Academic literature on the topic 'Nonsense Codon'
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Journal articles on the topic "Nonsense Codon"
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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.
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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.
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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.
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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.
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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.
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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.
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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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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.
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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.
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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.
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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.
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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.
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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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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.
Dissertations / Theses on the topic "Nonsense Codon"
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Min, Ei Ei. "Yeast Upf1 Associates With RibosomesTranslating mRNA Coding Sequences Upstream of Normal Termination Codons: A Dissertation." eScholarship@UMMS, 2004. http://escholarship.umassmed.edu/gsbs_diss/780.
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Nonsense-mediated mRNA decay (NMD) specifically targets mRNAs with premature translation termination codons for rapid degradation. NMD is a highly conserved translation-dependent mRNA decay pathway, and its core Upf factors are thought to be recruited to prematurely terminating mRNP complexes, possibly through the release factors that orchestrate translation termination. Upf1 is the central regulator of NMD and recent studies have challenged the notion that this protein is specifically targeted to aberrant, nonsense-containing mRNAs. Rather, it has been proposed that Upf1 binds to most mRNAs in a translation-independent manner. In this thesis, I investigated the nature of Upf1 association with its substrates in the yeast Saccharomyces cerevisiae. Using biochemical and genetic approaches, the basis for Upf1 interaction with ribosomes was evaluated to determine the specificity of Upf1 association with ribosomes, and the extent to which such binding is dependent on prior association of Upf1’s interacting partners. I discovered that Upf1 is specifically associated with Rps26 of the 40S ribosomal subunit, and that this association requires the N-terminal Upf1 CH domain. In addition, using selective ribosome profiling, I investigated when during translation Upf1 associates with ribosomes and showed that Upf1 binding was not limited to polyribosomes that were engaged in translating NMD substrate mRNAs. Rather, Upf1 associated with translating ribosomes on most mRNAs, binding preferentially as ribosomes approached the 3’ ends of open reading frames. Collectively, these studies provide new mechanistic insights into NMD and the dynamics of Upf1 during translation.
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Min, Ei Ei. "Yeast Upf1 Associates With RibosomesTranslating mRNA Coding Sequences Upstream of Normal Termination Codons: A Dissertation." eScholarship@UMMS, 2015. https://escholarship.umassmed.edu/gsbs_diss/780.
Full textAbstract:
Nonsense-mediated mRNA decay (NMD) specifically targets mRNAs with premature translation termination codons for rapid degradation. NMD is a highly conserved translation-dependent mRNA decay pathway, and its core Upf factors are thought to be recruited to prematurely terminating mRNP complexes, possibly through the release factors that orchestrate translation termination. Upf1 is the central regulator of NMD and recent studies have challenged the notion that this protein is specifically targeted to aberrant, nonsense-containing mRNAs. Rather, it has been proposed that Upf1 binds to most mRNAs in a translation-independent manner. In this thesis, I investigated the nature of Upf1 association with its substrates in the yeast Saccharomyces cerevisiae. Using biochemical and genetic approaches, the basis for Upf1 interaction with ribosomes was evaluated to determine the specificity of Upf1 association with ribosomes, and the extent to which such binding is dependent on prior association of Upf1’s interacting partners. I discovered that Upf1 is specifically associated with Rps26 of the 40S ribosomal subunit, and that this association requires the N-terminal Upf1 CH domain. In addition, using selective ribosome profiling, I investigated when during translation Upf1 associates with ribosomes and showed that Upf1 binding was not limited to polyribosomes that were engaged in translating NMD substrate mRNAs. Rather, Upf1 associated with translating ribosomes on most mRNAs, binding preferentially as ribosomes approached the 3’ ends of open reading frames. Collectively, these studies provide new mechanistic insights into NMD and the dynamics of Upf1 during translation.
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Bond, Andrew Thomas. "The Role of Dbp2p in Both Nonsense-Mediated mRNA Decay and rRNA Processing: A Dissertation." eScholarship@UMMS, 2002. http://escholarship.umassmed.edu/gsbs_diss/150.
