine Nxf1. Mice heterozygous for these loss-of-function Nxf1 mutations exhibit thrombocytopenia and lymphopenia, together with milder hematological defects. This is primarily caused by cell-intrinsic defects in the survival of platelets and peripheral lymphocytes, which are sensitized to intrinsic apoptosis. In contrast, Nxf1 mutations have almost no effect on red blood cell homeostasis. Comparative transcriptome analysis of platelets, lymphocytes, and erythrocytes from Nxf1-mutant mice shows that, in response to impaired Nxf1 function, the cytoplasmic representation of transcripts encoding regulators of RNA metabolism is altered in a unique, lineage-specific way. Thus, blood cell lineages exhibit differential requirements for Nxf1-mediated global mRNA export.

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Braun, Isabelle C., Andrea Herold, Michaela Rode, and Elisa Izaurralde. "Nuclear Export of mRNA by TAP/NXF1 Requires Two Nucleoporin-Binding Sites but Not p15." Molecular and Cellular Biology 22, no. 15 (August 1, 2002): 5405–18. http://dx.doi.org/10.1128/mcb.22.15.5405-5418.2002.

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ABSTRACT Metazoan NXF1/p15 heterodimers promote export of bulk mRNA through nuclear pore complexes (NPC). NXF1 interacts with the NPC via two distinct structural domains, the UBA-like domain and the NTF2-like scaffold, which results from the heterodimerization of the NTF2-like domain of NXF1 with p15. Both domains feature a single nucleoporin-binding site, and they act synergistically to promote NPC translocation. Whether the NTF2-like scaffold (and thereby p15) contributes only to NXF1/NPC association or is also required for other functions, e.g., to impart directionality to the export process by regulating NXF1/NPC or NXF1/cargo interactions, remains unresolved. Here we show that a minimum of two nucleoporin-binding sites is required for NXF1-mediated export of cellular mRNA. These binding sites can be provided by an NTF2-like scaffold followed by a UBA-like domain (as in the wild-type protein) or by two NTF2-like scaffolds or two UBA-like domains in tandem. In the latter case, the export activity of NXF1 is independent of p15. Thus, as for the UBA-like domain, the function of the NTF2-like scaffold is confined to nucleoporin binding. More importantly, two copies of either of these domains are sufficient to promote directional transport of mRNA cargoes across the NPC.

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Forler, Daniel, Gwénaël Rabut, Francesca D. Ciccarelli, Andrea Herold, Thomas Köcher, Ricarda Niggeweg, Peer Bork, Jan Ellenberg, and Elisa Izaurralde. "RanBP2/Nup358 Provides a Major Binding Site for NXF1-p15 Dimers at the Nuclear Pore Complex and Functions in Nuclear mRNA Export." Molecular and Cellular Biology 24, no. 3 (February 1, 2004): 1155–67. http://dx.doi.org/10.1128/mcb.24.3.1155-1167.2004.

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ABSTRACT Metazoan NXF1-p15 heterodimers promote the nuclear export of bulk mRNA across nuclear pore complexes (NPCs). In vitro, NXF1-p15 forms a stable complex with the nucleoporin RanBP2/Nup358, a component of the cytoplasmic filaments of the NPC, suggesting a role for this nucleoporin in mRNA export. We show that depletion of RanBP2 from Drosophila cells inhibits proliferation and mRNA export. Concomitantly, the localization of NXF1 at the NPC is strongly reduced and a significant fraction of this normally nuclear protein is detected in the cytoplasm. Under the same conditions, the steady-state subcellular localization of other nuclear or cytoplasmic proteins and CRM1-mediated protein export are not detectably affected, indicating that the release of NXF1 into the cytoplasm and the inhibition of mRNA export are not due to a general defect in NPC function. The specific role of RanBP2 in the recruitment of NXF1 to the NPC is highlighted by the observation that depletion of CAN/Nup214 also inhibits cell proliferation and mRNA export but does not affect NXF1 localization. Our results indicate that RanBP2 provides a major binding site for NXF1 at the cytoplasmic filaments of the NPC, thereby restricting its diffusion in the cytoplasm after NPC translocation. In RanBP2-depleted cells, NXF1 diffuses freely through the cytoplasm. Consequently, the nuclear levels of the protein decrease and export of bulk mRNA is impaired.

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Schmidt, Ute, Karsten Richter, Axel Bernhard Berger, and Peter Lichter. "In vivo BiFC analysis of Y14 and NXF1 mRNA export complexes: preferential localization within and around SC35 domains." Journal of Cell Biology 172, no. 3 (January 23, 2006): 373–81. http://dx.doi.org/10.1083/jcb.200503061.

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The bimolecular fluorescence complementation (BiFC) assay, which allows the investigation of interacting molecules in vivo, was applied to study complex formation between the splicing factor Y14 and nuclear export factor 1 (NXF1), which evidence indicates are functionally associated with nuclear mRNA. Y14 linked to the COOH terminus of yellow fluorescent protein (YFP; YC-Y14), and NXF1 fused to the NH2 terminus of YFP (YN-NXF1) expressed in MCF7 cells yielded BiFC upon specific binding. Fluorescence accumulated within and around nuclear speckles, suggesting the involvement of speckles in mRNA processing and export. Accordingly, BiFC depended on transcription and full-length NXF1. Coimmunoprecipitation of YC-Y14 with YN-NXF1, NXF1, Y14, and RNA indicated that YC-Y14 and YN-NXF1 functionally associate with RNA. Fluorescence recovery after photobleaching and fluorescence loss in photobleaching revealed that roughly half of the accumulated BiFC complexes were immobile in vivo. This immobile fraction was readily depleted by adenosine triphosphate (ATP) administration in permeabilized cells. These results suggest that a fraction of RNA, which remains in the nucleus for several hours despite its association with splicing and export proteins, accumulates in speckles because of an ATP-dependent mechanism.

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Herold, Andrea, Mikita Suyama, João P. Rodrigues, Isabelle C. Braun, Ulrike Kutay, Maria Carmo-Fonseca, Peer Bork, and Elisa Izaurralde. "TAP (NXF1) Belongs to a Multigene Family of Putative RNA Export Factors with a Conserved Modular Architecture." Molecular and Cellular Biology 20, no. 23 (December 1, 2000): 8996–9008. http://dx.doi.org/10.1128/mcb.20.23.8996-9008.2000.

