STE50, a novel gene required for activation of conjugation at an early step in mating in Saccharomyces cerevisiae

Mol Gen Genet. 1992 Dec;236(1):145-54. doi: 10.1007/BF00279653.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • Conjugation, Genetic*
  • DNA, Recombinant
  • Fungal Proteins / genetics*
  • GTP-Binding Protein beta Subunits*
  • GTP-Binding Proteins / genetics
  • GTP-Binding Proteins / metabolism
  • Gene Expression
  • Genes, Fungal*
  • Heterotrimeric GTP-Binding Proteins*
  • Molecular Sequence Data
  • Mutation
  • Pheromones / metabolism
  • Saccharomyces cerevisiae / cytology*
  • Saccharomyces cerevisiae Proteins*


  • DNA, Recombinant
  • Fungal Proteins
  • GTP-Binding Protein beta Subunits
  • Pheromones
  • STE50 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Ste4 protein, S cerevisiae
  • GTP-Binding Proteins
  • Heterotrimeric GTP-Binding Proteins

Associated data

  • GENBANK/Z11116