Opposing chromatin remodeler activities control initiation frequency and start site selection

Using an integrated analysis of chromatin remodeler binding in unperturbed cells and nucleosome displacement activity upon rapid remodeler depletion or degradation, we investigate the interplay between these enzymes and their functional consequences. We show that many promoters are acted upon by multiple remodelers that operate either cooperatively or in opposition to determine the precise location of the key transcription start site-associated +1 nucleosome. Functional assays indicate that +1 nucleosome positioning reflects a trade-off between maximizing RNA Polymerase II recruitment and minimizing transcription initiation at incorrect sites. Interestingly, in the absence of any remodeling activity +1 nucleosomes largely maintain their positions. Our results provide a detailed picture of fundamental mechanisms linking promoter nucleosome architecture to productive transcription initiation. Overall design: Nucleosome occupancy, TBP binding, RNA Pol II and transcription initiation sites were measured upon depletion of chromatin remodelers of budding yeast.