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Galina A Zhouravleva - One of the best experts on this subject based on the ideXlab platform.
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The Translation Termination Factor eRF1 (Sup45p) of Saccharomyces cerevisiae is required for pseudohyphal growth and invasion.
FEMS yeast research, 2015Co-Authors: Alexandra Petrova, Svetlana V Chabelskaya, Denis Kiktev, O. M. Zemlyanko, Svetlana Moskalenko, Olga Leonidovna Askinazi, Galina A ZhouravlevaAbstract:Mutations in the essential genes SUP45 and SUP35, encoding yeast Translation Termination Factors eRF1 and eRF3, respectively, lead to a wide range of phenotypes and affect various cell processes. In this work, we show that nonsense and missense mutations in the SUP45, but not the SUP35, gene abolish diploid pseudohyphal and haploid invasive growth. Missense mutations that change phosphorylation sites of Sup45 protein do not affect the ability of yeast strains to form pseudohyphae. Deletion of the C-terminal part of eRF1 did not lead to impairment of filamentation. We show a correlation between the filamentation defect and the budding pattern in sup45 strains. Inhibition of Translation with specific antibiotics causes a significant reduction in pseudohyphal growth in the wild-type strain, suggesting a strong correlation between Translation and the ability for filamentous growth. Partial restoration of pseudohyphal growth by addition of exogenous cAMP assumes that sup45 mutants are defective in the cAMP-dependent pathway that control filament formation.
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The paradox of viable sup45 STOP mutations: a necessary equilibrium between Translational readthrough, activity and stability of the protein.
Molecular Genetics and Genomics, 2009Co-Authors: Denis Kiktev, Svetlana Moskalenko, Jean-pierre Rousset, Olga Murina, Agnès Baudin-baillieu, Galina A ZhouravlevaAbstract:The mechanisms leading to non-lethality of nonsense mutations in essential genes are poorly understood. Here, we focus on the Factors influencing viability of yeast cells bearing premature Termination codons (PTCs) in the essential gene SUP45 encoding Translation Termination Factor eRF1. Using a dual reporter system we compared readthrough efficiency of the natural Termination codon of SUP45 gene, spontaneous sup45-n (nonsense) mutations, nonsense mutations obtained by site-directed mutagenesis (76Q --> TAA, 242R --> TGA, 317L --> TAG). The nonsense mutations in SUP45 gene were shown to be situated in moderate contexts for readthrough efficiency. We showed that readthrough efficiency of some of the mutations present in the sup45 mutants is not correlated with full-length Sup45 protein amount. This resulted from modification of both sup45 mRNA stability which varies 3-fold among sup45-n mutants and degradation rate of mutant Sup45 proteins. Our results demonstrate that some substitutions in the place of PTCs decrease Sup45 stability. The viability of sup45 nonsense mutants is therefore supported by diverse mechanisms that control the final amount of functional Sup45 in cells.
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Viable nonsense mutants for the SUP45 gene in the yeast Saccharomyces cerevisiae are lethal at increased temperature
Russian Journal of Genetics, 2007Co-Authors: Galina A Zhouravleva, S. E. Moskalenko, Olga Murina, S G Inge-vechtomovAbstract:Nonlethal nonsense mutations obtained earlier in the essential gene SUP45 encoding the Translation Termination Factor eRF1 in the yeast Saccharomyces cerevisiae were further characterized. Strains carrying these mutations retain the viability, since the full-length eRF1 protein is present in these strains, although in decreased amounts as compared to wild-type cells, together with a trucated eRF1. All nonsense mutations are likely to be located in a weak Termination context, because a change in the stop codon UGAA (in the case of mutation sup45-107 ) to UAGA ( sup45-107.2 ) led to the alteration of the local context from a weak to strong and to the lethality of the strain carrying sup45-107.2 . All nonsense mutations studied are characterized by thermosensitivity expressed as cell mortality after cultivation at 37°C. When grown under nonpermissive conditions (37°C), cells of nonsense mutants sup45-104, sup45-105 , and sup45-107 display a decrease in the amount of the truncated eRF1 protein without reduction in the amount of the full-length eRF1 protein. The results of this study suggest that the N-terminal eRF1 fragment is indispensable for cell viability of nonsense mutants due to the involvement in Termination of Translation.
