Multiple regulation of STE2, a mating-type-specific gene of Saccharomyces cerevisiae.

The Saccharomyces cerevisiae STE2 gene, which is required for pheromone response and conjugation specifically in mating-type a cells, was cloned by complementation of the ste2 mutation. Transcription of STE2 is repressed by the MAT alpha 2 gene product, so that the 1.4-kilobase STE2 RNA is detected only in a or mat alpha 2 strains, not in alpha or a/alpha cells. However, STE2 RNA levels are also increased by the mating pheromone alpha-factor and decreased in strains bearing mutations in the nonspecific STE4 gene. Regulation of STE2 expression in a cells is therefore achieved by several mechanisms.