Cells were cross-linked with 1% formaldehyde for 10 min at room temperature and formaldehyde was then inactivated by the addition of 125 mM glycine for 5min. Sonicated DNA fragments with 100–300 bp were pre-cleared and then immunoprecipitated with Protein A+G Magnetic beads coupled with Anti-H3K27Ac antibody (ab4729, Abcam). After reverse crosslinking, immunoprecipitated DNAs and input DNAs were end-repaired and ligated adapters to the DNA fragments using NEBNext Ultra End-Repair/dA-Tailing Module (E7442, NEB) and NEBNext Ultra Ligation Module (E7445, NEB).