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1、Severeacuterespiratorysyndrome(SARS)associatedcoronavirus(SARS-CoV)IntroductionProteinsLifecyclePathogenesisandEvasionTherapyContentBrief IntroductionSARS-CoVcontainsasinglestrandedandpositivesenseRNAgenomeofabout29.7kb.Spikeproteinsformacrown-likecoronathatgivesthevirusitsnameItsRNAgenomehasa5capan
2、da3polyAtractcontaining14openreadingframes(ORFs)ClassificationFamily:CoronaviridaeGenus:CoronavirusClinicalfeaturesTheincubationperiod(潜伏期)ofSARSisgenerally214days.high feverDyspneacoughmalaisefatiguemyalgiaheadacherigorchillClinical featuresSARS-CoVtransmissionThemostlikelyexplanationfortheemergenc
3、eofSARS-CoVisanimal-to-humaninterspeciestransmissionLikemostotherrespiratoryvirusinfections,SARSismainlytransmittedbyrespiratorydroplets,directcontactwithinfectioussecretions(分泌物)orcontactwithcontaminatedfomites(污染物).ProteinsofSARScoronavirusR.Hilgenfeld,M.Peiris/Antiviral Research 100(2013)286295Sp
4、ikeProtein(Sprotein)：canbesubdividedintoanN-terminalhalf(S1)andC-terminalhalf(S2).S1isresponsibleforvariationsinhostrangeandtissuetropismaccordingtoitsreceptorspecificity,whereasS2isresponsibleforcellentryfollowingvirusandhostcellmembranefusion.NucleocapsidProtein(Nprotein):canbindtothegenomicRNAvia
5、aleadersequence,recognisesastreachofRNAthatservesasapackagingsignalandleadstotheformationofthehelicalribonucleoprotein(RNP)complexduringassembly.StructuralProteinsSpikeProtein(Sprotein)：canbesubdividedintoanN-terminalhalf(S1)andC-terminalhalf(S2).Twofunctions:bindingreceptor：receptor-bindingdomain(R
6、BD)viralfusionNucleocapsidProtein(Nprotein):Itsprimaryfunctionistopackagethe30kbsinglestranded,5-cappedpositivestrandviralgenomeRNAmoleculeintoaribonucleoprotein(RNP)complexcalledthecapsid.AccessoryProteinsEightaccessoryproteinshavebeenidentifiedinSARS-CoV:P3a,P3b,P6,P7a,P7b,P8a,P8bandP9b.Non-Struct
7、uralProteins（nsps）Papain-likeprotease(PLpro)：afunctionaldomainofnsp3Mainprotease(Mpro)：nsp5nsp1,ahostgeneexpressionsuppressor;nsp2,functionsininteractingwiththetwohostproteins;nsp3,amulti-domaincomplex;nsp4/nsp6,transmembraneproteins;nsp5,theMpro;nsp7/nsp8,primases;nsp9,asingle-strandedRNA-bindingpr
8、otein;nsp12,anRNA-dependentRNApolymerase;nsp13,5-to-3RNAhelicase/NTPase/RNA5-triphosphatase;nsp14,3-to-5exoribonuclease;nsp15,uridylate-specificendoribonuclease;nsp16,2-O-methyltransferasensp3/nsp5nsp9：anssRNA-bindingproteinnsp12:RdRpco-factor:nsp7/nsp8nsp10/nsp14：3-5 exoribonucleasensp14-ExoNiscapa
9、bleofremovingsingle3mismatchednucleotidesandthatthisactivityisstimulatedbythenon-enzymaticproteinnsp10.N7-methyltransferase(N7-MTase)nsp10/nsp16 2-O-methyltransferasensp13TheRNA5-triphosphatase(RTPase)SARS-CoVRNACappingPathway(1)anRNA5triphosphatase(RTPase)hydrolysesthe5-phosphateofthenascentmRNA(2)
10、aguanylyltransferase(GTase)catalysesthetransferofaguanosinemonophosphate(GMP)tothediphosphatemRNA5end(3)anRNAmethyltransferase(MTase)addsamethylgroupattheN7positionofthecapguanine(4)2-O-MTase(nsp16/nsp10)transfersamethylgrouptothe2OpositionofthefirstmRNAnucleotideThe life cycle of SARS-CoVMain targe
11、t cells:1.Lungepithelialcells（肺上皮细胞）2.lymphocytes（淋巴细胞）3.Intestinalmucosalcells（肠粘膜细胞）4.NervecellsSARS-CoV infects Lung epithelial cells to produce offspring viruses.Genome replication of SARS-CoV3 Discontinuous extension of sg-RNA(+)(-)ThepathogenesisofSARS-CoV（SARS-CoV的致病机制）AngI（AngiotensinI）:血管紧张
12、素I AngII（AngiotensinII）:血管紧张素II ACE（Angiotensin-convertingenzyme,血管紧张素转换酶）Function:ACEcleavesAngItogenerateAngII;ACEpromotesacutelunginjuryandACE2alleviatesit.ACE2（Angiotensin-convertingEnzyme2,血管紧张素转换酶2）Function:ReceptoroftheenvelopeSpikeprotein;DegradationofAngII,ACE2cleavesAngIItogenerateAngI;Pro
