Structural architecture of Galdieria sulphuraria DCN1L

NEDD8ylation is a major regulatory event for cullin-RING E3 ubiquitin ligases (CRL). NEDD8ylation activates the ubiquitylation activity of CRLs, which serves to regulate a wide variety of cellular processes by selecting specific targets for destruction in the proteasome. NEDD8 E3 ligases catalyze ligation of the ubiquitin-like protein NEDD8 (Rub1 in yeast) to the C-terminal winged-helix domain of the CRL 'cullin' subunit. NEDD8ylation increases the ubiquitin (Ub) ligase activity of CRLs by enhancing binding of the CRL RING subunit to Ub-charged Ub-conjugating (E2) enzymes and by driving conformational changes that permit the RING subunit to productively orient Ub-E2 conjugates with bound CRL substrates for catalysis. However, it is unclear how the NEDD8 E3 ligase catalyzes its reaction, what its exact composition is, and how it is regulated. Moreover, current structural and functional models of the NEDD8 E3 ligase are based on the Saccharomyces cerevisiae system, in which, an integral NEDD8 E3 ligase subunit DCN1, has low sequence identity to mammalian DCN1-like proteins, and several amino acid insertions, which together may impede understanding of NEDD8 E3 function in a mammalian system.