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Evolution of Translation Termination Factor eRF3: is GSPT2 generated by retrotransposition of GSPT1's mRNA?
IUBMB life, 2006Co-Authors: Galina A Zhouravleva, V. V. Schepachev, A. V. Petrova, Oleg V. Tarasov, Sergey G. Inge-vechtomovAbstract:Two release Factors (eRF1 and eRF3) are responsible for correct Termination of Translation in eukaryotes. While the structure and functions of different domains of eRF1 have been sufficiently characterized, the role of eRF3 in Translation Termination remains unclear. Moreover, the N-terminal domain of eRF3, which is dispensable for Termination, is highly divergent. Mammalian eRF3 exists in two isotypes, eRF3a and eRF3b, encoded by genes GSPT1 and GSPT2, respectively. Here we propose that GSPT2 originated through retrotransposition of processed GSPT1 transcript into the genome. Comparison of the 5' non-coding sequences of both genes revealed existence of potential promoter element in 5'UTR of GSPT1 which we suppose to be responsible for GSPT2 transcription.
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Nonsense mutations in the essential gene SUP35 of Saccharomyces cerevisiae are non-lethal.
Molecular Genetics and Genomics, 2004Co-Authors: Svetlana V Chabelskaya, Sergei G Inge-vechtomov, Michel Philippe, Denis Kiktev, Galina A ZhouravlevaAbstract:In the present work we have characterized for the first time non-lethal nonsense mutations in the essential gene SUP35, which codes for the Translation Termination Factor eRF3 in Saccharomyces cerevisiae. The screen used was based on selection for simultaneous suppression of two auxotrophic nonsense mutations. Among 48 mutants obtained, sixteen were distinguished by the production of a reduced amount of eRF3, suggesting the appearance of nonsense mutations. Fifteen of the total mutants were sequenced, and the presence of nonsense mutations was confirmed for nine of them. Thus a substantial fraction of the sup35 mutations recovered are nonsense mutations located in different regions of SUP35, and such mutants are easily identified by the fact that they express reduced amounts of eRF3. Nonsense mutations in the SUP35 gene do not lead to a decrease in levels of SUP35 mRNA and do not influence the steady-state level of eRF1. The ability of these mutations to complement SUP35 gene disruption mutations in different genetic backgrounds and in the absence of any tRNA suppressor mutation was demonstrated. The missense mutations studied, unlike nonsense mutations, do not decrease steady-state amounts of eRF3.
Lev L. Kisselev - One of the best experts on this subject based on the ideXlab platform.
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Three distinct peptides from the N domain of Translation Termination Factor eRF1 surround stop codon in the ribosome.
RNA (New York N.Y.), 2010Co-Authors: Konstantin Bulygin, P. M. Kolosov, Ludmila Frolova, Lev L. Kisselev, Yulia S. Khairulina, Aliya G. Ven'yaminova, Dmitri Graifer, Yuri N. Vorobjev, Galina G. KarpovaAbstract:To study positioning of the polypeptide release Factor eRF1 toward a stop signal in the ribosomal decoding site, we applied photoactivatable mRNA analogs, derivatives of oligoribonucleotides. The human eRF1 peptides cross-linked to these short mRNAs were identified. Cross-linkers on the guanines at the second, third, and fourth stop signal positions modified fragment 31–33, and to lesser extent amino acids within region 121–131 (the ‘‘YxCxxxF loop’’) in the N domain. Hence, both regions are involved in the recognition of the purines. A cross-linker at the first uridine of the stop codon modifies Val66 near the NIKS loop (positions 61–64), and this region is important for recognition of the first uridine of stop codons. Since the N domain distinct regions of eRF1 are involved in a stop-codon decoding, the eRF1 decoding site is discontinuous and is not of ‘‘protein anticodon’’ type. By molecular modeling, the eRF1 molecule can be fitted to the A site proximal to the P-site-bound tRNA and to a stop codon in mRNA via a large conformational change to one of its three domains. In the simulated eRF1 conformation, the YxCxxxF motif and positions 31–33 are very close to a stop codon, which becomes also proximal to several parts of the C domain. Thus, in the A-site-bound state, the eRF1 conformation significantly differs from those in crystals and solution. The model suggested for eRF1 conformation in the ribosomal A site and cross-linking data are compatible.