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ABSTRACT Vertebrate TAP (also called NXF1) and its yeast orthologue, Mex67p, have been implicated in the export of mRNAs from the nucleus. The TAP protein includes a noncanonical RNP-type RNA binding domain, four leucine-rich repeats, an NTF2-like domain that allows heterodimerization with p15 (also called NXT1), and a ubiquitin-associated domain that mediates the interaction with nucleoporins. Here we show that TAP belongs to an evolutionarily conserved family of proteins that has more than one member in higher eukaryotes. Not only the overall domain organization but also residues important for p15 and nucleoporin interaction are conserved in most family members. We characterize two of four human TAP homologues and show that one of them, NXF2, binds RNA, localizes to the nuclear envelope, and exhibits RNA export activity. NXF3, which does not bind RNA or localize to the nuclear rim, has no RNA export activity. Database searches revealed that although only one p15(nxt) gene is present in the Drosophila melanogaster and Caenorhabditis elegans genomes, there is at least one additional p15 homologue (p15-2 [also called NXT2]) encoded by the human genome. Both human p15 homologues bind TAP, NXF2, and NXF3. Together, our results indicate that the TAP-p15 mRNA export pathway has diversified in higher eukaryotes compared to yeast, perhaps reflecting a greater substrate complexity.

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Wiegand, Heather L., Glen A. Coburn, Yan Zeng, Yibin Kang, Hal P. Bogerd, and Bryan R. Cullen. "Formation of Tap/NXT1 Heterodimers Activates Tap-Dependent Nuclear mRNA Export by Enhancing Recruitment to Nuclear Pore Complexes." Molecular and Cellular Biology 22, no. 1 (January 1, 2002): 245–56. http://dx.doi.org/10.1128/mcb.22.1.245-256.2002.

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ABSTRACT The Tap protein has been shown to activate the nuclear export of mRNA species bearing retroviral constitutive transport elements and is also believed to play an essential role in the sequence nonspecific export of cellular mRNAs. However, it has remained unclear how Tap activity is regulated in vivo. Here, we report that the small NXT1/p15-1 protein functions as a critical cofactor for Tap-mediated mRNA export in both human and invertebrate cells. In the absence of NXT1 binding, the Tap protein is unable to effectively interact with components of the nuclear pore complex and both Tap nucleocytoplasmic shuttling and the nuclear export of mRNA molecules tethered to Tap are therefore severely attenuated. Formation of a Tap/NXT1 heterodimer enhances nucleoporin binding both in vitro and in vivo and induces the formation of a Tap/NXT1/nucleoporin ternary complex that is likely to be a key intermediate in the process of nuclear mRNA export. The critical importance of NXT1 for the nuclear export of poly(A)+ RNA is emphasized by the finding that specific inhibition of the expression of the Drosophila homolog of human NXT1, by using RNA interference, results in the nuclear accumulation of poly(A)+ RNA in cultured insect cells. These data suggest that NXT1 may act as a molecular switch that regulates the ability of Tap to mediate nuclear mRNA export by controlling the interaction of Tap with components of the nuclear pore.

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Black, Ben E., James M. Holaska, Lyne Lévesque, Batool Ossareh-Nazari, Carol Gwizdek, Catherine Dargemont, and Bryce M. Paschal. "Nxt1 Is Necessary for the Terminal Step of Crm1-Mediated Nuclear Export." Journal of Cell Biology 152, no. 1 (January 8, 2001): 141–56. http://dx.doi.org/10.1083/jcb.152.1.141.

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Soluble factors are required to mediate nuclear export of protein and RNA through the nuclear pore complex (NPC). These soluble factors include receptors that bind directly to the transport substrate and regulators that determine the assembly state of receptor–substrate complexes. We recently reported the identification of NXT1, an NTF2-related export factor that stimulates nuclear protein export in permeabilized cells and undergoes nucleocytoplasmic shuttling in vivo (Black, B.E., L. Lévesque, J.M. Holaska, T.C. Wood, and B.M. Paschal. 1999. Mol. Cell. Biol. 19:8616–8624). Here, we describe the molecular characterization of NXT1 in the context of the Crm1-dependent export pathway. We find that NXT1 binds directly to Crm1, and that the interaction is sensitive to the presence of Ran-GTP. Moreover, mutations in NXT1 that reduce binding to Crm1 inhibit the activity of NXT1 in nuclear export assays. We show that recombinant Crm1 and Ran are sufficient to reconstitute nuclear translocation of a Rev reporter protein from the nucleolus to an antibody accessible site on the cytoplasmic side of the NPC. Further progress on the export pathway, including the terminal step of Crm1 and Rev reporter protein release, requires NXT1. We propose that NXT1 engages with the export complex in the nucleoplasm, and that it facilitates delivery of the export complex to a site on the cytoplasmic side of NPC where the receptor and substrate are released into the cytoplasm.

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Chen, I.-Hsiung Brandon, Ling Li, Lindsey Silva, and Rozanne M. Sandri-Goldin. "ICP27 Recruits Aly/REF but Not TAP/NXF1 to Herpes Simplex Virus Type 1 Transcription Sites although TAP/NXF1 Is Required for ICP27 Export." Journal of Virology 79, no. 7 (April 1, 2005): 3949–61. http://dx.doi.org/10.1128/jvi.79.7.3949-3961.2005.

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ABSTRACT Herpes simplex virus type 1 (HSV-1) protein ICP27 interacts with the cellular export adaptor protein Aly/REF, which is part of the exon junction complex implicated in cellular mRNA export. We previously reported that Aly/REF was no longer associated with splicing factor SC35 sites during infection but instead colocalized with ICP27 in distinct structures. Here we show that these structures colocalize with ICP4 and are sites of HSV-1 transcription. ICP27 mutants with lesions in the region required for the interaction with Aly/REF failed to recruit Aly/REF to viral transcription sites; however, ICP27 export to the cytoplasm was unimpaired, indicating that the interaction of ICP27 with Aly/REF is not required for ICP27 shuttling. ICP27 has also been shown to interact with the cellular mRNA export receptor TAP/NXF1. We report that ICP27 interacts directly with TAP/NXF1 and does not require Aly/REF to bridge the interaction. The C terminus of ICP27 is required; however, the N-terminal leucine-rich region also contributes to the interaction of ICP27 with TAP/NXF1. In contrast to the results found for Aly/REF, mutants that failed to interact with TAP/NXF1 were not exported to the cytoplasm, and TAP/NXF1 was not recruited to sites of HSV-1 transcription. Therefore, the interaction of ICP27 with TAP/NXF1 occurs after ICP27 leaves viral transcription sites. We conclude that ICP27 and the viral RNAs to which it binds are exported via the TAP/NXF1 export receptor.

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Black, Ben E., Lyne Lévesque, James M. Holaska, Todd C. Wood, and Bryce M. Paschal. "Identification of an NTF2-Related Factor That Binds Ran-GTP and Regulates Nuclear Protein Export." Molecular and Cellular Biology 19, no. 12 (December 1, 1999): 8616–24. http://dx.doi.org/10.1128/mcb.19.12.8616.

