library_construction_protocol: The cell was fixed in 1% formaldehyde for 10 min at room temperature. After quenching cell was treated with cell lysis buffer and nucleus was collected by centrifuging at 2000g for 5min. Then, nucleus was treated with nucleus lysis buffer and sonicated to fragment chromatin DNA. The high-throughput DNA sequencing libraries were prepared by using VAHTS Universal DNA Library Prep Kit for Illumina V3（Catalog NO. ND607, Vazyme）. The library products corresponding to 200-500 bp were enriched and quantified.