For ChIP-seq, fixation was stopped by adding Glycine (0.125M) and incubating for 5 min at RT, followed by washing with PBS twice. Chromatin DNA was sheared to 300–500 bp average in size through sonication. Resultant was immunoprecipitated with control IgG or specific antibodies overnight at 4°C, followed by incubation with protein G magnetic beads (Invitrogen) for an additional 2 h. After washing and elution, the protein–DNA complex was reversed by heating at 65°C overnight. Immunoprecipitated DNA was purified by using QIAquick spin columns (Qiagen). The libraries were constructed following Illumina’s Chip-Seq Sample prep kit. Briefly, Chip DNA was end-blunted and added with an ‘A’ base so the adaptors from Illumina with a ‘T’ can ligate on the ends. Then 200–400 bp fragments are gel-isolated and purified. The library was amplified by 18 cycles of PCR.