Cells were treated with 1% formaldehyde for 9 min at 37 °C. After cell lysis, nuclei were re-suspended in RIPA buffer (10 mM Tris/HCl pH 7.5, 150 mM NaCl, 1% NP40, 1% deoxycholic acid (DOC), 0.1% SDS, 1 mM EDTA), 6% of murine spike-in were added, and DNA was fragmented to a size <300 bp using a Branson sonifier. Chromatin was immunoprecipitated with 10-15 µg of corresponding antibody for 6 hours. Chromatin was eluted with 1% SDS and crosslinking was reverted overnight. For purification, chloroform/phenol extraction was used. NEBNext® Ultra II DNA Library Prep with Sample Purification Beads®. Purified DNA was end-repaired, A-tailed, ligated to Illumina adaptors, size-selected (200 bp) and purified with Sample Purification Beads. DNA fragments were amplified by 18 cycles of PCR and library size was tested with the Fragment Analyzer (Advanced Analytical).