DNA elements tether canonical Polycomb Repressive Complex 1 to human genes

Development of multicellular animals requires epigenetic repression by Polycomb group proteins. The latter assemble in multi-subunit complexes, of which two kinds, Polycomb Repressive Complex 1 (PRC1) and Polycomb Repressive Complex 2 (PRC2), act together to effect the repression of key developmental genes. How PRC1 and PRC2 recognize specific genes remains an open question. Here we report that small adjustment in the next generation sequencing of the Immunoprecipitated Chromatin (ChIP-seq) allows identification of several hundreds of DNA elements that tether canonical PRC1 to human developmental genes. Their analysis indicates that sequence features associated with canonical PRC1 tethering differ from those that favour the retention of PRC2. Throughout the genome, the two kinds of sequence features mix in different proportions to yield a gamut of DNA elements that range from those tethering predominantly PRC1 to ones capable of tethering both PRC1 and PRC2 or the elements that retain exclusively PRC2. The emerging picture is similar to paradigmatic targeting of Polycomb complexes by Polycomb Response Elements (PREs) of Drosophila but providing for unexpected degree of plasticity. Overall design: ChIP-seq of the Polycomb group proteins SUZ12, MEL18/BMI1 and RING, and the histone modification H3K27me3, performed on the cell lines NT2-D1, TIG-3, and KBM7-1-55-S2-24 clone F10. Each experiment was done in two replicates. DNA isolated from corresponding chromatins prior to immunoprecipitation (Input) were sequenced as controls.