Neddylated species are UBE2M dependent. WT and NEDP1 KO HEK 293 cells were left untreated or treated with the indicated siRNA for 48 hours. Lysed cells were then processed for Western blot analysis. Neddylated species are reduced when NEDD8 E2 UBE2M was depleted after siRNA treatment (si2M), but not with control siRNA (siCTRL) or when NEDD8 E2 UBE2F was depleted (si2F). The double knockdown (si2M/2F) does not further reduce NEDD8 modified proteins. 