Cells were crosslinked with 1% formaldehyde (Thermo Scientific, Cat# 28908) in PBS for 10 min at r.t. To shear chromatin, sonication was performed using the E220 ultrasonicator (Covaris). The mouse embryonic fibroblast spike-in chromatin was added to the sample chromatin. Immunoprecipitation was performed using Dynabeads Protein G (ThermoFisher, Cat# 10004D) at 4°C. Protein degradation using proteinase K (Roche, Cat# 3115828001) and reverse crosslinking were performed at 65°C overnight. The immunoprecipitated DNA was purified using QIAquick PCR Purification Kit (Qiagen, Cat# 28106). The ChIP-seq library was prepared using KAPA HTP library preparation kit (Roche, Cat# 07961901001).