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Dbp2p, a member of the large family of DEAD-box proteins and a yeast homolog of human p68, was shown to interact with Upf1p, an essential component of the nonsense-mediated mRNA decay pathway. Dbp2p:Upf1p interaction occurs within a large conserved region in the middle of Upf1p that is largely distinct from its Nmd2p and Sup35/45p interaction domains. Deletion of DBP2, or point mutations within its highly conserved DEAD-box motifs, increased the abundance of nonsense-containing transcripts, leading us to conclude that Dbp2p also functions in the nonsense-mediated mRNA decay pathway. Dbp2p, like Upf1p, acts before or at decapping, is predominantly cytoplasmic, and associates with polyribosomes. Interestingly, Dbp2p also plays an important role in rRNA processing. In dbp2Δ cells, polyribosome profiles are deficient in free 60S subunits and the mature 25S rRNA is greatly reduced. The ribosome biogenesis phenotype, but not the mRNA decay function, of dbp2Δ cells can be complemented by the human p68 gene. We propose a unifying model in which Dbp2p affects both nonsense-mediated mRNA decay and rRNA processing by altering rRNA structure, allowing specific processing events in one instance and facilitating dissociation of the translation termination complex in the other.
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Bugaud, Olivier. "Suppression traductionnelle des codons stop chez les mammifères." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS222.
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Entre 10% et 30% des maladies humaines sont liées à l'apparition d'une mutation non-sens (PTC). La synthèse protéique est alors arrêté prématurément. Cet arrêt peut être inhibé par des molécules inductrices de translecture qui permettent l’incorporation d’un ARNt suppresseur naturel au niveau du PTC (translecture). Le ribosome peut alors franchir le PTC et restaurer l’expression de la protéine.Au cours de ma thèse, je me suis intéressé à la suppression des codons stop en caractérisant de nouvelles molécules inductrices de translecture et en analysant les mécanismes de la fidélité de la traduction.J’ai tout d’abord mis au point un système de criblage innovant avec lequel j’ai testé plus de 17 000 molécules et identifié la molécule TLN468. J’ai pu mettre en évidence que cette molécule est capable d’induire la réexpression d’une protéine p53 active.J'ai aussi caractérisé de nouveaux composés dérivés d’aminoglycosides. J’ai pu montré que le NB124 est capable d’induire l’apoptose de cellules tumorales via la réexpression de la protéine p53 tout ayant une toxicité bien plus faible que la gentamicine.En parallèle, j’ai développé une approche en molécule unique permettant d’étudier les erreurs programmées du ribosome (recodage). J’ai ainsi pu analyser la cinétique d’élongation des ribosomes eucaryotes et montré que l’initiation de la traduction sur un site d’entrée interne (IRES) ralentit le ribosome lors des premiers cycles d’élongationNonsense mutations, also known as premature termination codons (PTCs) are responsible for 10% to 30% of all human genetic diseases. Nonsense translation suppression can be induced by readthrough inducers. The presence of such PTC leads to premature translation termination. These stop therapeutic strategies have emerged which attempt to use molecules that facilitate tRNA incorporation at the PTC (readthrough). The, translation continue in the same reading frame until the next stop codon. I first developed an innovative screening system I used to test more than 17,000 molecules and have identified one hit, TLN468 molecule. I have shown that this molecule is able to induce re-expression of an active p53 protein.I also characterized new compounds derived from aminoglycosides. I have shown that the NB124 induces apoptosis of tumor cells by re-expressing p53 protein while having a much lower toxicity than gentamicin.I developed a single molecule approach for studying the ribosome programmed errors (recoding). I was able to analyze the kinetics of elongation eukaryotic ribosomes and showed that the initiation of translation at an internal entry site (IRES) slows the ribosome during the first elongation cycle
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Gonzalez-Hilarion, Sara Sofia. "Identification d'inhibiteurs du nonsense-mediated mRNA decay (NMD) et utilisation comme approche thérapeutique dans certaines maladies génétiques." Phd thesis, Université du Droit et de la Santé - Lille II, 2011. http://tel.archives-ouvertes.fr/tel-01017363.
