library_construction_protocol: Trypsinised Neuro2a cells (1×10^6)  transfected with pCAG-Gcm1-3xHA expression plasmid or pCAG-3xHA control plasmid were collected and fixed with 1% formaldehyde at room temperature for 5  min. Crosslinking reaction was quenched with 200 mM glycine (ChIP Reagent, Nippon Gene Co., Ltd.) for 10 min. The cells were resuspended in SDS lysis buffer (ChIP Reagent, Nippon Gene Co., Ltd.), and the lysate was sonicated to fragment chromatin using a Covaris S220 (Covaris, Woburn, MA, USA). The sonicated lysate was subjected to immunoprecipitation with a mouse monoclonal antibody against HA (HA124) (Nacalai Tesque: 06340-54). The immunoprecipitated and reverse-crosslinked DNA was purified using AMPure XP beads (Beckman Coulter, Inc., Pasadena, CA, USA) according to the manufacturer's instructions. ChIP or input DNA (0.1 ~ 1 ng) was subjected to end repair, dA-tailing, and adaptor-ligation using NEBNext Ultra II DNA Library Prep Kit for Illumina (NEB E7645), and amplified by 6-13 cycles of PCR.