YEAST TAF170 IS ENCODED BY MOT1 AND EXISTS IN A TATA BOX-BINDING PROTEIN (TBP)-TBP-ASSOCIATED FACTOR COMPLEX DISTINCT FROM TRANSCRIPTION FACTOR-IID

Our characterization of the Saccharomyces cerevisiae TATA box-binding protein (TBP) has led to the identification of nine specific yeast TBP -associated factors (TAFs) ranging in size from 170 to 25 kDa. The ami no acid sequence derived from a purified TAF with an apparent M(r) of 170,000 indicates that yeast Taf170 is encoded by the essential yeast gene MOT1. We describe in this report a series of experiments that dem onstrate that the protein encoded by MOT1 is a bona fide yeast TAF and that Taf170 forms a separate complex with TBP distinct from the RNA p olymerase II-specific multisubunit transcription factor IID TBP-TAF co mplex. The significance of this unique TBP.Taf170 complex regarding tr anscriptional regulation is discussed.