E3 ubiquitin-protein ligase that regulates several biological processes through the ubiquitin-mediated proteasomal degradation of various target proteins. Ubiquitinates the caspases CASP8 and CASP10, promoting their proteasomal degradation, to negatively regulate cell death downstream of death domain receptors in the extrinsic pathway of apoptosis. May mediate 'Lys-48'-linked polyubiquitination of RIPK1 and its subsequent proteasomal degradation thereby indirectly regulating the tumor necrosis factor-mediated signaling pathway. Negatively regulates p53/TP53 through its direct ubiquitination and targeting to proteasomal degradation. Indirectly, may also negatively regulate p53/TP53 through ubiquitination and degradation of SFN. Mediates PPARGC1A proteasomal degradation probably through ubiquitination thereby indirectly regulating the metabolism of brown fat cells. Possibly involved in innate immunity, through 'Lys-48'-linked polyubiquitination of NOD1 and its subsequent proteasomal degradation. 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. Protein modification; protein ubiquitination. Interacts with CASP8 and CASP10. Interacts with p53/TP53; involved in p53/TP53 ubiquitination. Interacts (via RING-type zinc finger) with MDM2; the interaction stabilizes MDM2. Interacts (via RING-type zinc finger) with PPARGC1A. Interacts with NOD1. The RING-type zinc finger is required for the ubiquitination of target proteins. The FYVE-type zinc finger domain is required for localization and may confer affinity for cellular compartments enriched in phosphatidylinositol 5-phosphate and phosphatidylinositol 3-phosphate phospholipids. Autoubiquitinated (in vitro). Proteolytically cleaved by caspases upon induction of apoptosis by TNF.