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ABSTRACT Active transport of macromolecules between the nucleus and cytoplasm requires signals for import and export and their recognition by shuttling receptors. Each class of macromolecule is thought to have a distinct receptor that mediates the transport reaction. Assembly and disassembly reactions of receptor-substrate complexes are coordinated by Ran, a GTP-binding protein whose nucleotide state is regulated catalytically by effector proteins. Ran function is modulated in a noncatalytic fashion by NTF2, a protein that mediates nuclear import of Ran-GDP. Here we characterize a novel component of the Ran system that is 26% identical to NTF2, which based on its function we refer to as NTF2-related export protein 1 (NXT1). In contrast to NTF2, NXT1 preferentially binds Ran-GTP, and it colocalizes with the nuclear pore complex (NPC) in mammalian cells. These properties, together with the fact that NXT1 shuttles between the nucleus and the cytoplasm, suggest an active role in nuclear transport. Indeed, NXT1 stimulates nuclear protein export of the NES-containing protein PKI in vitro. The export function of NXT1 is blocked by the addition of leptomycin B, a compound that selectively inhibits the NES receptor Crm1. Thus, NXT1 regulates the Crm1-dependent export pathway through its direct interaction with Ran-GTP.

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Johnson, Lisa A., Ling Li, and Rozanne M. Sandri-Goldin. "The Cellular RNA Export Receptor TAP/NXF1 Is Required for ICP27-Mediated Export of Herpes Simplex Virus 1 RNA, but the TREX Complex Adaptor Protein Aly/REF Appears To Be Dispensable." Journal of Virology 83, no. 13 (April 15, 2009): 6335–46. http://dx.doi.org/10.1128/jvi.00375-09.

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ABSTRACT Herpes simplex virus 1 (HSV-1) protein ICP27 has been shown to shuttle between the nucleus and cytoplasm and to bind viral RNA during infection. ICP27 was found to interact with the cellular RNA export adaptor protein Aly/REF, which is part of the TREX complex, and to relocalize Aly/REF to viral replication sites. ICP27 is exported to the cytoplasm through the export receptor TAP/NXF1, and ICP27 must be able to interact with TAP/NXF1 for efficient export of HSV-1 early and late transcripts. We examined the dynamics of ICP27 movement and its localization with respect to Aly/REF and TAP/NXF1 in living cells during viral infection. Recombinant viruses with a yellow fluorescent protein (YFP) tag on the N or C terminus of ICP27 were constructed. While the N-terminally tagged ICP27 virus behaved like wild-type HSV-1, the C-terminally tagged virus was defective in viral replication and gene expression, and ICP27 was confined to the nucleus, suggesting that the C-terminal YFP tag interfered with ICP27's C-terminal interactions, including the interaction with TAP/NXF1. To assess the role of Aly/REF and TAP/NXF1 in viral RNA export, these factors were knocked down using small interfering RNA. Knockdown of Aly/REF had little effect on the export of ICP27 or poly(A)+ RNA during infection. In contrast, a decrease in TAP/NXF1 levels severely impaired export of ICP27 and poly(A)+ RNA. We conclude that TAP/NXF1 is essential for ICP27-mediated export of RNA during HSV-1 infection, whereas Aly/REF may be dispensable.

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Johnson, Lisa A., and Rozanne M. Sandri-Goldin. "Efficient Nuclear Export of Herpes Simplex Virus 1 Transcripts Requires both RNA Binding by ICP27 and ICP27 Interaction with TAP/NXF1." Journal of Virology 83, no. 3 (November 19, 2008): 1184–92. http://dx.doi.org/10.1128/jvi.02010-08.

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ABSTRACT Herpes simplex virus 1 (HSV-1) regulatory protein ICP27 has been reported to bind viral RNA and to interact with the nuclear export adaptor Aly/REF and the major cellular mRNA nuclear export receptor TAP/NXF1. Using in situ hybridization and in vitro export assays, we show here that poly(A)+ RNA was retained in the nucleus of cells infected with viral ICP27 mutants that either cannot bind RNA or that do not interact with TAP/NXF1. Microarray analysis of nuclear and cytoplasmic RNA fractions demonstrated that efficient export of the majority of viral transcripts requires that ICP27 be able to bind RNA and to interact with TAP/NXF1. We conclude that ICP27 is the major export adaptor for HSV-1 mRNA and that it links bound transcripts to the TAP/NXF1 export receptor.

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Gatfield, David, and Elisa Izaurralde. "REF1/Aly and the additional exon junction complex proteins are dispensable for nuclear mRNA export." Journal of Cell Biology 159, no. 4 (November 18, 2002): 579–88. http://dx.doi.org/10.1083/jcb.200207128.

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The metazoan proteins UAP56, REF1, and NXF1 are thought to bind sequentially to mRNA to promote its export to the cytoplasm: UAP56 is thought to recruit REF1 to nascent mRNA; REF1 acts as an adaptor protein mediating the association of NXF1 with mRNA, whereas NXF1 translocates the mRNA across the nuclear pore complex. REF1 is a component of the exon–exon junction complex (EJC); thus, the EJC is thought to play a role in the export of spliced mRNA. NXF1 and UAP56 are essential for mRNA export. An essential role for metazoan REF1 or the additional EJC proteins in this process has not been established. Contrary to expectation, we show that REF1 and the additional components of the EJC are dispensable for export of bulk mRNA in Drosophila cells. Only when REF1 and RNPS1 are codepleted, or when all EJC proteins are simultaneously depleted is a partial nuclear accumulation of polyadenylated RNAs observed. Because a significant fraction of bulk mRNA is detected in the cytoplasm of cells depleted of all EJC proteins, we conclude that additional adaptor protein(s) mediate the interaction between NXF1 and cellular mRNAs in metazoa. Our results imply that the essential role of UAP56 in mRNA export is not restricted to the recruitment of REF1.

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Ben-Yishay, Rakefet, Amir Mor, Amit Shraga, Asaf Ashkenazy-Titelman, Noa Kinor, Avital Schwed-Gross, Avi Jacob, et al. "Imaging within single NPCs reveals NXF1’s role in mRNA export on the cytoplasmic side of the pore." Journal of Cell Biology 218, no. 9 (August 2, 2019): 2962–81. http://dx.doi.org/10.1083/jcb.201901127.

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Translocation of mRNA through the nuclear pore complex (NPC) requires interactions with different NPC regions. To determine the interactions that are crucial for effective mRNA export in living cells, we examined mRNA export within individual pores by applying various types of mRNA export blocks that stalled mRNPs at different stages of transition. Focusing on the major mRNA export factor NXF1, we found that initial mRNP binding to the NPC did not require NXF1 in the NPC, whereas release into the cytoplasm did. NXF1 localization in the NPC did not require RNA or RNA binding. Superresolution microscopy showed that NXF1 consistently occupied positions on the cytoplasmic side of the NPC. Interactions with specific nucleoporins were pinpointed using FLIM-FRET for measuring protein–protein interactions inside single NPCs, showing that Dbp5 helicase activity of mRNA release is conserved in yeast and humans. Altogether, we find that specific interactions on the cytoplasmic side of the NPC are fundamental for the directional flow of mRNA export.

