786-O cells were lysed in IP buffer and processed for immunoprecipitation with anti-USP15 or normal rabbit IgG for 6 h at 4 °C. The immune complexes were incubated with Pierce Protein A/G Magnetic Beads (Thermo Scientific) overnight at 4 °C and washed with IP buffer. After SDS-PAGE and Coomassie brilliant blue staining, the gel was cut into sections and digested with trypsin. For each sample, 2 µg of total peptides were separated and analyzed with a nano-UPLC (nanoElute2) coupled to a timsTOF Pro2 mass spectrometer (Bruker) with a nano-electrospray ion source. Then the raw MS files were processed using PaSER software (Version 2023) and the built-in DDA-ProluCID-GPU search engine.