曹雪涛院士研究组近期接连发表了最新成果,在抗病毒免疫研究中取得了新进展:在11月21日发表于NatureImmunology杂志上题为“NuclearRNF2inhibitsinterferonfunctionbypromotingK33-linkedSTAT1disassociationfromDNA”的一项成果中,研究组成员发现E3泛素连接酶RNF2通过诱导STAT1发生一种新型的泛素化修饰方式即K33连接的多聚泛素化修饰,促进STAT1与DNA解离,抑制STAT1的转录功能,进而抑制了STAT1下游一系列干扰素刺激基因(ISGs)的表达,最终抑制了干扰素介导的抗病毒天然免疫功能。
这一研究结果进一步深化了对抗病毒天然免疫调控机制的认识,对病毒感染及相关的炎症性疾病等的治疗及药物研发提供了新的策略和潜在靶点。
在这篇文章中,研究人员利用高内涵筛选体系对E3泛素连接酶RNF家族蛋白在抗病毒天然免疫应答反应中的调控作用进行了筛选,发现Ringfingerprotein2(RNF2)能够负向调控I型干扰素介导的抗病毒反应。
I型干扰素刺激靶细胞后,触发RNF2与STAT1的DNAbindingdomain相互作用,通过其E3泛素连接酶活性促进STAT1第379位赖氨酸发生K33连接的多聚泛素化修饰,从而促进STAT1从其结合的DNA上解离,最终降低了下游ISGs基因的表达。
研究人员还发现RNF家族的多个分子参与抗病毒天然免疫反应的调控,其中表观调控蛋白RNF2能够不依赖于其对染色质及组蛋白的调控而抑制STAT1对ISGs的转录。髓系细胞特异性敲除RNF2的小鼠对多种病毒感染的抵抗能力增强并伴随抗病毒ISGs表达增加,从而进一步证实了RNF2参与I型干扰素信号通路及抗病毒反应的负向调控作用。
同时研究组在Science杂志上也发文,揭示了一种由病毒诱导lncRNA介导的病毒感染代谢反馈方式,也为研发广谱抗病毒治疗剂提供了一个潜在的靶标。
研究人员发现了一种特殊的lncRNA,这种lncRNA并不是通过I型干扰素(IFN-I)诱导,而是由多种病毒诱导。
研究人员发现如果缺失lncRNA-ACOD1,那么就会极大的消弱通过IFN-I/IRF3非依赖性途径的病毒感染,而且细胞质中的lncRNA-ACOD1能直接结合代谢酶glutamic-oxaloacetictransaminase(GOT2),增加后者的催化活性。重组GOT2蛋白及其代谢物可以挽救lncRNA-ACOD1缺陷后导致的病毒复制,增加致死率。
由此可见,这项工作揭示了一种由病毒诱导lncRNA介导的病毒感染代谢反馈方式,也为研发广谱抗病毒治疗剂提供了一个潜在的靶标。
Abstract:
Prolongedactivationofinterferon–STAT1signalingiscloselyrelatedtoinflammatoryautoimmunedisorders,andthereforetheidentificationofnegativeregulatorsofthesepathwaysisimportant.Throughhigh-contentscreeningof115mouseRING-domainE3ligases,weidentifiedtheE3ubiquitinligaseRNF2asapotentinhibitorofinterferon-dependentantiviralresponses.RNF2deficiencysubstantiallyenhancedinterferon-stimulatedgene(ISG)expressionandantiviralresponses.Mechanistically,nuclearRNF2directlyboundtoSTAT1afterinterferonstimulationandincreasedK33-linkedpolyubiquitinationoftheDNA-bindingdomainofSTAT1atpositionK379,inadditiontopromotingthedisassociationofSTAT1/STAT2fromDNAandconsequentlysuppressingISGtranscription.Ourstudyprovidesinsightintotheregulationofinterferon-dependentresponsesviaapreviouslyunrecognizedpost-translationalmodificationofSTAT1inthenucleus.