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Sheng, Iris Yeong Fung, Yu-Wei Chen, Moshe Chaim Ornstein, Timothy D. Gilligan, Brian I. Rini, and Jorge A. Garcia. "Implications of the United States Preventive Services Task Force (USPSTF) recommendations on prostate cancer (PCa) stage migration." Journal of Clinical Oncology 37, no. 15_suppl (May 20, 2019): 5071. http://dx.doi.org/10.1200/jco.2019.37.15_suppl.5071.

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5071 Background: Prostate specific antigen (PSA) screening has been controversial, given unrefined screening guidelines leading to overdiagnosis and overtreatment of “indolent” PCa. In 2008, the USPSTF recommended against PSA screening for men aged ≥75 and in 2012 broadened this recommendation to include all men. The impact of these changes is unstudied. We hypothesize that these screening changes could delay the diagnosis of advanced PCa. Methods: The Surveillance, Epidemiology and End Results Program (SEER) was used to identify men (age 55-69) diagnosed with PCa between 2004-2015. PCa stage was categorized as nodal (N1M0) and metastatic (NxM1). Trend analysis was stratified based on year 2004-2008 (group 1), 2009-2012 (group 2), and 2012-2015 (group 3). Using group 2 as a reference, multivariable logistic regression was used to identify predictors for N1M0 and NxM1 in each group. Results: From 2004-2015, there were 603,323 eligible men diagnosed with PCa (group 1: 262,240 men, group 2: 210,045 men, group 3: 131,038 men). In group 1, 1.4% had N1M0 and 2.8% had NxM1. In group 2, 1.6% had N1M0 and 3.7% had NxM1. In group 3, 1.4% had N1M0, and 6.1% had NxM1. The adjusted odds ratio (AOR) of N1M0 was 0.78 (95%CI 0.74-0.82; p<0.0001) in group 1 and 1.71 (95%CI 1.63-1.80; p<0.0001) in group 3. Similar AOR trends were seen in NxM1 (group 1, 0.71; 95%CI 0.68-0.73, p< 0.0001 vs. group 3, 1.70; 95% CI 1.63-1.75, p<0.0001). (Table) Subset analysis of non-eligible patients (age >70 and <55) showed a similar stage migration. Conclusions: With each USPSTF recommendation, there have been significantly more diagnoses of advanced PCa; suggesting stage migration. The sequelae of having advanced PCa include more aggressive treatments, increased financial burden, and reduced quality of life. Future population studies are warranted to investigate whether the updated 2018 USPSTF recommendation now encapsulates the best target population.[Table: see text]

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Ossareh-Nazari, Batool, Christèle Maison, Ben E. Black, Lyne Lévesque, Bryce M. Paschal, and Catherine Dargemont. "RanGTP-Binding Protein NXT1 Facilitates Nuclear Export of Different Classes of RNA In Vitro." Molecular and Cellular Biology 20, no. 13 (July 1, 2000): 4562–71. http://dx.doi.org/10.1128/mcb.20.13.4562-4571.2000.

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ABSTRACT To better characterize the mechanisms responsible for RNA export from the nucleus, we developed an in vitro assay based on the use of permeabilized HeLa cells. This new assay supports nuclear export of U1 snRNA, tRNA, and mRNA in an energy- and Xenopusextract-dependent manner. U1 snRNA export requires a 5′ monomethylated cap structure, the nuclear export signal receptor CRM1, and the small GTPase Ran. In contrast, mRNA export does not require the participation of CRM1. We show here that NXT1, an NTF2-related protein that binds directly to RanGTP, strongly stimulates export of U1 snRNA, tRNA, and mRNA. The ability of NXT1 to promote export is dependent on its capacity to bind RanGTP. These results support the emerging view that NXT1 is a general export factor, functioning on both CRM1-dependent and CRM1-independent pathways of RNA export.

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van der Graaf, Kevin, Katia Jindrich, Robert Mitchell, and Helen White-Cooper. "Roles for RNA export factor, Nxt1, in ensuring muscle integrity and normal RNA expression in Drosophila." G3 Genes|Genomes|Genetics 11, no. 1 (December 24, 2020): 1–15. http://dx.doi.org/10.1093/g3journal/jkaa046.

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Abstract The mRNA export pathway is responsible for the transport of mRNAs from the nucleus to the cytoplasm, and thus is essential for protein production and normal cellular functions. A partial loss of function allele of the mRNA export factor Nxt1 in Drosophila shows reduced viability and sterility. A previous study has shown that the male fertility defect is due to a defect in transcription and RNA stability, indicating the potential for this pathway to be implicated in processes beyond the known mRNA transport function. Here we investigate the reduced viability of Nxt1 partial loss of function mutants, and describe a defect in growth and maintenance of the larval muscles, leading to muscle degeneration. RNA-seq revealed reduced expression of a set of mRNAs, particularly from genes with long introns in Nxt1 mutant carcass. We detected differential expression of circRNA, and significantly fewer distinct circRNAs expressed in the mutants. Despite the widespread defects in gene expression, muscle degeneration was rescued by increased expression of the costamere component tn (abba) in muscles. This is the first report of a role for the RNA export pathway gene Nxt1 in the maintenance of muscle integrity. Our data also links the mRNA export pathway to a specific role in the expression of mRNA and circRNA from common precursor genes, in vivo.

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Matzat, Leah H., Stephen Berberoglu, and Lyne Lévesque. "Formation of a Tap/NXF1 Homotypic Complex Is Mediated through the Amino-Terminal Domain of Tap and Enhances Interaction with Nucleoporins." Molecular Biology of the Cell 19, no. 1 (January 2008): 327–38. http://dx.doi.org/10.1091/mbc.e07-03-0255.

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Nuclear export of mRNAs is mediated by the Tap/Nxt1 pathway. Tap moves its RNA cargo through the nuclear pore complex by direct interaction with nucleoporin phenylalanine-glycine repeats. This interaction is strengthened by the formation of a Tap/Nxt1 heterodimer. We now present evidence that Tap can form a multimeric complex with itself and with other members of the NXF family. We also show that the homotypic Tap complex can interact with both Nxt1 and nucleoporins in vitro. The region mediating this oligomerization is localized to the first 187 amino acids of Tap, which overlaps with its RNA-binding domain. Removal of this domain greatly reduces the ability of Tap to bind nucleoporins in vitro and in vivo. This is the first report showing that the Tap amino terminus modulates the interaction of Tap with nucleoporins. We speculate that this mechanism has a regulatory role for RNA export independent of RNA binding.

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Björk, Petra, Jan-Olov Persson, and Lars Wieslander. "Intranuclear binding in space and time of exon junction complex and NXF1 to premRNPs/mRNPs in vivo." Journal of Cell Biology 211, no. 1 (October 12, 2015): 63–75. http://dx.doi.org/10.1083/jcb.201412017.

