细胞分子生物学第11章基因表达的转录调控

11TRANSCRIPTIONALCONTROLOFGENEEXPRESSION11.1OverviewofEukaryoticGeneControlandRNAPolymerases11.2RegulatorySequencesinProtein-CodingGenes11.3ActivatorsandRepressorsofTranscription11.4TranscriptionInitiationbyRNAPolymeraseII11.5MolecularMechanismsofTranscriptionActivationandRepression11.6RegulationofTranscription-FactorActivity11.7RegulatedElongationandTerminationofTranscription11.8OtherEukaryoticTranscriptionSystems11.1OverviewofEukaryoticGeneControlandRNAPolymerasesThenucleiofalleukaryoticcellscontainthreedifferentRNApolymeras,designatedI,II,andIII.RNApolymeraseI,locatedinthenucleolus,transcribesgenesencodingprecursorrRNA(pre-rRNA).RNApolymeraseIItranscribesallprotein-codinggenes;RNApolymeraseIIItranscribesgenesencodingtRNAs.11.2RegulatorySequencesinProtein-CodingGenesGeneralpatternofcontrolelementsthatregulategeneexpressioninmulticellulareukaryotesandyeast

Enhancer:能增强转录起始的序列；

promoter-proximalelements：

(近端启动子元件)位于起始位点上游100-200个碱基。某些情况下，具有细胞类型特异性，

只在特殊的分化细胞类型中起作用11.3ActivatorsandRepressorsofTranscriptionActivatorsAreModularProteinsComposedofDistinctFunctionalDomainsRepressorsAretheFunctionalConverseofActivators

Likeactivators,mosteukaryoticrepressorsaremodularproteinsthathavetwofunctionaldomains:aDNA-bindingdomainandarepressiondomain11.4TranscriptionInitiationbyRNAPolymeraseIIGeneralTranscriptionFactors(TF)PositionRNAPolymerasesIIatStartSitesandAssistinInitiationSequentialAssemblyofProteinsFormsthePolIITranscriptionPreinitiationComplexTATAbox–bindingprotein(TBP)carboxyl-terminaldomain(CTD):Tyr-Ser-Pro-Thr-Ser-Pro-Ser11.5MolecularMechanismsofTranscription

ActivationandRepression激活子和抑制子通过与DNA的特殊部位结合来调节蛋白基因的表达，主要有2种机制：1激活子和抑制子与其他蛋白协作调节染色质的结构，从而影响一般转录因子与启动子的结合；2激活子和抑制子与多蛋白复合物（转录复合物的调节子）相互作用，这一调节子与PolII结合调节转录起始复合物的作用；11.8OtherEukaryoticTranscriptionSystemsothertwoeukaryoticnuclearRNApolymerases,PolIandPolIII,andbythedistinctpolymerasesthattranscribemitochondrialandchloroplastDNA.TheprocessoftranscriptioninitiationbyPolIandPolIIIissimilartothatbyPolIIbutrequiresdifferentgeneral