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Interface of the interaction of the middle domain of human Translation Termination Factor eRF1 with eukaryotic ribosomes
Molecular Biology, 2008Co-Authors: Elena Ivanova, Elena Alkalaeva, P. M. Kolosov, Berry Birdsall, Vladimir I. Polshakov, Lev L. KisselevAbstract:Translation Termination in eukaryotes is governed by the interaction of two, class 1 and class 2, polypeptide chain release Factors with the ribosome. The middle (M) domain of the class 1 Factor eRF1 contains the strictly conserved GGQ motif and is involved in hydrolysis of the peptidyl-tRNA ester bond in the peptidyl transferase center of the large ribosome subunit. Heteronuclear NMR spectroscopy was used to map the interaction interface of the M domain of human eRF1 with eukaryotic ribosomes. The protein was found to specifically interact with the 60S subunit, since no interaction was detected with the 40S subunit. The amino acid residues forming the interface mostly belong to long helix α1 of the M domain. Some residues adjacent to α1 and belonging to strand β5 and short helices α2 and α3 are also involved in the protein-ribosome contact. The functionally inactive G183A mutant interacted with the ribosome far more weakly as compared with the wild-type eRF1. The interaction interfaces of the two proteins were nonidentical. It was concluded that long helix α1 is functionally important and that the conformational flexibility of the GGQ loop is essential for the tight protein-ribosome contact.
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Role of the individual domains of Translation Termination Factor eRF1 in GTP binding to eRF3
Proteins, 2008Co-Authors: A V Kononenko, Vladimir A. Mitkevich, Alexander A. Makarov, V. I. Dubovaya, Peter M. Kolosov, Lev L. KisselevAbstract:Eukaryotic Translational Termination is triggered by polypeptide release Factors eRF1, eRF3, and one of the three stop codons at the ribosomal A-site. Isothermal titration calorimetry shows that (i) the separated MC, M, and C domains of human eRF1 bind to eRF3; (ii) GTP binding to eRF3 requires complex formation with either the MC or M + C domains; (iii) the M domain interacts with the N and C domains; (iv) the MC domain and Mg2+ induce GTPase activity of eRF3 in the ribosome. We suggest that GDP binding site of eRF3 acquires an ability to bind γ-phosphate of GTP if altered by cooperative action of the M and C domains of eRF1. Thus, the stop-codon decoding is associated with the N domain of eRF1 while the GTPase activity of eRF3 is controlled by the MC domain of eRF1 demonstrating a substantial structural uncoupling of these two activities though functionally they are interrelated. Proteins 2008. © 2007 Wiley-Liss, Inc.
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how does euplotes Translation Termination Factor erf1 fail to recognize the uga stop codon
Molecular Biology, 2007Co-Authors: Sergey Lekomtsev, P. M. Kolosov, L. Bidou, Jean-pierre Rousset, Yu L Frolova, Lev L. KisselevAbstract:Class 1 eukaryotic release Factor 1 (eRF1) recognizes all three stop codons (UAA, UAG, and UGA) in standard-code organisms. In some ciliates with variant genetic codes, one or two stop codons are used to encode amino acids and are not recognized by eRF1; e.g., UAA and UAG are reassigned to Gln in Stylonychia and UGA is reassigned to Cys in Euplotes. Stop codon recognition is due to the N-terminal domain of eRF1 in standard-code organisms. Since variant-code ciliates most likely originate from universal-code ancestors, the N-domain sequence of their eRF1 was assumed to harbor the residues that are responsible for the changes in stop codon recognition specificity. To identify the N-domain regions determining the UGA-only specificity of Euplotes aediculatus eRF1, chimeric proteins were constructed by swapping various N-domain fragments of the E. aediculatus for their human counterparts; the MC domain was from human eRF1. Functional analysis of the chimeric eRF1 in vivo revealed two regions (residues 38–50 and 123–145) restricting the E. aediculatus eRF1 specificity to UAR. The change in stop codon recognition specificity of eRF1 was regarded as the first step in the origin of the variant genetic code in ciliates.
