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Insights into promoter chromatin remodeling from the structure of ISW1a complex bound to the dinucleosome

ABSTRACT: Nucleosomes, the basic repeating units of chromatin, form evenly spaced arrays inside the cell. Chromatin remodelers alter the positions of nucleosomes, and are vital in regulating chromatin organization and gene expression. Here we report the cryoEM structure of the chromatin remodeler ISW1a complex bound to the dinucleosome. Both subunits of the complex recognize one nucleosome. The motor subunit binds at the canonical position of the nucleosome, with two arginine anchors recognizing the acidic patch. The DNA-binding module interacts with the entry linker DNA at the nucleosome edge, consistent with the protein ruler model in nucleosome spacing. The Ioc3 subunit recognizes the disk face of the adjacent nucleosome, being important for the spacing activity in vitro, and for chromatin organization in vivo. Together, our findings illustrate a new mode of chromatin remodeling in the context of higher-order chromatin

ORGANISM(S): Saccharomyces cerevisiae

PROVIDER: GSE203073 | GEO | 2023/05/15

REPOSITORIES: GEO

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Structure of the ISW1a complex bound to the dinucleosome

Project description:Nucleosomes are basic repeating units of chromatin, and form regularly spaced arrays in cells. Chromatin remodelers alter the positions of nucleosomes, and are vital in regulating chromatin organization and gene expression. Here we report the cryoEM structure of chromatin remodeler ISW1a complex bound to the dinucleosome. Each subunit of the complex recognizes a different nucleosome. The motor subunit binds to the mobile nucleosome and recognizes the acidic patch through two arginine residues, and the DNA-binding module interacts with the entry DNA at the nucleosome edge. This nucleosome-binding mode provides the structural basis for linker DNA sensing of the motor. Notably, the Ioc3 subunit recognizes the disk face of the adjacent nucleosome through interacting with the H4 tail, the acidic patch and the nucleosomal DNA, which plays a role in the spacing activity in vitro, and in nucleosome organization and cell fitness in vivo. Together, these findings support the nucleosome spacing activity of ISW1a, and add a new mode of nucleosome remodeling in the context of a chromatin environment.

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