Represses p73/TP73 activity. Proposed to enhance ubiquitin ligase activity of RING-type zinc finger-containing E3 ubiquitin-protein ligases. In vitro enhances ubiquitin ligase activity of TRIM28 and stimulates p53/TP53 ubiquitination by TRIM28 potentially in presence of Ubl-conjugating enzyme UBE2H. Proposed to act through recruitment and/or stabilization of the Ubl-conjugating enzyme (E2) at the E3:substrate complex. May play a role in embryonal development and tumor transformation or aspects of tumor progression. In vitro promotes cell viability in melanoma cell lines. Antigen recognized on a melanoma by autologous cytolytic T-lymphocytes. Negatively regulates acetylation and sumoylation of PML and represses PML-induced p53/TP53 acetylation and activation. Reduces p53/TP53 transactivation function through recruitment of HDAC3 to p53/TP53 transcription sites.