May contribute 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; neddylation of cullins play an essential role in the regulation of SCF-type complexes activity (By similarity). Regulates responses to the synthetic auxin 2,4-dichlorophenoxyacetic acid (2,4-D) in roots, probably by modulating the SCF(TIR1) ubiquitin E3 ligase complex-mediated proteolysis (PubMed:17905859). The DCUN1 domain, also known as PONY domain, mediates the interaction with different cullins. Root growth resistance to the anti-auxin p-chlorophenoxyisobutyric acid (PCIB), which inhibits auxin action by interfering the upstream auxin-signaling events (PubMed:17905859). Also resistant to the auxin analog 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide (PubMed:17905859).