Systematic proteomic profiling of the human Polycomb interactome

Polycomb group (PcG) proteins are major determinants of gene silencing and epigenetic 1 memory in higher eukaryotes. Here, we used a robust affinity purification mass spec2 trometry (AP-MS) approach to systematically map the human PcG protein interactome, 3 uncovering an unprecedented breadth of PcG complexes. The obtained high density 4 protein interaction data identified new modes of combinatorial PcG complex formation 5 with proteins previously not associated with the PcG system, thus providing new insights 6 into their molecular function and recruitment mechanisms to target genes. Importantly, 7 we identified two human PR-DUB de-ubiquitination complexes, which comprise the O8 linked N-acetylglucosamine transferase OGT1 and a number of transcription factors. By 9 further mapping chromatin binding of PR-DUB components genome-wide, we conclude 10 that the human PR-DUB and PRC1 complexes bind distinct sets of target genes and 11 impact on different cellular processes in mammals. 12