Main:
TypeIinterferonsplaycrucialrolesininnateantiviralresponsesviatheinductionofmultipleantiviralgenesandhavebeenusedtotreathepatitisBandCviralinfections.Apartfrominterferons’essentialactionsinantiviralimmunity,prolongedorexaggeratedactivationofthetypeIinterferonpathwayhasbeencloselylinkedtoimmunedysregulationandtissuepathogenesisinvariousimmunologicaldisorderssuchasautoimmunediseasesandpersistentinfections1,2.Moreover,antibodyblockadeoftypeIinterferonsignalingcontributestothepromotionofviralclearanceandthepreventionoftissuedamageduringchronicinfection3,4.Thus,themagnitudeanddurationoftypeIinterferonsignalingneedtobetightlyregulatedinorderforproperantiviralimmunitytobeachievedandforunwantedimmunepathogenesistobeavoided.Theidentificationofnewnegativeregulatorsandoftheunderlyingmechani
smsoftypeIinterferonsignalingisthereforecriticalforabetterunderstandingofthecompleximmuneresponsestriggeredbytypeIinterferon,andmayleadtothedevelopmentofnewapproachesforthepreventionandtreatmentofviralinfectionsandautoimmunediseases.
TypeIinterferons,includingIFN-αandIFN-β,areexpressedandsecretedbyalargenumberofimmuneandnon-immunecellsandcantriggerpotentantiviralresponsesintargetcells.UponengagementwiththeIFN-αreceptor(IFNAR),typeIinterferoninducesphosphorylationofthekinasesJAK1andTYK2,whichsubsequentlypromotetyrosinephosphorylationofthetranscriptionfactorsSTAT1andSTAT2.PhosphorylatedSTAT1(pY-STAT1)interactswithpY-STAT2andthetranscriptionregulatorIRF9toformthetranscriptionalcomplexISGF3,whichtranslocatestothenucleusandbindsspecificpromotersequencescalledinterferon-stimulatedresponseelements(ISREs)toinitiatethetranscriptionofantiviralISGs.AlthoughthecrucialroleofSTAT1inmediatingtypeIinterferonsignalinghasbeenintensivelystudied,thepreciseregulationofSTAT1-mediatedtranscriptionofISGsisnotfullyunderstood.
Post-translationalmodificationhasemergedasacriticalmechanismfortheregulationoftypeIinterferonsignaling5,6.Phosphorylation,acetylation,ubiquitinationandmethylationpotentlyregulatethetranscriptionalactivitytriggeredbytypeIinterferon,aswellasSTAT1functions7,8,9,10.Proteinubiquitinationisanimportantenzymaticpost-translationalmodificationwithdistinctfunctionsinseveralcellularresponses11.Sofar,poly-linkagesviasevenlysineresidues(K6,K11,K27,K29,K33,K48andK63)andlinearlinkageviamethionine1andglycine76ofubiquitinhavebeenshowntoexertdifferentfunctions.K48-linkedandK63-linkedpolyubiquitinationhaveoppositerolesintheregulationofSTAT1activityandactbyinducingproteasome-mediateddegradationofSTAT1andbypromotingthephosphorylationandtranscriptionalactivityofSTAT1,respectively12,13.However,thefunctionofothertypesofubiquitinationintheregulationofSTAT1transcriptionalactivityandtypeIinterferonsignalingremainslargelyunknown.
AsidefromTRIMproteins14,therolesofotherRING-domainE3ligasesandtheunderlyingmechanismsbywhichtheyregulatetypeIinterferonsignalingandantiviralinnateimmunityremainunclear.RNF2isanuclearessentialcomponentoftheepigeneticrepressivecomplexPRC1andcancatalyzemonoubiquitinationofhistoneH2A15.RNF2participatesinmanybiologicalprocesses,suchastissuedevelopmentandtumorigenesis16,17.However,theroleofRNF2ininnateimmuneresponseandinflammationhasnotbeenreportedyet,andwhetherRNF2couldmediatetheubiquitinationofnon-histonestoregulatecellularsignalingalsoremainsunclear.Herewecarriedouthigh-contentscreening(HCS)of115mouseRING-domainE3s(excludingTRIM-familyproteinsandothermembersthathavenotbeenclearlyclassified)todeterminetheirrolesintype-I-interferon-mediatedinhibitionofviralinfection,andidentifiedRNF2asacriticalinhibitorofantiviralimmuneresponsestriggeredbytypeIinterferon.WeshowthatRNF2promotedK33-linkedpolyubiquitinationatK379ofSTAT1andthuspromotedSTAT1/STAT2disassociationfromDNA,withconsequentinhibitionoftypeIinterferonsignalingandantiviralresponses.