FIG. 6.

Creation of a repressive chromatin domain by targeted recruitment of the Sin3-Rpd3 histone deacetylase complex. The Ume6 repressor binds URS1 (shown as occurring in the context of a nucleosomal template) and recruits the Sin3-Rpd3 corepressor complex to the promoter. As a consequence, histones H3 and H4 (lysines 5 and 12 and to a lesser extent lysine 16) are deacetylated (“Ac” does not appear) over a range of one to two nucleosomes from the site of recruitment. Thick arrows indicate sites of frequent histone deacetylation, whereas dashed arrows indicate histone tails that are infrequently modified. Nucleosomes further downstream and upstream are not specifically deacetylated (Ac). This region of local histone deacetylation is defined with respect to the promoter analyzed in this paper; it includes the UAS element but probably ends upstream of the TATA elements (T). Analogous regions of other Sin3-Rpd3 repressed promoters might vary in length and position. The TATA elements are indicated in the spacer region for clarity of the figure; there is no information on the nucleosomal position of these TATA elements in vivo. Although transcriptional repression is associated with the generation of a domain of localized histone deacetylation, the figure is not intended to suggest any particular mechanism of repression (e.g., inhibiting access of activators, TFIID, or the Pol II holoenzyme or inhibiting the communication between these components).