ChIP was performed on two independent pools of GC cells, each comprising 3-5 donors. 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 4ug 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 10nM, pooled and sequenced in an Illumina HiSeq 2500 instrument as single-end 101 bp reads, obtaining on average 25x10^6 reads/sample.