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NMR assignments of the C-terminal domain of human polypeptide release Factor eRF1
Biomolecular NMR assignments, 2007Co-Authors: Alexey B. Mantsyzov, P. M. Kolosov, Lev L. Kisselev, Elena Ivanova, Berry Birdsall, Vladimir I. PolshakovAbstract:We report NMR assignments of the protein backbone of the C-terminal domain (163 a.a.) of human class 1 Translation Termination Factor eRF1. It was found that several protein loop residues exist in two slowly interconverting conformational states.
Sergei G Inge-vechtomov - One of the best experts on this subject based on the ideXlab platform.
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Nonsense mutations in the essential gene SUP35 of Saccharomyces cerevisiae are non-lethal.
Molecular Genetics and Genomics, 2004Co-Authors: Svetlana V Chabelskaya, Sergei G Inge-vechtomov, Michel Philippe, Denis Kiktev, Galina A ZhouravlevaAbstract:In the present work we have characterized for the first time non-lethal nonsense mutations in the essential gene SUP35, which codes for the Translation Termination Factor eRF3 in Saccharomyces cerevisiae. The screen used was based on selection for simultaneous suppression of two auxotrophic nonsense mutations. Among 48 mutants obtained, sixteen were distinguished by the production of a reduced amount of eRF3, suggesting the appearance of nonsense mutations. Fifteen of the total mutants were sequenced, and the presence of nonsense mutations was confirmed for nine of them. Thus a substantial fraction of the sup35 mutations recovered are nonsense mutations located in different regions of SUP35, and such mutants are easily identified by the fact that they express reduced amounts of eRF3. Nonsense mutations in the SUP35 gene do not lead to a decrease in levels of SUP35 mRNA and do not influence the steady-state level of eRF1. The ability of these mutations to complement SUP35 gene disruption mutations in different genetic backgrounds and in the absence of any tRNA suppressor mutation was demonstrated. The missense mutations studied, unlike nonsense mutations, do not decrease steady-state amounts of eRF3.
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Characterization of Missense Mutations in the SUP45 Gene of Saccharomyces cerevisiaeEncoding Translation Termination Factor eRF1*
Russian Journal of Genetics, 2004Co-Authors: S. E. Moskalenko, Svetlana V Chabelskaya, Galina A Zhouravleva, M. Y. Soom, K. V. Volkov, O. M. Zemlyanko, M. Philippe, L. N. Mironova, Sergei G Inge-vechtomovAbstract:Collection of missense mutations in the SUP45 gene of Saccharomyces cerevisiae encoding Translation Termination Factor eRF1 has been obtained by different approaches. It has been shown that most of isolated mutations cause amino acid substitutions in the N-terminal part of eRF1 and do not decrease the eRF1 amount. Most of mutations studied do not abolish eRF1–eRF3 interaction. The role of the N-terminal part of eRF1 in stop codon recognition is discussed.
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Characterization of missense mutations in the SUP45 gene of Saccharomyces cerevisiae encoding Translation Termination Factor eRF1
Genetika, 2004Co-Authors: Svetlana Moskalenko, Svetlana V Chabelskaya, Galina A Zhouravleva, Michel Philippe, M. Y. Soom, K. V. Volkov, O. M. Zemlyanko, L. N. Mironova, Sergei G Inge-vechtomovAbstract:Collection of missense mutations in the SUP45 gene of Saccharomyces cerevisiae encoding Translation Termination Factor eRF1 has been obtained by different approaches. It has been shown that most of isolated mutations cause amino acid substitutions in the N-terminal part of eRF1 and do not decrease the eRF1 amount. Most of mutations studied do not abolish eRF1–eRF3 interaction. The role of the N-terminal part of eRF1 in stop codon recognition is discussed.