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Le NMD (nonsense-mediated mRNA decay) est un mécanisme qui reconnaît et dégrade les ARNm portant un codon stop prématuré afin d'empêcher la synthèse de protéines tronquées qui pourraient avoir des effets néfastes pour la cellule ou tout simplement être non fonctionnelles. Cependant, dans un certain nombre de cas, selon la position du codon stop prématuré, la protéine tronquée qui serait synthétisée si le NMD n'existait pas, pourrait remplir complètement ou partiellement la fonction de la protéine sauvage. Il faut noter qu'un codon stop prématuré est retrouvé dans le gène responsable d'une pathologie dans un tiers des maladies génétiques et de nombreuses formes de cancer. Dans la plus grande majorité des cas, la maladie se développe non pas parce qu'une protéine tronquée non fonctionnelle ou instable est synthétisée, mais plutôt parce que le gène muté n'est pas exprimé du fait de l'intervention du NMD sur l'ARNm qui en dérive. Une nouvelle approche thérapeutique de ces maladies serait d'inhiber le NMD afin de permettre la synthèse de protéines tronquées fonctionnelles et sauver le phénotype clinique. Nous avons donc décidé de rechercher des inhibiteurs du mécanisme du NMD parmi des petites molécules chimiques. Pour cela, nous avons mis au point un système de criblage en culture cellulaire reliant l'efficacité du NMD dans une cellule avec une activité luciférase mesurable directement sur les cultures cellulaires, au moyen d'un luminomètre. A partir d'un premier criblage d'environ 1500 composés chimiques, nous avons identifié une nouvelle molécule capable d'inhiber efficacement le NMD. De façon intéressante, cette nouvelle molécule est capable également d'induire la synthèse de protéines entières à partir d'un ARNm portant un codon stop prématuré. Nous avons utilisé cet inhibiteur dans des expériences pour déterminer son potentiel thérapeutique sur des modèles cellulaires de maladies génétiques tels que la dystrophie musculaire de Duchenne, la mucoviscidose et le cancer. Nos résultats démontrent que l'inhibition du NMD peut être en effet envisagée comme une nouvelle approche thérapeutique pour des maladies causées par l'apparition d'une mutation non sens. Nous avons aussi identifié une autre molécule chimique capable d'inhiber le NMD et permettant de faire un lien entre efficacité du NMD et intégrité du cytosquelette.
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Gonzalez-Hilarion, Sara Sofia. "Identification d’inhibiteurs du nonsense-mediated mRNA decay (NMD) et utilisation comme approche thérapeutique dans certaines maladies génétiques." Thesis, Lille 2, 2011. http://www.theses.fr/2011LIL2S049/document.
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Le NMD (nonsense-mediated mRNA decay) est un mécanisme qui reconnaît et dégrade les ARNm portant un codon stop prématuré afin d’empêcher la synthèse de protéines tronquées qui pourraient avoir des effets néfastes pour la cellule ou tout simplement être non fonctionnelles. Cependant, dans un certain nombre de cas, selon la position du codon stop prématuré, la protéine tronquée qui serait synthétisée si le NMD n’existait pas, pourrait remplir complètement ou partiellement la fonction de la protéine sauvage. Il faut noter qu’un codon stop prématuré est retrouvé dans le gène responsable d’une pathologie dans un tiers des maladies génétiques et de nombreuses formes de cancer. Dans la plus grande majorité des cas, la maladie se développe non pas parce qu’une protéine tronquée non fonctionnelle ou instable est synthétisée, mais plutôt parce que le gène muté n’est pas exprimé du fait de l’intervention du NMD sur l’ARNm qui en dérive. Une nouvelle approche thérapeutique de ces maladies serait d’inhiber le NMD afin de permettre la synthèse de protéines tronquées fonctionnelles et sauver le phénotype clinique. Nous