library_construction_protocol: Chromatin was sonicated to approximately one nucleosome using the Bioruptor Pico (Diagenode), 10 cycles of 30s ON/30 s OFF in a 4°C water bath. ubH2B ChIP was performed using ~28 µg of chromatin with 3 µl of ubH2B antibody (Cell Signaling; #5546S) by overnight incubation at 4 °C. Protein-chromatin-pull down followed with a 1:1 mix of protein A and protein G Dynabeads (Thermo Fisher; 10001D, 10003D). ChIP samples were extensively washed and purified using Qiagen MinElute kit. Sample libraries were prepared using Hifi Kapa sample prep kit and A-T mediated ligation of Nextflex adapters or xGen UDI-UMI adapters. Samples were sequenced using an Illumina NovaSeq X, using paired-end sequencing with 150 bp from each end.