ChIP was performed as previously described (Huang et al., 2019 (link)). In brief, 1% paraformaldehyde (PFA) (Electron Microscopy Sciences) was used for cell cross-linking, followed by the addition of 125 mM glycine to quench the reaction. Cells were then re-suspended by CE buffer and centrifuged to pellet nuclei, which were further incubated with SDS lysis buffer and sonicated to generate DNA fragments. Nuclear lysates were diluted with CHIP dilution buffer and incubated with antibodies recognizing the targeted proteins or control mouse/rabbit IgG, followed by the incubation with protein A/G magnetic beads that were pre-blocked with 0.5 mg/mL BSA and 0.125 mg/mL herring sperm DNA (Invitrogen). The beads were subsequently washed with low-salt buffer, high-salt buffer, LiCl buffer, and TE buffer, and the IPed protein-DNA complexes were eluted by elution buffer. To recover DNA samples, the elutes were treated with 0.2 M NaCl and incubated at 65°C for overnight, followed by the treatment of EDTA, Tris-HCl (pH 6.5), and proteinase K. DNA samples were extracted by phenol/chloroform/isoamyl alcohol (25:24:1). DNA pellets were re-suspended in nuclease-free water, which were used for qPCR analysis. Input (5%) was also included.