Purified cells were cross-linked with 1% formaldehyde for 10 min at room temperature, quenched by the addition of glycine to a final concentration of 0.125 M, and frozen. Cell lysis and nuclei isolation was performed using the TruChIP Chromatin Shearing Kit High Cell SDS (Covaris). Nuclei were sonicated using the S220 Ultrasonicator (Covaris) in order to obtain chromatin fragments of 200-500bp. ChIP-seq libraries were constructed starting from 3ng of ChIP or Input DNA as reported in Blecher-Gonen et al., 2013, Nature protocol. Libraries were quantified using the KAPA SYBR FAST Universal qPCR Kit (KAPA Biosystems), normalized to 15nM, pooled and sequenced in an Illumina HiSeq 4000 instrument as paired-end 150 bp reads, obtaining on average 25x10^6 reads/sample.