Cells were crosslinked with 1% formaldehyde for 10' at 37°C. After cell lysis, nuclei were resuspended in RIPA buffer and sonicated (Bransson) until average fragment size was below 500 bps. Antibodies were bound to Dyna beads and incubated with the chromatin. After sequential washing and elution with 1% SDS, crosslinking was reverted and DNA was purified using Qiagen PCR purification columns. Libraries were constructed following manufacturer's instructions (NEBNext ChIP-Seq Sample Prep Kit). Briefly, ChIP DNA was end repaired, A tailed and Illumina adaptors were ligated. DNA fragments of about 200 bps were cut out of an agarose gel and extracted with a Qiagen PCR purification column. Afterwards, DNA was enriched with 18 PCR cycles, fragment size was controlled with Biorad Experion system and quantified using picogreen assay.