library_construction_protocol: Briefly, HEK293T cells expressing K/C-III were fixed with 4% formaldehyde for 10 minutes at room temperature and then quenched with glycine. The fixed cells were lysed in L1 buffer (50 mM Tris-HCl pH 8.0, 2 mM EDTA, 0.1% NP-40, 10% glycerol, 1× protease inhibitors, 1 mM PMSF, 2 mM DTT) on ice for 5 minutes. Following centrifugation, the nuclear pellet was resuspended in ice-cold wash buffer D (50 mM Tris–HCl pH 8.0, 0.1 mM EDTA, 5 mM Mg acetate, 5 mM DTT, 25% glycerol) and incubated for 5 minutes before centrifuging at 2,000g for 5 minutes. The pellet was resuspended in 400 μL MNase buffer (10 mM Tris–HCl pH 7.4, 15 mM NaCl, 60 mM KCl, 1 mM CaCl₂, 250 mM sucrose, 0.5 mM DTT) and underwent two freeze-thaw cycles in liquid nitrogen to disrupt nuclei. Chromatin was sonicated with a Diagenode Bruptor Plus (low-power mode, 8 cycles of 30 seconds ON and 30 seconds OFF). Next, 2 U of MNase was used to digest fixed chromatin at 25°C for 30 minutes with shaking at 1200 rpm. Digestion was halted with EDTA, and 1 mL of buffer V (50 mM Tris pH 7.4, 50 mM NaCl, 5 mM EDTA) was added. The supernatant was pre-cleaned with rProtein A/G beads (Smart Lifesciences, SA032005). Samples were incubated overnight at 4°C with 5 μg H3K4me2 antibody and 15 μL rProtein A/G beads. Beads were washed three times with MNase buffer, followed by a second MNase digestion (15 μL MNase buffer containing 2 U MNase) at 25°C for 30 minutes with shaking. The reaction was stopped with 34 mM EDTA and treated with proteinase K. DNA was purified by phenol-chloroform extraction and ethanol precipitation. ChIP-MNase libraries were prepared using the NEBNext Ultra II DNA library prep kit for Illumina.