Western blot analysis of whole cell lysates from HEK 293 WT and NEDP1 KO cells reveals a loss of free NEDD8 (indicated by asterisk) and an accumulation of NEDD8 reactive species in the NEDP1 KO lysate. The predicted molecular weight sizes of putative, unanchored, poly-NEDD8 chains are denoted by N2 through to N5. Unconjugated NEDD8 is denoted by N1. 