Nuclear lysates were sonicated using a Branson 250 Sonifier (power setting 2, 100% duty cycle for 7 x 30-s intervals). Clarified lysates corresponding to 20 million cells were treated with 1-5ug of antibody against H3K27ac [Abcam #4729]) coupled to Protein G Dynabeads (Life Technologies #10003D, New York). The protein-DNA complexes were washed with RIPA buffer and eluted in 1% SDS TE at 65 °C ChIP DNA sequencing libraries were generated according to Illumina DNA TruSeq DNA Sample Preparation Kit Instructions (Illumina Part # FC-121-2001, San Diego, CA).