Cells were cross-linked with 1% (vol/vol) formaldehyde for 10 min, and the cross-linking was quenched by 0.125 M final concentration glycine. The cross-linked tissue was then homogenized, and rinsed with PBS, and frozen in liquid nitrogen. Later, Crosslinked tissues were fragmented to the size range of 100–500 bp using a Bioruptor (Bioruptor Next Gen; Diagenode). Antibodies for each mark were incubated with beads for 6 h before incubating with sonicated chromatin overnight. Resulting immunoprecipitated DNA was prepared for high-throughput sequencing using a library preparation kit from Beckman Coulter (catalog #A88267). Libraries were sequenced on an Illumina platform following the manufacturer’s standard protocol.