Yeast TFIID Serves as a Coactivator for Rap1p by Direct Protein-Protein Interaction

Abstract

In vivo studies have previously shown that Saccharomyces cerevisiae ribosomal protein (RP) gene expression is controlled by the transcription factor repressor activator protein 1 (Rap1p) in a TFIID-dependent fashion. Here we have tested the hypothesis that yeast TFIID serves as a coactivator for RP gene transcription by directly interacting with Rap1p. We have found that purified recombinant Rap1p specifically interacts with purified TFIID in pull-down assays, and we have mapped the domains of Rap1p and subunits of TFIID responsible. In vitro transcription of a UAS_RAP1 enhancer-driven reporter gene requires both Rap1p and TFIID and is independent of the Fhl1p-Ifh1p coregulator. UAS_RAP1 enhancer-driven transactivation in extracts depleted of both Rap1p and TFIID is efficiently rescued by addition of physiological amounts of these two purified factors but not TATA-binding protein. We conclude that Rap1p and TFIID directly interact and that this interaction contributes importantly to RP gene transcription.

We thank our lab colleagues for freely sharing reagents, constructive criticism, and advice throughout the course of this work. We are grateful to Emmanuel Bessay, Allistair Chambers, Jackie Corbin, Ray Jacobson, Kevin Struhl, and Jon Warner for kindly supplying reagents and yeast strains used in this work.

The financial support of the NIH (grant GM52461) is gratefully acknowledged.