




版權(quán)說明:本文檔由用戶提供并上傳,收益歸屬內(nèi)容提供方,若內(nèi)容存在侵權(quán),請(qǐng)進(jìn)行舉報(bào)或認(rèn)領(lǐng)
文檔簡(jiǎn)介
DNACytoplasmNucleusEukaryoticmRNATranscriptsareProcessedExportGAAAAAARNATranscriptionNuclearporesGAAAAAARNAProcessingmRNAA“Simple”EukaryoticGeneTerminatorSequencePromoter/ControlRegionTranscriptionStartSite5’UTR3’UTRExonsIntrons3’5’Exon2Exon3Int.2Exon1Int.13’5’Exon2Exon3Exon1Int.2Int.1TranscriptionUnprocessedRNATranscriptProcessingofeukaryoticmRNARNAprocessingachievesthreethings:1)RemovalofIntrons2)Additionofa5’cap3)Additionofa3’tailThemRNAthenmovesoutofthenucleusandistranslatedinthecytoplasm.3’PolyATailProteinCodingRegion
3’UTR
5’UTRG5’CapExon2Exon3Exon1Int.2Int.1AAAAATranslationalcontrolStructureofeukaryoticandprokaryoticmRNAs:Modelofeukaryoticribosome?rRNAsarebelievedtoplayacatalyticroleinproteinsynthesis.?
Afterremovalof95%oftheribosomalproteins,the60Ssubunitcancatalyzeformationofpeptidebonds.?RibosomalproteinsarenowbelievedtohelpfoldtherRNAsproperlyandtopositionthetRNAs.Small&largeribosomalsubunits.ABindingsitefor themRNAispresentonsmallsubunit.Twobindingsites (P&A)bindtRNAsonlargesubunit.Psite–holdsthetRNAcarryingthegrowingpolypeptidechain.Asite–holdsthetRNAwiththenextAAtobeadded.
RibosomesholdthemRNAandtRNAstogetherandconnecttheaminoacidsattheAsitetothegrowingpolypeptide.RibosomeStructureStructureoftRNA
Alignseachaminoacidwiththecorrespondingcodon?70-80ntlong?3’endhasthe5’-CCAsequencetowhichaaarelinked?Theoppositeendcontainstheanticodonloop?
Containsmodifiedbases
ManyRNAViruseshavecappedgenomicRNAssimilartoeukaryotichostmRNAs?MosteukaryoticmRNAsarecappedat the5’endduringnuclearprocessing.?Theterminal5’phosphateisfirst removedbya5’triphosphatase.?GuanyltransferasetransfersGMPfrom GTPtothe5’endofthemRNAtoadd theGpppNcapstructure.?The5’terminalinvertedGresidueis thenmodifiedbymethylation.?ManyRNAvirusesreplicateinthe cytoplasmandmustuseaviral dependentcappingmechanism suppliedbytheRNA-Dependent-RNA Polymerase.?TheCapstructure,m7GpppN,ismost commoninviralandmammalian mRNAs.Threedistinctstagesoftranslation
Initiation
?Ratelimitingstep
?RequireshydrolysisofATPandGTP
?ResultsinformationofacomplexcontainingthemRNA,theribosomeandtheinitiatorMet-tRNA
A.
5’end(Cap)dependentinitiation?Theinitiationcomplexbindstothe5’capstructureandscansina5’to3’directionuntilinitiatingAUGisencounteredB.Internalribosomeentry
Initiationcomplexbindsupstreamofinitiationcodon?Thefirststepistherecognitionofthe5’capbyeIF4F,whichconsistsofthreeproteins,eIF4E,eIF4GandeIF4A.Capbindingprotein,eIF4E,bindstocap?TheN-terminusofeIF4GbindseIF4EandtheC-terminusbindseIF4A?The40SsubunitbindstoeIF4GviaeIF35’end(cap)dependentinitiation:The40Scomplexthenscansdownthe5’untranslatedregiontothefirstAUGcodon.AGTPhydrolysisstepbyeIF5triggersGDPbindingofeIF2andreleaseofinitiationproteins.The60Ssubunitjoinsthecomplexandthe80SribosomeinitiatestranslatetheORF.Aninitiationcomplexformsatthecapwiththe40Sribosomalsubunitandothertranslationinitiationfactors.Cap-DependentInitiationofProteinSynthesisinEukaryotesRibosomeselectsaminoacylatedtRNAeEF1aandGTPareboundtoaminoacylatedtRNARibosomecatalyzesformationofapeptidebondTranslocationisdependentoneEF2andGTPhydrolysisManyribosomesmaytranslatemRNAssimultaneouslyonthesamestrand.ElongationPAeEF1aeEF2GTPGTPTerminationTranslationisterminatedatoneofthreestopcodons(UAA,UAG&UGA).
