Cells were cross-linked sequentially with 1.25mM EGS (ethylene glycol-bis(succinic acid N-hydroxysuccinimide ester)) and 1% formaldehyde in PBS. Sonication and ChIP were performed as described previously (Koues et al., Immunity, 2015). At least 10 ng of ChIP, or input DNA was used for indexed library preparation. Samples were indexed and pooled (9-11 per lane) and subjected to 50 bp single-end sequencing according to the manufacturer's protocol (Illumina HiSeq3000, San Diego, CA, USA) by the Genome Technology Access Center at Washington University in St. Louis.