Cells were trypsinized, washed with PBS and crosslinked with 1% formaldehyde in PBS for 10 min at RT. After PBS washing, cells were resuspended in 400 μl of lysis buffer (1% SDS, 20 mM EDTA and 50 mM Tris-HCl (pH 8.0)) containing protease inhibitors (Roche, Indianapolis, IN), incubated for 10 min on ice and sonicated using Misonix cup-horn sonicator to achieve, on average, 200bp fragments for ChIP-seq and 500bp fragments for ChIP-PCR. The lysate was diluted 10 times with ChIP dilution buffer containing 0.01% SDS, 1.1% Triton X-100, 1.2 mM EDTA and 16.7 mM Tris-HCl (pH 8.1) and immunoprecipitatied with 4 ug of corresponding antibody overnight at 4 degrees. 20 μl of the lysates were used as input. The complexes were captured using protein A Dynabeads (Invitrogen, Grand Island, NY) and washed twice with the following buffers: low-salt immune complex wash buffer (0.1% SDS, 1% Triton X-100, 2 mM EDTA, 20 mM Tris-HCl (pH 8.1); high-salt immune complex wash buffer (0.1% SDS, 1% Triton X-100, 2 mM EDTA, 20 mM Tris-HCl (pH 8.1) and 500 mM NaCl); LiCl wash buffer (0.25 M LiCl, 1% NP40, 1% deoxycholate, 1 mM EDTA and 10 mM Tris-HCl (pH 8.1)) and TE (10 mM Tris-HCl and 1 mM EDTA (pH 8.0)). After elution with 50 mM Tris-HCl, pH 8.0, 1 mM EDTA, and 1% SDS, crosslinks were reversed by overnight incubation at 65°C. Samples were then treated with RNase A for 30 min at 37°C and proteinase K for 2 h at 56°C. DNA was subsequently purified using Qiagen MinElute Columns according to manufacturers instructions. DNA concentration was measured using a Qubit (Invitrogen, Grand Island, NY). The library for sequencing was constructed using Ovation Ultralow IL Multiplex System 1-8 according to manufacturer's instructions (Nugen, San Carlos CA). Libraries were sequenced using HIseq-2000 (Illumina, San Diego, CA) to obtain 50 bp long reads.