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Suppression of Nonsense and Frameshift Mutations Obtained by Different Methods for Inactivating the Translation Termination Factor eRF3 in Yeast Saccharomyces cerevisiae
Russian Journal of Genetics, 2003Co-Authors: S. P. Zadorsky, A. S. Borchsenius, Yu. V. Sopova, V. A. Starzev, Sergei G Inge-vechtomovAbstract:Mutations in genes of omnipotent nonsense suppressors SUP35 and SUP45 in yeast Saccharomyces cerevisiae encoding Translation Termination Factors eRF3 and eRF1, respectively, and prionization of the eRF3 protein may lead to the suppression of some frameshift mutations (CPC mutations). Partial inactivation of the Translation Termination Factor eRF3 was studied in strains with unstable genetically modified prions and also in transgenic yeast S. cerevisiae strains with the substitution of the indigenous SUP35 gene for its homolog from Pichia methanolica or for a recombinant S. cerevisiae SUP35 gene. It was shown that this partial inactivation leads not only to nonsense suppression, but also to suppression of the frameshift lys2-90 mutation. Possible reasons for the correlation between nonsense suppression and suppression of the CPC lys2-90 mutation and mechanisms responsible for the suppression of CPC mutations during inactivation of Translation Termination Factors are discussed.
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Viable nonsense mutants for the essential gene SUP45 of Saccharomyces cerevisiae
BMC Molecular Biology, 2003Co-Authors: Svetlana E Moskalenko, Svetlana V Chabelskaya, Sergei G Inge-vechtomov, Michel Philippe, Galina A ZhouravlevaAbstract:Background Termination of protein synthesis in eukaryotes involves at least two polypeptide release Factors (eRFs) – eRF1 and eRF3. The highly conserved Translation Termination Factor eRF1 in Saccharomyces cerevisiae is encoded by the essential gene SUP45 . Results We have isolated five sup45-n (n from nonsense) mutations that cause nonsense substitutions in the following amino acid positions of eRF1: Y53 → UAA, E266 → UAA, L283 → UAA, L317 → UGA, E385 → UAA. We found that full-length eRF1 protein is present in all mutants, although in decreased amounts. All mutations are situated in a weak Termination context. All these sup45-n mutations are viable in different genetic backgrounds, however their viability increases after growth in the absence of wild-type allele. Any of sup45-n mutations result in temperature sensitivity (37°C). Most of the sup45-n mutations lead to decreased spore viability and spores bearing sup45-n mutations are characterized by limited budding after germination leading to formation of microcolonies of 4–20 cells. Conclusions Nonsense mutations in the essential gene SUP45 can be isolated in the absence of tRNA nonsense suppressors.
Svetlana V Chabelskaya - One of the best experts on this subject based on the ideXlab platform.
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The Translation Termination Factor eRF1 (Sup45p) of Saccharomyces cerevisiae is required for pseudohyphal growth and invasion.
FEMS yeast research, 2015Co-Authors: Alexandra Petrova, Svetlana V Chabelskaya, Denis Kiktev, O. M. Zemlyanko, Svetlana Moskalenko, Olga Leonidovna Askinazi, Galina A ZhouravlevaAbstract:Mutations in the essential genes SUP45 and SUP35, encoding yeast Translation Termination Factors eRF1 and eRF3, respectively, lead to a wide range of phenotypes and affect various cell processes. In this work, we show that nonsense and missense mutations in the SUP45, but not the SUP35, gene abolish diploid pseudohyphal and haploid invasive growth. Missense mutations that change phosphorylation sites of Sup45 protein do not affect the ability of yeast strains to form pseudohyphae. Deletion of the C-terminal part of eRF1 did not lead to impairment of filamentation. We show a correlation between the filamentation defect and the budding pattern in sup45 strains. Inhibition of Translation with specific antibiotics causes a significant reduction in pseudohyphal growth in the wild-type strain, suggesting a strong correlation between Translation and the ability for filamentous growth. Partial restoration of pseudohyphal growth by addition of exogenous cAMP assumes that sup45 mutants are defective in the cAMP-dependent pathway that control filament formation.
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Nonsense mutations in the essential gene SUP35 of Saccharomyces cerevisiae are non-lethal.
