E3 ubiquitin-protein ligase. Mediates 'Lys-63'-linked polyubiquitination and stabilization of the JUN coactivator RNF187 in response to growth factor signaling via the MEK/ERK pathway, thereby regulating JUN transactivation and cellular proliferation (PubMed:25851810). Promotes the TLR4-mediated signaling activation through its E3 ligase domain leading to production of pro-inflammatory cytokines and type I interferon (By similarity). Also plays a negative role in the regulation of exogenous cytosolic DNA virus-triggered immune response. Mechanistically, enhances the 'Lys-48'-linked ubiquitination of STING1 leading to its proteasome-dependent degradation (PubMed:32126128). (Microbial infection) Promotes Zika virus replication by mediating envelope protein E ubiquitination. 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. Forms homodimers, and heterodimers with GNIP2 (PubMed:14984203, PubMed:25851810). Interacts with GYG (PubMed:11916970, PubMed:14984203). Interacts with RNF187 (via C-terminus) (PubMed:25851810). Skeletal muscle and placenta, at lower levels in heart, brain and pancreas. Isoform 1 is widely expressed with high level in testis, kidney and heart. The B30.2 domain mediates interaction with GYG. The coiled-coil region mediates homodimerization and heterodimerization. Phosphorylated at Ser-107 by RPS6KA5/MSK1, which stimulates the ubiquitin ligase activity. Belongs to the TRIM/RBCC family.