The ChIP protocol was adapted from the Millipore ChIP Assay Kit (17-295). Cells were cross-linked with 1% formaldehyde at 37°C for 10min in PBS/0.5% BSA and lysed in 1% Triton X-100, 50 mM MgCl2, 100 mM Tris-HCl ([pH 7.1), 11% sucrose, 1x PIC buffer. Pelleted nuclei were then lysed in 1% SDS lysis buffer and sonicated to 200-500 bp fragments using a Bioruptor 200 (Diagenode). Chromatin samples were incubated with the appropriate antibodies. DNA was purified using the iPure Kit (Diagenode). Libraries were prepared according to standard Illumina protocols, and were validated with the Agilent Bioanalyzer.