The yeast STE12 protein binds to the DNA sequence mediating pheromone induction

The STE12 gene product of Saccharomyces cerevisiae is required for the transcription of two sets of cell-type-specific genes: the a-specific genes (active only in a cells) and the alpha-specific genes (active only in alpha cells). We show that radiolabeled STE12 protein, prepared by in vitro transcription and translation, is capable of forming complexes with unlabeled DNA fragments from two a-specific genes. Wild-type yeast, but not a ste12 mutant, produce a factor that forms complexes with labeled DNA from these same two genes. We use assays with yeast extracts to localize the binding site for the STE12-dependent activity. This site corresponds to the sequence identified as the pheromone induction element, which is responsible for increased transcription of genes when cells are exposed to alpha-factor or a-factor. Thus the STE12 protein may be an ultimate effector in the signal transduction pathway triggered by pheromone.