avons donc décidé de rechercher des inhibiteurs du mécanisme du NMD parmi des petites molécules chimiques. Pour cela, nous avons mis au point un système de criblage en culture cellulaire reliant l’efficacité du NMD dans une cellule avec une activité luciférase mesurable directement sur les cultures cellulaires, au moyen d’un luminomètre. A partir d’un premier criblage d’environ 1500 composés chimiques, nous avons identifié une nouvelle molécule capable d’inhiber efficacement le NMD. De façon intéressante, cette nouvelle molécule est capable également d’induire la synthèse de protéines entières à partir d’un ARNm portant un codon stop prématuré. Nous avons utilisé cet inhibiteur dans des expériences pour déterminer son potentiel thérapeutique sur des modèles cellulaires de maladies génétiques tels que la dystrophie musculaire de Duchenne, la mucoviscidose et le cancer. Nos résultats démontrent que l’inhibition du NMD peut être en effet envisagée comme une nouvelle approche thérapeutique pour des maladies causées par l’apparition d’une mutation non sens. Nous avons aussi identifié une autre molécule chimique capable d’inhiber le NMD et permettant de faire un lien entre efficacité du NMD et intégrité du cytosqueletteMRNAs harboring a premature termination codon are rapidly degraded by a mechanism called nonsense-mediated mRNA decay (NMD). NMD is a surveillance pathway that prevents the synthesis of truncated proteins that could be harmful for the cell or simply be non-functional. However in some cases, depending on the position of the premature stop codon, the truncated protein that would be synthesized if there were no NMD would be partially or fully as functional as the wild-type protein. It is noteworthy that premature termination codons are found in approximately one-third of inherited genetic disorders and several forms of cancer. In most of cases the disease arises not because a non-functional or unstable truncated protein is synthesized, but instead because the degradation of the transcript by NMD leads to complete loss of protein production. Therefore, NMD inhibition could be an interesting therapeutic approach in some cases of nonsense-related genetic diseases in which functional truncated proteins can restore the clinical phenotype. We decided to search for NMD inhibitors among thousands of small molecules. We developed a cell-based screening method which couples NMD efficiency into the cell to a luciferase activity that can be measured directly into cells by a luminometer. From a screening of approximately 1500 compounds, we have identified one molecule capable of efficiently inhibit NMD. Interestingly, this compound is also able to induce the synthesis of full-length proteins from an mRNA bearing a premature termination codon. We evaluated the therapeutic potential of this compound in different cellular models of genetic disorders such as Duchenne’s muscular dystrophy, cystic fibrosis and cancer. Our results demonstrate that NMD inhibition in general can be considered as an useful therapeutic approach to rescue PTC consequences in genetic diseases provoked by the apparition of a nonsense mutation. We have also identified another compound that inhibits NMD and uncovers a relationship between the NMD efficiency and the integrity of the cytoskeleton
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Chen, Biao. "Association of a nonsense mutation at the codon for Glu 54 in the GM2A gene with AB variant G¦M¦2 gangliosidosis, characterizing the intron/exon junctions of the gene." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0001/MQ46040.pdf.
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Benhabiles, Hana. "Etude de la correction de mutations non sens par de nouvelles molécules pouvant servir d'approches thérapeutiques ciblées." Thesis, Lille 2, 2017. http://www.theses.fr/2017LIL2S046.
