title: Suppression of a dominant G-protein beta-subunit mutation in yeast by G alpha protein expression.
abstract: SCG1/GPA1, STE4 and STE18 encode the alpha, beta and gamma components of the G protein involved in mating pheromone signal transduction in Saccharomyces cerevisiae. Responses, including G1 arrest and expression of genes such as FUS1, are activated by beta gamma, which is negatively controlled by alpha(GDP). We previously demonstrated that overexpression of Scg1 suppresses responses to alpha factor and that expression of certain hybrids between Scg1 and mammalian G alpha proteins has the same effect and also suppresses growth arrest in an scg1-null mutant. Effects were attributed to sequestration of beta gamma. We now show that effects on growth rate, morphology and FUS1 expression are consistent with this model. The STE4HPL allele causes dominant activation of the response pathway, and is presumed to encode a beta subunit insensitive to control by alpha(GDP). Scg1 overexpression suppresses the growth arrest due to STE4HPL; normal alpha-factor responses and fertility are restored. A model based on sequestration of beta gamma reconciles this result with the apparent paradox that the same level of Scg1 overexpression inhibits responses and mating in wild-type cells. A G alpha i hybrid also restores growth and allows inefficient mating in the STE4HPL strain.
authors.affiliation: Department of Molecular Genetics and Microbiology, University of Massachusetts Medical Center, Worcester 01655.
authors.forename: M
authors.initials: M
authors.lastname: Zhang
authors.forename: D J
authors.initials: DJ
authors.lastname: Tipper
mesh_terms: D002453:Cell Cycle / Q000235:genetics; D005656:Fungal Proteins / Q000096:biosynthesis* / Q000235:genetics*; D044385:GTP-Binding Protein alpha Subunits; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D044387:GTP-Binding Protein beta Subunits; D044388:GTP-Binding Protein gamma Subunits; D019204:GTP-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D016153:Genes, Suppressor; D020962:Heterotrimeric GTP-Binding Proteins; D000072235:Mating Factor; D008565:Membrane Proteins; D009154:Mutation; D010455:Peptides / Q000502:physiology; D011956:Receptors, Cell Surface / Q000235:genetics; D043562:Receptors, G-Protein-Coupled; D051964:Receptors, Mating Factor; D018000:Receptors, Peptide / Q000235:genetics; D043563:Receptors, Pheromone; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D015398:Signal Transduction / Q000502:physiology; D014157:Transcription Factors
chemical_list: C490024:FUS1 protein, S cerevisiae; D005656:Fungal Proteins; D044385:GTP-Binding Protein alpha Subunits; D044387:GTP-Binding Protein beta Subunits; D044388:GTP-Binding Protein gamma Subunits; D008565:Membrane Proteins; D010455:Peptides; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D051964:Receptors, Mating Factor; D018000:Receptors, Peptide; D043563:Receptors, Pheromone; D011993:Recombinant Fusion Proteins; C084294:STE18 protein, S cerevisiae; C081863:STE3 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C067576:Ste4 protein, S cerevisiae; D014157:Transcription Factors; D000072235:Mating Factor; D019204:GTP-Binding Proteins; C084293:GPA1 protein, S cerevisiae; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D020962:Heterotrimeric GTP-Binding Proteins