Chromatin immunoprecipitation (ChIP) assay
ChIP assays were performed using the ChIP Assay Kit (ChIP-IT High Sensitive Kit, Active Motif, CA, USA) according to the manufacturer’s instructions. Briefly, cells were cross-linked and lysed and the chromatin was then sheared by sonication to produce fragments from 100 to 500 bps. The complexes were immunoprecipitated using anti-IgG control or anti-Brd4 antibody, followed by incubation with protein G-agarose beads. Cross-links were reversed and immunoprecipitated DNA was purified. The presence of potential Brd4 binding sites was measured by qPCR using the primers listed in supplemental Table S4.