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Eukaryotic gene expression requires the ordered association of numerous factors with precursor messenger RNAs (premRNAs)/messenger RNAs (mRNAs) to achieve efficiency and regulation. Here, we use the Balbiani ring (BR) genes to demonstrate the temporal and spatial association of the exon junction complex (EJC) core with gene-specific endogenous premRNAs and mRNAs. The EJC core components bind cotranscriptionally to BR premRNAs during or very rapidly after splicing. The EJC core does not recruit the nonsense-mediated decay mediaters UPF2 and UPF3 until the BR messenger RNA protein complexes (mRNPs) enter the interchromatin. Even though several known adapters for the export factor NXF1 become part of BR mRNPs already at the gene, NXF1 binds to BR mRNPs only in the interchromatin. In steady state, a subset of the BR mRNPs in the interchromatin binds NXF1, UPF2, and UPF3. This binding appears to occur stochastically, and the efficiency approximately equals synthesis and export of the BR mRNPs. Our data provide unique in vivo information on how export competent eukaryotic mRNPs are formed.

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Wang, Dongming, Ni Gao, Tingting Zhou, Qiangye Zhang, Jian Wang, and Aiwu Li. "Effect of Neuroligin1 and Neurexin1 on the Colonic Motility in a Mouse Model of Neuronal Intestinal Dysplasia." Gastroenterology Research and Practice 2020 (January 4, 2020): 1–9. http://dx.doi.org/10.1155/2020/9818652.

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Aim. To investigate the expressions of neuroligin1 (NL1) and neurexin1 (NX1) in a mouse model of neuronal intestinal dysplasia (Tlx2-/- mice) and to explore their effects on colonic motility. Methods. Immunohistochemistry staining was employed to explore the histological appearances of NL1, NX1, the presynaptic marker of glutamatergic synapses VGLUT1, and the subunit of NMDA receptors of NR1 in the colon of mice with or without Tlx2 mutation. Western blotting and qRT-PCR were performed to detect their relative expressions in the colon. Colonic motility was measured by a glass bead technique. Then, the Tlx2-/- mice were intervened by Huperzine A. Variations on expressions of NL1, NX1, VGLUT1, and NR1 and variations on colonic motility were measured. Additionally, serum concentrations of Glu were measured by ELISA. Results. Immunohistochemistry staining reveals that NL1, NX1, VGLUT1, and NR1 were mainly concentrated in the myenteric plexus of ENS. Compared to those in WT and Tlx2+/- mice, expressions of NL1 and NX1 in colon of Tlx2-/- mice were upregulated with increased VGLUT1 and NR1 abundances and impaired colonic motility (P<0.05). After intervention, the upregulated expressions of NL1 and NX1 were decreased with a correlated reduce of VGLUT1 and NR1 and a recovery of the impaired colonic motility (P<0.05). Variations of serum concentrations of Glu measured by ELISA were in concordance with the variations of glutamatergic synapses and colonic motility (P<0.05). Conclusion. NL1 and NX1 are closely related to the colonic motility through their effects of targeting the formation of glutamatergic synapses and may be involved in the pathogenesis of NID. The variations of serum Glu seem to be a potential and less painful auxiliary measure for colonic motility and NID.

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Mamon, Ludmila, Anna Yakimova, Daria Kopytova, and Elena Golubkova. "The RNA-Binding Protein SBR (Dm NXF1) Is Required for the Constitution of Medulla Boundaries in Drosophila melanogaster Optic Lobes." Cells 10, no. 5 (May 10, 2021): 1144. http://dx.doi.org/10.3390/cells10051144.

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Drosophila melanogaster sbr (small bristles) is an orthologue of the Nxf1 (nuclear export factor 1) genes in different Opisthokonta. The known function of Nxf1 genes is the export of various mRNAs from the nucleus to the cytoplasm. The cytoplasmic localization of the SBR protein indicates that the nuclear export function is not the only function of this gene in Drosophila. RNA-binding protein SBR enriches the nucleus and cytoplasm of specific neurons and glial cells. In sbr12 mutant males, the disturbance of medulla boundaries correlates with the defects of photoreceptor axons pathfinding, axon bundle individualization, and developmental neurodegeneration. RNA-binding protein SBR participates in processes allowing axons to reach and identify their targets.

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Lévesque, Lyne, Yeou-Cherng Bor, Leah H. Matzat, Li Jin, Stephen Berberoglu, David Rekosh, Marie-Louise Hammarskjöld, and Bryce M. Paschal. "Mutations in Tap Uncouple RNA Export Activity from Translocation through the Nuclear Pore Complex." Molecular Biology of the Cell 17, no. 2 (February 2006): 931–43. http://dx.doi.org/10.1091/mbc.e04-07-0634.

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Interactions between transport receptors and phenylalanine-glycine (FG) repeats on nucleoporins drive the translocation of receptor-cargo complexes through nuclear pores. Tap, a transport receptor that mediates nuclear export of cellular mRNAs, contains a UBA-like and NTF2-like folds that can associate directly with FG repeats. In addition, two nuclear export sequences (NESs) within the NTF2-like region can also interact with nucleoporins. The Tap-RNA complex was shown to bind to three nucleoporins, Nup98, p62, and RanBP2, and these interactions were enhanced by Nxt1. Mutations in the Tap-UBA region abolished interactions with all three nucleoporins, whereas the effect of point mutations within the NTF2-like domain of Tap known to disrupt Nxt1 binding or nucleoporin binding were nucleoporin dependent. A mutation in any of these Tap domains was sufficient to reduce RNA export but was not sufficient to disrupt Tap interaction with the NPC in vivo or its nucleocytoplasmic shuttling. However, shuttling activity was reduced or abolished by combined mutations within the UBA and either the Nxt1-binding domain or NESs. These data suggest that Tap requires both the UBA- and NTF2-like domains to mediate the export of RNA cargo, but can move through the pores independently of these domains when free of RNA cargo.

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Corbin-Lickfett, Kara A., Santos Rojas, Ling Li, Melanie J. Cocco, and Rozanne M. Sandri-Goldin. "ICP27 Phosphorylation Site Mutants Display Altered Functional Interactions with Cellular Export Factors Aly/REF and TAP/NXF1 but Are Able To Bind Herpes Simplex Virus 1 RNA." Journal of Virology 84, no. 5 (December 16, 2009): 2212–22. http://dx.doi.org/10.1128/jvi.01388-09.

