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1、Vum.sReseurch,I(1987)99-10299ElsevierVRR00319MeetingReportCoronaviruses:agroupwithuniquefeaturesThirdInternationalCoronavirusSymposiumOrganizedbyM.LaiandS.StohlmanHeldatAsilomar,California,September14-18,1986Recentprogressinthestudyofcoronaviruseshasr
2、evealedmanyuniquefeaturesoftheseviruses,whichwerepresentedatthisInternationalSymposium.Progresswasevidentinboththeareaofmolecularbiologyandinviralpathogenesis.Ofparticularinterestwerestudiesrevealingthenovelstructureandtheuniquemecha-nismofsynthesisof
3、coronavirusRNA,aswellasthecharacterizationofenvelopeglycoproteins,targetcellspecificityandtheimmunemodulatoryroleoftheseviruses.Duringthefirsthalfofthemeetingmolecularbiologicalaspectswerediscussed.Coronavirusesformalargegroupofinfectiousagentswhoseke
4、ymembersare:mousehepatitisvirus(MHV);avianinfectiousbronchitisvirus(IBV);porcinetransmissiblegastroenteritisvirus(TGEV);felineinfectiousperitonitisvirus;andhumancoronavirus.Thesevirusescontainaninfectioussingle-strandedRNAge-nome,untilrecentlythoughtt
5、obe18-20kilobases(kb)long.Ininfectedcells,sixtosevenspeciesofmRNAaremade,whichforma3coterminalnestedsetstructure.EachmRNAisphysicallypolycistronicbutfunctionallymonocistronic.Onlytheunique5terminalsequenceswhichdonotoverlapwiththenextsmallestRNAareuse
6、dfortranslation.Thus,coronavirusgenomescontainonlysixtosevengenes,despitethelargesizeofthevirionRNA.ThefactthatcoronavirusesdocontainaverylargegenomewasdemonstratedbythecompletesequencingoftheIBVgenome(M.Boursnell,HoughtonPoultryResearchStation,U.K.).
7、Surprisingly,thisRNAis27.6kblong,considerablygreaterthanpreviouslyestimated;itisthelargestviral,andstable,RNAspeciesknown.EighteenkbofthisRNAisasinglegeneatthe5endthatprobablyencodestheRNA-dependentRNApolymerase.Analysisofthepredictedtranslationprod-u
8、ctsrevealstwooverlappingopenreadingframes,withthecapacitytocodefortwoproteinsof440kDaand300kDa.Itisconceivablethatribosomalframeshiftingcouldresultinasingleproteinproduct.TheseproteinshaveyettobeidentifiedinIBV-infectedcells.Whydoescoronavirus
