Chromatin immunoprecipitation (ChIP) was carried out essentially as previously described (Jermann et al. PNAS 2014). Library Construction Protocol: Libraries for ChIP-seq were prepared according to standard Illumina library preparation protocols. Twelve cycles of PCR (NEB Q5 Hot Start HiFi PCR) were performed on end-repaired, A-tailed and adapter-ligated DNA prior to gel size-selection. Quality of the libraries and size distribution was assessed on an Agilent 2100 Bioanalyzer (Agilent Technologies). Sequencing was performed on an Illumina HiSeq 2500 machine (50 bp read length, single end) according to Illumina standards.