Cloning of Saccharomyces cerevisiae STE5 as a suppressor of a Ste20 protein kinase mutant: structural and functional similarity of Ste5 to Far1.
The beta and gamma subunits of the mating response G-protein in the yeast Saccharomyces cerevisiae have been shown to transmit the mating pheromone signal to downstream components of the pheromone response pathway. A protein kinase homologue encoded by the STE20 gene has recently been identified as a potential G beta gamma target. We have searched multicopy plasmid genomic DNA libraries for high gene dosage suppressors of the signal transduction defect of ste20 mutant cells. This screen identified the STE5 gene encoding an essential component of the pheromone signal transduction pathway. We provide genetic evidence for a functional interrelationship between the STE5 gene product and the Ste20 protein kinase. We have sequenced the STE5 gene, which encodes a predicted protein of 917 amino acids and is specifically transcribed in haploid cells. Transcription is slightly induced by treatment of cells with pheromone. Ste5 has homology with Far1, a yeast protein required for efficient mating and the pheromone-inducible inhibition of a G1 cyclin, Cln2. A STE5 multicopy plasmid is able to suppress the signal transduction defect of far1 null mutant cells suggesting that Ste5, at elevated levels, is able functionally to replace Far1. The genetically predicted point of function of Ste5 within the pheromone signalling pathway suggests that Ste5 is involved in the regulation of a G beta gamma-activated protein kinase cascade which links a G-protein coupled receptor to yeast homologues of mitogen-activated protein kinases.
Leberer
E
E
Biotechnology Research Institute, National Research Council of Canada, Montreal, Quebec.
Dignard
D
D
Harcus
D
D
Hougan
L
L
Whiteway
M
M
Thomas
D Y
DY
D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D001483:Base Sequence; D002352:Carrier Proteins; D002453:Cell Cycle; D018797:Cell Cycle Proteins; D003001:Cloning, Molecular; D050756:Cyclin-Dependent Kinase Inhibitor Proteins; D004271:DNA, Fungal; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D005800:Genes, Fungal; D016153:Genes, Suppressor; D047908:Intracellular Signaling Peptides and Proteins; D020930:MAP Kinase Kinase Kinases; D024101:Mitochondrial Proteins; D008969:Molecular Sequence Data; D009154:Mutation; D010940:Plant Proteins / Q000235:genetics*; D010957:Plasmids; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism; D012097:Repressor Proteins; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013329:Structure-Activity Relationship
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D050756:Cyclin-Dependent Kinase Inhibitor Proteins; D004271:DNA, Fungal; C081353:FAR1 protein, S cerevisiae; D005656:Fungal Proteins; D047908:Intracellular Signaling Peptides and Proteins; D024101:Mitochondrial Proteins; D010940:Plant Proteins; D012097:Repressor Proteins; C080321:STE5 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D017346:Protein Serine-Threonine Kinases; D020930:MAP Kinase Kinase Kinases; C078754:STE20 protein, S cerevisiae; D019204:GTP-Binding Proteins