Control of adaptation to mating pheromone by G protein beta subunits of Saccharomyces cerevisiae

• Published in: Genetics (Austin) Vol. 138; no. 4; pp. 1081 - 1092
• Main Authors: Grishin, A.V. (Washington University School of Medicine, St. Louis, MO.), Weiner, J.L, Blumer, K.J
• Format: Journal Article
• Language: English
• Published: United States Genetics Society of America 01.12.1994
• Subjects: ACCOUPLEMENT; ADAPTACION; ADAPTATION; Adaptation, Physiological; Amino Acid Sequence; Base Sequence; COMPOSICION QUIMICA; COMPOSITION CHIMIQUE; COPULA; FENOTIPOS; FEROMONAS; Fungal Proteins - genetics; Fungal Proteins - physiology; GENE; GENES; Genetics; GTP-Binding Protein beta Subunits; GTP-Binding Proteins - physiology; Heterotrimeric GTP-Binding Proteins; Investigations; Mating Factor; Molecular Sequence Data; MUTACION INDUCIDA; MUTANT; MUTANTES; MUTATION PROVOQUEE; NUCLEOTIDE; NUCLEOTIDOS; Peptides - genetics; Peptides - physiology; PHENOTYPE; PHEROMONE; PROTEINAS AGLUTINANTES; PROTEINE DE LIAISON; Proteins; SACCHAROMYCES CEREVISIAE; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - physiology; Saccharomyces cerevisiae Proteins; Signal Transduction; Yeast
• ISSN: 0016-6731; 1943-2631; 1943-2631
• DOI: 10.1093/genetics/138.4.1081

The STE4 gene of the yeast Saccharomyces cerevisiae encodes the beta subunit of a heterotrimeric G protein that mediates response to mating pheromones and influences recovery from pheromone-induced growth arrest. To explore how G(beta) subunits regulate response and recovery (adaptation), we isolated and characterized signaling-defective STE4 alleles (STE4(sd)). STE4(sd) mutations resulted in amino acid substitutions in the N-terminal region of Ste4p, proximal to the first of seven repeat units conserved in G protein beta subunits. Genetic tests indicated that STE4(sd) mutations disrupted functions of Ste4p required for inducing pheromone responses. Wild-type cells that overexpressed STE4(sd) alleles displayed apparently normal initial responses to pheromone as judged by quantitative mating, G1 arrest and transcriptional assays. However, after undergoing initial G1 arrest, wild-type cells overexpressing STE4(sd) a,leles recovered more quickly from division arrest, suggestive of a hyperadaptive phenotype. Because hyperadaptation occurred when STE4(sd) alleles were overexpressed in cells lacking Sst1p (Bar1p), Sst2p or the C-terminal domain of the alpha-factor receptor, this phenotype did not involve three principal modes of adaptation in yeast. However, hyperadaptation was abolished when STE4(sd) mutations were combined in cis with a deletion that removes a segment of Ste4p (residues 310-346) previously implicated in adaptation to pheromone. These results indicate that G beta subunits possess two independent activities, one required for triggering pheromone response and another that promotes adaptation. Potential models for G beta subunit-mediated adaptation are discussed