Molecular Genetics and Genomics, 2004Co-Authors: Svetlana V Chabelskaya, Sergei G Inge-vechtomov, Michel Philippe, Denis Kiktev, Galina A ZhouravlevaAbstract:In the present work we have characterized for the first time non-lethal nonsense mutations in the essential gene SUP35, which codes for the Translation Termination Factor eRF3 in Saccharomyces cerevisiae. The screen used was based on selection for simultaneous suppression of two auxotrophic nonsense mutations. Among 48 mutants obtained, sixteen were distinguished by the production of a reduced amount of eRF3, suggesting the appearance of nonsense mutations. Fifteen of the total mutants were sequenced, and the presence of nonsense mutations was confirmed for nine of them. Thus a substantial fraction of the sup35 mutations recovered are nonsense mutations located in different regions of SUP35, and such mutants are easily identified by the fact that they express reduced amounts of eRF3. Nonsense mutations in the SUP35 gene do not lead to a decrease in levels of SUP35 mRNA and do not influence the steady-state level of eRF1. The ability of these mutations to complement SUP35 gene disruption mutations in different genetic backgrounds and in the absence of any tRNA suppressor mutation was demonstrated. The missense mutations studied, unlike nonsense mutations, do not decrease steady-state amounts of eRF3.
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Characterization of Missense Mutations in the SUP45 Gene of Saccharomyces cerevisiaeEncoding Translation Termination Factor eRF1*
Russian Journal of Genetics, 2004Co-Authors: S. E. Moskalenko, Svetlana V Chabelskaya, Galina A Zhouravleva, M. Y. Soom, K. V. Volkov, O. M. Zemlyanko, M. Philippe, L. N. Mironova, Sergei G Inge-vechtomovAbstract:Collection of missense mutations in the SUP45 gene of Saccharomyces cerevisiae encoding Translation Termination Factor eRF1 has been obtained by different approaches. It has been shown that most of isolated mutations cause amino acid substitutions in the N-terminal part of eRF1 and do not decrease the eRF1 amount. Most of mutations studied do not abolish eRF1–eRF3 interaction. The role of the N-terminal part of eRF1 in stop codon recognition is discussed.
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Characterization of missense mutations in the SUP45 gene of Saccharomyces cerevisiae encoding Translation Termination Factor eRF1
Genetika, 2004Co-Authors: Svetlana Moskalenko, Svetlana V Chabelskaya, Galina A Zhouravleva, Michel Philippe, M. Y. Soom, K. V. Volkov, O. M. Zemlyanko, L. N. Mironova, Sergei G Inge-vechtomovAbstract:Collection of missense mutations in the SUP45 gene of Saccharomyces cerevisiae encoding Translation Termination Factor eRF1 has been obtained by different approaches. It has been shown that most of isolated mutations cause amino acid substitutions in the N-terminal part of eRF1 and do not decrease the eRF1 amount. Most of mutations studied do not abolish eRF1–eRF3 interaction. The role of the N-terminal part of eRF1 in stop codon recognition is discussed.
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Viable nonsense mutants for the essential gene SUP45 of Saccharomyces cerevisiae
BMC Molecular Biology, 2003Co-Authors: Svetlana E Moskalenko, Svetlana V Chabelskaya, Sergei G Inge-vechtomov, Michel Philippe, Galina A ZhouravlevaAbstract:Background Termination of protein synthesis in eukaryotes involves at least two polypeptide release Factors (eRFs) – eRF1 and eRF3. The highly conserved Translation Termination Factor eRF1 in Saccharomyces cerevisiae is encoded by the essential gene SUP45 . Results We have isolated five sup45-n (n from nonsense) mutations that cause nonsense substitutions in the following amino acid positions of eRF1: Y53 → UAA, E266 → UAA, L283 → UAA, L317 → UGA, E385 → UAA. We found that full-length eRF1 protein is present in all mutants, although in decreased amounts. All mutations are situated in a weak Termination context. All these sup45-n mutations are viable in different genetic backgrounds, however their viability increases after growth in the absence of wild-type allele. Any of sup45-n mutations result in temperature sensitivity (37°C). Most of the sup45-n mutations lead to decreased spore viability and spores bearing sup45-n mutations are characterized by limited budding after germination leading to formation of microcolonies of 4–20 cells. Conclusions Nonsense mutations in the essential gene SUP45 can be isolated in the absence of tRNA nonsense suppressors.
Sergey G. Inge-vechtomov - One of the best experts on this subject based on the ideXlab platform.
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N-terminal extension of Saccharomyces cerevisiae Translation Termination Factor eRF3 influences the suppression efficiency of sup35 mutations.
