5 million cells were used per sample. Cells were fixed with 1% formaldehyde for 10 min. Fixed chromatin was fragmented using an S220 Focused-ultrasonicator (Covaris) to an average size of 200-500 bp. Immunoprecipitation was then performed using a mixture of Protein A and Protein G Dynabeads (Life Technologies). Fragmented Drosophila melanogaster DNA was added at the immunoprecipitation step at a ratio of DNA from 1 Drosophila cell to 4 mouse/human cells, for the purpose of normalization (Orlando et al., Quantitative ChIP-Seq normalization reveals global modulation of the epigenome. Cell Rep 2014). However, reads mapping to the Drosophila melanogaster genome were not used for analysis. The NEBNext Ultra II DNA Library Prep Kit for Illumina, with NEBNext Multiplex Oligos for Illumina (New England BioLabs) was used to prepare DNA samples for sequencing as directed. Sequencing was performed using the Illumina NextSeq 500 platform.