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1
Cheng, J., P. Belgrader, X. Zhou, and L. E. Maquat. "Introns are cis effectors of the nonsense-codon-mediated reduction in nuclear mRNA abundance." Molecular and Cellular Biology 14, no. 9 (September 1994): 6317–25. http://dx.doi.org/10.1128/mcb.14.9.6317.
Full textAbstract:
The translation of human triosephosphate isomerase (TPI) mRNA normally terminates at codon 249 within exon 7, the final exon. Frameshift and nonsense mutations of the type that cause translation to terminate prematurely at or upstream of codon 189 within exon 6 reduce the level of nuclear TPI mRNA to 20 to 30% of normal by a mechanism that is not a function of the distance of the nonsense codon from either the translation initiation or termination codon. In contrast, frameshift and nonsense mutations of another type that cause translation to terminate prematurely at or downstream of codon 208, also within exon 6, have no effect on the level of nuclear TPI mRNA. In this work, quantitations of RNA that derived from TPI alleles in which nonsense codons had been generated between codons 189 and 208 revealed that the boundary between the two types of nonsense codons resides between codons 192 and 195. The analysis of TPI gene insertions and deletions indicated that the positional feature differentiating the two types of nonsense codons is the distance of the nonsense codon upstream of intron 6. For example, the movement of intron 6 to a position downstream of its normal location resulted in a concomitant downstream movement of the boundary between the two types of nonsense codons. The analysis of intron 6 mutations indicated that the intron 6 effect is stipulated by the 88 nucleotides residing between the 5' and 3' splice sites. Since the deletion of intron 6 resulted in only partial abrogation of the nonsense codon-mediated reduction in the level of TPI mRNA, other sequences within TPI pre-mRNA must function in the effect. One of these sequences may be intron 2, since the deletion of intron 2 also resulted in partial abrogation of the effect. In experiments that switched introns 2 and 6, the replacement of intron 6 with intron 2 was of no consequence to the effect of a nonsense codon within either exon 1 or exon 6. In contrast, the replacement of intron 2 with intron 6 was inconsequential to the effect of a nonsense codon in exon 6 but resulted in partial abrogation of a nonsense codon in exon 1.
2
Cheng, J., P. Belgrader, X. Zhou, and L. E. Maquat. "Introns are cis effectors of the nonsense-codon-mediated reduction in nuclear mRNA abundance." Molecular and Cellular Biology 14, no. 9 (September 1994): 6317–25. http://dx.doi.org/10.1128/mcb.14.9.6317-6325.1994.
Full textAbstract:
The translation of human triosephosphate isomerase (TPI) mRNA normally terminates at codon 249 within exon 7, the final exon. Frameshift and nonsense mutations of the type that cause translation to terminate prematurely at or upstream of codon 189 within exon 6 reduce the level of nuclear TPI mRNA to 20 to 30% of normal by a mechanism that is not a function of the distance of the nonsense codon from either the translation initiation or termination codon. In contrast, frameshift and nonsense mutations of another type that cause translation to terminate prematurely at or downstream of codon 208, also within exon 6, have no effect on the level of nuclear TPI mRNA. In this work, quantitations of RNA that derived from TPI alleles in which nonsense codons had been generated between codons 189 and 208 revealed that the boundary between the two types of nonsense codons resides between codons 192 and 195. The analysis of TPI gene insertions and deletions indicated that the positional feature differentiating the two types of nonsense codons is the distance of the nonsense codon upstream of intron 6. For example, the movement of intron 6 to a position downstream of its normal location resulted in a concomitant downstream movement of the boundary between the two types of nonsense codons. The analysis of intron 6 mutations indicated that the intron 6 effect is stipulated by the 88 nucleotides residing between the 5' and 3' splice sites. Since the deletion of intron 6 resulted in only partial abrogation of the nonsense codon-mediated reduction in the level of TPI mRNA, other sequences within TPI pre-mRNA must function in the effect. One of these sequences may be intron 2, since the deletion of intron 2 also resulted in partial abrogation of the effect. In experiments that switched introns 2 and 6, the replacement of intron 6 with intron 2 was of no consequence to the effect of a nonsense codon within either exon 1 or exon 6. In contrast, the replacement of intron 2 with intron 6 was inconsequential to the effect of a nonsense codon in exon 6 but resulted in partial abrogation of a nonsense codon in exon 1.
3
Romão, Luı́sa, Ângela Inácio, Susana Santos, Madalena Ávila, Paula Faustino, Paula Pacheco, and João Lavinha. "Nonsense mutations in the human β-globin gene lead to unexpected levels of cytoplasmic mRNA accumulation." Blood 96, no. 8 (October 15, 2000): 2895–901. http://dx.doi.org/10.1182/blood.v96.8.2895.
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Abstract Generally, nonsense codons 50 bp or more upstream of the 3′-most intron of the human β-globin gene reduce mRNA abundance. In contrast, dominantly inherited β-thalassemia is frequently associated with nonsense mutations in the last exon. In this work, murine erythroleukemia (MEL) cells were stably transfected with human β-globin genes mutated within each of the 3 exons, namely at codons 15 (TGG→TGA), 39 (C→T), or 127 (C→T). Primer extension analysis after erythroid differentiation induction showed codon 127 (C→T) mRNA accumulated in the cytoplasm at approximately 20% of the normal mRNA level. Codon 39 (C→T) mutation did not result in significant mRNA accumulation. Unexpectedly, codon 15 (TGG→TGA) mRNA accumulated at approximately 90%. Concordant results were obtained when reticulocyte mRNA from 2 carriers for this mutation was studied. High mRNA accumulation of codon 15 nonsense-mutated gene was revealed to be independent of the type of nonsense mutation and the genomic background in which this mutation occurs. To investigate the effects of other nonsense mutations located in the first exon on the mRNA level, nonsense mutations at codons 5, 17, and 26 were also cloned and stably transfected into MEL cells. After erythroid differentiation induction, mRNAs with a mutation at codon 5 or 17 were detected at high levels, whereas the mutation at codon 26 led to low mRNA levels. These findings suggest that nonsense-mediated mRNA decay is not exclusively dependent on the localization of mutations relative to the 3′-most intron. Other factors may also contribute to determine the cytoplasmic nonsense-mutated mRNA level in erythroid cells.
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Romão, Luı́sa, Ângela Inácio, Susana Santos, Madalena Ávila, Paula Faustino, Paula Pacheco, and João Lavinha. "Nonsense mutations in the human β-globin gene lead to unexpected levels of cytoplasmic mRNA accumulation." Blood 96, no. 8 (October 15, 2000): 2895–901. http://dx.doi.org/10.1182/blood.v96.8.2895.h8002895_2895_2901.
Full textAbstract:
Generally, nonsense codons 50 bp or more upstream of the 3′-most intron of the human β-globin gene reduce mRNA abundance. In contrast, dominantly inherited β-thalassemia is frequently associated with nonsense mutations in the last exon. In this work, murine erythroleukemia (MEL) cells were stably transfected with human β-globin genes mutated within each of the 3 exons, namely at codons 15 (TGG→TGA), 39 (C→T), or 127 (C→T). Primer extension analysis after erythroid differentiation induction showed codon 127 (C→T) mRNA accumulated in the cytoplasm at approximately 20% of the normal mRNA level. Codon 39 (C→T) mutation did not result in significant mRNA accumulation. Unexpectedly, codon 15 (TGG→TGA) mRNA accumulated at approximately 90%. Concordant results were obtained when reticulocyte mRNA from 2 carriers for this mutation was studied. High mRNA accumulation of codon 15 nonsense-mutated gene was revealed to be independent of the type of nonsense mutation and the genomic background in which this mutation occurs. To investigate the effects of other nonsense mutations located in the first exon on the mRNA level, nonsense mutations at codons 5, 17, and 26 were also cloned and stably transfected into MEL cells. After erythroid differentiation induction, mRNAs with a mutation at codon 5 or 17 were detected at high levels, whereas the mutation at codon 26 led to low mRNA levels. These findings suggest that nonsense-mediated mRNA decay is not exclusively dependent on the localization of mutations relative to the 3′-most intron. Other factors may also contribute to determine the cytoplasmic nonsense-mutated mRNA level in erythroid cells.
5
Zhang, Jing, Xiaolei Sun, Yimei Qian, Jeffrey P. LaDuca, and Lynne E. Maquat. "At Least One Intron Is Required for the Nonsense-Mediated Decay of Triosephosphate Isomerase mRNA: a Possible Link between Nuclear Splicing and Cytoplasmic Translation." Molecular and Cellular Biology 18, no. 9 (September 1, 1998): 5272–83. http://dx.doi.org/10.1128/mcb.18.9.5272.
