Cells were cross-linked for ChIP-seq with 1% formaldehyde at room temperature for 10 minutes. The formaldehyde was quenched with 2.5M glycine at room temperature for 10 minutes. Fixed cells were spun down at 6000xg for 3 minutes at 4°C. Cells were washed with cold PBS twice and resuspended in 100ul ChIP lysis buffer (1% SDS, 10mM EDTA, 50mM Tri-HCl at pH 8.1) before being snap frozen in liquid nitrogen. Immunoprecipitation was carried out as previously described (Lesch et al 2016) DNA integrity and fragment size were confirmed on a BioAnalyzer.  Approximately 5-10ng of DNA was end-repaired, A-tailed, adapter-ligated, and PCR enriched (8-10 cycles) using the KAPA Hyper Library Preparation kit (KAPA Biosystems, #KK8504).