5.3 transcription in eukaryotes

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1、5.TranscriptionIncluding5.1Transcriptioninprokaryotes5.2Regulationoftranscriptioninprokaryotes5.3Transcriptionineukaryotes5.4Regulationoftranscriptionineukaryotes5.5rRNAprocessandRNPs5.3Transcriptionineukaryotes5.3.1ThethreeRNApolymerases5.3.2RNAPolⅠgenes:theribosomalrepeat5.3.3RNAPolⅢg

2、enes:5sandtRNAtranscription5.3.4RNAPolⅡgenes:promotersandenhancers5.3.5GeneralTranscriptionFactorsandRNAPolⅡinitiation5.3.1ThethreeeukaryoticRNApolymerases:characterizationandfunction3RNAeukaryoticpolymerasestranscribedifferentsetsofgenes.Theiractivitiesaredistinguishedbytheirdifferents

3、ensitivitiestothefungaltoxinα-amanitin鹅膏藫碱.Ⅰ--mostrRNA----nucleoli(核仁)--insensitive;Ⅱ---mRNA;smallnuclearRNAs---nucleoplasm（核质）---verysensitive.Ⅲ---5srRNA,tRNA,U6snandotherRNAs---nucleoplasm---moderatelysensitive真核生物的RNA聚合酶种类　　分布　　合成的RNA类型　对α-鹅膏蕈碱的敏感性Ⅰ核仁rRNA不敏感Ⅱ核质hnRNA低浓度敏感Ⅲ核质tRNA，5sRNA

4、高浓度敏感Mt线粒体　　　　线粒体RNAs不敏感RNApolymerasesubunitsAll3polymerasearelargeenzymescontaining12ormoresubunits.ThegeneencodingthetwolargestsubunitsofeachRNApolymerasehavehomologytoeachother.TheyhavehomologytoE.colicoreRNApolymerase.Thelargestsubunit---β';Thesecondlargestsubunit---β2commonsubunits

5、(Ⅰ,Ⅲ),1furthersubunit(Ⅱ)---σAtleast5subunitsarecommon,4to7areonlypresentinonetype.EukaryoticRNApolymeraseactivitiesLikebacterialRNApolymerase5'to3'AntisensetemplatestrandRequireATP,GTP,CTP,UTP;notrequireprimerUnlikebacterialenzymesRequirethepresenceofadditionalinitiationproteinsbeforeth

6、eyareabletopromoteandinitiatetranscription.TheCTDofRNApolⅡCTD(carboxyl-terminaldomain,羧基末端结构域)ThecarboxylendofRNApolⅡcontainsastretchofsevenaminoacid,Tyr(酪)-Ser(丝)-Pro(脯)-Thr(苏)-Ser-Pro-Ser.52repeats-mouse,26repeats–yeast,thisrepeatsareessentialforviability(活性).TheCTDsequencemaybephosph

7、orylated(磷酸化).TheCTDhasbeenshowntobeanimportanttargetfordifferentactivationoftranscriptionelongation.5.3.2RNAPolⅠgenes:theribosomalrepeatRibosomalRNAgenesPre-rRNAtranscriptionunitscontainthreesequencesthatencodethe18S,5.8Sand28SrRNAs.Pre-rRNAtranscriptionunitsarearrangedinclust