Neddylation of cullins is decreased in NEDP1 KO cells and is rescued by re-expression of NEDP1 by transient transfection. Western blot analysis from HEK 293 WT, NEDP1 KO cells and NEDP1 KO cells rescued with transient transfection of NEDP1 reveals that upon NEDP1 re-expression, the intensity of the NEDD8 reactive bands is reduced and the levels of free NEDD8 are increased. NEDP1 re-expression also increased the neddylation of each Cullin. The neddylated band of each Cullin is denoted with a star. Quantification and graph of the mean ± S.E.M. of the percentage neddylation of each Cullin in (E). 