13、tectaginstacutelunginjury;Sprotein blindstoACEACE2 AngI AngII AngI AngIItype1aReceptor leadsto acutelunginjury Conclusion TheblindingofSproteintoACE2leadstodownregulationofACE2,itcontributestoacutelunginjury.Immuneevasion(免疫逃逸)EvasionoftheinnateimmuneresponsebySARS-CoVSARS-CoVusesseveralstrategiesto
14、avoidtheinnateimmuneresponse.1.Pro-inflammatorycytokines（致炎性因子）andIFNs；2.Antiviralproteins；HowdoesPro-inflammatorycytokines（致炎性因子）andIFNscomeabout.TheinnateimmuneresponseisactivatedbyPAMPs(pathogen-associatedmolecularpatterns)ItisrecognizedbyPRRs(hostpatternrecognitionreceptors),suchasRIG-IandMDA5.F
15、ollowingPRR-mediateddetectionofaPAMP,theresultinginteractionofPRRswithMAVS(mitochondrialantiviral-signallingprotein)activatesNF-B(nuclearfactor-B)throughasignallingcascadeinvolvingseveralkinases.ActivatedNF-Btranslocatestothenucleus,whereitinducesthetrans-criptionofproinflam-matorycytokines.Thekinas
16、esalsophosphorylateIRF3(IFNregulatoryfactor3)andIRF7,whichformhomodimersandheterodimersandenterthenucleustoinitiatethetranscriptionoftypeIinterferons(typeIIFNs).SARS-CoVhasdevelopedmechanismstointerferewiththesesignallingpathwaysasshown;thesesubversionstrategiesinvolvebothstructuralproteins(membrane
17、(M)andnucleocapsid(N)andnon-structuralproteins(nsp1,nsp3b,nsp4a,nsp4b,nsp5,nsp6andPLpro(papain-likeprotease，木瓜蛋白酶);Howdoesantiviralproteinscomeabout.antiviralproteinsBindingoftypeIIFNstotheirdimericreceptor,IFN/receptor(IFNAR),activatestheJanuskinase(JAK)signaltransducerandactivatoroftranscription(S
18、TAT)signallingpathway.JAK1andTYK2kinasesphosphorylateSTAT1andSTAT2.JAK1andTYK2kinasespho-sphorylateSTAT1andSTAT2,whichformcomplexeswithIRF9.ThesecomplexesmoveintothenucleustoinitiatethetranscriptionofIFN-stimulatedgenes(ISGs，干扰素刺激基因)andproduceantiviralproteins.，underthecontrolofpromotersthatcontaina
19、nIFN-stimulatedresponseelement(ISRE，干扰素刺激反应元件)，Antiviral proteinsSARS-CoVhasdevelopedmechanismstointerferewiththissignallingpathwaytoinhibittheproductionofantiviralproteinsthatareencodedbyISGs，itinvolvesnsp1,nsp3bandnsp6.（1）Proteaseinhibitors（2）SARS-CoVhelicaseinhibitors（3）Peptides（4）RNAproductsProt
20、ease inhibitors(1)3CLProinducesautolyticcleavageofpolyproteinpp1a/1abandthusassistinthematurationprocessofSARS-CoV.(2)PLProisinvolvedinprocessingtheviralpolyproteinandalsoadeubiquitinatingenzyme.Thedeubiquitinationmightprotectreplicasesubunitagainstproteosomaldegradation.3CLPro inhibitorsFigure 1Fig
21、ure 2Figure 3Figure 5Figure 4PLPro inhibitorsFigure 6SARS-CoV helicase inhibitorsSARS-CoVhelicaseisanon-structuralprotein,acleavageproductofpp1ab,whichbindsto5overhangandmovesin53polaritytobringaboutnegativesupercoilingofdouble-strandRNAItsroleinunwindingofDNAorRNAmakesitindispensableforviralreplica
22、tionandis,therefore,anattractivetargetforantiviralagents.Figure 7Peptides(1)Thymosin1(TA1)peptide,asynthetic28aminoacidpeptides,forpreventionortreatmentofSARS-CoVinfection.(2)DipeptidecompoundwithdualpurposeofdetectionandinhibitionofSARS-CoV.ThesedipeptidesareselectedbasedontheirdockingwithSARS-CoVe
23、nvelopeproteins(PDBID2AMQ)Figure 8RNA products（1）Ribozyme,an antisense RNA molecule with catalytic activity.Figure 9(2)UsingsmallinterferenceRNAtoinhibitSARS-CoVsMproteinexpression.Thedesigneddouble-strandedRNA,namedsiRNA-M1,hassequenceof5-gggugacuggcgggauugcgau-3,complementarytothesequenceofMproteinmRNA220-241nucleotides.AnothersiRNA-M2,5-gggcgcugugacauuaaggac-3,iscomplementarytothe460-480nucleotidesofMproteinmRNA.Thankyou
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