ATAC-seq was performed as previously described (Buenrostro et al, 2015). Briefly, transposition was performed from 5000 parental or UBR7KO 293T cells resuspended in 50 uL of ATAC buffer (25 uL 2x TD buffer, 2.5 uL TDE1 transposase, Nextera; 0.5uL Digitonin, Promega; 22uL nuclease-free water) for 30 m at 37C with 300 rpm agitation. Fragmented DNA was collected using a Qiagen MinElute PCR kit (Qiagen 28004). Sequencing libraries were prepared by PCR and quality controlled as described (Buenrostro et al., 2015). Libraries were sequenced on the NextSeq 500 to generate 50 bp single-end reads.