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. Author manuscript; available in PMC: 2014 Sep 1.
Published in final edited form as: Trends Biochem Sci. 2013 Jul 16;38(9):467–475. doi: 10.1016/j.tibs.2013.06.009

Fig. 1. Sequence of binding events at the HO promoter.

Fig. 1

The top panel shows the structure of the HO promoter including the URS1 promoter element (blue), with two Swi5 binding sites (blue-filled squares), and the URS2 promoter element (yellow) with eight SBF binding sites (yellow-filled squares). The lower panels show nucleosome eviction events as well as binding by factors at time points following release from the G2/M arrest. The G2/M arrest is at 0 min, and at 25°C cells pass START, the commitment point for the G1/S transition, at 30–40 min following release. At 20 min Swi5 binds and recruits SWI/SNF, SAGA, and Mediator, leading to nucleosome eviction within URS1 (indicated by grey dashed-lined nucleosomes). FACT recruitment at 20 min facilitates nucleosome loss and SBF binding at 25 min at the upstream part of URS2, and subsequent recruitment of SWI/SNF, SAGA, and Mediator at 30 min. At 35 min Asf1-dependent nucleosome loss at the downstream end of URS2 permits subsequent SBF binding in this region. The partial repopulation of nucleosomes at URS1 is indicated by grey solid-lined nucleosomes. Finally, at 45 min the gene is transcribed.