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ABSTRACT Herpes simplex virus 1 (HSV-1) protein ICP27 is a multifunctional regulatory protein that is phosphorylated. Phosphorylation can affect protein localization, protein interactions, and protein function. The major sites of ICP27 that are phosphorylated are serine residues 16 and 18, within a CK2 site adjacent to a leucine-rich region required for ICP27 export, and serine 114, within a PKA site in the nuclear localization signal. Viral mutants bearing serine-to-alanine or glutamic acid substitutions at these sites are defective in viral replication and gene expression. To determine which interactions of ICP27 are impaired, we analyzed the subcellular localization of ICP27 and its colocalization with cellular RNA export factors Aly/REF and TAP/NXF1. In cells infected with phosphorylation site mutants, ICP27 was confined to the nucleus even at very late times after infection. ICP27 did not colocalize with Aly/REF or TAP/NXF1, and overexpression of TAP/NXF1 did not promote the export of ICP27 to the cytoplasm. However, in vitro binding experiments showed that mutant ICP27 was able to bind to the same RNA substrates as the wild type. Nuclear magnetic resonance (NMR) analysis of the N terminus of ICP27 from amino acids 1 to 160, compared to mutants with triple substitutions to alanine or glutamic acid, showed that the mutations affected the overall conformation of the N terminus, such that mutant ICP27 was more flexible and unfolded. These results indicate that these changes in the structure of ICP27 altered in vivo protein interactions that occur in the N terminus but did not prevent RNA binding.

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Wang, Ke, Lantian Wang, Jianshu Wang, Suli Chen, Min Shi, and Hong Cheng. "Intronless mRNAs transit through nuclear speckles to gain export competence." Journal of Cell Biology 217, no. 11 (September 7, 2018): 3912–29. http://dx.doi.org/10.1083/jcb.201801184.

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Nuclear speckles (NSs) serve as splicing factor storage sites. In this study, we unexpectedly found that many endogenous intronless mRNAs, which do not undergo splicing, associate with NSs. These associations do not require transcription, polyadenylation, or the polyA tail. Rather, exonic splicing enhancers present in intronless mRNAs and their binding partners, SR proteins, promote intronless mRNA localization to NSs. Significantly, speckle targeting of mRNAs promotes the recruitment of the TREX export complex and their TREX-dependent nuclear export. Furthermore, TREX, which accumulates in NSs, is required for releasing intronless mRNAs from NSs, whereas NXF1, which is mainly detected at nuclear pores, is not. Upon NXF1 depletion, the TREX protein UAP56 loses speckle concentration but coaccumulates with intronless mRNAs and polyA RNAs in the nucleoplasm, and these RNAs are trapped in NSs upon UAP56 codepletion. We propose that the export-competent messenger RNP assembly mainly occurs in NSs for intronless mRNAs and that entering NSs serves as a quality control step in mRNA export.

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Juillard, Franceline, Edwige Hiriart, Nicolas Sergeant, Valérie Vingtdeux-Didier, Hervé Drobecq, Alain Sergeant, Evelyne Manet, and Henri Gruffat. "Epstein-Barr Virus Protein EB2 Contains an N-Terminal Transferable Nuclear Export Signal That Promotes Nucleocytoplasmic Export by Directly Binding TAP/NXF1." Journal of Virology 83, no. 24 (September 30, 2009): 12759–68. http://dx.doi.org/10.1128/jvi.01276-09.

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ABSTRACT The Epstein-Barr virus early protein EB2 (also called BMLF1, Mta, or SM), which allows the nuclear export of a subset of early and late viral mRNAs derived from intronless genes, is essential for the production of infectious virions. An important feature of mRNA export factors is their capacity to shuttle continuously between the nucleus and the cytoplasm. In a previous study, we identified a novel CRM1-independent transferable nuclear export signal (NES) at the N terminus of EB2, between amino acids 61 and 146. Here we show that this NES contains several small arginine-rich domains that cooperate to allow efficient interaction with TAP/NXF1. Recruitment of TAP/NXF1 correlates with this NES-mediated efficient nuclear export when it is fused to a heterologous protein. Moreover, the NES can export mRNAs bearing MS2 RNA-binding sites from the nucleus when tethered to the RNA via the MS2 phage coat protein RNA-binding domain.

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Desjardins, John P., Elizabeth A. Abbott, David L. Emerson, Blake E. Tomkinson, Jeremy D. Leray, Eric N. Brown, Marta Hamilton, et al. "Biodistribution of NX211, liposomal lurtotecan, in tumor-bearing mice." Anti-Cancer Drugs 12, no. 3 (March 2001): 235–45. http://dx.doi.org/10.1097/00001813-200103000-00009.

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Floyd, Jennifer A., David A. Gold, Dorothy Concepcion, Tiffany H. Poon, Xiaobo Wang, Elizabeth Keithley, Dan Chen, et al. "A natural allele of Nxf1 suppresses retrovirus insertional mutations." Nature Genetics 35, no. 3 (September 28, 2003): 221–28. http://dx.doi.org/10.1038/ng1247.

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Guzik, Brian W., Lyne Levesque, Susan Prasad, Yeou-Cherng Bor, Ben E. Black, Bryce M. Paschal, David Rekosh, and Marie-Louise Hammarskjöld. "NXT1 (p15) Is a Crucial Cellular Cofactor in TAP-Dependent Export of Intron-Containing RNA in Mammalian Cells." Molecular and Cellular Biology 21, no. 7 (April 1, 2001): 2545–54. http://dx.doi.org/10.1128/mcb.21.7.2545-2554.2001.

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ABSTRACT TAP, the human homologue of the yeast protein Mex67p, has been proposed to serve a role in mRNA export in mammalian cells. We have examined the ability of TAP to mediate export of Rev response element (RRE)-containing human immunodeficiency virus (HIV) RNA, a well-characterized export substrate in mammalian cells. To do this, the TAP gene was fused in frame to either RevM10 or RevΔ78–79. These proteins are nonfunctional Rev mutant proteins that can bind to HIV RNA containing the RRE in vivo but are unable to mediate the export of this RNA to the cytoplasm. However, the fusion of TAP to either of these mutant proteins gave rise to chimeric proteins that were able to complement Rev function. Significantly, cotransfection with a vector expressing NXT1 (p15), an NTF2-related cellular factor that binds to TAP, led to dramatic enhancement of the ability of the chimeric proteins to mediate RNA export. Mutant-protein analysis demonstrated that the domain necessary for nuclear export mapped to the C-terminal region of TAP and required the domain that interacts with NXT1, as well as the region that has been shown to interact with nucleoporins. RevM10-TAP function was leptomycin B insensitive. In contrast, the function of this protein was inhibited by ΔCAN, a protein consisting of part of the FG repeat domain of CAN/Nup214. These results show that TAP can complement Rev nuclear export signal function and redirect the export of intron-containing RNA to a CRM1-independent pathway. These experiments support the role of TAP as an RNA export factor in mammalian cells. In addition, they indicate that NXT1 serves as a crucial cellular cofactor in this process.

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Ruepp, Marc-David, Chiara Aringhieri, Silvia Vivarelli, Stefano Cardinale, Simona Paro, Daniel Schümperli, and Silvia M. L. Barabino. "Mammalian pre-mRNA 3′ End Processing Factor CF Im68 Functions in mRNA Export." Molecular Biology of the Cell 20, no. 24 (December 15, 2009): 5211–23. http://dx.doi.org/10.1091/mbc.e09-05-0389.