Full textAbstract:
ABSTRACT Mammalian cells have established mechanisms to reduce the abundance of mRNAs that harbor a nonsense codon and prematurely terminate translation. In the case of the human triosephosphate isomerase (TPI gene), nonsense codons located less than 50 to 55 bp upstream of intron 6, the 3′-most intron, fail to mediate mRNA decay. With the aim of understanding the feature(s) of TPI intron 6 that confer function in positioning the boundary between nonsense codons that do and do not mediate decay, the effects of deleting or duplicating introns have been assessed. The results demonstrate that TPI intron 6 functions to position the boundary because it is the 3′-most intron. Since decay takes place after pre-mRNA splicing, it is conceivable that removal of the 3′-most intron from pre-mRNA “marks” the 3′-most exon-exon junction of product mRNA so that only nonsense codons located more than 50 to 55 nucleotides upstream of the “mark” mediate mRNA decay. Decay may be elicited by the failure of translating ribosomes to translate sufficiently close to the mark or, more likely, the scanning or looping out of some component(s) of the translation termination complex to the mark. In support of scanning, a nonsense codon does not elicit decay if some of the introns that normally reside downstream of the nonsense codon are deleted so the nonsense codon is located (i) too far away from a downstream intron, suggesting that all exon-exon junctions may be marked, and (ii) too far away from a downstream failsafe sequence that appears to function on behalf of intron 6, i.e., when intron 6 fails to leave a mark. Notably, the proposed scanning complex may have a greater unwinding capability than the complex that scans for a translation initiation codon since a hairpin structure strong enough to block translation initiation when inserted into the 5′ untranslated region does not block nonsense-mediated decay when inserted into exon 6 between a nonsense codon residing in exon 6 and intron 6.
6
Belinky, Frida, Ishan Ganguly, Eugenia Poliakov, Vyacheslav Yurchenko, and Igor B. Rogozin. "Analysis of Stop Codons within Prokaryotic Protein-Coding Genes Suggests Frequent Readthrough Events." International Journal of Molecular Sciences 22, no. 4 (February 14, 2021): 1876. http://dx.doi.org/10.3390/ijms22041876.
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Nonsense mutations turn a coding (sense) codon into an in-frame stop codon that is assumed to result in a truncated protein product. Thus, nonsense substitutions are the hallmark of pseudogenes and are used to identify them. Here we show that in-frame stop codons within bacterial protein-coding genes are widespread. Their evolutionary conservation suggests that many of them are not pseudogenes, since they maintain dN/dS values (ratios of substitution rates at non-synonymous and synonymous sites) significantly lower than 1 (this is a signature of purifying selection in protein-coding regions). We also found that double substitutions in codons—where an intermediate step is a nonsense substitution—show a higher rate of evolution compared to null models, indicating that a stop codon was introduced and then changed back to sense via positive selection. This further supports the notion that nonsense substitutions in bacteria are relatively common and do not necessarily cause pseudogenization. In-frame stop codons may be an important mechanism of regulation: Such codons are likely to cause a substantial decrease of protein expression levels.
7
Morozov, Igor Y., Susana Negrete-Urtasun, Joan Tilburn, Christine A. Jansen, Mark X. Caddick, and Herbert N. Arst. "Nonsense-Mediated mRNA Decay Mutation in Aspergillus nidulans." Eukaryotic Cell 5, no. 11 (September 8, 2006): 1838–46. http://dx.doi.org/10.1128/ec.00220-06.
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ABSTRACT An Aspergillus nidulans mutation, designated nmdA1, has been selected as a partial suppressor of a frameshift mutation and shown to truncate the homologue of the Saccharomyces cerevisiae nonsense-mediated mRNA decay (NMD) surveillance component Nmd2p/Upf2p. nmdA1 elevates steady-state levels of premature termination codon-containing transcripts, as demonstrated using mutations in genes encoding xanthine dehydrogenase (hxA), urate oxidase (uaZ), the transcription factor mediating regulation of gene expression by ambient pH (pacC), and a protease involved in pH signal transduction (palB). nmdA1 can also stabilize pre-mRNA (unspliced) and wild-type transcripts of certain genes. Certain premature termination codon-containing transcripts which escape NMD are relatively stable, a feature more in common with certain nonsense codon-containing mammalian transcripts than with those in S. cerevisiae. As in S. cerevisiae, 5′ nonsense codons are more effective at triggering NMD than 3′ nonsense codons. Unlike the mammalian situation but in common with S. cerevisiae and other lower eukaryotes, A. nidulans is apparently impervious to the position of premature termination codons with respect to the 3′ exon-exon junction.
8
Phillips-Jones, M. K., L. S. Hill, J. Atkinson, and R. Martin. "Context effects on misreading and suppression at UAG codons in human cells." Molecular and Cellular Biology 15, no. 12 (December 1995): 6593–600. http://dx.doi.org/10.1128/mcb.15.12.6593.
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The effect of the 3' codon context on the efficiency of nonsense suppression in mammalian tissue culture cells has been tested. Measurements were made following the transfection of cells with a pRSVgal reporter vector that contained the classical Escherichia coli lacZ UAG allele YA559. The position of this mutation was mapped by virtue of its fortuitous creation of a CTAG MaeI restriction enzyme site. Determination of the local DNA sequence revealed a C-->T mutation at codon 600 of the lacZ gene: CAG-->TAG. Site-directed mutagenesis was used to create a series of vectors in which the base 3' to the nonsense codon was either A, C, G, or U. Suppression of the amber-containing reporter was achieved by cotransfection with genes for human tRNA(Ser) or tRNA(Gln) UAG nonsense suppressors and by growth in the translational error-promoting aminoglycoside drug G418. Nonsense suppression was studied in the human cell lines 293 and MRC5V1 and the simian line COS-7. Overall, the rank order for the effect of changes to the base 3' to UAG was C < G = U < A. This study confirms and extends earlier findings that in mammalian cells 3' C supports efficient nonsense suppression while 3' A is unsympathetic for read-through at nonsense codons. The rules for the mammalian codon context effect on nonsense suppression are therefore demonstrably different from those in E. coli.
9
Lu, Zixian. "Interaction of nonsense suppressor tRNAs and codon nonsense mutations or termination codons." Advances in Biological Chemistry 02, no. 03 (2012): 301–14. http://dx.doi.org/10.4236/abc.2012.23038.
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10
Hall, GW, and S. Thein. "Nonsense codon mutations in the terminal exon of the beta-globin gene are not associated with a reduction in beta-mRNA accumulation: a mechanism for the phenotype of dominant beta-thalassemia." Blood 83, no. 8 (April 15, 1994): 2031–37. http://dx.doi.org/10.1182/blood.v83.8.2031.2031.
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Abstract We present in vivo evidence that there is no reduction in beta-mRNA accumulation in patients with nonsense codons in the terminal exon of the beta-globin gene. Using reverse transcriptase/polymerase chain reaction (RT-PCR), beta-globin cDNA was isolated from the reticulocytes of individuals heterozygous for nonsense codon mutations in exons II and III of the beta-globin gene. Clinically asymptomatic individuals heterozygous for mutations causing premature termination of translation in exon II [beta(0)39(C-T) and F/S71/72(+A)] were found to have almost no mutant beta-cDNA, whereas patients with nonsense codon mutations in exon III [beta 121(G-T) and beta 127(C-T)] with the clinical phenotype of thalassemia intermedia had comparable levels of mutant and normal beta-cDNA. Translation of the mutant beta-mRNA from patients with nonsense codon mutations in exon III would give rise to truncated beta- globin chains, which could explain the more severe phenotype seen in these individuals.
11
Hall, GW, and S. Thein. "Nonsense codon mutations in the terminal exon of the beta-globin gene are not associated with a reduction in beta-mRNA accumulation: a mechanism for the phenotype of dominant beta-thalassemia." Blood 83, no. 8 (April 15, 1994): 2031–37. http://dx.doi.org/10.1182/blood.v83.8.2031.bloodjournal8382031.
Full textAbstract:
We present in vivo evidence that there is no reduction in beta-mRNA accumulation in patients with nonsense codons in the terminal exon of the beta-globin gene. Using reverse transcriptase/polymerase chain reaction (RT-PCR), beta-globin cDNA was isolated from the reticulocytes of individuals heterozygous for nonsense codon mutations in exons II and III of the beta-globin gene. Clinically asymptomatic individuals heterozygous for mutations causing premature termination of translation in exon II [beta(0)39(C-T) and F/S71/72(+A)] were found to have almost no mutant beta-cDNA, whereas patients with nonsense codon mutations in exon III [beta 121(G-T) and beta 127(C-T)] with the clinical phenotype of thalassemia intermedia had comparable levels of mutant and normal beta-cDNA. Translation of the mutant beta-mRNA from patients with nonsense codon mutations in exon III would give rise to truncated beta- globin chains, which could explain the more severe phenotype seen in these individuals.
12
Cohen, Sarit, Lior Kramarski, Shahar Levi, Noa Deshe, Oshrit Ben David, and Eyal Arbely. "Nonsense mutation-dependent reinitiation of translation in mammalian cells." Nucleic Acids Research 47, no. 12 (May 2, 2019): 6330–38. http://dx.doi.org/10.1093/nar/gkz319.
Full textAbstract:
AbstractIn-frame stop codons mark the termination of translation. However, post-termination ribosomes can reinitiate translation at downstream AUG codons. In mammals, reinitiation is most efficient when the termination codon is positioned close to the 5′-proximal initiation site and around 78 bases upstream of the reinitiation site. The phenomenon was studied mainly in the context of open reading frames (ORFs) found within the 5′-untranslated region, or polycicstronic viral mRNA. We hypothesized that reinitiation of translation following nonsense mutations within the main ORF of p53 can promote the expression of N-truncated p53 isoforms such as Δ40, Δ133 and Δ160p53. Here, we report that expression of all known N-truncated p53 isoforms by reinitiation is mechanistically feasible, including expression of the previously unidentified variant Δ66p53. Moreover, we found that significant reinitiation of translation can be promoted by nonsense mutations located even 126 codons downstream of the 5′-proximal initiation site, and observed when the reinitiation site is positioned between 6 and 243 bases downstream of the nonsense mutation. We also demonstrate that reinitiation can stabilise p53 mRNA transcripts with a premature termination codon, by allowing such transcripts to evade the nonsense mediated decay pathway. Our data suggest that the expression of N-truncated proteins from alleles carrying a premature termination codon is more prevalent than previously thought.
