Cells were harvested, washed in cold PBS, and viability assessed by trypan blue exclusion. 50,000 viable cells per sample were used for library preparation. Sequencing libraries were prepared using the ATAC-Seq Express Kit (Active Motif) following manufacturer's instructions. Post-amplification libraries were purified with SPRI beads and quantified using Qubit dsDNA HS Assay. Equimolar pools were sequenced on Illumina NextSeq 550 in 2×75 bp paired-end configuration across four lanes per library.