ChIP-seq: Cells were fixed with 1% formaldehyde and quenched with glycine (125mM). After washing, cells were lysed (0.5%SDS, 10mM EDTA, 50mM Tris-HCl pH 8.1) and sonicated (Diagenode Biorupter, Belgium). Chromatin was immunoprecipitated using antibodies indicated. Eluted chromatin was heated to reverse cross-linking, treated with proteinase-K, RNaseA and purified on a qiagen PCR pufircation column. Libraries were prepared using PrepX Complete ILMN DNA library kit (#400076, Wafergen) by the High-Throughput Genomics Group at the Wellcome Trust Centre for Human Genetics, Oxford, UK.