title: Viable nonsense mutants for the essential gene SUP45 of Saccharomyces cerevisiae.
abstract: 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 degrees 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.
authors.affiliation: Université de Rennes 1, CNRS UMR 6061, IFR 97, France. smoskalenko@hotmail.com
authors.forename: Svetlana E
authors.initials: SE
authors.lastname: Moskalenko
authors.forename: Svetlana V
authors.initials: SV
authors.lastname: Chabelskaya
authors.forename: Sergei G
authors.initials: SG
authors.lastname: Inge-Vechtomov
authors.forename: Michel
authors.initials: M
authors.lastname: Philippe
authors.forename: Galina A
authors.initials: GA
authors.lastname: Zhouravleva
mesh_terms: D000483:Alleles; D018389:Codon, Nonsense / Q000235:genetics*; D018388:Codon, Terminator / Q000235:genetics; D020043:Genes, Essential / Q000235:genetics*; D005800:Genes, Fungal / Q000235:genetics*; D005804:Genes, Lethal / Q000235:genetics; D008540:Meiosis / Q000235:genetics; D010454:Peptide Termination Factors; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics*; D013489:Suppression, Genetic / Q000235:genetics
chemical_list: D018389:Codon, Nonsense; D018388:Codon, Terminator; D010454:Peptide Termination Factors; C080775:SUP45 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins