Contributes to the neddylation of all cullins by transferring NEDD8 from N-terminally acetylated NEDD8-conjugating E2s enzyme to different cullin C-terminal domain-RBX complexes. May interact (via the DCUN1 domain) with unneddylated cullins. The DCUN1 domain, also known as PONY domain, may mediate the interaction with cullins.