Full textAbstract:
Les mutations non sens introduisent un codon stop prématuré dans une phase ouverte de lecture. Ce type de mutation est retrouvé chez environ 11% des patients atteints de maladies génétiques et dans de nombreux cancers. En effet, entre 5 et 40% des mutations affectant des gènes suppresseurs de tumeurs sont des mutations non sens. La conséquence de la présence d’une mutation non sens dans un gène est la dégradation rapide de l’ARN messager correspondant, par l’activation d’un mécanisme de surveillance des ARN appelé NMD (pour nonsense-mediated mRNA decay) conduisant à une absence d’expression du gène mutant. Dans le cas des cancers, l’absence d’expression d’un gène suppresseur de tumeurs tel que TP53, perturbe un ensemble de processus biologiques dont l’apoptose, facilitant ainsi la progression tumorale.En utilisant un système de criblage moyen débit permettant d’identifier des molécules capables de ré-exprimer des gènes porteurs d’une mutation non sens en inhibant le NMD et/ou en activant la translecture, plusieurs molécules ont été identifiées. La translecture est un mécanisme naturel conduisant à l’incorporation d’un acide aminé à la position du codon stop prématuré au cours de la traduction. Parmi les molécules identifiées, je me suis intéressée à un extrait végétal nommé H7 et au composé CNSM1 (pour corrector of nonsense mutation 1) qui permettent une ré-expression très efficace du gène TP53 lorsqu’il est porteur d’une mutation non sens. J’ai caractérisé ces composés en montrant notamment la ré-expression du gène TP53 porteur d’une mutation non sens dans différentes lignées cellulaires issues de différents cancers. J’ai montré également la très faible toxicité de ces molécules, validant leur potentielle utilisation en clinique. Mon étude a aussi permis de montrer que la protéine p53 synthétisée est fonctionnelle puisqu'elle est capable d’induire l’activation transcriptionnelle d’un de ses gènes cibles, le gène TP21.En permettant la ré-expression du gène suppresseur de tumeur mutant, des molécules comme CNSM1 ou H7 restaurent la capacité des cellules à entrer en apoptose et pourraient aussi réduire certaines résistances à la chimiothérapie.De plus, par une approche d’édition du génome, j’ai confirmé le lien existant entre le blocage du cytosquelette et l’inhibition du NMD. J’ai aussi identifié deux protéines impliquées dans le réarrangement du cytosquelette qui pourraient être ciblées pour inhiber le NMD en thérapie et ré-exprimer une protéine tronquée fonctionnelle. L’utilisation de H7 ou de CNMS1 pourrait ainsi être couplée à une inhibition du NMD pour optimiser la correction des mutations non sens. Ces molécules correctrices de mutations non sens représentent de nouvelles approches thérapeutiques ciblées du cancer et des maladies rares liées aux mutations non sensNonsense mutations generate premature termination codons (PTC) within an open reading frame. This type of mutation is found in about 11% of patients with genetic disorders. Concerning cancer, 5 to 40% of mutations affecting tumor-suppressing genes are nonsense mutations. The presence of a PTC in a gene leads to rapid degradation of its mRNA mediated by the RNA surveillance mechanism named NMD (Nonsense-mediated mRNA decay) preventing the synthesis of truncated proteins. In cancer, the absence of expression of tumor suppressing genes such as TP53 interferes with many biological pathways including apoptosis enabling tumor progression.A screening system that allows identifying molecules capable of re-expressing genes harboring nonsense mutations by inhibiting the NMD system and/or by activating readthrough has been developed in the lab. Readthrough is a natural mechanism, which occurs during translation, leading to the incorporation of an amino acid at the PTC position. Among the molecules that have been identified thanks to the screen, a natural extract named H7 and a compound named CNSM1 efficiently rescues the expression of the nonsense-mutated TP53 gene carrying a PTC.CNSM1 and H7 induces the expression of full-length proteins from PTC-containing genes indicating that these compounds are capable of activating readthrough. I validated the screen results on several cancer cell lines harboring an endogenous nonsense mutation in TP53 gene and showed that the function of p53 was restored in the presence of CNSM1 or H7. I also investigated the cellular toxicity related with the use of CMNS1 on cultured cells and the in vivo effect of H7 in a mouse model harboring a nonsense mutation in dystrophin gene. My results demonstrate that these compounds have a mild cellular toxicity. In addition, using a genome editing approach I confirmed the relationship between the cytoskeletal blockage and the NMD inhibition. I identified two proteins that are implicated in the cytoskeletal rearrangement, which might be targeted to induce NMD inhibition and then the expression of truncated but functional protein from the mutated mRNA. H7 or CNMS1 might be coupled to an NMD inhibition strategy to improve the nonsense mutation correction. Knowing CNSM1 and H7 are so far the most efficient molecule capable of rescuing the expression of PTC-containing genes, these compounds represents a realistic hope for a new-targeted therapy for pathologies associated with nonsense mutations
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Durand, Sébastien. "Développement de molécules chimiques capables d’inhiber l’épissage et le Nonsense-Mediated mRNA Decay (NMD)." Montpellier 2, 2008. http://www.theses.fr/2008MON20072.
