Has E2-dependent E3 ubiquitin-protein ligase activity. Ubiquitinates MAGED1 antigen leading to its subsequent degradation by proteasome (By similarity). May be involved in protein sorting. S-ubiquitinyl-[E2 ubiquitin-conjugating enzyme]-L-cysteine + [acceptor protein]-L-lysine = [E2 ubiquitin-conjugating enzyme]-L-cysteine + N(6)-ubiquitinyl-[acceptor protein]-L-lysine. Binds ubiquitin-conjugating enzymes (E2s). In vitro, interacts with the ubiquitin-conjugating enzyme, UBE2D2. Expressed in various regions of the brain including the cerebellum, cerebral cortex, medulla, occipital pole, frontal lobe, temporal lobe and putamen. Highest levels in the cerebral cortex. The RING-type zinc finger domain interacts with an ubiquitin-conjugating enzyme (E2) and facilitates ubiquitination. Substrate for E2-dependent ubiquitination. PubMed:12036302 reported that isoform 2 arises by alternative initiation. Truncated N-terminus.