Genome wide co-localization of Polycomb orthologs and their effects on gene expression in human fibroblasts

We have identfied antibodies that support chromatin immunoprecipitation (ChIP) of 11 components of Polycomb repressive complex 1 (PRC1) and shown that multiple variants of PRC1 associate with the same DNA. By performing ChIP-seq with antibodies against CBX6, CBX7, CBX8, RING1 and RING2, in two strains of human fibroblasts, we find that all five proteins co-localize at multiple sites in the genome. The binding profiles have inherent architecture that is conserved between the two strains, but there are also a substantial number of differences between the strains, possibly reflecting their anatomical position. The presence of PcG proteins does not equate with gene silencing and their genomic position does not change at senescence. Overall design: Chromatin immunoprecipitation and sequencing (ChIP-seq) in two strains of human fibroblasts using antibodies against three Pc orthologs (CBX6, CBX7 and CBX8) and both Psc orthologs (RING1 and 2). Validation by ChIP-PCR and re-ChIP. Strand specific RNA-seq and validation by qRT-PCR.