冠状病毒Coronavirusl论文-1996 Recombination in large RNA viruses_ Coronaviruses.pdf

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1、seminarsinVIROLOGY,Vol7,1996:pp381–388RecombinationinlargeRNAviruses:CoronavirusesMichaelM.C.LaiCoronavirusescontainaverylargeRNAgenome,whichingtoboththegeneticstabilityanddiversityofundergoesrecombinationataveryhighfrequencyofnearlycoronavirusesinnature.25%fortheentiregenome.Recombination

2、hasbeendemonstratedtooccurbetweenviralgenomesandbetweendefective-interfering(DI)RNAsandviralRNA.ItprovidesCharacteristicsofcoronavirusRNAanditsanevolutionarytoolforbothviralRNAsandDIRNAandsynthesismayaccountforthediversityinthegenomicstructureofcoronaviruses.Thecapacityofcoronavirusestound

3、ergoThecoronavirusRNAgenomeisasinglespeciesofrecombinationmayberelatedtoitsmRNAtranscriptionsingle-stranded,positive-sensedRNA27–31kbinmechanism,whichinvolvesdiscontinuousRNAsynthesis,2length(seeLai1990).Itconsistsofsevento10genes,suggestingthenonprocessivenatureoftheviralpolymerase.oneofw

4、hich(gene1)encodesaprecursorofRNARecombinationisusedasatoolforthemutagenesisofviralpolymeraseofapproximately750–800kDa.GenegenomicRNA.compositionandarrangementvaryamongthediffer-Keywords:defective-interferingRNA/mousehepatitisentcoronaviruses(Figure1).Theenormoussizevirus/RNAevolution/RNAr

5、ecombination(22kb)ofthepolymerasegenesuggeststhatthepolymerasehasmultiplefunctions.Eachgeneis©1996AcademicPressLtdexpressedthroughoneofthemRNAs,whichare3'-coterminalandhaveanested-setstructure.OnlyCORONAVIRUSESCONTAINanextraordinarilylargeRNAthe5'-mostgeneofeachmRNAisfunctionalforgenome(27

6、–31kb).ThislargeRNAsizeimposesaproteintranslation.EachmRNAhasaleadersevereburdenonthevirusbecausesuchanRNAcansequenceof70–90nucleotidesderivedfromthebeexpectedtoaccumulatealargenumberoferrors5'-endofthegenomeRNA.mRNAtranscriptionisduringRNAreplication,assumingthattheerrorcarriedoutbyadisco

7、ntinuoustranscriptionmecha-frequencyofcoronaviralRNApolymeraseiscompara-nismwhichfusestheleaderRNAtothetranscriptionbletothatofotherRNAviruses.Thus,coronavirusesstartsignal(intergenicsequence).ThemRNAleadermustdevelopgeneticmechanismstocounterthesequenceisusua