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L'épissage des pré-ARNm, le processus nucléaire conduisant à l'assemblage des séquences "exons" de l'ARN messager par élimination des séquences intercalaires ou "introns", est une étape décisive de l'expression de la plupart des gènes chez les métazoaires. Au cours de ce processus, beaucoup d'erreurs peuvent survenir avec des conséquences plus ou moins graves pour le bon fonctionnement de la cellule. Afin de limiter les effets délétères de telles erreurs, différents mécanismes de contrôle de qualité des ARNm épissés ont été mis en place. Parmi eux, le Nonsense-Mediated mRNA Decay (NMD) permet de dégrader les ARNm contenant des codons non-sens prématurés (PTC), évitant ainsi l'apparition de protéines tronquées. De par leur ampleur en tant que mécanismes centraux de l'expression génique chez l'homme, l'épissage et le NMD sont fréquemment impliqués dans des pathologies d'origine génétique. Dans certains cas comme l'ataxie télangiectasie ou la neurofibromatose de type I, 54% des mutations responsables de la maladie affectent l'épissage. Environ un tiers des maladies génétiques sont dues à l'apparition de PTC qui induisent le NMD. Dans certains cas, une protéine tronquée pourrait conserver les mêmes propriétés que la protéine sauvage mais le mécanisme de NMD empêche sa synthèse. Par conséquent, l'épissage et le NMD représentent des cibles tout à fait intéressantes qui permettraient, soit de restaurer un épissage correct, soit de permettre l'expression de protéines tronquées et fonctionnelles. Au cours de cette thèse nous avons recherché des inhibiteurs d'épissage et/ou de NMD parmi une collection de 6 000 composés chimiques. Nous avons ainsi pu identifier des composés capables de moduler l'épissage en affectant l'activité de facteurs clefs de la sélection des sites d'épissage, les protéines SR. Nous avons également mis en évidence le premier inhibiteur spécifique du NMD qui bloque spécifiquement la fonction du facteur hUpf1. Ces molécules nous ont permis de disséquer le fonctionnement de ces processus, de proposer un nouveau modèle décrivant le transit des mRNP soumises au NMD par les P-Bodies et ouvrent maintenant la voie à la mise en place de nouvelles stratégies thérapeutiques utilisant ces composésRNA splicing involves the processing of pre-messenger RNA molecules by the excision of introns and the precise joining of exons to form the mature messenger RNA that is exported from the nucleus for translation. Exon usage is often alternative, i. E. The cell decides whether to remove a part of the pre-mRNA as an intron or include this part in the mature mRNA as an alternative exon. Alternative splicing is therefore, a genetically economical process that enables a single gene to increase its coding capacity, allowing the synthesis of several structurally and functionally distinct protein isoforms. To avoid accumulation of aberrantly spliced mRNAs, several quality control processes determine the fate of mRNA in the cell. Among these processes, Nonsense-Mediated mRNA decay (NMD), is able to degrade mRNA containing premature termination codons (PTCs), preventing accumulation of truncated with deleterious effects for the cell. As central mechanisms controlling gene expression any disturbance of either splicing or NMD can lead to genetic diseases. Indeed, the numbers of diseases shown to be caused by a defect in pre-mRNA splicing or NMD is rapidly growing. For example, in ataxia telengectasia or type I neurofibromatosis, 54% of disease-inducing mutations affect mRNA splicing. Moreover, one third of acquired and inherited pathologies are due to nonsense creation that elicits NMD. Consequently, mRNA splicing and NMD represent a potential targets for new therapeutic strategies. During this thesis, we have screened a small chemical library to find splicing and NMD inhibitors. We have identified some molecules that modulate mRNA splicing efficiency by affecting SR proteins activity. We have also isolated the first specific inhibitor of NMD that blocks hUpf1 functions. These compounds allowed us to decipher splicing and NMD mechanisms and to propose a new model to describe the NMD-subjected mRNP transit trough the processing-Bodies. The next challenge will be to demonstrate the functional utility of these molecules in preclinical models of human disease
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Anderson, Raymond Dillard. "Introducing new protein functions through multiple nonsense codon suppression /." 2003. http://wwwlib.umi.com/dissertations/fullcit/3097288.