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Export of mRNA from the nucleus is linked to proper processing and packaging into ribonucleoprotein complexes. Although several observations indicate a coupling between mRNA 3′ end formation and export, it is not known how these two processes are mechanistically connected. Here, we show that a subunit of the mammalian pre-mRNA 3′ end processing complex, CF Im68, stimulates mRNA export. CF Im68 shuttles between the nucleus and the cytoplasm in a transcription-dependent manner and interacts with the mRNA export receptor NXF1/TAP. Consistent with the idea that CF Im68 may act as a novel adaptor for NXF1/TAP, we show that CF Im68 promotes the export of a reporter mRNA as well as of endogenous mRNAs, whereas silencing by RNAi results in the accumulation of mRNAs in the nucleus. Moreover, CF Im68 associates with 80S ribosomes but not polysomes, suggesting that it is part of the mRNP that is remodeled in the cytoplasm during the initial stages of translation. These results reveal a novel function for the pre-mRNA 3′ end processing factor CF Im68 in mRNA export.

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Lee, Eliza S., Eric J. Wolf, Sean S. J. Ihn, Harrison W. Smith, Andrew Emili, and Alexander F. Palazzo. "TPR is required for the efficient nuclear export of mRNAs and lncRNAs from short and intron-poor genes." Nucleic Acids Research 48, no. 20 (October 22, 2020): 11645–63. http://dx.doi.org/10.1093/nar/gkaa919.

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Abstract While splicing has been shown to enhance nuclear export, it has remained unclear whether mRNAs generated from intronless genes use specific machinery to promote their export. Here, we investigate the role of the major nuclear pore basket protein, TPR, in regulating mRNA and lncRNA nuclear export in human cells. By sequencing mRNA from the nucleus and cytosol of control and TPR-depleted cells, we provide evidence that TPR is required for the efficient nuclear export of mRNAs and lncRNAs that are generated from short transcripts that tend to have few introns, and we validate this with reporter constructs. Moreover, in TPR-depleted cells reporter mRNAs generated from short transcripts accumulate in nuclear speckles and are bound to Nxf1. These observations suggest that TPR acts downstream of Nxf1 recruitment and may allow mRNAs to leave nuclear speckles and properly dock with the nuclear pore. In summary, our study provides one of the first examples of a factor that is specifically required for the nuclear export of intronless and intron-poor mRNAs and lncRNAs.

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Zhang, T. J. Shields, G. W. H. Silc, J. "Behavior of Plywood Lining in Full Scale Room Fire Tests." Journal of Applied Fire Science 8, no. 1 (October 1, 1998): 1. http://dx.doi.org/10.2190/99lr-hc49-nxu1-chck.

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Miller, Jeffrey S. "Unintended Effects of Preannouncements on Investor Reactions to Earnings News*." Contemporary Accounting Research 23, no. 4 (December 2006): 1073–103. http://dx.doi.org/10.1506/nx14-108l-581w-1q00.

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Zolotukhin, Andrei S., Wei Tan, Jenifer Bear, Sergey Smulevitch, and Barbara K. Felber. "U2AF Participates in the Binding of TAP (NXF1) to mRNA." Journal of Biological Chemistry 277, no. 6 (November 27, 2001): 3935–42. http://dx.doi.org/10.1074/jbc.m107598200.

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Burek, Jan, and Michał Chlost. "Influence of modification of an asymmetric outline on teeth deformation in the spur gears." Mechanik 92, no. 7 (July 8, 2019): 477–79. http://dx.doi.org/10.17814/mechanik.2019.7.62.

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The aim of the article was to determine the value of deformation of straight teeth with an asymmetrical outline with variation of the pressure angle and minimization of tooth undercutting. The geometry of the gear was developed as a parametric model in the NX 10 system. Simulation tests of tooth deflection were performed using the Pre/Pos module available in the NX10 program.

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Quaresma, Alexandre Jose Christino, Rachel Sievert, and Jeffrey A. Nickerson. "Regulation of mRNA export by the PI3 kinase/AKT signal transduction pathway." Molecular Biology of the Cell 24, no. 8 (April 15, 2013): 1208–21. http://dx.doi.org/10.1091/mbc.e12-06-0450.

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UAP56, ALY/REF, and NXF1 are mRNA export factors that sequentially bind at the 5′ end of a nuclear mRNA but are also reported to associate with the exon junction complex (EJC). To screen for signal transduction pathways regulating mRNA export complex assembly, we used fluorescence recovery after photobleaching to measure the binding of mRNA export and EJC core proteins in nuclear complexes. The fraction of UAP56, ALY/REF, and NXF1 tightly bound in complexes was reduced by drug inhibition of the phosphatidylinositide 3-kinase (PI3 kinase)/AKT pathway, as was the tightly bound fraction of the core EJC proteins eIF4A3, MAGOH, and Y14. Inhibition of the mTOR mTORC1 pathway decreased the tight binding of MAGOH. Inhibition of the PI3 kinase/AKT pathway increased the export of poly(A) RNA and of a subset of candidate mRNAs. A similar effect of PI3 kinase/AKT inhibition was observed for mRNAs from both intron-containing and intronless histone genes. However, the nuclear export of mRNAs coding for proteins targeted to the endoplasmic reticulum or to mitochondria was not affected by the PI3 kinase/AKT pathway. These results show that the active PI3 kinase/AKT pathway can regulate mRNA export and promote the nuclear retention of some mRNAs.

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Zolotukhin, Andrei S., Daniel Michalowski, Sergey Smulevitch, and Barbara K. Felber. "Retroviral Constitutive Transport Element Evolved from Cellular TAP(NXF1)-Binding Sequences." Journal of Virology 75, no. 12 (June 15, 2001): 5567–75. http://dx.doi.org/10.1128/jvi.75.12.5567-5575.2001.

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ABSTRACT The constitutive transport element (CTE) of type D retroviruses serves as a signal of nuclear export of unspliced viral RNAs. The human TAP(NXF1) protein, a cellular mRNA export factor, directly binds to CTE and mediates nuclear export of CTE-containing RNAs. Here, we use genomic SELEX (systematic evolution of ligands by exponential enrichment) to show that the human genome encodes a family of high-affinity TAP ligands. These TAP-binding elements (TBE) are 15-bp minisatellite repeats that are homologous to the core TAP-binding sites in CTE. The repeats are positioned similarly in the RNA secondary structures of CTE and TBE. Like CTE, TBE is an active nuclear export signal. CTE elements of different species share sequence similarities to TBE in the regions that are neutral for CTE function. This conservation points to a possible common ancestry of the two elements, and in fact, TBE has properties expected from a primordial CTE. Additionally, a molecular fossil of a TBE-like minisatellite is found in the genome of a modern retroelement. These findings constitute direct evidence of an evolutionary link between TBE-related minisatellites and CTE.