?TerminationcodonattheAsiteisrecognizedbythereleasefactorinsteadofatRNA?Thereleasefactorbindstheterminationcodon?ThepeptidechainisthenreleasedfollowedbydissociationofthetRNAandtheribosome?The5’enddependentinitiationisstimulatedbythepoly(A)bindingproteinPabp1p,whichinteractswitheIF4G?ThisinteractioncircularizesthemRNAandfacilitatesformationoftheinitiationcomplexMechanismtoensurethatonlyintactmRNAistranslatedClosedloopmodel:?mRNAsofpicornaviruseslack5’capRibosomesbindinternallyratherthanatthemRNA5’end5’endofpoliovirusRNApromotesinternalbindingof40Ssubunitatinternalribosomeentrysite(IRES)InpoliovirusinfectedcellseIF4Giscleaved,inactivatingtranslationofcellularmRNAsTheinitiationintheIRESdoesnotdependonthepresenceofacapstructure,butrequiresC-terminalfragmentofeIF4Gtorecruitthe40SsubunitthroughinteractionwitheIF3.5’end(cap)independentinitiation:PoliovirusFivedifferenttypesofIRESsequencesarefoundonviralRNAs:
TypeI-enteroandrhinoviruses(poliovirus) Initiationcodonislocatedpastthe3’endoftheIRES
40SbindstoIRESscanstoAUGTypeII-cardioandapthoviruses(EMCV) Initiationcodonisatthe3’endoftheIRES 40SbindsatornearAUGnoscanningoccursTypeIII-hepatitisAvirus initiationcodonislocatedpastthe3’endoftheIRES requiresallofinitiationproteins,includingeIF4ETypeIV-hepatitisCvirus The3’endofthehepatitisCvirusIRESextends beyondtheAUGcodonTypeV-cricketparalysisvirus
IRESendsattheinitiationcodon,althoughitisnotan AUGcodon,noinitiationfactorsarerequired initiationcodonisplacedattheAsiteinsteadoftheP siteFourtypesofIRES:polivirusEncephelomyocarditisvirus(EMCV)HepatitisCCricketparalysisvirusHepatitisCvirusIRES:40SribosomalsubunitbindsdirectlytoHepatitisCvirusIRESintheabsenceofmostinitiationfactorsAdramaticchangeintheconformationofthe40SsubunitoccurswhenitbindsHepatitisCvirusIRESsettingtheAUGatthePsiteeIF3alsobindstotheHepatitisCvirusIRESBicistronicmRNAassayforIRESelementsViraltranslationstrategiesPolyproteinsynthesis
Picornaviruses-Entire(+)senseRNAgenomeistranslatedintoasinglelargepolyprotein.Processingiscarriedoutbytwovirusencodedproteases2Aproand3Cpro.
Flaviviruses-Viralprecursorproteinsareprocessedbycellularproteases.The(+)senseRNAgenomeistranslatedintoapolyproteinprecursorprocessedbyviralserineproteaseandbyhostsignalpeptidase.
Potyvirusgroupofplantviruses-PotatovirusYandtobaccoetchviruscontaina(+)sensegenomeRNAofaround10,000baseswhichhasasingleopenreadingframe.Thispolyproteinisprocessedbyviralencodedproteases.PolyproteinprocessinginenterovirusesandflavivirusesPoliovirus:Flavivirus:
Leakyscanning
AlthoughmajorityofeukaryoticmRNAsaremonocistronic,someviralmRNAsencodeoverlappingreadingframes.Thefirststartsiteisinapoorcontext,someribosomescanbypassitandinitiateatthesecondAUG,whichhasabettercontext.Thiswillresultintranslationoftwodifferentproteins.Reinitiation
Rareineukaryotes,butverycommoninprokaryoticcellularandviralmRNAs.SomeeukaryoticmRNAscontainupstreamAUGcodonsthatterminatebeforethedownstreamreadingframe.Theupstreamopenreadingframesmaybetranslated,withreinitiationoccurringatthedownstreamopenreadingframe.
IninfluenzaBvirusmRNA,M2initiationcodonispartoftheterminationcodonforM1protein.M2synthesisisnotefficientanddependentonM1synthesisReinitiationoftranslationininfluenzaBvirusSuppressionoftermination
SuppressionofterminationoccursduringtranslationofmayviralmRNAsasameansofgeneratingasecondproteinwithextendedcarboxyterminus.Inretroviruses,gagandpolgenesareencodedbyasinglemRNAandseparatedbyanamberterminationcodonUAG.Translationalsuppressionoftheambercodonallowssynthesisofthegagpolprecursor.
Asimilarstrategyisusedbytobaccomosaicvirustotranslateitsreplicaseproteins.
TranslationsuppressionismediatedbysuppressortRNAsthatcanrecognizeterminationcodonsandinsertaspecificaminoacid.Thenucleotidesequence3’oftheterminationcodonalsoplaysanimportantroleintheefficiencyoftranslationalsuppression.SuppressionofterminationcodonsinalphavirusesandretrovirusesPseudonotalphavirusretrovirusRibosomalframeshifting
Ribosomalframeshiftingisaprocessinwhichribosomesmovetoadifferentreadingframeandcontinuetranslationinthatreadingframe.
ItwasdiscoveredincellsinfectedwithRoussarcomavirusandhassincebeendescribedformanyothervirusesincludingotherretroviruses,(+)strandRNAvirusesandherpessimplexvirus.
