林木分子-RNA的转录.ppt

第4章RNA转录(RNAtranscription)4.1转录的基本概念基因表达的第一步DNA转录原点记为+1，其上游记为负值，下游记为正值4.2转录起始●-60-70~-40upelementCAP—cAMPbindingsitePromoterregionidentifiedbyDNAaseIfootprintingmethodCorepromoterregionincludingα因子β因子σ因子(sigmafactor)σ亚基离开全酶后可以重复使用l基本水平转录的cis-factor(promoterorbasicfactor)Corepromoter(Capsite,TATAbox必需因子)UPE(UpstreamPromoterElement)(CAATbox,GCbox)Forhousekeepinggene(constitutiveexpression)l特异诱导高效表达的cis-factorEnhancerForluxurygene(inducibleexpression)Promoterforbasictranscription(classIIrecognizedbyRNApolymeraseII)lTATAbox/Hognessbox/Goldberg-Hognessbox(-30)RichATandrichGCflankedrichGC------TATAA(T)AA(T)------richGC8297938563(37)8350(37)lGCisland(Cnomethylated)andCAATbox(CATboxUPE)(-70)GCGC-----GGC(T)CAATCT----ResponsetoeffectoftranscriptionRange30bp±lPromoterfunctionsCAATbox(modulator)controllingtranscriptionalefficiency(GCisland!!)TATAbox(selector)controllingstartingpointandefficiency30bpfromTATAboxtoIsiteisrequiredIsite(initiator)determinationinitiationpointandcappingofmRNACis-factorforinducibleexpressionEnhancerEnhancer的结构与功能EnhancerEn.Elem.En.ElemEn.Elem.-250-180Silencer沉默子Insulator:(绝缘子)ElementsthatpreventthepassageofactivatingorinactivatingeffectsInsulator(绝缘子)具有两种功能a)Whenaninsulatorisplacedbetweenenhancer&promoter,itpreventstheenhancerfromactivatingthepromoterInsulator(绝缘子)具有两种功能b)Whenaninsulatorisplacedbetweenactivegene&heterochromatin,itprovidesabarrierthatprotectsthegeneagainsttheinactivatingeffectthatspreadsfromtheheterochromatin与基本转录相关的T.F.GeneraltranscriptionfactorsRNApol.I,II,IIIRNApolII---Forpre-mRNAtranscription---Locatedinnucleoplasm---L’maximumsubunit240kD&havespecificCOOH-endnamedCTD(CarboxylTerminalDomain)onlyinRNApolIICTD-end：7aarepeats&highfrequencyphosphorylationTyr—SerP—Pro—ThrP—SerP—Pro—SerP与基本转录相关的T.F.（转录因子）Generaltranscriptionfactors(GTF)TFIIB:OnceTFIIDhasboundtoDNATFIIBbindstoTBPofTFIIDandRNApol.IITFIIBasabridgingfactorallowingrecruitmentofRNApolIItoTICtogetherwithRAP30ofTFIIFTFIIH:Largecomplexmadeupof>5subunitsHelicaseactivity(ATPase,RAD25