library_construction_protocol: Following lysate clarification by centrifugation at 16,000 x g for 30 minutes at 4°C, pellets were resuspended in NP-40 ChIP lysis buffer and samples were sonicated for 15 minutes, 30 seconds on, 60 seconds off, at high power at 4°C with a Bioruptor® Plus sonicator (Diagenode). Immunoprecipitation was carried out with anti-MYC (9E10) mouse monoclonal antibody following incubation followed by incubation with Dynabeads M-280 Sheep Anti-Mouse IgG (Life Technologies). Washing steps and reverse crosslinks were performed as reported in (46)(Ferrari, PLoS Genet., 11, e1004928). Inputs and IPs were purified using Wizard® SV Gel and PCR Clean-Up System (Promega, A9281); DNA was eluted in 80-100 µl of nuclease-free water.  DNA obtained from two independent pooled ChIP experiment was quantified using the Qubit dsDNA High Sensitivity Assay Kit (Invitrogen, Q32851). ChIP-seq libraries were generated starting from 5 ng of DNA using an in house protocol (47), quality checked on a Bioanalyzer High-Sensitivity DNA Chip (Agilent) and sequenced on an Illumina HiSeq 2000 at 50 bp read length.