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Belgrader, P., and L. E. Maquat. "Nonsense but not missense mutations can decrease the abundance of nuclear mRNA for the mouse major urinary protein, while both types of mutations can facilitate exon skipping." Molecular and Cellular Biology 14, no. 9 (September 1994): 6326–36. http://dx.doi.org/10.1128/mcb.14.9.6326.
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In an effort to understand the mechanisms by which nonsense codons affect RNA metabolism in mammalian cells, nonsense mutations were generated within the gene for the secretory major urinary protein (MUP) of mice. The translation of MUP mRNA normally begins within exon 1 and terminates within exon 6, the penultimate exon. Through the use of Northern (RNA) blot hybridization and assays that couple reverse transcription and PCR, a nonsense mutation within codon 50 of exon 2 or codon 143 of exon 5 was found to reduce the abundance of fully spliced, nuclear MUP mRNA to 10 to 20% of normal without an additional reduction in the abundance of cytoplasmic mRNA. In contrast, a nonsense mutation within codon 172 of exon 5 was found to have no effects on the abundance of MUP mRNA. These findings suggest that a boundary between nonsense mutations that do and do not reduce the abundance of nuclear mRNA exists within the exon preceding the exon that harbors the normal site of translation termination. In this way, the boundary is analogous to the boundary that exists within the penultimate exon of the human gene for the cytosolic enzyme triosephosphate isomerase. Assays for exon skipping, i.e., the removal of an exon as a part of the flanking introns during the process of splicing, reveal that 0.1, 2.0, and 0.1% of MUP mRNA normally lack exon 5, exon 6, and exons 5 plus 6, respectively. Relative to normal, the two nonsense mutations within exon 5 increase the abundance of RNA lacking exon 5 on average 20-fold and increase the abundance of RNA lacking exons 5 plus 6 on average 5-fold. Since only one of these nonsense mutations also reduces the abundance of fully spliced nuclear mRNA to 10 to 20% of normal, the two mechanisms by which a nonsense mutation can alter nuclear RNA metabolism must be distinct. The analysis of missense mutations within codons 143 and 172, some of which retain the nonsense mutation, indicates that the reduction in the abundance of fully spliced nuclear mRNA is dependent upon the premature termination of MUP mRNA translation, whereas skipping is attributable to nonsense mutation-mediated changes in exon 5 structure rather than to the premature termination of translation. The increase in exon 5 skipping by either the nonsense or missense mutations within codon 172 correlates with a decrease in the complementarity of exon 5 to U1 snRNA. This suggests that a 5' splice site may extend as far as 12 nucleotides into the upstream exon, which is, to our knowledge, the largest extension.
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Belgrader, P., and L. E. Maquat. "Nonsense but not missense mutations can decrease the abundance of nuclear mRNA for the mouse major urinary protein, while both types of mutations can facilitate exon skipping." Molecular and Cellular Biology 14, no. 9 (September 1994): 6326–36. http://dx.doi.org/10.1128/mcb.14.9.6326-6336.1994.
Full textAbstract:
In an effort to understand the mechanisms by which nonsense codons affect RNA metabolism in mammalian cells, nonsense mutations were generated within the gene for the secretory major urinary protein (MUP) of mice. The translation of MUP mRNA normally begins within exon 1 and terminates within exon 6, the penultimate exon. Through the use of Northern (RNA) blot hybridization and assays that couple reverse transcription and PCR, a nonsense mutation within codon 50 of exon 2 or codon 143 of exon 5 was found to reduce the abundance of fully spliced, nuclear MUP mRNA to 10 to 20% of normal without an additional reduction in the abundance of cytoplasmic mRNA. In contrast, a nonsense mutation within codon 172 of exon 5 was found to have no effects on the abundance of MUP mRNA. These findings suggest that a boundary between nonsense mutations that do and do not reduce the abundance of nuclear mRNA exists within the exon preceding the exon that harbors the normal site of translation termination. In this way, the boundary is analogous to the boundary that exists within the penultimate exon of the human gene for the cytosolic enzyme triosephosphate isomerase. Assays for exon skipping, i.e., the removal of an exon as a part of the flanking introns during the process of splicing, reveal that 0.1, 2.0, and 0.1% of MUP mRNA normally lack exon 5, exon 6, and exons 5 plus 6, respectively. Relative to normal, the two nonsense mutations within exon 5 increase the abundance of RNA lacking exon 5 on average 20-fold and increase the abundance of RNA lacking exons 5 plus 6 on average 5-fold. Since only one of these nonsense mutations also reduces the abundance of fully spliced nuclear mRNA to 10 to 20% of normal, the two mechanisms by which a nonsense mutation can alter nuclear RNA metabolism must be distinct. The analysis of missense mutations within codons 143 and 172, some of which retain the nonsense mutation, indicates that the reduction in the abundance of fully spliced nuclear mRNA is dependent upon the premature termination of MUP mRNA translation, whereas skipping is attributable to nonsense mutation-mediated changes in exon 5 structure rather than to the premature termination of translation. The increase in exon 5 skipping by either the nonsense or missense mutations within codon 172 correlates with a decrease in the complementarity of exon 5 to U1 snRNA. This suggests that a 5' splice site may extend as far as 12 nucleotides into the upstream exon, which is, to our knowledge, the largest extension.
15
Buzina, Alla, and Marc J. Shulman. "Infrequent Translation of a Nonsense Codon Is Sufficient to Decrease mRNA Level." Molecular Biology of the Cell 10, no. 3 (March 1999): 515–24. http://dx.doi.org/10.1091/mbc.10.3.515.
Full textAbstract:
In many organisms nonsense mutations decrease the level of mRNA. In the case of mammalian cells, it is still controversial whether translation is required for this nonsense-mediated RNA decrease (NMD). Although previous analyzes have shown that conditions that impede translation termination at nonsense codons also prevent NMD, the residual level of termination was unknown in these experiments. Moreover, the conditions used to impede termination might also have interfered with NMD in other ways. Because of these uncertainties, we have tested the effects of limiting translation of a nonsense codon in a different way, using two mutations in the immunoglobulin μ heavy chain gene. For this purpose we exploited an exceptional nonsense mutation at codon 3, which efficiently terminates translation but nonetheless maintains a high level of μ mRNA. We have shown 1) that translation of Ter462 in the double mutant occurs at only ∼4% the normal frequency, and 2) that Ter462 in cis with Ter3 can induce NMD. That is, translation of Ter462 at this low (4%) frequency is sufficient to induce NMD.
16
Barker, G. F., and K. Beemon. "Rous sarcoma virus RNA stability requires an open reading frame in the gag gene and sequences downstream of the gag-pol junction." Molecular and Cellular Biology 14, no. 3 (March 1994): 1986–96. http://dx.doi.org/10.1128/mcb.14.3.1986.
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The intracellular accumulation of the unspliced RNA of Rous sarcoma virus was decreased when translation was prematurely terminated by the introduction of nonsense codons within its 5' proximal gene, the gag gene. Subcellular fractionation of transfected cells suggested that nonsense codon-mediated instability occurred in the cytoplasm. Analysis of constructs containing an in-frame deletion in the nucleocapsid domain of gag, which prevents interaction between the Gag protein and viral RNA, showed that an open reading frame extending to approximately 30 nucleotides from the natural gag termination codon was needed for RNA stability. Sequences at the gag-pol junction necessary for ribosomal frameshifting were not required for RNA stability; however, sequences located 100 to 200 nucleotides downstream of the natural gag termination codon were found to be necessary for stable RNA. The stability of RNAs lacking this downstream sequence was not markedly affected by premature termination codons. We propose that this downstream RNA sequence may interact with ribosomes translating gag to stabilize the RNA.
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Barker, G. F., and K. Beemon. "Rous sarcoma virus RNA stability requires an open reading frame in the gag gene and sequences downstream of the gag-pol junction." Molecular and Cellular Biology 14, no. 3 (March 1994): 1986–96. http://dx.doi.org/10.1128/mcb.14.3.1986-1996.1994.
Full textAbstract:
The intracellular accumulation of the unspliced RNA of Rous sarcoma virus was decreased when translation was prematurely terminated by the introduction of nonsense codons within its 5' proximal gene, the gag gene. Subcellular fractionation of transfected cells suggested that nonsense codon-mediated instability occurred in the cytoplasm. Analysis of constructs containing an in-frame deletion in the nucleocapsid domain of gag, which prevents interaction between the Gag protein and viral RNA, showed that an open reading frame extending to approximately 30 nucleotides from the natural gag termination codon was needed for RNA stability. Sequences at the gag-pol junction necessary for ribosomal frameshifting were not required for RNA stability; however, sequences located 100 to 200 nucleotides downstream of the natural gag termination codon were found to be necessary for stable RNA. The stability of RNAs lacking this downstream sequence was not markedly affected by premature termination codons. We propose that this downstream RNA sequence may interact with ribosomes translating gag to stabilize the RNA.