Full textBooks on the topic "Nonsense Codon"
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Association of a nonsense mutation at the codon for Glu 54 in the GM2A gene with AB variant G(M2) gangliosidosis: Characterizing the intron/exon junctions of the gene. Ottawa: National Library of Canada, 1999.
Find full textBook chapters on the topic "Nonsense Codon"
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Gooch, Jan W. "Nonsense Codon." In Encyclopedic Dictionary of Polymers, 910. New York, NY: Springer New York, 2011. http://dx.doi.org/10.1007/978-1-4419-6247-8_14338.
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Tharp, Jeffery M., and Wenshe R. Liu. "Using Amber and Ochre Nonsense Codons to Code Two Different Noncanonical Amino Acids in One Protein Gene." In Methods in Molecular Biology, 147–54. New York, NY: Springer New York, 2018. http://dx.doi.org/10.1007/978-1-4939-7574-7_9.
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"Nonsense Codon." In Encyclopedia of Genetics, Genomics, Proteomics and Informatics, 1359. Dordrecht: Springer Netherlands, 2008. http://dx.doi.org/10.1007/978-1-4020-6754-9_11535.
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"Nonsense Codon." In Brenner's Encyclopedia of Genetics, 102. Elsevier, 2001. http://dx.doi.org/10.1016/b978-0-12-374984-0.01061-5.
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"Nonsense Codon." In Encyclopedia of Genetics, 1350. Elsevier, 2001. http://dx.doi.org/10.1006/rwgn.2001.1930.
Full textConference papers on the topic "Nonsense Codon"
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Bertagnolo, V., S. Volinia, C. Legnani, G. Rodorigo, V. De De Rosa, and F. Bernardi. "TWO FVIII GENE LESIONS DETECTED IN SEVERE AND MODERATE HAEMOPHILIA A." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644048.
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DNAs from 15 haemophilia A patients from different families have been hybridized to FVIII cDNA probes for the exons 14-26.In a severely affected patient (FVIII:C 2 %) the TaqI site of exon 24 is absent originating an abnormal band of 4.2 Kb. A C toT transition in the CG dinucleotide of the TaqI site (TCGA) is the probable gene mutation. Since the transition in the sense strand should originate an additional Hind III site, which is not detected in our patient, we infer that the mutation occurred in the antisensestrand causing an aminoacid change (CGA →CAA, Arg → Gin). This isin accordance with the low activity of FVIII and with the absence of inhibitor. Infact Gitschier et Al reported in a patient with ahigh titre of anti-FVIII antibody and with <1% FVIII activity a C → T transition in the coding strand, originating a nonsense codon in the TaqI site of exon 24.In the Hindlll pattern from a moderately affected patient (FVIII:C 4%) the fragment containing the exon 18 is 2.5 Kb in size (normal 2.6 Kb). Since the patterns with other restriction enzymes are indistinguishable from normal a small mutation originating a new Hind III site is likely. Both altered patterns have been detected in the patients' mothers.Work supported by Ricerca Sanitaria Finalizzata Regione Emilia Romagna
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Bernaedi, F., V. Bertagnolo, S. Bartolai, L. Rossi, F. Panicucci, and F. Conconi. "A POINT MUTATION AND A GENE DELETION OF FVIII GENE IN SEVERE HAEMOPHILIA." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644047.
