E3 ubiquitin-protein ligase that participates in multiple biological processes including cell death, glucose metabolism, and in particular, the innate immune response. Mediates 'Lys-63'-linked polyubiquitination of TRAF3 thereby promoting type I interferon production via DDX58/RIG-I signaling pathway. Can also catalyze 'Lys-48'-linked polyubiquitination and proteasomal degradation of viral proteins such as influenza virus PB2. Acts as a negative feedback regulator of TLR7- and TLR9-triggered signaling. Mechanistically, promotes the 'Lys-48'-linked ubiquitination of IRF7 and induces its degradation via a proteasome-dependent pathway. Reduces FGFR1-dependent tyrosine phosphorylation of PKM, inhibiting PKM-dependent lactate production, glucose metabolism, and cell growth. 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 PKM isoform M2, but not isoform M1; this interaction may compete with that between PKM and FGFR1, and hence reduces FGFR1-dependent tyrosine phosphorylation of PKM. Interacts with IRF7; this interaction promotes IRF7 proteasomal degradation. Interacts with TRAF3; this interaction promotes TRAF3 activation. Found predominantly in cytoplasm with a granular distribution. Found in punctuate nuclear bodies. The RING finger domain and the coiled-coil region are required for the apoptosis-inducing activity.