| dc.description.abstract | TFIID is a multi-subunit protein complex that regulates activation of gene transcription. The coactivator model proposes that a given transcription factor activates transcription of its target gene by recruiting TFIID to the gene promoter through direct, mutationally sensitive interactions with a subset of TFIID subunits. However, the coactivator model was developed from in vitro studies. To test the coactivator hypothesis in vivo, I examined the role of yeast TFIID in activating transcription through the cell-cycle regulated transcription factor, Swi6p. Through in vitro analysis, I found that Swi6p, in the context of the transcriptional complex SBF, interacts directly and selectively with a subset of TFIID subunits (Taf12p, Taf4p, and Taf5p). Through RNA blotting studies, I found that one of these interacting subunits, Taf12p, regulates the expression of several cell-cycle regulated genes. Finally, I found that Swi6p co-immunoprecipitates with Taf12p and Taf4p from yeast whole cell extract, and that this interaction is disrupted in yeast that harbor a mutation in another TFIID subunit, Taf9p (the taf9W133stop mutation). Analyses of protein expression and growth rates of various taf9W133stop mutant clones revealed an unexpected role for Taf9p in the regulation of cellular protein expression levels. I propose a model in which TFIID coordinately regulates protein expression and cell cycle progression by mediating transcription through the transcription factors, Rap1p and SBF, respectively, through a mechanism that involves a common set of TFIID subunits, Taf12p, Taf4p, Taf5p and Taf9p. | |
