Interplay between Nsd1 and PRC2 demarcates regions of H3K27me2 and H3K27me3

The core Polycomb Repressor Complex 2 (PRC2) is composed of Ezh1/2, Suz12, Eed and is responsible for mediating both H3K27me2 and H3K27me3. However, the mechanisms by which PRC2 demarcates these two repressive modifications in the genome are unknown. In a functional screen, we identified the H3K36 dimethyltransferase Nsd1 as a modulator of PRC2-mediated di- and trimethylation of H3K27. ChIP-Seq analysis following the depletion of Nsd1 revealed a global reduction in H3K36me2 and an increase in H3K27me3 at sites previously marked by H3K27me2. We show that the H3K36me2 at H3K27me2 marks co-occupy regions and provide evidence that the presence of H3K36me2 functions to restrict the spatial distribution of Polycomb mediated H3K27me3 domains. Overall design: Immuno-precipitation of formaldehyde cross-linked chromatin prepared from mouse embryonic stem cells transduced with shRNA targeting Nsd1 (pLKO.TRC1shNsd1.1 and pLKO.TRC1shNsd1.2) and non-targeting control shRNA (pLKO.TRC1shLuciferase). For H3K27me3, ChIP with spike-in using Drosophila melanogaster chromatin was performed.