The cells were prepared in triplicate and pooled for ChIP. Cells were crosslinked with 1 % (v/v) formaldehyde (10 min. at 22 degrees Celsius) and washed twice with PBS, after which they were collected in a cold room in Farham Lysis Buffer. After centrifugation, the cell pellets were resuspended in RIPA buffer. Chromatin was sonicated to an average fragment size of 200-400 bp using Bioruptor UCD-300-TO (Diagenode). The chromatin was immunoprecipitated for ChIP-seq with V5-tag antibody (R960-25, Invitrogen). ChIP-seq samples were processed according to Illumina's instructions and DNA libraries were sequenced using Illumina HiSeq System (Illumina) in the EMBL Gene Core Facility (Heidelberg, Germany).