Regulated displacement of TBP from the PHO8 promoter in vivo requires Cbf1 and the Isw1 chromatin remodeling complex.

Regulated binding of TBP to a promoter is a key event in transcriptional regulation. We show here that on glucose depletion, the S. cerevisiae Isw1 chromatin remodeling complex is required for the displacement of TBP from the PHO8 promoter. Displacement of TBP also requires the sequence-specific bHLH-LZ factor Cbf1p that targets Isw1p to the PHO8 UAS. Cbf1p- and Isw1p-dependent displacement of TBP is also observed at the PHO84 promoter, but not at the ADH1 promoter, where loss of TBP is Cbf1p- and Isw1p independent. The results point to a promoter-specific Isw1p-dependent mechanism for targeted regulation of basal transcription by displacement of TBP from a promoter.