UBA3 encodes a subunit of the NEDD8 (603171)-activating enzyme (NAE), essential for the control of activity of the cullin-RING subtype of ubiquitin ligases (summary by Soucy et al., 2009).

Ubiquitin (191339) is covalently attached to target proteins by a multienzymatic system consisting of E1 (ubiquitin-activating), E2 (ubiquitin-conjugating), and E3 (ubiquitin-ligating) enzymes. Osaka et al. (1998) found that NEDD8 (603171), a ubiquitin-like protein, is conjugated to proteins in a manner analogous to ubiquitylation. They found that beta-amyloid precursor protein-binding protein-1 (APPBP1; 603385) can bind to NEDD8 in rabbit reticulocyte lysates. However, since APPBP1 shows similarity to only the N-terminal domain of an E1 enzyme, the authors reasoned that it must interact with a protein showing similarity to the C-terminal region of E1s. By searching sequence databases, Osaka et al. (1998) identified cDNAs encoding UBA3, the human homolog of yeast Uba3. The predicted 442-amino acid UBA3 protein shares 43% sequence identity with yeast Uba3. In vitro, UBA3 formed a complex with APPBP1 and a thioester linkage with NEDD8. Osaka et al. (1998) suggested that the APPBP1/UBA3 complex functions as an E1-like enzyme for the activation of NEDD8.

To identify novel steroid receptor-interacting proteins, Fan et al. (2002) performed yeast 2-hybrid screening of a rat uterine luminal epithelium cDNA library using the ligand-binding and hinge region of ER-alpha (133430) as bait. They cloned and characterized a cDNA encoding a protein homologous to yeast and human UBA3, the catalytic subunit of the activating enzyme of the ubiquitin-like NEDD8 conjugation pathway (known as neddylation). Sequence analysis revealed that Uba3 contains multiple nuclear receptor (NR)-interacting motifs (NR boxes), which are known to mediate interactions between coregulatory proteins and ligand-activated NRs. Yeast 2-hybrid and glutathione-S-transferase pull-down assays demonstrated that Uba3 directly interacts with ligand-occupied ER-alpha and ER-beta (601663). Transient transfection of Uba3 in mammalian cells inhibited ER-mediated transactivation in a time-dependent fashion. The authors concluded that UBA3 inhibits transcription induced by steroid hormone receptors through a novel mechanism that involves the neddylation pathway.

Gross (2022) mapped the UBA3 gene to chromosome 3p14.1 based on an alignment of the UBA3 sequence (GenBank BC022853) with the genomic sequence (GRCh38).

The NEDD8-activating enzyme, or NAE, composed of NAE1 (603385) and UBA3 subunits, is an essential component of the NEDD8 contribution pathway that controls the activity of the cullin-RING subtype of ubiquitin ligases, thereby regulating the turnover of a subset of proteins upstream of the proteasome. Substrates of cullin-RING ligases have important roles in cellular processes associated with cancer cell growth and survival pathways. Soucy et al. (2009) described MLN4924, a potent and selective inhibitor of NAE. MLN4924 disrupts cullin-RING ligase-mediated protein turnover leading to apoptotic death in human tumor cells by a new mechanism of action, the deregulation of S-phase DNA synthesis. MLN4924 suppressed the growth of human tumor xenografts in mice at compound exposures that were well tolerated. Soucy et al. (2009) concluded that NAE inhibitors may hold promise for the treatment of cancer.

Walden et al. (2003) reported the structure and mutational analysis of human APPBP1-UBA3, the heterodimeric E1 enzyme for NEDD8. Each E1 activity is specified by a domain: an adenylation domain resembling bacterial adenylating enzymes, an E1-specific domain organized around the catalytic cysteine, and a domain involved in E2 recognition resembling ubiquitin. The domains are arranged around 2 clefts that coordinate protein and nucleotide binding so that each of E1's reactions drives the next, in an assembly-line fashion.

Bohnsack and Haas (2003) purified APPBP1-UBA3 from human erythrocytes and analyzed the kinetics of NEDD8 activation. In the presence of radiolabeled ATP and radiolabeled recombinant NEDD8, APPBP1-UBA3 rapidly formed a stable stoichiometric ternary complex composed of tightly bound NEDD8 adenylate and UBA3-NEDD8 thiol ester. Isotope exchange kinetics showed that the heterodimer followed a pseudo-ordered mechanism with ATP the leading and NEDD8 the trailing substrate. Ala72 of NEDD8 was critical in binding APPBP1-UBA3. Bohnsack and Haas (2003) concluded that the mechanism of NEDD8 activation by APPBP1-UBA3 shows a high degree of conservation with ubiquitin activation by UBA1.

Huang et al. (2007) reported the structural analysis of a trapped ubiquitin-like protein (UBL) activation complex for the human NEDD8 pathway containing NEDD8's heterodimeric E1 (APPBP1-UBA3), 2 NEDD8s (1 thioester-linked to E1, 1 noncovalently associated for adenylation), a catalytically inactive E2 (UBC12; 603173), and MgATP. The results suggested that a thioester switch toggles E1-E2 affinities. Two E2 binding sites depend on NEDD8 being thioester-linked to E1. One is unmasked by a striking E1 conformational change. The other comes directly from the thioester-bound NEDD8. After NEDD8 transfer to E2, reversion to an alternate E1 conformation would facilitate release of the covalent E2-NEDD8 thioester product. Thus, Huang et al. (2007) concluded that transferring the UBL's thioester linkage between successive conjugation enzymes can induce conformational changes and alter interaction networks to drive consecutive steps in UBL cascades.