NEDD8 and neoplasm: In the crystal structure model of the NEDD8 E1 ubiquitin-fold domain and the UBE2F core [42], the extra peptide would be inserted in an exposed disordered region between β2 and β3 sheets, potentially introducing a new interaction surface; however, the impact on neddylation, degradation of pro-apoptotic NOXA [45] or tumor growth remains to be characterized.