Cells on six 15 cm plates of MDA-MB-231 per IP were fixed with 1% formaldehyde for 20 min., washed with PBS, scraped and lysed in Lysis Buffer - 50 mM HEPES pH 7.9, 140 mM NaCl, 1 mM EDTA, 10% glycerol, 0.5% NP-40, 0.25% Triton X-100, nuclei spun down, washed in 10 mM Tris-HCl, pH 7.5, 200 mM NaCl, 1mM EDTA and resuspended in Sheraing Buffer - 0.1% SDS, 1mM EDTA, 10 mM Tris, pH 7.5. Samples were sonicated using Bioruptor sonicator (Diagenode) for the total time of 30 min., to achieve average size of 250-300 bp of the sonicated chromatin fragments. The Shearing Buffer was then supplemented to RIPA buffer and the rest of the protocol followed as described in Girardini et al, Cancer Cell, 2011. 2–10 ng DNA resulting form the ChIP procedure was prepared for HiSeq2000 sequencing with TruSeq ChIP Sample Prep Kit (Illumina) following the manufacturer’s instructions