(Left) The 25-kDa neddylated species induced by oxidative stress increases with time in WT U2OS cells. U2OS WT or NEDP1 KO cells were treated with 600 μM H2O2 for the indicated time and then lysed in LDS sample loading buffer and processed for Western blot analysis. (Right) The same 25 kDa NEDD8 species, which is strongly induced in WT cells, is present in untreated NEDP1 KO cells and does not further increase after oxidative stress induced by H2O2 (as indicated by the arrow). 