For each cell line (MUG-Chor1 and U-CH2), 50,000 cells were lysed for 10 minutes at 4°C in lysis buffer (10 mM Tris-HCl pH 7.4, 10 mM NaCl, 3 mM MgCl2, 0.1% IGEPAL CA-360). After lysis, the pellets were subject to a transposition reaction (37°C, 60 minutes) using the 2X TD buffer and transposase enzyme (Illumina Nextera DNA preparation kit, FC-121-1030). The transposition mixture was purified using a Qiagen MinElute PCR purification kit. Library amplification was performed using custom Nextera primers and the number of total cycles determined by running a SYBR-dye based qPCR reaction and calculating the cycle number that corresponds to ¼ the maximum. Amplified libraries were purified using a Qiagen PCR purification kit and sequenced with paired-end 100 bp reads on an Illumina HiSeq 2000.