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Muhlrad, Denise, and Roy Parker. "Recognition of Yeast mRNAs as “Nonsense Containing” Leads to Both Inhibition of mRNA Translation and mRNA Degradation: Implications for the Control of mRNA Decapping." Molecular Biology of the Cell 10, no. 11 (November 1999): 3971–78. http://dx.doi.org/10.1091/mbc.10.11.3971.
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A critical step in the degradation of many eukaryotic mRNAs is a decapping reaction that exposes the transcript to 5′ to 3′ exonucleolytic degradation. The dual role of the cap structure as a target of mRNA degradation and as the site of assembly of translation initiation factors has led to the hypothesis that the rate of decapping would be specified by the status of the cap binding complex. This model makes the prediction that signals that promote mRNA decapping should also alter translation. To test this hypothesis, we examined the decapping triggered by premature termination codons to determine whether there is a down-regulation of translation when mRNAs were recognized as “nonsense containing.” We constructed an mRNA containing a premature stop codon in which we could measure the levels of both the mRNA and the polypeptide encoded upstream of the premature stop codon. Using this system, we analyzed the effects of premature stop codons on the levels of protein being produced per mRNA. In addition, by using alterations either in cis or intrans that inactivate different steps in the recognition and degradation of nonsense-containing mRNAs, we demonstrated that the recognition of a nonsense codon led to a decrease in the translational efficiency of the mRNA. These observations argue that the signal from a premature termination codon impinges on the translation machinery and suggest that decapping is a consequence of the change in translational status of the mRNA.
19
Morais, Pedro, Hironori Adachi, and Yi-Tao Yu. "Suppression of Nonsense Mutations by New Emerging Technologies." International Journal of Molecular Sciences 21, no. 12 (June 20, 2020): 4394. http://dx.doi.org/10.3390/ijms21124394.
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Nonsense mutations often result from single nucleotide substitutions that change a sense codon (coding for an amino acid) to a nonsense or premature termination codon (PTC) within the coding region of a gene. The impact of nonsense mutations is two-fold: (1) the PTC-containing mRNA is degraded by a surveillance pathway called nonsense-mediated mRNA decay (NMD) and (2) protein translation stops prematurely at the PTC codon, and thus no functional full-length protein is produced. As such, nonsense mutations result in a large number of human diseases. Nonsense suppression is a strategy that aims to correct the defects of hundreds of genetic disorders and reverse disease phenotypes and conditions. While most clinical trials have been performed with small molecules, there is an increasing need for sequence-specific repair approaches that are safer and adaptable to personalized medicine. Here, we discuss recent advances in both conventional strategies as well as new technologies. Several of these will soon be tested in clinical trials as nonsense therapies, even if they still have some limitations and challenges to overcome.
20
Chen, Chyi-Ying A., and Ann-Bin Shyu. "Rapid Deadenylation Triggered by a Nonsense Codon Precedes Decay of the RNA Body in a Mammalian Cytoplasmic Nonsense-Mediated Decay Pathway." Molecular and Cellular Biology 23, no. 14 (July 15, 2003): 4805–13. http://dx.doi.org/10.1128/mcb.23.14.4805-4813.2003.
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ABSTRACT Nonsense-mediated mRNA decay (NMD) is an RNA surveillance pathway that detects and destroys aberrant mRNAs containing nonsense or premature termination codons (PTCs) in a translation-dependent manner in eukaryotes. In yeast, the NMD pathway bypasses the deadenylation step and directly targets PTC-containing messages for decapping, followed by 5′-to-3′ exonuclease digestion of the RNA body. In mammals, most PTC-containing mRNAs are subject to active nucleus-associated NMD. Here, using two distinct transcription-pulsing approaches to monitor mRNA deadenylation and decay kinetics, we demonstrate the existence of an active cytoplasmic NMD pathway in mammalian cells. In this pathway, a nonsense codon triggers accelerated deadenylation that precedes decay of the PTC-containing mRNA body. Transcript is stabilized when accelerated deadenylation is impeded by blocking translation initiation; by ectopically expressing two RNA-binding proteins, UNR and NSAP1; or by ectopically expressing a UPF1 dominant-negative mutant. These results are consistent with the notion that the nonsense codon can function in the cytoplasm by promoting rapid removal of the poly(A) tail as a necessary first step in the decay process.
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Viel, Kevin R., Manana Khachidze, Laura Almasy, Arthur R. Thompson, and Tom E. Howard. "Potential Spectrum of Missense and Nonsense Factor (F)VIII Gene (F8) Alleles Based on Single Nucleotide Substitutions - How Many Remain To Be Identified?." Blood 108, no. 11 (November 16, 2006): 4039. http://dx.doi.org/10.1182/blood.v108.11.4039.4039.
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Abstract Regardless of advances in prenatal diagnosis, carrier detection and gene therapy for hemophilia-A, new patients with bleeding diatheses due to inadequate plasma FVIII activity (FVIII:C) levels will still require specialized management at treatment centers. In the ‘post-genome era’ the possibility exists for personalized medicine, in which an individual’s genetic information will be used to tailor prophylactic and/or treatment regimens that will optimize patient outcomes. As listed in the HAMSTeRS database, ~1,000 distinct loss-of-function F8 variants, representing all mutation types including inversions, insertion/deletions and single nucleotide substitutions (SNSs), have been associated with deficiencies of FVIII. To estimate how soon a complete catalogue of every possible mutation affecting FVIII:C levels may become available, we first determined the theoretical number of potential missense and nonsense F8 alleles, whether loss-of-function or not, based on each possible SNS in the coding region as compared to the reference sequence. While the impact of a missense change on FVIII:C, if any, is not always obvious, in contrast to premature-termination codons (PTCs), which are almost always deleterious, findings from a recent resequencing study raises the possibility that non-hemophilic structural differences between a patient’s endogenous FVIII protein and the infused “wildtype” molecule may increase risk of alloimmunization during replacement therapy. Wildtype FVIII contains 2,351 amino acid (aa) residues: 2,332 in the mature protein and 19 in the signal peptide (SP). Appropriate SNSs within the codons for 793 of these residues would create a PTC (UAA, UAG, UGA). Since three distinct base substitutions are possible at each of the three codon positions, 996 nonsense alleles could theoretically arise naturally. As only 123 distinct nonsense mutations are listed in HAMSTeRS, <15% of the theoretical number, many more likely await discovery. Since suitable SNSs within codons for every residue allow for as many as 15,631 naturally-occurring missense variations, of which 462 are in HAMSTeRS, only 2% of all possible alleles, even more mutations of this type likely remain to be identified. The Table presents the number of possible nonsense and missense F8 alleles and the FVIII protein domain/region affected. Although substantial time and diligent surveillance will be required to document the complete allelic architecture of hemophilia-A, since SNS-mutations can occur at every F8 nucleotide, not just those already identified, doing so could potentially have far reaching implications with respect to personalizing both the current strategy of replacement therapy, based on intravenous infusions and future gene-based methods. Table. Potential nonsense and missense F8 alleles based on the FVIII domain/region and position in codon Nucleotide Position in Codon Domain/Region Amino Acids 1st Codon 2nd Codon 3rd Codon Nonsense (Missense) Nonsense (Missense) Nonsense (Missense) SP 0001–0019 3 (51) 1 (56) 3 (23) A1 0001–0336 61 (911) 27 (981) 38 (317) a1 0337–0372 6 (101) 0 (108) 2 (50) A2 0373–0719 70 (935) 41 (1000) 55 (353) a2 0720–0740 5 (55) 3 (60) 4 (26) B 0741–1648 221 (2400) 139 (2585) 35 (1032) a3 1649–1689 12 (111) 4 (119) 4 (53) A3 1690–2019 71 (887) 15 (975) 45 (364) C1 2020–2172 30 (417) 17 (442) 20 (154) C2 2173–2332 35 (432) 14 (466) 15 (167)
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Higgs, J. E., E. F. Harkness, N. L. Bowers, E. Howard, A. J. Wallace, F. Lalloo, W. G. Newman, and D. G. Evans. "TheBRCA2polymorphic stop codon: stuff or nonsense?" Journal of Medical Genetics 52, no. 9 (June 3, 2015): 642–45. http://dx.doi.org/10.1136/jmedgenet-2015-103206.
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Chao, Anna T., Herman A. Dierick, Tracie M. Addy, and Amy Bejsovec. "Mutations in Eukaryotic Release Factors 1 and 3 Act as General Nonsense Suppressors in Drosophila." Genetics 165, no. 2 (October 1, 2003): 601–12. http://dx.doi.org/10.1093/genetics/165.2.601.
