The function of MAGEA3 (MAGE family member A3, Ensembl gene identifier ENSG00000221867) is as follows. Activator of ubiquitin ligase activity of RING-type zinc finger-containing E3 ubiquitin-protein ligases that acts as a repressor of autophagy (PubMed:20864041, PubMed:31267705). May enhance ubiquitin ligase activity of TRIM28 and stimulate p53/TP53 ubiquitination by TRIM28. Proposed to act through recruitment and/or stabilization of the Ubl-conjugating enzyme (E2) at the E3:substrate complex (PubMed:17942928, PubMed:20864041). May play a role in embryonal development and tumor transformation or aspects of tumor progression (PubMed:17942928, PubMed:20864041). In vitro promotes cell viability in melanoma cell lines (PubMed:17942928). Antigen recognized on a melanoma by autologous cytolytic T-lymphocytes (PubMed:8113684). {ECO:0000269|PubMed:17942928, ECO:0000269|PubMed:20864041, ECO:0000269|PubMed:31267705, ECO:0000269|PubMed:8113684}.