ChIP experiments were performed as previously described (Huang et al., 2013). Briefly, 1 × 107 cells were crosslinked with 1% formaldehyde for 10 min at room temperature. Then the reaction was stopped by adding glycine (final concentration, 0.125 M). The cells were sonicated in SDS lysis buffer containing 1 × protease inhibitor cocktails and 1 mM PMSF to achieve a chromatin sized of 100-500 bp. The sonicated chromatin was incubated with indicated antibodies coupled with dynabeads protein A and G (1:1 mixed) overnight at 4°C with rotation. Immune complexes were washed with the following buffers: low salt wash buffer (0.1% SDS, 1%Triton X-100, 2 mM EDTA, 20 mM Tris-HCl (pH 8.0), 150 mM NaCl), high salt wash buffer (0.1% SDS, 1% Triton X-100, 2 mM EDTA, 20 mM Tris-HCl (pH 8.0), 500 mM NaCl), LiCl wash buffer (0.25 M LiCl, 1% IGEPAL-CA630, 1% deoxycholic acid (sodium salt), 1 mM EDTA, 10 mM Tris-HCl (pH 8.0)) and TE buffer (10 mM Tris-HCl (pH 8.0), 1 mM EDTA). Antibody-bound chromatin was reverse-crosslinked, and the ChIPed DNA samples were purified for sequencing. Libraries were prepared according to Illumina's instructions accompanying the DNA Sample Kit (Part# 0801-0303). Briefly, DNA was end-repaired using a combination of T4 DNA polymerase, E. coli DNA Pol I large fragment (Klenow polymerase) and T4 polynucleotide kinase. The blunt, phosphorylated ends were treated with Klenow fragment (32 to 52 exo minus) and dATP to yield a protruding 3- 'A' base for ligation of Illumina's adapters which have a single 'T' base overhang at the 3’ end. After adapter ligation DNA was PCR amplified with Illumina primers for 15 cycles and library fragments of ~250 bp (insert plus adaptor and PCR primer sequences) were band isolated from an agarose gel. The purified DNA was captured on an Illumina flow cell for cluster generation. Libraries were sequenced on the Genome Analyzer following the manufacturer's protocols.