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1、11.1 Overview of Eukaryotic Gene Control and RNA PolymerasesThe nuclei of all eukaryotic cells contain three different RNA polymeras,designated I,II,and III.RNA polymerase I,located in the nucleolus,transcribes genes encoding precursor rRNA(pre-rRNA).RNA polymerase II transcribes all protein-coding
2、genes;RNA polymerase III transcribes genes encoding tRNAs.第1页/共10页11.2 Regulatory Sequences in Protein-Coding GenesGeneral pattern of control elements that regulate gene expression in multicellular eukaryotes and yeastEnhancer:能增强转录起始的序列；promoter-proximal elements：(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
3、有细胞类型特异性，只在特殊的分化细胞类型中起作用第2页/共10页11.3 Activators and Repressors of TranscriptionActivators Are Modular Proteins Composed of Distinct Functional DomainsRepressors Are the Functional Converse of Activators Like activators,most eukaryotic repressors are modular proteins that have two functional domains:
4、a DNA-binding domain and a repression domain第3页/共10页11.4 Transcription Initiation by RNA Polymerase IIGeneral Transcription Factors (TF)Position RNA Polymerases II at Start Sites and Assist in InitiationSequential Assembly of Proteins Forms the Pol II Transcription Preinitiation ComplexTATA boxbindi
5、ng protein(TBP)carboxyl-terminal domain(CTD):Tyr-Ser-Pro-Thr-Ser-Pro-Ser第4页/共10页11.5 Molecular Mechanisms of Transcription Activation and Repression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Pol II结合调节转录起始复合物的作用；第5页/共10页11.
6、6 Regulation of Transcription-Factor ActivityHormone Binding to a Nuclear Receptor Regulates Its Activity as a Transcription FactorAll Nuclear Receptors Share a Common Domain Structure第6页/共10页11.7 Regulated Elongation and Termination of Transcription第7页/共10页11.8 Other Eukaryotic Transcription System
7、sother two eukaryotic nuclear RNA polymerases,Pol I and Pol III,and by the distinct polymerases that transcribe mitochondrial and chloroplast DNA.The process of transcription initiation by Pol I and Pol III is similar to that by Pol II but requires different general transcription factors,is directed by different promoter elements,and does not require ATP hydrolysis.第8页/共10页第9页/共10页感谢您的观看！第10页/共10页