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 and may play a role in the cell cycle progression by regulating the SCF ubiquitin E3 ligase complex, after UV damage (PubMed:23201271, PubMed:19617556, PubMed:27542266, PubMed:18823379). At the cell membrane, can promote and as well inhibit cullins neddylation (PubMed:19617556, PubMed:26906416, PubMed:25349211). Part of a complex containing DCUN1D3, CUL3 and RBX1 (PubMed:19617556). 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, PubMed:27542266). Interacts preferentially with CUL3; this interaction triggers the relocalization of CUL3 to the cell membrane where CUL3 is neddylated (PubMed:19617556). Interacts (via DCUN1 domain) with RBX1 (PubMed:26906416, PubMed:25349211). May also interact with regulators or subunits of cullin-RING ligases such as RNF7, ELOB and DDB1; these interactions are bridged by cullins (PubMed:26906416). Interacts (via DCUN1 domain) with CAND1; this interaction is bridged by cullins and strongly inhibits cullin neddylation (PubMed:26906416, PubMed:27542266). These CAND-cullin-DCNL complexes can only be neddylated in the presence of a substrate adapter (PubMed:26906416). Interacts (via DCUN1 domain) with the N-terminally acetylated form of UBE2M and UBE2F (PubMed:23201271, PubMed:25349211, PubMed:19617556). After UVC treatment, the protein enters to the nucleus gradually (PubMed:18823379). Cell membrane localization is essential for CUL3 neddylation (PubMed:19617556). Tends to be down-regulated in different type of cancers, including lung neuroendocrine carcinoma, thyroid Huerthle cell carcinoma and lung squamous cell carcinoma (PubMed:25349211). Mostly expressed in testis and brain (PubMed:26906416). Highly expressed in liver, bladder and renal normal tissue than their tumor tissue counterparts (PubMed:18823379). Palmitoylation stabilizes DCUN1D3 at the cell membrane (PubMed:19617556). Increases by UVC treatment. The DCUN1 domain, also known as PONY domain, mediates the interaction with different cullins (PubMed:23201271, PubMed:19617556). 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). This domain is also involved in CAND1-, cullins- and RBX1-binding (PubMed:25349211, PubMed:26906416).