Requiresa“slippery”sequenceX-XXY-YYZ(inRoussarcomavirusA-AAU-UUA)andanRNAsecondarystructurecalledapseudoknotfivetoeightnucleotidesdownstream.
TwotRNAsinthezeroreadingframeslipbackbyonenucleotidetothe–1phaseandeachtRNAbasepairswiththemRNAinthefirsttwonucleotidesofeachcodon.
AsaresultoftheframeshiftaGag-polfusionisproducedatabout5%ofthelevelofGagprotein.
RibosomalframeshiftingRoussarcomavirusmRNAencodesGagandPolproteinsthatoverlapina–1readingframe
REGULATIONOFTRANSLATIONDURINGVIRALINFECTION
Interferonsareproducedinresponsetoviralinfectionaspartoftherapidinnateimmune
溫馨提示
- 1. 本站所有資源如無(wú)特殊說明,都需要本地電腦安裝OFFICE2007和PDF閱讀器。圖紙軟件為CAD,CAXA,PROE,UG,SolidWorks等.壓縮文件請(qǐng)下載最新的WinRAR軟件解壓。
- 2. 本站的文檔不包含任何第三方提供的附件圖紙等,如果需要附件,請(qǐng)聯(lián)系上傳者。文件的所有權(quán)益歸上傳用戶所有。
- 3. 本站RAR壓縮包中若帶圖紙,網(wǎng)頁(yè)內(nèi)容里面會(huì)有圖紙預(yù)覽,若沒有圖紙預(yù)覽就沒有圖紙。
- 4. 未經(jīng)權(quán)益所有人同意不得將文件中的內(nèi)容挪作商業(yè)或盈利用途。
- 5. 人人文庫(kù)網(wǎng)僅提供信息存儲(chǔ)空間,僅對(duì)用戶上傳內(nèi)容的表現(xiàn)方式做保護(hù)處理,對(duì)用戶上傳分享的文檔內(nèi)容本身不做任何修改或編輯,并不能對(duì)任何下載內(nèi)容負(fù)責(zé)。
- 6. 下載文件中如有侵權(quán)或不適當(dāng)內(nèi)容,請(qǐng)與我們聯(lián)系,我們立即糾正。
- 7. 本站不保證下載資源的準(zhǔn)確性、安全性和完整性, 同時(shí)也不承擔(dān)用戶因使用這些下載資源對(duì)自己和他人造成任何形式的傷害或損失。
最新文檔
- 2025-2026學(xué)年吉林省四平市鐵西區(qū)某中學(xué)高二上學(xué)期開學(xué)英語(yǔ)試卷(解析版)
- 2025年河北邢臺(tái)內(nèi)丘縣人力資源和社會(huì)保障局就業(yè)見習(xí)245個(gè)崗位考前自測(cè)高頻考點(diǎn)模擬試題及答案詳解(易錯(cuò)題)
- 2025湖北武漢市中南財(cái)經(jīng)政法大學(xué)教師招錄模擬試卷及答案詳解(全優(yōu))
- 企業(yè)文化建設(shè)方案模板跨行業(yè)
- 2025內(nèi)蒙古鄂爾多斯市水發(fā)燃?xì)庥邢薰菊衅?人模擬試卷及完整答案詳解1套
- 《初中物理力學(xué)平衡原理及其應(yīng)用教案》
- 2025貴州安順學(xué)院高層次人才引進(jìn)考前自測(cè)高頻考點(diǎn)模擬試題及答案詳解(必刷)
- 2025湖南懷化市溆浦縣衛(wèi)健局招聘鄉(xiāng)鎮(zhèn)衛(wèi)生院編外專技人員20人考前自測(cè)高頻考點(diǎn)模擬試題附答案詳解(突破訓(xùn)練)
- 企業(yè)知識(shí)產(chǎn)權(quán)保護(hù)登記及維護(hù)方案
- 2025黑龍江齊齊哈爾市訥河市發(fā)展和改革局所屬事業(yè)單位選調(diào)9人考前自測(cè)高頻考點(diǎn)模擬試題及答案詳解(歷年真題)
- 2025教科版三年級(jí)科學(xué)上冊(cè)教學(xué)計(jì)劃、教學(xué)設(shè)計(jì)(附目錄)
- 木質(zhì)素降解微生物促進(jìn)秸稈飼料化營(yíng)養(yǎng)價(jià)值提升的機(jī)制研究
- 深圳2025中考英語(yǔ)真題及答案
- 全科醫(yī)學(xué)進(jìn)修匯報(bào)
- 六年級(jí)下學(xué)期英語(yǔ)期末考試質(zhì)量分析
- 三基培訓(xùn)及知識(shí)課件
- 監(jiān)控運(yùn)維:方案與實(shí)施
- 河南歷史課件
- 全國(guó)青少年“學(xué)憲法、講憲法”知識(shí)競(jìng)賽題庫(kù)及答案
- 單元四-一般道路駕駛(教案)
- 油庫(kù)消防培訓(xùn)課件
評(píng)論
0/150
提交評(píng)論