Add info After ectopic expression of Flag-USP38 or an empty vector in HEK293T cells for 48 hours, cells were lysed, and the supernatant after lysis was added to magnetic beads coupled with Flag antibodies. The mixture was incubated at 4°C overnight for pull-down. Subsequently, the magnetic beads were washed three times with lysis buffer and once with PBS. The magnetic bead pellet was retained for mass spectrometry identification and analysis.