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 is necessary for the activation of cullin-RING E3 ubiquitin ligases (CRLs). May play a role in DNA damage response and may participate in cell proliferation and anchorage-independent cell growth. Part of a complex that contains DCUN1D5, CUL1 and RBX1; this interaction is bridged by CUL1. 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. Interacts (via DCUN1 domain) with UBE2M (N-terminally acetylated form) and probably with UBE2F (N-terminally acetylated form). May also interact with regulators or subunits of cullin-RING ligases such as RBX1, RNF7, ELOB and DDB1; these interactions are bridged by cullins. Interacts with CAND1; this interaction is bridged by cullins and strongly inhibits the neddylation of cullins. These CAND-cullin-DCNL complexes can only be neddylated in the presence of a substrate adapter. Subcellular localization is independent of the interaction with cullins. Highly expressed in testis (PubMed:26906416). Lower expressed in skin, thymus, spleen, lymph nodes and lung (PubMed:26906416). The DCUN1 domain, also known as PONY domain, mediates the interaction with different cullins. 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. Phosphorylation at Ser-41 is independent of cullin's interaction and neddylation (PubMed:29958295). Phosphorylated in response to both TICAM1 and MYD88 dependent Toll-like receptor (TLR) pathway activation (PubMed:29958295). Phosphorylated in response to IL1B stimulation (By similarity).