Mutations in a gene encoding the alpha subunit of a Saccharomyces cerevisiae G protein indicate a role in mating pheromone signaling.
Mutations which allowed conjugation by Saccharomyces cerevisiae cells lacking a mating pheromone receptor gene were selected. One of the genes defined by such mutations was isolated from a yeast genomic library by complementation of a temperature-sensitive mutation and is identical to the gene GPA1 (also known as SCG1), recently shown to be highly homologous to genes encoding the alpha subunits of mammalian G proteins. Physiological analysis of temperature-sensitive gpa1 mutations suggests that the encoded G protein is involved in signaling in response to mating pheromones. Mutational disruption of G-protein activity causes cell-cycle arrest in G1, deposition of mating-specific cell surface agglutinins, and induction of pheromone-specific mRNAs, all of which are responses to pheromone in wild-type cells. In addition, mutants can conjugate without the benefit of mating pheromone or pheromone receptor. A model is presented where the activated G protein has a negative impact on a constitutive signal which normally keeps the pheromone response repressed.
D000373:Agglutinins / Q000378:metabolism; D003227:Conjugation, Genetic; D005656:Fungal Proteins / Q000235:genetics / Q000502:physiology*; D019204:GTP-Binding Proteins / Q000235:genetics / Q000502:physiology*; D009154:Mutation; D010641:Phenotype; D010675:Pheromones / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000502:physiology*; D014158:Transcription, Genetic; D014161:Transduction, Genetic
D000373:Agglutinins; D005656:Fungal Proteins; D010675:Pheromones; D019204:GTP-Binding Proteins