library_construction_protocol: Briefly, 106-107 ESCs were trypsinized and collected by centrifugation at 1,000 g for 5 min at 4°C. The cell pellet was resuspended in ice-cold permeablization buffer (10 mM Tris-HCl (pH 7.4), 300 mM sucrose, 10 mM KCl, 5 mM MgCl2, 1 mM EGTA, 0.05% Tween-20, 0.1% NP-40, 0.5 mM DTT, 4 U/mL RNase inhibitor,  proteinase inhibitor cocktail) and incubated on ice for 5 min before centrifugation. The extracted nuclei were washed twice with permeabilization buffer and stored in 100 μL storage buffer (10 mM Tris-HCl (pH 8.0), 25% glycerol, 5 mM MgCl2, 0.1 mM EDTA, and 5 mM DTT) at -80°C. VAHTS Universal V6 RNA-seq Library Prep kit (Vazyme #NR604) was used for RNA library construction. Library construction was conducted according to the manufacturer's protocol (with UMI barcoded dual index, RK21702) and the libraries were sequenced on the Illumina platform.