Lysates were clarified from sonicated nuclei and protein-DNA complexes were isolated with antibody. 5ng-10ng of ChIP DNA and Input DNA were used separately to prepare DNA library for Illumina sequencing. Firstly, DNA fragments were repaired to blunt ends by Klenow fragments enzyme, T4 DNA polymerase and a phosphate group was added to the 5'-ends of DNA fragment by T4 PNK. Next, a single 'A' base was added to the repaired 3'-end with Klenow (3'→5' exo-) for adaptor ligation. Subsequently, a pair of barcoded TruSeq adapters with 3'-end 'T' overhang was ligated to both ends of A-tailed DNA fragment with T4 DNA ligase. Eventually, the ligation products were subjected to amplification by using adaptor primers, the resultant library with size of 250bp-500bp was gel purified by QIAGEN kit to remove adaptor dimers and other contamination. After quantification and quality control, the purified library was used for pair-end sequencing on Illumina Hiseq 2000 platform.