ChIP was essentially performed as described previously (Mohn et al., 2008). Briefly, after trypsinization and quenching 25 million Hap ES cells were washed once in PBS before fixing for 7 min by addition of formaldehyde to a final concentration of 1%. Crosslinking was then quenched by addition of 2.5 M glycine (0.125 M final concentration) and cells were then incubated on ice. Crosslinked cells were spun at 600 3 g for 5 min, nuclei were prepared by consecutive washes with Rinse 1 buffer (final: 50 mM HEPES pH 8.0, 140 mM NaCl, 10% glycerol, 0.5% NP40, 0.25% Triton X100, 1 mM EDTA) followed by Rinse 2 buffer (final: 10 mM Tris pH 8.0, 1 mM EDTA, 0.5 mM EGTA, 200 mM NaCl). Pellets were resuspended in 2 ml total volume of Sonication buffer (0.1% SDS, 1mM EDTA, pH 8, 10mM Tris HCl, pH 8 with protease inhibitors complete mini (Roche)) and then sonicated with a Covaris E220 sonicator (Covaris settings: 5% duty cycle, PIP 140, 200cyles/ burst, 15 minutes). ChIP was perfomed in ChIP buffer (final: 50 mM HEPES/KOH pH 7.5, 300 mM NaCl , 1 mM EDTA, 1 % Triton X100, 0.1 % DOC, 0.1% SDS) with the indicated antibody. Illumina NEBNext kit