FEMS yeast research, 2007Co-Authors: K. V. Volkov, Kirill V. Osipov, Igor Valouev, Sergey G. Inge-vechtomov, L. N. MironovaAbstract:The eukaryotic Translation Termination Factor eRF3 stimulates release of nascent polypeptides from the ribosome in a GTP-dependent manner. In most eukaryotes studied, eRF3 consists of an essential, conserved C-terminal domain and a nonessential, nonconserved N-terminal extension. However, in some species, this extension is required for efficient Termination. Our data show that the N-terminal extension of Saccharomyces cerevisiae eRF3 also participates in regulation of Termination efficiency, but acts as a negative Factor, increasing nonsense suppression efficiency in sup35 mutants containing amino acid substitutions in the C-terminal domain of the protein.
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Evolution of Translation Termination Factor eRF3: is GSPT2 generated by retrotransposition of GSPT1's mRNA?
IUBMB life, 2006Co-Authors: Galina A Zhouravleva, V. V. Schepachev, A. V. Petrova, Oleg V. Tarasov, Sergey G. Inge-vechtomovAbstract:Two release Factors (eRF1 and eRF3) are responsible for correct Termination of Translation in eukaryotes. While the structure and functions of different domains of eRF1 have been sufficiently characterized, the role of eRF3 in Translation Termination remains unclear. Moreover, the N-terminal domain of eRF3, which is dispensable for Termination, is highly divergent. Mammalian eRF3 exists in two isotypes, eRF3a and eRF3b, encoded by genes GSPT1 and GSPT2, respectively. Here we propose that GSPT2 originated through retrotransposition of processed GSPT1 transcript into the genome. Comparison of the 5' non-coding sequences of both genes revealed existence of potential promoter element in 5'UTR of GSPT1 which we suppose to be responsible for GSPT2 transcription.
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Yeast prions, mammalian amyloidoses, and the problem of proteomic networks
Russian Journal of Genetics, 2006Co-Authors: A P Galkin, L. N. Mironova, G. A. Zhuravleva, Sergey G. Inge-vechtomovAbstract:Prion proteins are infective amyloids and cause several neurodegenerative diseases in humans and animals. In yeasts, prions are detected as the cytoplasmic heritable determinants of a protein nature. Yeast prion [PSI], which results from a conformational rearrangement and oligomerization of Translation Termination Factor eRF3, is used as an example to consider the structural-functional relationships in a potentially prion molecule, specifics of its evolution, and interactions with other prions, which form so-called prion networks. In addition, the review considers the results of modeling mammalian prion diseases and other amyloidoses in yeast cells. A hypothesis of proteomic networks is proposed by analogy with prion networks, involving interactions of different amyloids in mammals.
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Prion variant maintained only at high levels of the Hsp104 disaggregase
Current Genetics, 2006Co-Authors: Andrey S. Borchsenius, Sergey G. Inge-vechtomov, Susanne Müller, Gary P. Newnam, Yury O. ChernoffAbstract:The yeast prion [ PSI ^ + ] is a self-perpetuating aggregated isoform of the Translation Termination Factor Sup35. [ PSI ^ + ] propagation is promoted by moderate levels and antagonized by high levels of the chaperone Hsp104. In agreement with the model postulating that excess Hsp104 acts on [ PSI ^ + ] by disaggregating prion polymers, we show that an increase in Sup35 levels, accompanied by an increase in size of prion aggregates, also partially protects [ PSI ^ + ] from elimination by excess Hsp104. Despite retention of [ PSI ^ + ], excess Hsp104 decreases toxicity of overproduced Sup35 in [ PSI ^ + ] strains. A heritable variant of [ PSI ^ + ], which has been isolated and is maintained only in the presence of increased levels of Hsp104, is characterized by an abnormally large aggregate size, and exhibits an altered response to overproduction of the Hsp70 chaperone Ssa1. These features resemble the previously described prion generated by a deletion derivative of Sup35, but are not associated with any sequence alteration and are controlled exclusively at the protein level. Our data provide a proof of the existence of conditionally stable prion variants maintained only at altered levels of Hsps, that could in principle be beneficial if the normal cellular function of a prion protein becomes detrimental to the cell in such conditions.
