E3 ubiquitin-protein ligase that promotes the ubiquitination of various substrates. In turn; participates in the regulation of many biological processes including cell cycle; apoptosis; osteoclastogenesis as well as innate or adaptive immunity. Acts as negative regulator of NF-kappa-B-dependent transcription by promoting the ubiquitination and stabilization of the NF-kappa-B inhibitor TNFAIP3. May promote the ubiquitination of TRAF6 as well. Acts also as a negative regulator of T-cell activation. Inhibits cellular dsRNA responses and interferon production by targeting MAVS component for proteasomal degradation. Ubiquitinates the CDK inhibitor CDKN1A leading to its degradationand probably also CDKN1B and CDKN1C. This activity stimulates cell cycle G1-to-S phase transition and suppresses cellular senescence. May play a role in spermatogenesis.