E3 ubiquitin-protein ligase RNF123

Catalytic subunit of the KPC complex that acts as E3 ubiquitin-protein ligase. Promotes the ubiquitination and proteasome-mediated degradation of CDKN1B which is the cyclin-dependent kinase inhibitor at the G0-G1 transition of the cell cycle. Functions also as an inhibitor of innate antiviral signaling mediated by RIGI and IFIH1 independently of its E3 ligase activity. Interacts with the N-terminal CARD domains of RIGI and IFIH1 and competes with the downstream adapter MAVS.