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Ivankova, Natalia, Irina Tretyakova, George T. Lyozin, Elina Avanesyan, Andrei Zolotukhin, Olga G. Zatsepina, Michael B. Evgen'ev, and Ludmila A. Mamon. "Alternative transcripts expressed by small bristles, the Drosophila melanogaster nxf1 gene." Gene 458, no. 1-2 (June 2010): 11–19. http://dx.doi.org/10.1016/j.gene.2010.02.013.

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Kim, Miri, Michel Bellini, and Stephanie Ceman. "Fragile X Mental Retardation Protein FMRP Binds mRNAs in the Nucleus." Molecular and Cellular Biology 29, no. 1 (October 20, 2008): 214–28. http://dx.doi.org/10.1128/mcb.01377-08.

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ABSTRACT The fragile X mental retardation protein FMRP is an RNA binding protein that associates with a large collection of mRNAs. Since FMRP was previously shown to be a nucleocytoplasmic shuttling protein, we examined the hypothesis that FMRP binds its cargo mRNAs in the nucleus. The enhanced green fluorescent protein-tagged FMRP construct (EGFP-FMRP) expressed in Cos-7 cells was efficiently exported from the nucleus in the absence of its nuclear export sequence and in the presence of a strong nuclear localization sequence (the simian virus 40 [SV40] NLS), suggesting an efficient mechanism for nuclear export. We hypothesized that nuclear FMRP exits the nucleus through its bound mRNAs. Using silencing RNAs to the bulk mRNA exporter Tap/NXF1, we observed a significantly increased number of cells containing EGFP-FMRP in the nucleus, which was further augmented by removal of FMRP's nuclear export sequence. Nuclear-retained SV40-FMRP could be released upon treatment with RNase. Further, Tap/NXF1 coimmunoprecipitated with EGFP-FMRP in an RNA-dependent manner and contained the FMR1 mRNA. To determine whether FMRP binds pre-mRNAs cotranscriptionally, we expressed hemagglutinin-SV40 FMRP in amphibian oocytes and found it, as well as endogenous Xenopus FMRP, on the active transcription units of lampbrush chromosomes. Collectively, our data provide the first lines of evidence that FMRP binds mRNA in the nucleus.

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Nappi, Filomena, Ralf Schneider, Andrei Zolotukhin, Sergey Smulevitch, Daniel Michalowski, Jenifer Bear, Barbara K. Felber, and George N. Pavlakis. "Identification of a Novel Posttranscriptional Regulatory Element by Using a rev- and RRE-Mutated Human Immunodeficiency Virus Type 1 DNA Proviral Clone as a Molecular Trap." Journal of Virology 75, no. 10 (May 15, 2001): 4558–69. http://dx.doi.org/10.1128/jvi.75.10.4558-4569.2001.

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ABSTRACT Human immunodeficiency virus (HIV) and all other lentiviruses utilize the essential viral protein Rev, which binds to RRE RNA, to export their unspliced and partially spliced mRNAs from the nucleus. We used a rev- and RRE-defective HIV type 1 (HIV-1) molecular clone in complementation experiments to establish a method for the rapid isolation of posttranscriptional regulatory elements from the mammalian genome by selecting for rescue of virus replication. Viruses rescued by this method contained a novel element with homology to rodent intracisternal A-particle (IAP) retroelements. A functional element was contained within a 247-nucleotide fragment named RNA transport element (RTE), which was able to promote replication of the Rev- and RRE-defective HIV-1 in both human lymphoid cell lines and primary lymphocytes, demonstrating its potent posttranscriptional function. RTE was functional in many cell types, indicating that the cellular factors that recognize RTE are widely expressed and evolutionarily conserved. RTE also promoted RNA export fromXenopus oocyte nuclei. RTE-mediated RNA transport was CRM1 independent, and RTE did not show high affinity for binding to mRNA export factor TAP/NXF1. Since CRM1 and TAP/NXF1 are critical export receptors associated with the two recognized mRNA export pathways, these results suggest that RTE functions via a distinct export mechanism. Taken together, our results identify a novel posttranscriptional control element that uses a conserved cellular export mechanism.

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Walsh, Matthew J., Guillaume M. Hautbergue, and Stuart A. Wilson. "Structure and function of mRNA export adaptors." Biochemical Society Transactions 38, no. 1 (January 19, 2010): 232–36. http://dx.doi.org/10.1042/bst0380232.

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The mRNA export adaptors provide an important link between multiple nuclear mRNA processing events and the mRNA export receptor TAP/NXF1/Mex67p. They are recruited to mRNA through transcriptional and post-transcriptional events, integrating this information to licence mRNA for export. Subsequently they hand mRNA over to TAP and switch TAP to a higher-affinity RNA-binding state, ensuring its stable association with mRNA destined for export. Here we discuss the structure and function of adaptors and how they are recruited to mRNA.

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Конягин, Сергей Владимирович, and Sergei Vladimirovich Konyagin. "Об иррегулярности конечных последовательностей." Trudy Matematicheskogo Instituta imeni V.A. Steklova 314 (September 2021): 97–102. http://dx.doi.org/10.4213/tm4187.

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Последовательность $(x_1,x_2,…,x_{N+d})$ чисел из $[0,1)$ называется $N$-регулярной с не более чем $d$ иррегулярностями, если для любого натурального числа $n\le N$ каждый из полуинтервалов $[0,1)$, $[1,2),…,[n-1,n)$ содержит хотя бы один элемент последовательности $(nx_1,nx_2,…,nx_{n+d})$. Наибольшее $N$, для которого существует $N$-регулярная последовательность с не более чем $d$ иррегулярностями, обозначается через $s(d)$. Показано, что $s(d)\ge 2d$ для любого натурального $d$ и $s(d)<200d$ для достаточно большого $d$.

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Grant, Richard P., Ed Hurt, David Neuhaus, and Murray Stewart. "Structure of the C-terminal FG-nucleoporin binding domain of Tap/NXF1." Nature Structural Biology 9, no. 4 (March 4, 2002): 247–51. http://dx.doi.org/10.1038/nsb773.

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Caporilli, Simona, Yachuan Yu, Jianqiao Jiang, and Helen White-Cooper. "The RNA Export Factor, Nxt1, Is Required for Tissue Specific Transcriptional Regulation." PLoS Genetics 9, no. 6 (June 6, 2013): e1003526. http://dx.doi.org/10.1371/journal.pgen.1003526.

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Lynam, Eric, Darla J. Landfair, and Marc E. Wiles. "Camptothecin Analogue Efficacy In Vitro: Effect of Liposomal Encapsulation of GI147211C (NX211)." Drug Delivery 6, no. 1 (January 1999): 51–62. http://dx.doi.org/10.1080/107175499267165.

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Journal articles on the topic 'NX11'

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