title: A mutant allele of the SUP45 (SAL4) gene of Saccharomyces cerevisiae shows temperature-dependent allosuppressor and omnipotent suppressor phenotypes.
abstract: Using a plasmid-based termination-read-through assay, the sal4-2 conditional-lethal (temperature-sensitive) allele of the SUP45 (SAL4) gene was shown to enhance the efficiency of the weak ochre suppressor tRNA SUQ5 some 10-fold at 30 degrees C. Additionally, this allele increased the suppressor efficiency of SRM2-2, a weak tRNA(Gln) ochre suppressor, indicating that the allosuppressor phenotype is not SUQ5-specific. A sup+ sal4-2 strain also showed a temperature-dependent omnipotent suppressor phenotype, enhancing readthrough of all three termination codons. Combining the sal4-2 allele with an efficient tRNA nonsense suppressor (SUP4) increased the temperature-sensitivity of that strain, indicating that enhanced nonsense suppressor levels contribute to the conditional-lethality conferred by the sal4-2 allele. However, UGA suppression levels in a sup+ sal4-2 strain following a shift to the non-permissive temperature reached a maximum significantly below that exhibited by a non-temperature sensitive SUP4 suppressor strain. Enhanced nonsense suppression may not therefore be the primary cause of the conditional-lethality of this allele. These data indicate a role for Sup45p in translation termination, and possibly in an additional, as yet unidentified, cellular process.
authors.affiliation: Research School of Biosciences, University of Kent, Canterbury, UK.
authors.forename: I
authors.initials: I
authors.lastname: Stansfield
authors.lastname: Akhmaloka
authors.forename: M F
authors.initials: MF
authors.lastname: Tuite
mesh_terms: D000483:Alleles; D001483:Base Sequence; D003001:Cloning, Molecular; D005800:Genes, Fungal; D005804:Genes, Lethal; D016153:Genes, Suppressor; D008969:Molecular Sequence Data; D009154:Mutation; D010641:Phenotype; D012362:RNA, Transfer, Ser; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D017422:Sequence Analysis, DNA; D013489:Suppression, Genetic; D013696:Temperature
chemical_list: D012362:RNA, Transfer, Ser