The yeast ISW1, CHD1 and RSC chromatin remodelers have additive effects on global chromatin structure

Monday, September 22, 2014 — Poster Session II
4:00 p.m. – 6:00 p.m.	FAES Academic Center	NICHD	GEN-12

* FARE Award Winner

Authors

• J Ocampo
• RV Chereji
• PR Eriksson
• DJ Clark

Abstract

In yeast most genes have a nucleosome depleted region at the promoter. We have addressed the roles of four chromatin remodeling complexes in nucleosome organization: ISW1, ISW2, CHD1 and RSC. We constructed strains with the essential RSC8 gene under the control of the GAL promoter and isw1, isw2 or chd1 null mutations in all possible combinations. In the absence of RSC we confirmed that all the nucleosomes shift towards the TSS with consequent narrowing and filling in of the NDR. Others have shown that the combined action of ISW1 and CHD1 is required to maintain nucleosome phasing. We confirm this observation and show that nucleosome spacing in the isw1 mutant is reduced by 6 bp, whereas the chd1 mutant shows little change. isw2 mutant does not show any changes. Chromatin structures of the double, triple and quadruple mutants represent the sum of the effects observed in the individual mutants. We propose that RSC determines the position of the +1 nucleosome, which is then used as a reference nucleosome by CHD1 and ISW1 to build nucleosomal arrays on genes. Although 6 bp is only a small change in linker DNA , a profound effect on chromatin higher order structure is predicted.

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