IMITATION SWITCH is required for normal chromatin structure and gene repression in PRC2 target domains
Masayuki Kamei, Abigail J. Ameri, Aileen R. Ferraro, Yael Bar-Peled, Fangzhou Zhao, Christina L. Ethridge, Kathleen Lail, Mojgan Amirebrahimi, Anna Lipzen, Vivian Ng, Igor V. Grigoriev, Robert J. Schmitz, Yi Liu, Zachary Lewis
Abstract
Significance Polycomb Repressive Complex 2 (PRC2) methylates histones to regulate multicellular development, maintenance of stem cell identity, X-chromosome inactivation, and other important processes. Given these essential roles, there is significant interest in identifying components that function with PRC2 to establish and maintain transcriptionally repressive heterochromatin. Here we document an unexpected new role for a well-studied and conserved chromatin remodeling factor, ISWI. We found that the Neurospora ISWI homolog is required for normal facultative heterochromatin structure and gene repression at PRC2 target regions, and we defined requirements for ATP-dependent catalytic activity and accessory regulatory proteins. These findings provide mechanistic insights into the formation and function of facultative heterochromatin in a model eukaryote.