A number of 40000000 TBC1D23 KO K562 cells, or cells expressing only TBC1D23-L or -S were collected for identifying and quantitating endogenous SUMO modifications. Intracellular SUMO Remnant Motif identification was performed using a PTMScan HS Ubiquitin/SUMO remnant kit (Cell Signaling Technologies, #59322) according to the instructions of manufacturers.