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. 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-40 is independent of cullin's interaction and neddylation. Phosphorylated in response to both TICAM1 and MYD88 dependent Toll-like receptor (TLR) pathway activation (By similarity). Phosphorylated in response to IL1B stimulation (By similarity).