ChIP-Seq: Cells were cross-linked and scrapped of the plate. The DNA was fragmented and the protein of interest was immunoprecipitated with indicated antibodies; GRO-Seq: Nuclei were isolated and global run-on was preformed in the presence of BrU analog. RNA was fragmented and isolated by a BrU immunoprecipitation. Adaptors were ligated to the 5' and 3' ends and the library was prepared for Illumina sequencing by a qPCR amplification step; RNA-Seq: Total RNA was extracted from MEFs via the RNA Easy Plus kit and PolyA containing mRNAs were isolated using Dynabeads. The mRNA was fragmented and reversely transcribed with Superscript III followed by second strand synthesis. RNA and ChIP libraries were prepared for sequencing using standard Illumina protocols; GRO-Seq: see extract protocol