Regulatory subunit of the dimeric UBA3-NAE1 E1 enzyme. E1 activates NEDD8 by first adenylating its C-terminal glycine residue with ATP, thereafter linking this residue to the side chain of the catalytic cysteine, yielding a NEDD8-UBA3 thioester and free AMP. E1 finally transfers NEDD8 to the catalytic cysteine of UBE2M. Necessary for cell cycle progression through the S-M checkpoint. Overexpression of NAE1 causes apoptosis through deregulation of NEDD8 conjugation. Binding of TP53BP2 to the regulatory subunit NAE1 decreases neddylation activity. Protein modification; protein neddylation. Heterodimer of UBA3 and NAE1. The complex binds NEDD8 and UBE2M. Binds APP and TP53BP2. Colocalizes with APP in lipid rafts. Expressed throughout the brain. In hippocampus, strongly expressed in granule cells and in the pyramidal cell layer. Strongly expressed in the piriform cortex. In the cerebellum, expressed only in Purkinje cells. Ubiquitinated by TRIP12, leading to its degradation by the proteasome. Belongs to the ubiquitin-activating E1 family. ULA1 subfamily.