Full textAbstract:
Abstract In a screen for suppressors of the Drosophila winglessPE4 nonsense allele, we isolated mutations in the two components that form eukaryotic release factor. eRF1 and eRF3 comprise the translation termination complex that recognizes stop codons and catalyzes the release of nascent polypeptide chains from ribosomes. Mutations disrupting the Drosophila eRF1 and eRF3 show a strong maternal-effect nonsense suppression due to readthrough of stop codons and are zygotically lethal during larval stages. We tested nonsense mutations in wg and in other embryonically acting genes and found that different stop codons can be suppressed but only a subset of nonsense alleles are subject to suppression. We suspect that the context of the stop codon is significant: nonsense alleles sensitive to suppression by eRF1 and eRF3 encode stop codons that are immediately followed by a cytidine. Such suppressible alleles appear to be intrinsically weak, with a low level of readthrough that is enhanced when translation termination is disrupted. Thus the eRF1 and eRF3 mutations provide a tool for identifying nonsense alleles that are leaky. Our findings have important implications for assigning null mutant phenotypes and for selecting appropriate alleles to use in suppressor screens.
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Rajavel, Kavitha S., and Elizabeth F. Neufeld. "Nonsense-Mediated Decay of HumanHEXA mRNA." Molecular and Cellular Biology 21, no. 16 (August 15, 2001): 5512–19. http://dx.doi.org/10.1128/mcb.21.16.5512-5519.2001.
Full textAbstract:
ABSTRACT Nonsense-mediated mRNA decay (NMD), the loss of mRNAs carrying premature stop codons, is a process by which cells recognize and degrade nonsense mRNAs to prevent possibly toxic effects of truncated peptides. Most mammalian nonsense mRNAs are degraded while associated with the nucleus, but a few are degraded in the cytoplasm; at either site, there is a requirement for translation and for an intron downstream of the early stop codon. We have examined the NMD of a mutant HEXA message in lymphoblasts derived from a Tay-Sachs disease patient homozygous for the common frameshift mutation 1278ins4. The mutant mRNA was nearly undetectable in these cells and increased to approximately 40% of normal in the presence of the translation inhibitor cycloheximide. The stabilized transcript was found in the cytoplasm in association with polysomes. Within 5 h of cycloheximide removal, the polysome-associated nonsense message was completely degraded, while the normal message was stable. The increased lability of the polysome-associated mutant HEXA mRNA shows that NMD of this endogenous mRNA occurred in the cytoplasm. Transfection of Chinese hamster ovary cells showed that expression of an intronless HEXA minigene harboring the frameshift mutation or a closely located nonsense codon resulted in half the normal mRNA level. Inclusion of multiple downstream introns decreased the abundance further, to about 20% of normal. Thus, in contrast to other systems, introns are not absolutely required for NMD ofHEXA mRNA, although they enhance the low-HEXA-mRNA phenotype.
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Michorowska, Sylwia. "Ataluren—Promising Therapeutic Premature Termination Codon Readthrough Frontrunner." Pharmaceuticals 14, no. 8 (August 9, 2021): 785. http://dx.doi.org/10.3390/ph14080785.
Full textAbstract:
Around 12% of hereditary disease-causing mutations are in-frame nonsense mutations. The expression of genes containing nonsense mutations potentially leads to the production of truncated proteins with residual or virtually no function. However, the translation of transcripts containing premature stop codons resulting in full-length protein expression can be achieved using readthrough agents. Among them, only ataluren was approved in several countries to treat nonsense mutation Duchenne muscular dystrophy (DMD) patients. This review summarizes ataluren’s journey from its identification, via first in vitro activity experiments, to clinical trials in DMD, cystic fibrosis, and aniridia. Additionally, data on its pharmacokinetics and mechanism of action are presented. The range of diseases with underlying nonsense mutations is described for which ataluren therapy seems to be promising. What is more, experiments in which ataluren did not show its readthrough activity are also included, and reasons for their failures are discussed.
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Bühler, Marc, Miles F. Wilkinson, and Oliver Mühlemann. "Intranuclear degradation of nonsense codon‐containing mRNA." EMBO reports 3, no. 7 (July 2002): 646–51. http://dx.doi.org/10.1093/embo-reports/kvf129.
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Monajemi, Hadieh, and Sharifuddin M. Zain. "How stop codon pseudouridylation induces nonsense suppression." Computational and Theoretical Chemistry 1204 (October 2021): 113414. http://dx.doi.org/10.1016/j.comptc.2021.113414.
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Cheng, J., and L. E. Maquat. "Nonsense codons can reduce the abundance of nuclear mRNA without affecting the abundance of pre-mRNA or the half-life of cytoplasmic mRNA." Molecular and Cellular Biology 13, no. 3 (March 1993): 1892–902. http://dx.doi.org/10.1128/mcb.13.3.1892.
Full textAbstract:
The abundance of the mRNA for human triosephosphate isomerase (TPI) is decreased to approximately 20% of normal by frameshift and nonsense mutations that cause translation to terminate at a nonsense codon within the first three-fourths of the reading frame. Results of previous studies inhibiting RNA synthesis with actinomycin D suggested that the decrease is not attributable to an increased rate of cytoplasmic mRNA decay. However, the step in TPI RNA metabolism that is altered was not defined, and the use of actinomycin D, in affecting all polymerase II-transcribed genes, could result in artifactual conclusions. In data presented here, the nonsense codon-mediated reduction in the level of TPI mRNA is shown to be characteristic of both nuclear and cytoplasmic fractions of the cell, indicating that the altered metabolic step is nucleus associated. Neither aberrancies in gene transcription nor aberrancies in RNA splicing appear to contribute to the reduction since there were no accompanying changes in the amount of nuclear run-on transcription, the level of any of the six introns in TPI pre-mRNA, or the size of processed mRNA in the nucleus. Deletion of all splice sites that reside downstream of a nonsense codon does not abrogate the reduction, indicating that the reduction takes place independently of the splicing of a downstream intron. Experiments that placed TPI gene expression under the control of the human c-fos promoter, which can be transiently activated by the addition of serum to serum-deprived cells, verified that there is no detectable effect of a nonsense codon on the turnover of cytoplasmic mRNA.
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Cheng, J., and L. E. Maquat. "Nonsense codons can reduce the abundance of nuclear mRNA without affecting the abundance of pre-mRNA or the half-life of cytoplasmic mRNA." Molecular and Cellular Biology 13, no. 3 (March 1993): 1892–902. http://dx.doi.org/10.1128/mcb.13.3.1892-1902.1993.
Full textAbstract:
The abundance of the mRNA for human triosephosphate isomerase (TPI) is decreased to approximately 20% of normal by frameshift and nonsense mutations that cause translation to terminate at a nonsense codon within the first three-fourths of the reading frame. Results of previous studies inhibiting RNA synthesis with actinomycin D suggested that the decrease is not attributable to an increased rate of cytoplasmic mRNA decay. However, the step in TPI RNA metabolism that is altered was not defined, and the use of actinomycin D, in affecting all polymerase II-transcribed genes, could result in artifactual conclusions. In data presented here, the nonsense codon-mediated reduction in the level of TPI mRNA is shown to be characteristic of both nuclear and cytoplasmic fractions of the cell, indicating that the altered metabolic step is nucleus associated. Neither aberrancies in gene transcription nor aberrancies in RNA splicing appear to contribute to the reduction since there were no accompanying changes in the amount of nuclear run-on transcription, the level of any of the six introns in TPI pre-mRNA, or the size of processed mRNA in the nucleus. Deletion of all splice sites that reside downstream of a nonsense codon does not abrogate the reduction, indicating that the reduction takes place independently of the splicing of a downstream intron. Experiments that placed TPI gene expression under the control of the human c-fos promoter, which can be transiently activated by the addition of serum to serum-deprived cells, verified that there is no detectable effect of a nonsense codon on the turnover of cytoplasmic mRNA.
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Galanello, R., E. Dessi, MA Melis, M. Addis, MA Sanna, C. Rosatelli, F. Argiolu, N. Giagu, MP Turco, and E. Cacace. "Molecular analysis of beta zero-thalassemia intermedia in Sardinia." Blood 74, no. 2 (August 1, 1989): 823–27. http://dx.doi.org/10.1182/blood.v74.2.823.823.
Full textAbstract:
Abstract In this study we have carried out alpha- and beta-globin gene analysis and defined the beta-globin gene polymorphisms in a group of patients with thalassemia intermedia of Sardinian descent. A group of patients (109) with thalassemia major of the same origin served as control. Characterization of the beta-thalassemia mutation showed either a frameshift mutation at codon 6 or a codon 39 nonsense mutation. We found that homozygotes for the frameshift mutation at codon 6 or compound heterozygotes for this mutation and for the codon 39 nonsense mutation develop thalassemia intermedia more frequently than thalassemia major. The frameshift mutation at codon 6 was associated with haplotype IX that contains the C-T change at position -158 5′ to the G gamma globin gene implicated in high gamma chain production and thus the mild phenotype. In patients' homozygotes for codon 39 nonsense mutation, those with thalassemia intermedia more frequently had the two- gene deletion form of alpha-thalassemia, or functional loss of the alpha 2 gene as compared with those with thalassemia major. In a few siblings with thalassemia major and intermedia, the thalassemia intermedia syndrome correlated with the presence of the -alpha/-alpha genotype. No cause for the mild phenotype was detected in the majority of patients who had not inherited either haplotype IX or alpha- thalassemia.
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Galanello, R., E. Dessi, MA Melis, M. Addis, MA Sanna, C. Rosatelli, F. Argiolu, N. Giagu, MP Turco, and E. Cacace. "Molecular analysis of beta zero-thalassemia intermedia in Sardinia." Blood 74, no. 2 (August 1, 1989): 823–27. http://dx.doi.org/10.1182/blood.v74.2.823.bloodjournal742823.
