Kin28 depletion increases association of TFIID subunits Taf1 and Taf4 with promoters in Saccharomyces cerevisiae. Saccharomyces cerevisiae

The Mediator complex, which assists in pre-initiation complex formation at promoters ofessentially all genes transcribed by RNA polymerase II (Pol II), normally occupies promoters only transiently. Mediator association can, however, be stabilized by inhibiting Pol II promoter escape by depleting or inactivating Kin28. Here we show that two subunits of TFIID, Taf1 and Taf4, similarly show increased occupancy as measured by chromatin immunoprecipitation (ChIP) upon depletion or inactivation of Kin28. In contrast, TBP occupancy is unaffected by depletion of Kin28, suggesting an uncoupling of Taf and TBP occupancy during the transcription cycle. Increased Taf1 occupancy upon Kin28 depletion is suppressed by depletion of TBP; however, depletion of TBP in the presence of Kin28 has little effect on Taf1 occupancy. Taf1 occupancy relative to TBP is higher at TFIID-dominated promoters and promoters having consensus TATA elements than at SAGA-dominated promoters and promoters lacking consensus TATA elements, consistent with prior work, and the increase in Taf occupancy upon depletion of Kin28 is more pronounced at TFIID-dominated promoters. Our results support the suggestion, based on recent structural studies, that TFIID may not remain bound to gene promoters through the transcription initiation cycle.