Cells were pelleted at 500g for 10 min and lysed in nuclei lysis buffer (10 mM Tris pH 7.4, 10 mM NaCl, 3 mM MgCl2, 0.1% IGEPAL). Nuclei were pelleted at 500g for 30 min and tagmented with Tn5 (Illumina) for 60 min at 37°C prior to protein digestion with 2 mL 10 mg/mL Proteinase K at 40°C for 40 minutes. Libraries were size selected with SPRI beads (AMPure) prior to 12 rounds of PCR amplification.