library_construction_protocol: HiChIP was performed using the Dovetail MNase-HiChIP kit (#21007, Dovetail Genomics) following manufacturer's instruction. 10x10^6 Kelly cells were collected and snap-frozen at -80C for at least 30 minutes. Cells were then crosslinked with disuccinimidyl glutarate (DSG, #A35392, Thermo Fisher) and 37% formaldehyde. Chromatin lysates extracted from C2C12 mouse cells were used as spike-in for AQuA-normalization and chromatin immunoprecipitation of H3K27ac (MABE647, Millipore) or Pol2 (CTD4H8, sc-47701 - Santa Cruz Biotechnology) was performed overnight. HiChIP libraries were prepared using the Dovetail MNase-HiChIP kit following manifacturer's instruction.