Approximately 2 x 10^7 cells were harvested and crosslinked at room temperature with 1% formaldehyde for 10 minutes. Crosslinking reaction was quenched with the addition of glycine to a final concentration of 125 mM for at least 15 minutes. Crosslinked cells were lysed on ice using 1 ml low-salt ChIP buffer (150 mM NaCl, 50 mM Tris-HCl (pH 7.5), 5 mM EDTA, 0.5% NP-40, 1.0%Triton X-100) and sonicated using a Qsonica Sonicator Q500 (Newtown, CT 0647) with the following settings: 90% amplitude; 30 seconds on/30 seconds off cycles; total sonication time of 35 minutes. Sonicated samples were centrifuged and the soluble chromatin (supernatant) was used for chromatin immunoprecipiation reactions. Briefly, 200 µl of lysate (~ 2 x 106 cells) was incubated with each antibody and immunoprecipitated chromatin was recovered using recombinant protein G beads or magnetic Dynabeads® (Invitrogen). ChIP samples were reverse crosslinked and DNA was purified using the phenol-chloroform extraction method. Aliquots of input (total genome) and ChIP DNA obtained from two independent experiments per antibody were used for ChIP library construction and high-throughput sequencing, per Illumina protocols.