MEFs two or seven days after retroviral transduction were crosslinked with 1% formaldehyde in PBS for 30 min and neutralized by the addition of glycine to a final concentration of 0.125M for 5min. MEFs were then harvested and washed with cold PBS for ChIP. For mouse heart sample preparation, ChIP was performed as previously described (Huang et al., 2016; Xu et al., 2012), or by using ChIP-IT Express ChIP kits (Active Motif) following the vender's protocol. ChIP-seq libraries were generated using KAPA Hyper Prep Kit following the manufacturer's protocol (Kapa Biosystems).