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The presence of Factor VIII (FVIII) gene lesions has been investigated in 100 haemophilia A patients using cDNA probes for the 3'part of FVIII gene (exons 14-26 ).In two related severe patients without inhibitor a deletion removesthe exon 26; the gene lesion has been confirmed with several restriction enzymes and has been shown by densitometry of the autoradiographic pattern in a woman of the same family. The complete deletionof the exon 26 has been described by Gitschier et al. in a patient with inhibitor. Thus the comparison of the end points of the two deletions could help to define the mechanism originating these gene lesions and the relation between gene lesions and the presence of antibody.In a patient with severe Haemophilia and without inhibitor a mutation removing the TaqI site in the exon 24 and originating an abnormal band of 4.2 Kb has been found. A C→T transition in this TaqI site, originating a nonsense codon and a new Hindlll site, has been reported by Gitschier et al in a patient presenting inhibitor. The DNA from our patient tested with Hindlll shows a normal pattern thus indicating a C→T transition in the antisense strand. This mutation should causean aminoacid change (CGA→CAA, Arg→Gln) possiblyresponsible for the FVIII inactivation but that does not remove theantigenic determinants present in the COOH terminal part of FVIII.In addition the same mutation has been observed in an unrelated (asdemonstrated by RFLPs analysis) Italian haemophilic patient confirming the observation of Youssoufian et al that TaqI sites are mutational hot spots in FVIII gene.
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Antonarakis, E. "The Molecular Genetics of Hemophilia A Stylianos." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643980.
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Hemophilia A is a common X linked hereditary disorder of blood coagulation due to deficiency of factor 8. The gene for factor 8 has been cloned and characterized (Nature 312:326-342, 1984). It is divided into 26 exons and 25 introns and spans 186 kb of DNA. The CGNA is 9 kb and codes for 2351 amino acids. The first 19 amino acids comprise the secretory leader peptide and the mature excreted polypeptide consists of 2332 amino acids. The nucleotide sequence of the exons and the exon-intron junctions is known and the complete amino acid sequence has been deducedSeveral laboratories have used cloned factor 8 DNA sequences as probes to characterized mutations that are responsible for hemophilia A in certain pedigrees. These mutations have been characterized by restriction analysis, oligonucleotide hybridization, cloning and sequencing of DNA from appropriate patientsIn about 500 patients with hemophilia A examined, the molecular defect has been recognized in 39. Both gross alterations (mainly deletions) and point mutations of the factor 8 gene have been found.A total of 19 different deletions have been observed. No two unrelated pedigrees share the same exact deletion.The size of the deleted DNA varies from 1.5 kb to more than 210 kb. All but one of these deletions are associated with severe hemophilia A. A deletion of 6 kb that contains exon 22 only is associated with moderate hemophilia. Some deletions are present in patients with inhibitors to factor 8. No correlation of the size or the position of the deletions can be found with the presence of inhibitors to factor 8.A total of 20 point mutations have been characterized. All are recognized by restriction analysis and involve Taq I sites. All are mutations of CpG dinucleotides and generate nonsense or missence codons. Unrelated pedigrees have the same single nucleotide change because of independent origin of the same mutation. In many instances de novo occurrence of a point mutation has been observed. CpG dinucleotides are hot spots for mutation to TG or CA presumably because of spontaneous deamination of methylcytosine. Some point mutations are present in patients with inhibitors but no correlation of the site of mutation and inhibitor formation has been found. The nonsense mutations are present in patients with severe hemophilia A. A missense mutation (Arg Gin) in exon 26 was found in a patient with mild hemophilia while another Arg Gin mutation in exon 24 has been observed in a patient with severe disease. The creation of a donor splice site in IVS 4 of factor 8 gene has been observed in a patient with mild hemophilia.Few DNA polymorphisms within the factor 8 gene and two other closely linked polymorphisms have been used for carrier detection and prenatal diagnosis of hemophilia A. These DNA markers are useful in more than 90% of families at risk for hemophilia A.The author thanks Drs. Gitschier, Din, Olek, Pirastou, Lawn for communication of their data prior to publication.The hemophilia project at Johns Hopkins was supported by an Institutional grant and NIH grant to S.S.A. and Haig H. Kazazian, Jr.