E14TG2a ESCs derived from 129/Ola were cultured in GMEM supplemented non-essential amino acids, 10% Knockout Serum Replacement, sodium pyruvate, L-glutamine, 2-mercaptoethanol, penicillin, streptomycin, and leukemia inhibitory factor without feeder cells.ChIP experiment with whole cell extract was performed as we have described previously. Samples destined for ChIP seq by Illumina HiSeq were prepared according to the manufacturer’s instructions.