ChIP was performed by standard protocols for ChIP-qPCR and ChIP (12 (link),26 (link)). Antibodies were specific for RNAPII (Abcam ab76123 for ChIP-qPCR or Cell Signaling Technology 14958S for ChIP-seq), CEBPβ (Santa Cruz sc-7962), H3K27Ac (Millipore 07-360), CTCF (Millipore 07-729) or rabbit IgG (Millipore 12-370). All ChIP-seq experiments were performed twice and irreproducible discovery rate (IDR) data are shown. Raw reads were processed using the AQUAS Transcription Factor and Histone ChIP-Seq processing pipeline (https://github.com/ENCODE-DCC/chip-seq-pipeline2) using the ENCODE (phase-3) guidelines on the hg19 reference genome. This includes mapping using BWA and peak calling with MACS2. Primer sequences used for qPCR are shown in Supplementary Table S2.