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 which are necessary for the activation of cullin-RING E3 ubiquitin ligases (CRLs). Interacts (via the DCUN1 domain) with the unneddylated cullins: interacts with CUL1, CUL2, CUL3, CUL4A, CUL4B and CUL5; these interactions promote the cullin neddylation and the identity of the cullin dictates the affinity of the interaction (PubMed:26906416, PubMed:23201271). Interacts with RBX1 and RNF7 (PubMed:26906416). Interacts with CAND1; this interaction is bridged by cullins such as CUL3 and strongly inhibits the neddylation of CUL3. These CAND-cullin-DCNL complexes can only be neddylated in the presence of a substrate adapter (PubMed:26906416). Interacts (via DCUN1 domain) with UBE2M (N-terminally acetylated form) and probably with UBE2F (N-terminally acetylated form) (PubMed:23201271). The DCUN1 domain, also known as PONY domain, mediates the interaction with different cullins (PubMed:23201271). The DCUN1 domain mediates the interaction with the N-terminally acetylated NEDD8-conjugating E2s enzyme leading to the NEDD8 transfer from N-terminally acetylated NEDD8-conjugating E2s enzyme to different cullin C-terminal domain-RBX complexes; the neddylation efficiency correlates with the DCUN1D5-cullin and DCUN1D5-E2 interaction affinities (PubMed:23201271).