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RNABiosynthesis(Transcription)RNABiosynthesis(transcription)RNA的生物合成课件11.复制和转录过程有什么相似之处?又各有什么特点?
2.试述真核细胞RNA转录后的加工修饰1.复制和转录过程有什么相似之处?又各有什么特点?
2.2Concept
TheprocessofcopyingDNAtoRNAbyanenzymecalledRNApolymerase(RNAP)ThetransferofgeneticinformationfromDNAintoRNAtranscriptionRNADNA
ConcepttranscriptionRNA3ContentTemplatesandEnzymesTheProcessofTranscriptionPost-transcriptionalModificationContentTemplatesandEnzymes4ThedifferencebetweenreplicationandtranscriptionThedifferencebetweenreplica5SubstancesfortranscriptionSubstrates:
NTP(ATP,UTP,GTP,CTP)
Template:
DNAEnzyme:
RNApolymerase(RNA-pol)OtherproteinfactorsSubstancesfortranscriptionSu6TemplatesandEnzymesSectionISectionI7TemplatefortranscriptionStructuralgene:aDNAfragmentcodingforanyRNAorproteinproductotherthanaregulatoryelementTemplatestrand(sensestrandorWatsonstrand)
:thestrandofDNAthattheRNApolymeraseusesasatemplatetoproducecomplementarymRNACodingstrand(antisensestrandorCrickstrand)
:thestrandthatisnotusedasthetemplateithasthesamebasesequenceastheRNAtranscriptproduced(althoughwiththyminereplacedbyuracil)TemplatefortranscriptionStru85′···GCAGTACATGTC···3′3′···cgtgatgtacag···5′5′···GCAGUACAUGUC···3′N······Ala·Val·His·Val······CCodingstandTemplatestrandmRNAProteintranscriptiontranslation5′···GCAGTACATGTC···3′3′···c95
3
3
5
TemplatestrandCodingstrandCodingstrandTemplatestrandStructuralgeneDirectionoftranscriptionDirectionoftranscription53TemplatestrandCodingstra10Asymmetrictranscription
certainregionofonlyonestrandofDNAservesasatemplatefortranscriptionThetemplatestandisnotalwaysrestrictedtothesamesingleDNAstrandAsymmetrictranscription11RNApolymeraseProkaryoticRNApolymeraseRNApolymeraseProkaryoticRNA12coreenzymeholoenzyme
coreenzymeholoenzyme13ThebindingsiteofRNApolholoenzymeonthetranscriptioninitiationregionThebindingsiteofRNApolhol14EukaryoticRNApolymeraseEukaryoticRNApolymerase15AsiteforRNApoltoidentifyandbindonthetemplateOperon:aunitoftranscriptioninprokaryotesincludingoneormorestructuralgenesandupstreamregulon
5
3
3
5
StructuralgeneregulonRNA-polpromoter:
thesiteonthetemplateDNAforRNApolbindingAsiteforRNApoltoidentify16RNApolymeraseprotectionassay目录RNApolymeraseprotectionassay17TranscriptioninitiationTTGACAAACTGT-35region(Pribnowbox)TATAATPuATATTAPy-10region1-30-5010-10-40-205
3
3
5
Prokaryoticpromoteconservativesequencerecognitionsite
5
5
RNApolprotectionregionStructuralgene3
3
TranscriptioninitiationTTG18
TATAbaxCAATbaxGCbaxenhancerCis-actinelementStructuralgene-GCGC---CAAT---TATATranscriptioninitiationEukaryoticpromoteconservativesequenceTATAbaxCAATbaxGCbaxenhan19TheProcessofTranscriptionSectionIISectionII20InitiationTwoissuesrequiredtobeaddressed
thebindingofRNApolymerasetotheinitialregionofthetranscriptiontemplatepreciselyonlyonestrandofDNA,thetemplatestrand,isusedtoproducemRNAProkaryotictranscriptionInitiationTwoissuesrequired21TheDNAisunwoundandbecomessingle-strandedinthevicinityoftheinitiationsite(definedas+1).RNApolholoenzyme(2)specificallybindingtothepromoterregiononDNA1stpolyreactioncatalyzedbyRNApolandtranscriptioninitiationcomplexisformedRNApol(
2
)-DNA-pppGpN-OH3
transcriptioninitiationcomplex5
-pppG-OH+
NTP
5
-pppGpN
-OH3
+ppiInitiationTheDNAisunwoundandbecome22Elongation
