Chromatins were cross-linked by 1% formaldehyde and extracted using EZ-ChIP Chromatin Immunoprecipitation kit (Millipore, 17-371). The chromatin was then sonicated to an average DNA fragment length of 100-500 bp on Covaris S2 . Sequencing libraries were generated, according to the manufacturer's instructions. Briefly, 4 ng of ChIP product was used for each library preparation. The NEBNext® Ultra™ II DNA Library Prep Kit for Illumina (E7645) was used to ligate adapters and for barcoding and amplification. Libraries was purified using SPRIselect® Reagent magnetic beads (Beckman Coulter, Inc. #B23317), quality-controlled by the Bioanalyzer, and quantified by qPCR.