H3 K27M and EZHIP impede H3K27-methylation spreading by inhibing allosterically stimulated PRC2 [S2_ATAC]

In this study, we report that EZHIP and H3 K27M preferentially interact with an allosterically activated form of PRC2 in vivo. The formation of H3 K27M- and EZHIP-PRC2 complexes occurs at CpG islands containing H3K27me3 and impedes PRC2 and H3K27me3 spreading. Moreover, we find that H3 K27M inhibits PRC2 in trans and can reduce H3K27me3 levels independent of chromatin incorporation. While EZHIP is not found outside of placental mammals, we find that expression of human EZHIP reduces H3K27me3 in Drosophila melanogaster through a conserved molecular mechanism. ATAC-seq chromatin accessibility profiling in drosophila S2 cells ATAC-seq was performed in duplicate.