The Ubiquitin E3 Ligase RAUL Negatively Regulates Type I Interferon through Ubiquitination of the Transcription Factors IRF7 and IRF3

SummaryIn the course of combating infectious agents, type I interferon (IFN) needs a timely downregulation mechanism to avoid detrimental overreaction. Here we showed a mechanism for restraining type I IFN responses, which relied on a HECT domain ubiquitin (Ub) E3 ligase, RAUL. RAUL limited type I IFN production by directly catalyzing lysine 48-linked polyubiquitination of both interferon regulatory factor 7 (IRF7) and IRF3 followed by proteasome-dependent degradation. Suppression of RAUL by dominant-negative RAUL or siRNA augmented both basal and virus-induced production of type I IFN, which resulted in reduced viral replication. The Kaposi's sarcoma-associated herpes virus immediate-early lytic cycle trigger protein RTA recruited this mechanism to augment its countermeasures against the host antiviral response. These results unveil a previously unrecognized “brake mechanism” for type I IFN that maintains proper low amounts of type I IFN under physiological conditions and restrains its magnitude when the antiviral response intensifies.

► Ub ligase RAUL limits type I IFN by catalyzing K48 ubiquitination of IRF7 and IRF3
► Suppression of RAUL augments production of type I IFN and reduces viral replication
► RAUL activity is positively regulated by deubiquitinase Usp7
► Virus KSHV RTA recruits the Usp7-RAUL mechanism to antagonize antiviral responses