Chromatin was prepared from 149 mm culture dishes first by crosslinking in 1% formaldehyde in PBS (10 minutes, RT). Cross-linking was stopped by adding glycine to a final concentration of 1 M (10 minutes, RT). The cells were washed twice in ice-cold PBS, and harvested in ice-cold lysis buffer (5 mM PIPES pH 8.0, 85 mM KCl, 0,5% NP-40). Nuclei were subsequently released using a Dounce homogenizer, and crude nuclei were resuspended at 10^7 nuclei / mL in RIPA buffer (1% NP-40, 0.5% sodium deoxycholate, 0.1% SDS) and sonicated at high setting in a Bioruptor-Twin (Diagenode) at a volume of 300 μL in 1.5-mL tubes for 40 cycles of 30 seconds on and 30 seconds off. The chromatin IPs were performed as described in (Siersbæk MS, et al. 2012. Mol Cell Biol. 32:3452-3463). ChIP-seq libraries were constructed according to the manufacturer's instructions (Illumina).