Cells were fixed using 1% formaldehyde and chromatin sheared to 300-500 bp in size using the Covaris E220 ultrasonicator. Resulting chromatin was incubated overnight with indicated antibodies. Purified immunoprecipitates were isolated and quantified by Qubit fluorometer. DNA sequencing libraries were prepared using the ThruPLEX-FD Prep kit (Rubicon Genomics). Libraries were sequenced using 75-bp reads on the Illumina platform at the Dana-Farber Cancer Institute.