STE12, a protein involved in cell-type-specific transcription and signal transduction in yeast, is part of protein-DNA complexes.

The STE12 gene of Saccharomyces cerevisiae is essential for the expression of genes required for mating, such as those involved in pheromone response, and for genes unrelated to mating but regulated by the presence of an adjacent copy of the transposable element Ty1. We show that the STE12 protein is a component of specific DNA-protein complexes that form with transcriptional control elements from Ty1 and the alpha-pheromone receptor gene STE2. Although a sequence involved in pheromone-dependent transcriptional activation is protected in both complexes, competition experiments indicate that the complexes are intrinsically different from each other. We show that another factor involved in cell-type-specific transcription, PRTF/GRM, is a component of the complex with the STE2 fragment but not the Ty1 fragment. We propose that the STE12 product interacts with different transcription factors in different sequence contexts and that PRTF/GRM is one of these factors.