Full textAbstract:
In this study we have carried out alpha- and beta-globin gene analysis and defined the beta-globin gene polymorphisms in a group of patients with thalassemia intermedia of Sardinian descent. A group of patients (109) with thalassemia major of the same origin served as control. Characterization of the beta-thalassemia mutation showed either a frameshift mutation at codon 6 or a codon 39 nonsense mutation. We found that homozygotes for the frameshift mutation at codon 6 or compound heterozygotes for this mutation and for the codon 39 nonsense mutation develop thalassemia intermedia more frequently than thalassemia major. The frameshift mutation at codon 6 was associated with haplotype IX that contains the C-T change at position -158 5′ to the G gamma globin gene implicated in high gamma chain production and thus the mild phenotype. In patients' homozygotes for codon 39 nonsense mutation, those with thalassemia intermedia more frequently had the two- gene deletion form of alpha-thalassemia, or functional loss of the alpha 2 gene as compared with those with thalassemia major. In a few siblings with thalassemia major and intermedia, the thalassemia intermedia syndrome correlated with the presence of the -alpha/-alpha genotype. No cause for the mild phenotype was detected in the majority of patients who had not inherited either haplotype IX or alpha- thalassemia.
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Belgrader, P., J. Cheng, X. Zhou, L. S. Stephenson, and L. E. Maquat. "Mammalian nonsense codons can be cis effectors of nuclear mRNA half-life." Molecular and Cellular Biology 14, no. 12 (December 1994): 8219–28. http://dx.doi.org/10.1128/mcb.14.12.8219.
Full textAbstract:
Frameshift and nonsense mutations within the gene for human triosephosphate isomerase (TPI) that generate a nonsense codon within the first three-fourths of the protein coding region have been found to reduce the abundance of the product mRNA that copurifies with nuclei. The cellular process and location of the nonsense codon-mediated reduction have proven difficult to elucidate for technical reasons. We show here, using electron microscopy to judge the purity of isolated nuclei, that the previously established reduction to 25% of the normal mRNA level is evident for nuclei that are free of detectable cytoplasmic contamination. Therefore, the reduction is likely to be characteristic of bona fide nuclear RNA. Fully spliced nuclear mRNA is identified by Northern (RNA) blot hybridization and a reverse transcription-PCR assay as the species that undergoes decay in experiments that used the human c-fos promoter to elicit a burst and subsequent shutoff of TPI gene transcription upon the addition of serum to serum-deprived cells. Finally, the finding that deletion of a 5' splice site of the TPI gene results predominantly but not exclusively in the removal by splicing (i.e., skipping) of the upstream exon as a part of the flanking introns has been used to demonstrate that decay is specific to those mRNA products that maintain the nonsense codon. This result, together with our previous results that implicate translation by ribosomes and charged tRNAs in the decay mechanism, indicate that nonsense codon recognition takes place after splicing and triggers decay solely in cis. The possibility that decay takes place during the process of mRNA export from the nucleus to the cytoplasm is discussed.
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Belgrader, P., J. Cheng, X. Zhou, L. S. Stephenson, and L. E. Maquat. "Mammalian nonsense codons can be cis effectors of nuclear mRNA half-life." Molecular and Cellular Biology 14, no. 12 (December 1994): 8219–28. http://dx.doi.org/10.1128/mcb.14.12.8219-8228.1994.
Full textAbstract:
Frameshift and nonsense mutations within the gene for human triosephosphate isomerase (TPI) that generate a nonsense codon within the first three-fourths of the protein coding region have been found to reduce the abundance of the product mRNA that copurifies with nuclei. The cellular process and location of the nonsense codon-mediated reduction have proven difficult to elucidate for technical reasons. We show here, using electron microscopy to judge the purity of isolated nuclei, that the previously established reduction to 25% of the normal mRNA level is evident for nuclei that are free of detectable cytoplasmic contamination. Therefore, the reduction is likely to be characteristic of bona fide nuclear RNA. Fully spliced nuclear mRNA is identified by Northern (RNA) blot hybridization and a reverse transcription-PCR assay as the species that undergoes decay in experiments that used the human c-fos promoter to elicit a burst and subsequent shutoff of TPI gene transcription upon the addition of serum to serum-deprived cells. Finally, the finding that deletion of a 5' splice site of the TPI gene results predominantly but not exclusively in the removal by splicing (i.e., skipping) of the upstream exon as a part of the flanking introns has been used to demonstrate that decay is specific to those mRNA products that maintain the nonsense codon. This result, together with our previous results that implicate translation by ribosomes and charged tRNAs in the decay mechanism, indicate that nonsense codon recognition takes place after splicing and triggers decay solely in cis. The possibility that decay takes place during the process of mRNA export from the nucleus to the cytoplasm is discussed.
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Roy, Bijoyita, Westley J. Friesen, Yuki Tomizawa, John D. Leszyk, Jin Zhuo, Briana Johnson, Jumana Dakka, et al. "Ataluren stimulates ribosomal selection of near-cognate tRNAs to promote nonsense suppression." Proceedings of the National Academy of Sciences 113, no. 44 (October 4, 2016): 12508–13. http://dx.doi.org/10.1073/pnas.1605336113.
Full textAbstract:
A premature termination codon (PTC) in the ORF of an mRNA generally leads to production of a truncated polypeptide, accelerated degradation of the mRNA, and depression of overall mRNA expression. Accordingly, nonsense mutations cause some of the most severe forms of inherited disorders. The small-molecule drug ataluren promotes therapeutic nonsense suppression and has been thought to mediate the insertion of near-cognate tRNAs at PTCs. However, direct evidence for this activity has been lacking. Here, we expressed multiple nonsense mutation reporters in human cells and yeast and identified the amino acids inserted when a PTC occupies the ribosomal A site in control, ataluren-treated, and aminoglycoside-treated cells. We find that ataluren’s likely target is the ribosome and that it produces full-length protein by promoting insertion of near-cognate tRNAs at the site of the nonsense codon without apparent effects on transcription, mRNA processing, mRNA stability, or protein stability. The resulting readthrough proteins retain function and contain amino acid replacements similar to those derived from endogenous readthrough, namely Gln, Lys, or Tyr at UAA or UAG PTCs and Trp, Arg, or Cys at UGA PTCs. These insertion biases arise primarily from mRNA:tRNA mispairing at codon positions 1 and 3 and reflect, in part, the preferred use of certain nonstandard base pairs, e.g., U-G. Ataluren’s retention of similar specificity of near-cognate tRNA insertion as occurs endogenously has important implications for its general use in therapeutic nonsense suppression.
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Smolskaya, Sviatlana, and Yaroslav Andreev. "Site-Specific Incorporation of Unnatural Amino Acids into Escherichia coli Recombinant Protein: Methodology Development and Recent Achievement." Biomolecules 9, no. 7 (June 28, 2019): 255. http://dx.doi.org/10.3390/biom9070255.
Full textAbstract:
More than two decades ago a general method to genetically encode noncanonical or unnatural amino acids (NAAs) with diverse physical, chemical, or biological properties in bacteria, yeast, animals and mammalian cells was developed. More than 200 NAAs have been incorporated into recombinant proteins by means of non-endogenous aminoacyl-tRNA synthetase (aa-RS)/tRNA pair, an orthogonal pair, that directs site-specific incorporation of NAA encoded by a unique codon. The most established method to genetically encode NAAs in Escherichia coli is based on the usage of the desired mutant of Methanocaldococcus janaschii tyrosyl-tRNA synthetase (MjTyrRS) and cognate suppressor tRNA. The amber codon, the least-used stop codon in E. coli, assigns NAA. Until very recently the genetic code expansion technology suffered from a low yield of targeted proteins due to both incompatibilities of orthogonal pair with host cell translational machinery and the competition of suppressor tRNA with release factor (RF) for binding to nonsense codons. Here we describe the latest progress made to enhance nonsense suppression in E. coli with the emphasis on the improved expression vectors encoding for an orthogonal aa-RA/tRNA pair, enhancement of aa-RS and suppressor tRNA efficiency, the evolution of orthogonal EF-Tu and attempts to reduce the effect of RF1.
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Bühler, Marc, Fabio Mohn, Lukas Stalder, and Oliver Mühlemann. "Transcriptional Silencing of Nonsense Codon-Containing Immunoglobulin Minigenes." Molecular Cell 18, no. 3 (April 2005): 307–17. http://dx.doi.org/10.1016/j.molcel.2005.03.030.
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Phoenix, Pauline, Michel Gravel, Muriel B. Herrington, and Léa Brakier-Gingras. "Neomycin is more efficient than streptomycin in suppressing frameshift mutations." Canadian Journal of Genetics and Cytology 27, no. 6 (December 1, 1985): 776–79. http://dx.doi.org/10.1139/g85-115.
Full textAbstract:
The effects of streptomycin and neomycin on the phenotypic suppression of frameshift mutations in the lacZ gene of Escherichia coli and on the efficiency of suppression of amber mutations in T4 phage by the informational supE tRNA nonsense suppressor were compared. Neomycin stimulated much more efficiently than streptomycin the phenotypic suppression of frameshift mutations. Because neomycin favors mismatches of the central codon base whereas streptomycin favors mismatches of the first codon base, this result suggests that mismatching of the central codon base pair and shifting of the reading frame are two correlated phenomena. In contrast, both streptomycin and neomycin stimulated about equally the efficiency of the tRNA nonsense suppressor, an effect probably related to their interference with the proofreading control in tRNA selection.Key words: streptomycin, neomycin, suppression of frameshift mutations, translational accuracy.
