ChIP-seq was done as previously described (Magnani et al. 2013 (link); Gallo et al. 2015 (link)) with some modifications. Antibodies used were anti-CTCF (Cell Signaling, #3418, Lot #1) and anti-H3K27ac (Active Motif, #39133, Lot# 31814008). ChIP-seq peaks were called using MACS2 callpeak (Zhang et al. 2008 (link)) on filtered alignments from BWA-MEM (Li and Durbin 2009 (link)). Superenhancer regions were then identified using ROSE (Lovén et al. 2013 (link); Whyte et al. 2013 (link)) on our H3K27ac data. See Supplemental Methods for the complete library generation protocol and analysis parameters.