library_construction_protocol: Samples were flash-frozen in liquid N2, followed by dry pulverization of frozen tissue through a cell crusher. Samples were cross-linked with 1% formaldehyde, quenched with 125 mM glycine, and washed with ice cold PBS with protease inhibitors (ThermoFisher, A32965). After pelleting, samples were resuspended in ice-cold swelling buffer (25 mM HEPES pH 7.9, 1.5 mM MgCl2, 10 mM KCl, 0.1% NP40, 5 mM NaF, 2 mM Na2VO4, 1 mM PMSF, 1X PIC) and dounced with both tight and loose pestle for 20 times on ice, followed by filtering through a 70 µm filter. After centrifugation (1,000xg 10 min 4°C), samples were resuspended in sonication buffer (50 mM HEPES pH 7.9, 140 mM NaCl, 1mM EDTA, 1% Triton X-100, 0.1 % Na-Deoxycholate, 0.1% SDS, 5mM NaF, 2 mM Na2VO4, 1mM PMSF, 1X PIC) and fragmented using Bioruptor at high setting for 30 second ON + 30 second OFF pulses for a total of 30 minutes. DNA libraries were constructed by Tn5 tagmentation. Briefly, primer A 5′-TCGTCGGCAGCGTCAGATGTGTATAAGAGACAG-3' or primer B 5′-GTCTCGTGGGCTCGGAGATGTGTATAAGAGACAG-3′ was annealed to Tn5-rev oligo 5′-[phos]CTGTCTCTTATACACATCT-3′. Transposons were assembled using Tn5 and primers A and B in DF buffer (100 mM HEPES, pH 7.2, 200 mM NaCl, 0.2 mM EDTA, 2 mM DTT, 0.2% Triton X-100, 20% glycerol). Tagmented DNA was PCR amplified and purified with AMpure XP beads (Beckman Coulter, A63880) and quality checked by running on 6% Native PAGE gels and Fragment Analyzer. The ChIP DNA libraries were sequenced with Illumina NextSeq500, 2x37 bp