MUL1

E3 ubiquitin-protein ligase activity, which accepts ubiquitin from an E2 ubiquitin-conjugating enzyme in the form of a thioester and then directly transfer the ubiquitin to targeted substrates. Can ubiquitinate AKT1 preferentially at 'Lys-284' involving 'Lys-48'-linked polyubiquitination and seems to be involved in regulation of Akt signaling by targeting phosphorylated Akt to proteasomal degradation. Mediates polyubiquitination of cytoplasmic p53/TP53 at 'Lys-24' which targets TP53 for proteasomal degradation, thus reducing TP53 levels in the cytoplasm and mitochondrion. Also involved in antiviral immunity by mediating 'Lys-63'-linked ubiquitination of STING1, promoting production of type I interferon (IFN-alpha and IFN-beta), whitout activating STING1-dependent NF-kappa-B signaling. Proposed to preferentially act as a SUMO E3 ligase at physiological concentrations. Involved in the modulation of innate immune defense against viruses by inhibiting RIGI-dependent antiviral response. Can mediate RIGI sumoylation and disrupt its polyubiquitination. Plays a role in the control of mitochondrial morphology by promoting mitochondrial fragmentation, and influences mitochondrial localization. Likely to promote mitochondrial fission through negatively regulating the mitochondrial fusion proteins MFN1 and MFN2, acting in a pathway that is parallel to the PRKN/PINK1 regulatory pathway. May also be involved in the sumoylation of the membrane fission protein DNM1L. Inhibits cell growth. When overexpressed, activates JNK through MAP3K7/TAK1 and induces caspase-dependent apoptosis..

Function from UniProtKB (Q969V5), read 2026-09-23. CC BY 4.0.