Approximately 5X107 cells were used for each ChIP-seq assay. The chromatin DNA precipitated by polyclonal antibodies against USP7, EZH2, H3K27me3 or H2BK120ub1. The DNA samples were purified with the Qiagen PCR purification kit before in-depth whole genome DNA sequencing was performed by CapitalBio Corporation (Beijing, China). The raw sequencing image data were examined by the Illumina analysis pipeline, aligned to the unmasked human reference genome (hg19) using Bowtie2, and further analyzed by MACS (Model-based Analysis for ChIP-seq).