Lysates were clarified from sonication which was performed to fragment chromatin to 200-700 bp size range using a Covaris E220 Focused-ultrasonicator. Immunoprecipitation was then performed on 5 million cells with H3K27me3 antibody Libraries were prepared according to Illumina's instructions. Briefly, DNA was end-repaired using End-It DNA End-Repair Kit (Epicenter Cat. No. ER0720) and 'A' Base was added to the 3' End of the DNA fragments. After Ligation of Adapters to the Ends of the DNA Fragments, adapter-modified DNA fragments were enriched by PCR. SPRI bead size selection was used to remove remaining primers and select a size-range of templates. The Libraries were sequenced with the Illumina NextSeq 500 platfom following the manufacturer's protocols.