title: STE50, a novel gene required for activation of conjugation at an early step in mating in Saccharomyces cerevisiae.
abstract: A new gene, STE50, which plays an essential role in cell differentiation in Saccharomyces cerevisiae was detected and analysed. STE50 expression is not cell type-specific and its expression in MATa and MAT alpha cells is unaffected by pheromones. When present on a high copy number plasmid, STE50 causes supersensitivity to alpha-pheromone, and increases the level of alpha-pheromone-induced transcription of FUS1 in haploid a cells. Mutants bearing either of the two gene disruptions, ste50-1 or ste50-2, are sterile and have a modulated sensitivity to alpha-pheromone. The overexpression of STE4 (G beta) in wild-type cells elicits a constitutive growth arrest signal, however this phenotype is suppressed by a C-terminal truncation mutation in STE50 (ste50-2). In contrast, the constitutive activation of the pheromone response pathway caused by disruption of GPA1 (G alpha) is not suppressed in ste50-2 mutants. The ste50-2 mutation partially suppresses the desensitisation defect of the sst2-1 mutation, and the resulting ste50-2 sst2-1 mutants restore fertility. Our results indicate that the ste50-2 mutant may have a defect in adaptation (hyperadaptation), and suggest a possible interaction of STE50-2 with the G alpha subunit of the G protein.
authors.affiliation: Institut für Mikrobiologie, Heinrich-Heine-Universität, Düsseldorf 1, FRG.
authors.forename: M R
authors.initials: MR
authors.lastname: Rad
authors.forename: G
authors.initials: G
authors.lastname: Xu
authors.forename: C P
authors.initials: CP
authors.lastname: Hollenberg
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D003227:Conjugation, Genetic; D004274:DNA, Recombinant; D005656:Fungal Proteins / Q000235:genetics*; D044387:GTP-Binding Protein beta Subunits; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D005800:Genes, Fungal; D020962:Heterotrimeric GTP-Binding Proteins; D008969:Molecular Sequence Data; D009154:Mutation; D010675:Pheromones / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology*; D029701:Saccharomyces cerevisiae Proteins
chemical_list: D004274:DNA, Recombinant; D005656:Fungal Proteins; D044387:GTP-Binding Protein beta Subunits; D010675:Pheromones; C079506:STE50 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C067576:Ste4 protein, S cerevisiae; D019204:GTP-Binding Proteins; D020962:Heterotrimeric GTP-Binding Proteins