The UAF1-USP1 Deubiquitinase Complex Stabilizes CGAS And Facilitates Antiviral Immune Responses

Cyclic guanosine monophosphate-adenosine monophosphate synthase(cGAS)serves as a key pattern recognition receptor to initiate innate immune responses.cGAS detects viral DNA or the emergence of DNA in cytoplasm caused by genomic instability,and generates the second messenger cGAMP,which in turn induces the expression of type I interferons(IFNs)via the adaptor STING.cGAS-STING pathway plays fundamental roles in antiviral responses.However,aberrant activation of cGAS following the recognition of cytosolic self-DNA has been implicated in autoinflammatory diseases,senescence and malignancy,etc.Therefore,cGAS activation should be tightly controlled to defense against viral infection and avoid harmful immune pathology.The magnitude of the response to DNA is determined by the expression level of cGAS.Varieties of posttranslational modifications,such as ubiquitination and SUMOylation,control cGAS protein stabilization and therefore fine-tunes its activation.The autophagy receptor p62 senses K48-linked polyubiquitination of cGAS to promote its autophagosomal degradation.The deubiquitinases USP14 and USP29 cleave K48linked ubiquitination to enhance cGAS stability.SUMOylation and DeSUMOylation of cGAS,mediated by TRIM38 and SENP2 respectively,also controls cGAS stability.However,the underlying mechanisms by which control cGAS stability,especially its feedback regulation during viral infection,remain largely unknown.Ubiquitin specific peptidase 1(USP1)-associated factor 1(UAF1,also called WDR48 or p80)is a chaperone protein of three deubiquitinating enzymes,including USP1,USP12,and USP46.UAF1 constitutively binds to USP1,USP12,and USP46,forms the deubiquitinating enzyme complexes,and thus enhances their deubiquitinase activity.UAF1/USP1 complex plays regulatory roles in a variety of biological processes,such as DNA damage response and tumor pathogenesis.UAF1/USP1 complex deubiquitinates and stabilizes inhibitors of DNA binding(ID)1,ID2 and ID3,thereby inhibited osteoblastic differentiation,and enhanced proliferation.UAF1/USP12 stabilizes B cell lymphoma/leukemia 10(BCL10)by deubiquitinating,and thereby activates CD4+T cell signaling.Previously,we report that UAF1/USP1 deubiquitinase complex stabilizes TBK1 and NLRP3,and enhances the activation of RLR and inflammasome.ML323,a specific inhibitor of UAF1/USP1 deubiquitinase complex,attenuates RLR-driven IFNs responses and ameliorates NLRP3-dependent inflammation in vivo.These findings suggest UAF1/USP1 as a promising target for drug design.However,whether UAF1 deubiquitinase complexes have other targets and its potential roles in cGAS activation,need to be clarified.In this study,we found that viral infection induced UAF1/USP1 expression.Uafl deficiency and ML323 both attenuated cGAS triggered antiviral responses and facilitated viral replication.UAF1 and USP1 both interacted with cGAS,cleaved its K48-linked polyubiquitination and thus stabilized its protein expression.Thus,our study uncovered a positive feedback mechanism of cGAS-dependent antiviral responses and suggested UAF1/USP1 complex as a potential target for the treatment of diseases caused by aberrant cGAS activation.