subunitdissociatesfromtheholoenzyme,andelongationproceeds
withtheeffectofthecoreenzyme,NTPmaintainpolymerization,RNAstrandelongated(NMP)n
+
NTP
(NMP)n+1
+PPiElongationsubunitdissociate23transcriptionbubble:RNA-pol(Coreenzyme)
····DA
····RNA目录transcriptionbubble:RNA-pol(24目录目录255
3
DNAFeatherphenomenaduringprokaryotictranscriptionribosomeRNARNApol53DNAFeatherphenomenadurin26Rho(ρ)factordependenttranscriptionterminationRho-independenttranscriptionterminationTerminationTheprocessoftheRNApolymerasestoppingonDNAtemplateandthedissociationoftheRNAfromthetranscriptioncomplexClassificationRho(ρ)factordependenttrans27ATPRho(ρ)factordependenttranscriptionterminationATPRho(ρ)factordependent28TerminationindependentonRhofactorTheterminatorsequencewithintheRNAforthestopofRNApolymerase.Theterminatorsequenceusuallyformsastem-loophairpinstructureleadingtothedissociationoftheRNAPfromtheDNAtemplateTerminationindependentonRho295`UUGCAGCCUGACAAAUCAGGCUGAUGGCUGGUGACUUUUUAGUCACCAGCCUUUUU...3`5`UUGCAGCCUGACAAAUCAGGCUGAUGGCUGGUGACUUUUUAGUCACCAGCCUUUUU...3`
RNA5
TTGCAGCCTGACAAATCAGGCTGATGGCTGGTGACTTTTTAGTCACCAGCCTTTTT...3
DNA
UUUU...…
UUUU...…5`UUGCAGCCUGACAAAUCAGGCUGAUGGCUGGUGACUUUUUAGUCACCAGCCUUUUU...3`stem-loop/hairpinstructure5`UUGCAGCCUGACAAAUCAGGCUGAUGGC30MechanisminvolvedintheterminationbystemloopallostericchangeofRNApolyforthestopoftranscriptiondissociationoftranscriptioncomplexforthereleaseofRNA5´pppG53
35RNA-polMechanisminvolvedintheterm31EukaryotictranscriptioninitiationinitiationAvarietyofupstreamcontrolelementsexistRNA-poldoesnotdirectlybindtothetemplateintheinitiationMuchmorecomplicatedthanprokaryotictranscriptionEukaryotictranscriptioniniti32TranscriptionInitiationnsiteTATAboxCAATboxGCboxenhancercis-actingelementTheupstreamregionfromthetranscriptioninitiationAATAAAExcisionandaddingtailTranscriptionTerminationsiteModificationsiteexonTranslationinitiationsiteintronOCT-1
OCT-1:ATTTGCAToctamerTranscriptionTATAboxCAATboxG33TranscriptionfactorTrans-actingfactors:TheproteinswithabilitytorecognizeandbinddirectlyorindirectlytotheupstreamcontrolelementofDNAHundredsfactorshavebeenreportedTranscriptionalfactors(TF):
Amongthetrans-actingfactors,theproteinswithabilityto
binddirectlyorindirectlytoRNApolTranscriptionfactorTrans-acti34参与RNA-polⅡ转录的TFⅡ
参与RNA-polⅡ转录的TFⅡ35Pre-initiationcomplex(PIC)Eukaryotictranscriptioninitiationrequireavarietyoftranscriptionfactor
becauseof
theindirectlybindingofEukaryoticRNA-poltoDNAPre-initiationcomplex(PIC)36POL-ⅡTFⅡFⅡAⅡBPICtranscriptioncatalyzedbyRNA-PolⅡPOL-ⅡTFⅡFⅡHⅡETBPTAFTFⅡD-ⅡA-ⅡB-DNAcomplexTATAⅡAⅡBTBPTAFTATAⅡHⅡECTD-PAfterPICassemble,CTDphosphorylationbyTFⅡH
POL-ⅡTFⅡFⅡAⅡBPICtranscription37Piecingtheory
Theeukaryotictranscriptionrequires3to5TFbindingtogetherandbecomingthecomplexfortheactivationofspecificgenetranscriptionPiecingtheoryTheeukaryotic38ElongationSimilartoprokaryotictranscriptionelongation.synchronoustranscriptionandtranslationisnotobservedbecauseofsegregationofnuclearmembraneTheforwardmovingprocessofRNA-polencounteringnucleosomeThetranslocationanddissociationofnucleosomesobservedduringthetranscriptionElongationSimilartoprokaryot39RNA-PolRNA-PolRNA-PolnucleosomeNucleosometranslocationduringelongationDirectionoftranscriptionRNA-PolRNA-PolRNA-Polnucleosom405------AAUAAA-5
