Coupling of cell identity to signal response in yeast: interaction between the alpha 1 and STE12 proteins.
In Saccharomyces cerevisiae, the STE12 protein mediates transcriptional induction of cell type-specific genes in response to pheromones. STE12 binds in vitro to the pheromone response elements (PREs) present in the control region of a-specific genes. STE12 is also required for transcription of alpha-specific genes, but there is no evidence that it binds directly to these genes. Instead, the MAT alpha-encoded protein alpha 1 and the MCM1 product bind to the DNA element that is responsible for alpha-specific and a-factor-inducible expression. To explore the role of STE12 in the pheromone induction of alpha-specific genes, we cloned STE12 and MAT alpha 1 homologs from the related yeast Kluyveromyces lactis. The K. lactis STE12 protein did not cooperate with the S. cerevisiae alpha 1 protein to promote the overall mating process or the induction of transcription of an alpha-specific gene. However, introduction of both K. lactis STE12 along with K. lactis alpha 1 did restore mating, suggesting that an interaction between STE12 and alpha 1 is important for alpha-specific gene activation. We also show that bacterially expressed STE12 and alpha 1 are able to form a complex in vitro. Thus, we demonstrate a coupling in alpha cells between a protein functioning in cell identity, alpha 1, with a protein responsive to the pheromone-induced signal STE12.
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Department of Microbiology, State University of New York, Stony Brook 11794-5222.
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D000595:Amino Acid Sequence; D001483:Base Sequence; D002454:Cell Differentiation / Q000235:genetics; D017124:Conserved Sequence; D004268:DNA-Binding Proteins / Q000502:physiology; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000502:physiology; D015966:Gene Expression Regulation, Fungal; D007716:Kluyveromyces / Q000235:genetics; D000072235:Mating Factor; D026341:Minichromosome Maintenance 1 Protein; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010675:Pheromones / Q000235:genetics*; D021382:Protein Sorting Signals / Q000737:chemistry / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D015533:Transcriptional Activation
D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D026341:Minichromosome Maintenance 1 Protein; D010455:Peptides; D010675:Pheromones; D021382:Protein Sorting Signals; C489241:STE12 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D000072235:Mating Factor; D019204:GTP-Binding Proteins