Activator of ubiquitin ligase activity of RING-type zinc finger-containing E3 ubiquitin-protein ligases that acts as a as 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). Interacts with TRIM28. Expressed in many tumors of several types, such as melanoma, head and neck squamous cell carcinoma, lung carcinoma and breast carcinoma, but not in normal tissues except for testes and placenta. Never expressed in kidney tumors, Leukemias and lymphomas. Ubiquitinated by the DCX(DCAF12) complex specifically recognizes the diglutamate (Glu-Glu) at the C-terminus, leading to its degradation. In vitro experiments measuring cell viability in melanoma cell lines used siRNA specific for MAGEA3 and MAGEA6.