Samples were crosslinked by 1% formaldehyde for 10 minutes, and the reaction was stopped by addition of glycine to 125 mM final concentration as previously described (Bernt et al. 2011 Cancer Cell). ChIP was performed as previously described (Bernt et al. 2011 Cancer Cell). Briefly, cells samples were crosslinked by 1% formaldehyde for 10 minutes, and the reaction was stopped by addition of glycine to 125 mM final concentration. The fixed cells were lysed in SDS buffer, and the chromatin was fragmented by sonication. The sheared chromatin was incubated with the indicated antibodies, and recovered by binding to protein A/G agarose (Millipore). Eluted DNA fragments were used directly for qPCR or subjected to high-throughput sequencing using Illumina HiSeq 2000 platform.