Lysates were clarified from sonicated nuclei and DNA complexes were isolated with antibody. 5-10 ng of ChIP DNA was used for generation of libraries for deep-sequencing using the NEXTflex™ ChIP-Seq Kit. Briefly, the DNA was end-repaired following adding an A-base to the end-repaired DNA fragments. Illumina adaptors (regular or multiplex) were ligated to the ChIP DNA fragments and 100-300 bp of size fractions were excised from 2% agarose gel. Adaptor-modified fragments library prep was validated in Bioanalyzer for quantity and size before putting into sequencing (The Beijing Genomics Institute, BGI).