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Hagan, K. W., M. J. Ruiz-Echevarria, Y. Quan, and S. W. Peltz. "Characterization of cis-acting sequences and decay intermediates involved in nonsense-mediated mRNA turnover." Molecular and Cellular Biology 15, no. 2 (February 1995): 809–23. http://dx.doi.org/10.1128/mcb.15.2.809.
Full textAbstract:
Several lines of evidence indicate that the processes of mRNA turnover and translation are intimately linked and that understanding this relationship is critical to elucidating the mechanism of mRNA decay. One clear example of this relationship is the observation that nonsense mutations can accelerate the decay of mRNAs in a process that we term nonsense-mediated mRNA decay. The experiments described here demonstrate that in the yeast Saccharomyces cerevisiae premature translational termination within the initial two-thirds of the PGK1 coding region accelerates decay of that transcript regardless of which of the stop codons is used. Nonsense mutations within the last quarter of the coding region have no effect on PGK1 mRNA decay. The sequences required for nonsense-mediated mRNA decay include a termination codon and specific sequences 3' to the nonsense mutation. Translation of two-thirds of the PGK1 coding region inactivates the nonsense-mediated mRNA decay pathway. This observation explains why carboxyl-terminal nonsense mutations are resistant to accelerated decay. Characterization of the decay of nonsense-containing HIS4 transcripts yielded results mirroring those described above, suggesting that the sequence requirements described for the PGK1 transcript are likely to be a general characteristic of this decay pathway. In addition, an analysis of the decay intermediates of nonsense-containing mRNAs indicates that nonsense-mediated mRNA decay flows through a pathway similar to that described for a class of wild-type transcripts. The initial cleavage event occurs near the 5' terminus of the nonsense-containing transcript and is followed by 5'-->3' exonucleolytic digestion. A model for nonsense-mediated mRNA decay based on these results is discussed.
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Capone, J. P., J. M. Sedivy, P. A. Sharp, and U. L. RajBhandary. "Introduction of UAG, UAA, and UGA nonsense mutations at a specific site in the Escherichia coli chloramphenicol acetyltransferase gene: use in measurement of amber, ochre, and opal suppression in mammalian cells." Molecular and Cellular Biology 6, no. 9 (September 1986): 3059–67. http://dx.doi.org/10.1128/mcb.6.9.3059.
Full textAbstract:
We have used oligonucleotide-directed site-specific mutagenesis to convert serine codon 27 of the Escherichia coli chloramphenicol acetyltransferase (cat) gene to UAG, UAA, and UGA nonsense codons. The mutant cat genes, under transcriptional control of the Rous sarcoma virus long terminal repeat, were then introduced into mammalian cells by DNA transfection along with UAG, UAA, and UGA suppressor tRNA genes derived from a human serine tRNA. Assay for CAT enzymatic activity in extracts from such cells allowed us to detect and quantitate nonsense suppression in monkey CV-1 cells and mouse NIH3T3 cells. Using such an assay, we provide the first direct evidence that an opal suppressor tRNA gene is functional in mammalian cells. The pattern of suppression of the three cat nonsense mutations in bacteria suggests that the serine at position 27 of CAT can be replaced by a wide variety of amino acids without loss of enzymatic activity. Thus, these mutant cat genes should be generally useful for the quantitation of suppressor activity of suppressor tRNA genes introduced into cells and possibly for the detection of naturally occurring nonsense suppressors.
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Capone, J. P., J. M. Sedivy, P. A. Sharp, and U. L. RajBhandary. "Introduction of UAG, UAA, and UGA nonsense mutations at a specific site in the Escherichia coli chloramphenicol acetyltransferase gene: use in measurement of amber, ochre, and opal suppression in mammalian cells." Molecular and Cellular Biology 6, no. 9 (September 1986): 3059–67. http://dx.doi.org/10.1128/mcb.6.9.3059-3067.1986.
Full textAbstract:
We have used oligonucleotide-directed site-specific mutagenesis to convert serine codon 27 of the Escherichia coli chloramphenicol acetyltransferase (cat) gene to UAG, UAA, and UGA nonsense codons. The mutant cat genes, under transcriptional control of the Rous sarcoma virus long terminal repeat, were then introduced into mammalian cells by DNA transfection along with UAG, UAA, and UGA suppressor tRNA genes derived from a human serine tRNA. Assay for CAT enzymatic activity in extracts from such cells allowed us to detect and quantitate nonsense suppression in monkey CV-1 cells and mouse NIH3T3 cells. Using such an assay, we provide the first direct evidence that an opal suppressor tRNA gene is functional in mammalian cells. The pattern of suppression of the three cat nonsense mutations in bacteria suggests that the serine at position 27 of CAT can be replaced by a wide variety of amino acids without loss of enzymatic activity. Thus, these mutant cat genes should be generally useful for the quantitation of suppressor activity of suppressor tRNA genes introduced into cells and possibly for the detection of naturally occurring nonsense suppressors.
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Beißel, Christian, Sebastian Grosse, and Heike Krebber. "Dbp5/DDX19 between Translational Readthrough and Nonsense Mediated Decay." International Journal of Molecular Sciences 21, no. 3 (February 6, 2020): 1085. http://dx.doi.org/10.3390/ijms21031085.
Full textAbstract:
The DEAD-box protein Dbp5 (human DDX19) remodels RNA-protein complexes. Dbp5 functions in ribonucleoprotein export and translation termination. Termination occurs, when the ribosome has reached a stop codon through the Dbp5 mediated delivery of the eukaryotic termination factor eRF1. eRF1 contacts eRF3 upon dissociation of Dbp5, resulting in polypeptide chain release and subsequent ribosomal subunit splitting. Mutations in DBP5 lead to stop codon readthrough, because the eRF1 and eRF3 interaction is not controlled and occurs prematurely. This identifies Dbp5/DDX19 as a possible potent drug target for nonsense suppression therapy. Neurodegenerative diseases and cancer are caused in many cases by the loss of a gene product, because its mRNA contained a premature termination codon (PTC) and is thus eliminated through the nonsense mediated decay (NMD) pathway, which is described in the second half of this review. We discuss translation termination and NMD in the light of Dbp5/DDX19 and subsequently speculate on reducing Dbp5/DDX19 activity to allow readthrough of the PTC and production of a full-length protein to detract the RNA from NMD as a possible treatment for diseases.
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Boehm, CD, CE Dowling, PG Waber, PJ Giardina, and HH Jr Kazazian. "Use of oligonucleotide hybridization in the characterization of a beta zero-thalassemia gene (beta 37 TGG----TGA) in a Saudi Arabian family [published erratum appears in Blood 1986 Jul;68(1):323]." Blood 67, no. 4 (April 1, 1986): 1185–88. http://dx.doi.org/10.1182/blood.v67.4.1185.1185.
Full textAbstract:
Abstract Analysis of restriction site polymorphisms in the beta-globin gene cluster of a Saudi Arabian female with beta zero-thalassemia demonstrated that both of her beta-globin genes were missing a nonpolymorphic AvaII site in exon 2. Examination of the normal nucleotide sequence surrounding this AvaII site revealed that either of two nucleotide substitutions, TGG----TAG or TGG----TGA, could produce a nonsense codon at codon 37 and eliminate the AvaII site. Consequently, two oligonucleotides (19-mers spanning codons 36 through 41 and containing either TAG or TGA at codon 37) were synthesized and hybridized against genomic DNA of the proband and her family. Specific hybridization with one of the oligomers demonstrated that the patient's beta o-thalassemia was the result of homozygosity for the TGG----TGA mutation at codon 37. In certain cases, oligonucleotide hybridization using genomic DNA may obviate the need for gene cloning and sequencing in the characterization of point mutations.
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Boehm, CD, CE Dowling, PG Waber, PJ Giardina, and HH Jr Kazazian. "Use of oligonucleotide hybridization in the characterization of a beta zero-thalassemia gene (beta 37 TGG----TGA) in a Saudi Arabian family [published erratum appears in Blood 1986 Jul;68(1):323]." Blood 67, no. 4 (April 1, 1986): 1185–88. http://dx.doi.org/10.1182/blood.v67.4.1185.bloodjournal6741185.
Full textAbstract:
Analysis of restriction site polymorphisms in the beta-globin gene cluster of a Saudi Arabian female with beta zero-thalassemia demonstrated that both of her beta-globin genes were missing a nonpolymorphic AvaII site in exon 2. Examination of the normal nucleotide sequence surrounding this AvaII site revealed that either of two nucleotide substitutions, TGG----TAG or TGG----TGA, could produce a nonsense codon at codon 37 and eliminate the AvaII site. Consequently, two oligonucleotides (19-mers spanning codons 36 through 41 and containing either TAG or TGA at codon 37) were synthesized and hybridized against genomic DNA of the proband and her family. Specific hybridization with one of the oligomers demonstrated that the patient's beta o-thalassemia was the result of homozygosity for the TGG----TGA mutation at codon 37. In certain cases, oligonucleotide hybridization using genomic DNA may obviate the need for gene cloning and sequencing in the characterization of point mutations.
