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1、VIROLOGY188,402-407(1992)CoronavirusmRNASynthesis:IdentificationofNovelTranscriptionInitiationSignalsWhichAreDifferentiallyRegulatedbyDifferentLeaderSequencesNICOLALAMONICA,’KYOKOYOKOMORI,ANDMICHAELM.C.LQ*HowardHughesMedicalInstituteandDepartmentofMicrobiology,UniversityofSouthernCaliforni
2、a,SchoolofMedicine,LosAngeles,California90033ReceivedNovember19,1991;acceptedFebruary19,1992ThemRNAsynthesisofmousehepatitisvirus(MHV)hasbeenproposedtobetheresultofinteractionbetweentheleaderRNAandtheintergenicsites.Previously,wehaveidentifiedatranscriptioninitiationsite(formRNA2-l),whichi
3、smoreefficientlytranscribedbyvirusescontainingtwocopiesofUCUAAsequenceintheleaderRNAthanbythosewiththreecopies.Inthisstudy,wehaveidentifiedseveralsiteswhichareregulatedintheoppositeway,namely,theyareefficientlytranscribedbytheleaderRNAwiththreeUCUAAcopiesbutnotbythosewithtwocopies.Thesesit
4、eswerecharacterizedbyprimerextensionandamplificationbypolymerasechainreaction.Oneofthesesitesisinthegene3regionofarecombinantvirusbetweenA59andJHMstrainsofMHV.Anotherisinthegene2regionofMHV-1strain.Bothofthesesiteshaveasequencesimilartobutdifferentfromtheconsensustranscriptioninitiationsig
5、nal(UCUAAUCUAUCandUUUAAUCUU,asopposedtoUCUAAAC).Thesetwonovelintergenicsequencesarenotpres-entinthegenomeoftheJHMstrain,consistentwiththeabsenceofthesemRNAsintheJHM-infectedcells.ThediscoveryofthistypeoftranscriptioninitiationsiteprovidesadditionalevidencefortheimportanceoftheleaderRNAinth
6、etranscriptioninitiationofMHVmRNAs.o1992AcademicPWSS.IIIC.Mousehepatitisvirus(MHV),amemberoftheCo-theleaderRNAmakesonlyasmallquantityofmRNAronaviridae,isanenvelopedviruscontaininganonseg-2-1,whilethesameviruswithtwocopiesmakesamentedpositive-sensedRNAgenomeof31kb(I,2).largequantityofthistr
7、anscript(7,10).TheamountsofMHVsynthesizesseventoeightvirus-specificmRNAssomeothermRNAs,e.g.,mRNA2and4,arealsoaf-thathavea3’-coterminalnested-setstructure(1,3).fected,buttoamuchsmallerextent(7,10).The5’uniqueportionofeachmRNAisutilizedforThelevelofmRNA2-lexpres
