Rapid nuclei isolation steps were performed on wet ice using ice-cold buffers as previously described (Nilson et al. 2017; Ball et al. 2019). Prior to digestion, spike-in 4T1 nuclei were mixed with SUP-B15 nuclei for DFF-ChIP. Following DFF digestion, nuclei were lightly sonicated for 20s and the soluble material was immunoprecipitated with 2.5 - 5 µg of antibodies. Library construction is detailed in the manuscript.