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Gorgoni, Barbara, Yun-Bo Zhao, J. Krishnan, and Ian Stansfield. "Destabilization of Eukaryote mRNAs by 5′ Proximal Stop Codons Can Occur Independently of the Nonsense-Mediated mRNA Decay Pathway." Cells 8, no. 8 (July 31, 2019): 800. http://dx.doi.org/10.3390/cells8080800.
Full textAbstract:
In eukaryotes, the binding of poly(A) binding protein (PAB) to the poly(A) tail is central to maintaining mRNA stability. PABP interacts with the translation termination apparatus, and with eIF4G to maintain 3′–5′ mRNA interactions as part of an mRNA closed loop. It is however unclear how ribosome recycling on a closed loop mRNA is influenced by the proximity of the stop codon to the poly(A) tail, and how post-termination ribosome recycling affects mRNA stability. We show that in a yeast disabled for nonsense mediated mRNA decay (NMD), a PGK1 mRNA with an early stop codon at codon 22 of the reading frame is still highly unstable, and that this instability cannot be significantly countered even when 50% stop codon readthrough is triggered. In an NMD-deficient mutant yeast, stable reporter alleles with more 3′ proximal stop codons could not be rendered unstable through Rli1-depletion, inferring defective Rli1 ribosome recycling is insufficient in itself to trigger mRNA instability. Mathematical modelling of a translation system including the effect of ribosome recycling and poly(A) tail shortening supports the hypothesis that impaired ribosome recycling from 5′ proximal stop codons may compromise initiation processes and thus destabilize the mRNA. A model is proposed wherein ribosomes undergo a maturation process during early elongation steps, and acquire competency to re-initiate on the same mRNA as translation elongation progresses beyond the very 5′ proximal regions of the mRNA.
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Baradaran-Heravi, Alireza, Aruna D. Balgi, Sara Hosseini-Farahabadi, Kunho Choi, Cristina Has, and Michel Roberge. "Effect of small molecule eRF3 degraders on premature termination codon readthrough." Nucleic Acids Research 49, no. 7 (March 25, 2021): 3692–708. http://dx.doi.org/10.1093/nar/gkab194.
Full textAbstract:
Abstract Premature termination codon (PTC) readthrough is considered a potential treatment for genetic diseases caused by nonsense mutations. High concentrations of aminoglycosides induce low levels of PTC readthrough but also elicit severe toxicity. Identifying compounds that enhance PTC readthrough by aminoglycosides or reduce their toxicity is a continuing challenge. In humans, a binary complex of eukaryotic release factors 1 (eRF1) and 3 (eRF3a or eRF3b) mediates translation termination. They also participate in the SURF (SMG1-UPF1-eRF1-eRF3) complex assembly involved in nonsense-mediated mRNA decay (NMD). We show that PTC readthrough by aminoglycoside G418 is considerably enhanced by eRF3a and eRF3b siRNAs and cereblon E3 ligase modulators CC-885 and CC-90009, which induce proteasomal degradation of eRF3a and eRF3b. eRF3 degradation also reduces eRF1 levels and upregulates UPF1 and selectively stabilizes TP53 transcripts bearing a nonsense mutation over WT, indicating NMD suppression. CC-90009 is considerably less toxic than CC-885 and it enhances PTC readthrough in combination with aminoglycosides in mucopolysaccharidosis type I-Hurler, late infantile neuronal ceroid lipofuscinosis, Duchenne muscular dystrophy and junctional epidermolysis bullosa patient-derived cells with nonsense mutations in the IDUA, TPP1, DMD and COL17A1 genes, respectively. Combination of CC-90009 with aminoglycosides such as gentamicin or ELX-02 may have potential for PTC readthrough therapy.
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Cheng, J., M. Fogel-Petrovic, and L. E. Maquat. "Translation to near the distal end of the penultimate exon is required for normal levels of spliced triosephosphate isomerase mRNA." Molecular and Cellular Biology 10, no. 10 (October 1990): 5215–25. http://dx.doi.org/10.1128/mcb.10.10.5215.
Full textAbstract:
The translation of human triosephosphate isomerase (TPI) mRNA normally terminates at codon 249 within exon 7, the final exon. Frameshift and nonsense mutations within the TPI gene that cause translation to terminate prematurely at or upstream of codon 189, within exon 6, result in a decreased level of TPI mRNA (I.O. Daar and L.E. Maquat, Mol. Cell. Biol. 8:802-813, 1988). For all mutations in this group, the decrease is to the same extent, i.e., to approximately 20% of the normal level. We show here that a second group of nonsense mutations that cause translation to terminate prematurely at or downstream of codon 208, in exon 6, did not affect TPI mRNA abundance. Deletion analysis demonstrated that the abundance of translationally active TPI mRNA is a function of both the distance and the polarity of the nonsense codon relative to the final intron in TPI pre-mRNA. Our results indicate that if translating ribosomes are unable to progress to at least a certain position within the penultimate exon relative to the final intron, then the level of the corresponding mRNA will be abnormally low. Studies inhibiting RNA synthesis with dactinomycin demonstrated that a block in translation does not affect the half-life of mature TPI mRNA. The simplest interpretation of our data is that the translation of TPI mRNA in the cytoplasm facilitates the splicing of TPI pre-mRNA or the transport of TPI mRNA across the nuclear envelope or both.
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Cheng, J., M. Fogel-Petrovic, and L. E. Maquat. "Translation to near the distal end of the penultimate exon is required for normal levels of spliced triosephosphate isomerase mRNA." Molecular and Cellular Biology 10, no. 10 (October 1990): 5215–25. http://dx.doi.org/10.1128/mcb.10.10.5215-5225.1990.
Full textAbstract:
The translation of human triosephosphate isomerase (TPI) mRNA normally terminates at codon 249 within exon 7, the final exon. Frameshift and nonsense mutations within the TPI gene that cause translation to terminate prematurely at or upstream of codon 189, within exon 6, result in a decreased level of TPI mRNA (I.O. Daar and L.E. Maquat, Mol. Cell. Biol. 8:802-813, 1988). For all mutations in this group, the decrease is to the same extent, i.e., to approximately 20% of the normal level. We show here that a second group of nonsense mutations that cause translation to terminate prematurely at or downstream of codon 208, in exon 6, did not affect TPI mRNA abundance. Deletion analysis demonstrated that the abundance of translationally active TPI mRNA is a function of both the distance and the polarity of the nonsense codon relative to the final intron in TPI pre-mRNA. Our results indicate that if translating ribosomes are unable to progress to at least a certain position within the penultimate exon relative to the final intron, then the level of the corresponding mRNA will be abnormally low. Studies inhibiting RNA synthesis with dactinomycin demonstrated that a block in translation does not affect the half-life of mature TPI mRNA. The simplest interpretation of our data is that the translation of TPI mRNA in the cytoplasm facilitates the splicing of TPI pre-mRNA or the transport of TPI mRNA across the nuclear envelope or both.
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Zhang, S., M. J. Ruiz-Echevarria, Y. Quan, and S. W. Peltz. "Identification and characterization of a sequence motif involved in nonsense-mediated mRNA decay." Molecular and Cellular Biology 15, no. 4 (April 1995): 2231–44. http://dx.doi.org/10.1128/mcb.15.4.2231.
Full textAbstract:
In both prokaryotes and eukaryotes, nonsense mutations in a gene can enhance the decay rate or reduce the abundance of the mRNA transcribed from that gene, and we call this process nonsense-mediated mRNA decay. We have been investigating the cis-acting sequences involved in this decay pathway. Previous experiments have demonstrated that, in addition to a nonsense codon, specific sequences 3' of a nonsense mutation, which have been defined as downstream elements, are required for mRNA destabilization. The results presented here identify a sequence motif (TGYYGATGYYYYY, where Y stands for either T or C) that can predict regions in genes that, when positioned 3' of a nonsense codon, promote rapid decay of its mRNA. Sequences harboring two copies of the motif from five regions in the PGK1, ADE3, and HIS4 genes were able to function as downstream elements. In addition, four copies of this motif can function as an independent downstream element. The sequences flanking the motif played a more significant role in modulating its activity when fewer copies of the sequence motif were present. Our results indicate the sequences 5' of the motif can modulate its activity by maintaining a certain distance between the sequence motif and the termination codon. We also suggest that the sequences 3' of the motif modulate the activity of the downstream element by forming RNA secondary structures. Consistent with this view, a stem-loop structure positioned 3' of the sequence motif can enhance the activity of the downstream element. This sequence motif is one of the few elements that have been identified that can predict regions in genes that can be involved in mRNA turnover. The role of these sequences in mRNA decay is discussed.
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Bidou, Laure, Valérie Allamand, Jean-Pierre Rousset, and Olivier Namy. "Sense from nonsense: therapies for premature stop codon diseases." Trends in Molecular Medicine 18, no. 11 (November 2012): 679–88. http://dx.doi.org/10.1016/j.molmed.2012.09.008.
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Oba, T., Y. Andachi, A. Muto, and S. Osawa. "CGG: an unassigned or nonsense codon in Mycoplasma capricolum." Proceedings of the National Academy of Sciences 88, no. 3 (February 1, 1991): 921–25. http://dx.doi.org/10.1073/pnas.88.3.921.
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