------AAUAAA--nuclease-GUGUGUGRNA-polAATAAAGTGTGTGModificationsitefortranscriptiontermination5
5
3
33addingtailAAAAAAA······3
mRNATermination——associatedwithpost-transcriptionalmodification5------AAUAAA-5------AAUAAA41Post-transcriptionalmodificationSctionIIISctionIII42ConceptIneukaryoticcells,ageneticprocessfortheconversionofaprimarytranscriptRNAtomatureRNAConcept43MajormodificationssplicingcleavagemodificationadditionMajormodificationssplicingcle44EukaryoticmRNAprocessingModificationstothe“head"(5')and“tail"(3')endsofthemRNA5
capping
(m7GpppGp—)3
polyadenylation
(polyAtail)EukaryoticmRNAprocessingModi455
capstructure5capstructure465pppGp…5GpppGp…pppGppiGMPtransferase5
m7GpppGp…methyltransferase
SAMTheformationof5
cap
5ppGp…phosphatasePi5pppGp…5GpppGp…pppGppiGMP47mRNAsplicinghetero-nuclearRNAa(hnRNA):theprimarymRNAwithinnucleussnRNA:aclassofsmallRNAmoleculeswithinthenucleus
ProteinswithinNuclear
smallnuclearribonucleoproteins
(splicesome)snRNAmRNAsplicinghetero-nuclearR48astrandofDNAcontainingbothintronsandexons.Mostadvancedeukaryoteshaveinterruptedgenesandintronsarelongerthanexons.TheresultinggeneismuchlongerthanitscodingregionInterruptedgene
CABDCodingregionA、B、C、DNon-codingregionastrandofDNAcontainingbot49ExonandintronexontheregionsofagenethatarerepresentedinmatureformofthemessengerRNA(mRNA)intronThesectionsofagenethatarepresentinprecursormRNA(pre-mRNA)andremovedbyaprocesscalledsplicingduringtheprocessingtomatureRNAExonandintronexon50ChickenOvalbuminGene
hnRNAModificationstothe"front"and"back"endshnRNAsplicingMaturemRNAChickenOvalbuminGeneanditsTranscriptionandPost-transcriptionalModification
目录ChickenOvalbuminGenehnRNAMo51Electron-microscopicpictureofthematuremRNAandDNAhybridizationofChickenOvalbuminDNAmRNA目录Electron-microscopicpictureo52Classificationofintrons
Fourclasses:accordingtogenetypesandsplicingmethodsI:mainlyfoundinmitochondria,chloroplast,andcertainlow-leveleukaryoticrRNAgenesII:foundinmitochondria,chloroplast,inmRNAgenesIII:frequentlyfoundinthesplicingafterloopformation,inmostmRNAgenesIV:tRNAgenesandprimarytranscriptionproductionintron,splicingrequiringenzymeandATPClassificationofintronsFour53mRNAsplicingtoremovetheintronsofhnRNAandligatetheexonsSplicesomeisformedbyligationofsnRNPandhnRNA目录①mRNAsplicingtoremovethein54②③UACUACA-AGUGU4U5U6E1E2U1U2UACUACA-AGUGU6E1E2U1、U4、U5②③UACUACA-AGUGU4U5U6E1E2U1U255pG-OH(ppG-OH,pppG-OH)U-OHGpUpGpA1STtransesterificationreaction
2nd
transesterificationreaction
UpAGpUExon1IntronExon2G-OHUpUpGpA剪接过程的二次转酯反应
pG-OHU-OHGpUpGpA1STtransester56DifferentialRNAprocessing:
RNAeditingshowsthatthecodingsequenceofgeneshasavarietyofdifferentialfunctionafterpost-transcriptionprocessingmRNAeditingHumanapoBgene
mRNA(14500Nucleotides)liverapoB100(MW500000)intestinalcellsapoB48(MW240000)mRNAeditingDifferentialRNAprocessing:57Post-transcriptionalprocessoftRNAtRNAprecursorRNApolⅢTGGCNNAGTGCGGTTCGANNCCDNA目录Post-transcriptionalprocesso58RNAaseP、endonuclease目录RNAaseP、endonuclease目录59tRNAnucleotidetransferase
、ligaseATPADP目录tRNAnucleotidetransferase、l60BasemodificationsReducedreactione.g.:UDHUTranslocationwithinnucleotidese.g.:UψDeaminationreaction
e.g.:A
Ie.g.:AAmMethylation(1)(1)(3)(2)(4)目录BasemodificationsReducedreac61transcription45S-rRNAsplice18S-rRNA5.8S
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