~2x107 cells were fixed for 10 min at room temperature by gently mixing in 10 mL crosslinking solution (1% formaldehyde, 50 mM Tris-HCl pH 8.0, 100 mM NaCl, 1 mM EDTA, 0.5 mM EGTA), crosslinking was quenched by adding 2M glycine to a final concentration of 240 mM. The cells were sequentially collected by centrifugation at 700 x g for 10 min and washed trice with 10 mL ice-cold PBS. These cell pellets were sonicated in parallel to obtain chromatin fragments of ~200 to 700 bp, each in 4 mL sonication buffer (10 mM Tris-HCl pH 8.0, 1 mM EDTA, 0.5 mM EGTA, Roche protease inhibitor cocktail) with a Sonic Dismembrator Model 500 (Fisher Scientific, 10 x 30 seconds on / 45 seconds off cycles, 50% power settings). After sonication, debris was removed by centrifugation at 4°C for 10 minutes at 13,000 rpm, and equal amount of 6M urea was added to the solution then incubated for 10 minutes at 4°C on a rotating wheel. The soluble chromatin was dialysed using a membrane with a molecular weight cut-off of 3.5 kDa, at 4°C against 2 L dialysis buffer (10 mM Tris-HCl pH 8.0, 1 mM EDTA, 0.5 mM EGTA, 4% glycerol) overnight. Insoluble debris was removed by quick centrifugation (7,500 rpm, 2 min). The libraries were prepared according to the manufacturer's instructions using the NEBNext kit (E6200). Briefly, DNA was fragmented by sonication to a maximum of 300 bp. Next the ends of the fragments were repaired with a combination of fill-in reactions and exonuclease activity to produce blunt ends that were then tailed with an A-base. Illumina-specific Adaptors were ligated followed by removal of unligated adaptors using AMpure XP beads (Beckman Coulter). Finally a PCR with 12-15 cycles for both kits was performed to enrich final adaptor-ligated fragments. Quality and quantity were assessed on an Agilent Bioanalyzer Chip DNA 7500 or High Sensitivity. For all libraries, sequencing was performed on the MiSeq platform, using v2, 300-cycle reagent kits (Illumina).