Cells were crosslinked with 1% formaldehyde for 10 min at 37◦C; then, crude nuclei were purified. Chromatin was fragmented by sonication to obtain fragments 200–2000 bp in length. Then chromatin was reverse-crosslinked and DNA was purifiied and quantified with a Qubit fluorometer using the Quant-iT dsDNA HS assay kit DNA was end-repaired, adenylated, and ligated to TruSeq sequencing adaptors. DNA was purified by AMPure beads or DNA purification kit according to the DNA amount. Library DNA was amplified by Phusion HF (NEB, Cat. M0530L). The amplified DNA was size selected using 2% agarose gel for 200-500bp DNA fragments.