Briefly, cells were cross-linked with 1% formaldehyde at room temperature for 10 min. And then the cross-linking was quenched with 0.125M glycine for 5 min. Chromatin was fragmented using a Bioruptor® Pico (Diagenode) for 10 min at high power, with an interval of 30 s between pulses to get around 200bp fragments and precleared using 20 μl Protein G Dynabeads (Life Technologies, Cat# 10009D). Subsequently, the soluble chromatin was incubated with 2-5 μg antibodies at 4°C overnight. Immunoprecipitated complexes were collected using 30 μl Protein G Dynabeads, which have been saturated with PBS/1% BSA over night at 4°C, per reaction. For all ChIPs, after de-crosslinking overnight at 65°C, final ChIP DNA was extracted and purified using QIAquick spin columns (QIAGEN). The libraries were constructed following Illumina's Chip-Seq Sample prep kit.