Chapter 09 Gene Regulation

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1、ChapterNineRegulationofGeneExpression:Operons1.TranscriptionalRegulation2.PosttranscriptionalRegulation1.TranscriptionalRegulation
NegativeTranscriptionalRegulation
PositiveTranscriptionalRegulation
AttenuationofTranscriptionNegativeTranscriptionalRegulation----------thelacOperonRepressionInd

2、uctionCataboliteRepressionLowglucoseLactoseavailablelacgenesstronglyexpressedHighglucoseLactoseunavailablelacgenesnotexpressedLowglucoseLactoseunavailablelacgenesnotexpressedHighglucoseLactoseavailableVerylow(basal)levelofgeneexpressionTheRoleofCRP/CAP(cyclicAMPreceptorprotein/cataboliteactiv

3、atorprotein)OperatorsofthelacOperonThelacoperonregulatoryregiononPromotersDerivedfromthelacPromoter•ThelacIqalleleisapromotermutationthatincreasestheintracellularconcentrationofLacIrepressor.PromotersDerivedfromthelacPromoter•lacUV5promoter(PlacUV5):amutatedversionofthelacpromoterwhosebasalac

4、tivityisdramaticallylesssensitivetointracellularlevelsofcyclicAMPmolecule•tacpromoter(Ptac):astronghybridpromotercomposedofthe-35regionofthetrppromoterandthe-10regionofthelacUV5promoter/operator.Promotersderivedfromthelacpromoter—T7PromoterMCSOverExpressionofProteinsbytheT7PromoterPositiveTra

5、nscriptionalRegulation---theL-araOperonRegulationoftheL-araOperonAttenuationofTranscription---thetrpOperonAttenuationofTranscription---thetrpOperonFeedbackInhibition(PostTranslationalRegulation)TrpETrp2.PosttranscriptionalRegulation•ThecontrolofgeneexpressionattheRNAlevel.•mRNAstability•Ribos

6、witch•SecondaryStructureinthemRNA•SmallRegulatoryRNAsRiboswitchInBacillussubtilis,11transcriptionalunits(about26genes)areinvolvedinbiosynthesisandtransportofmethionineandSAM(S-adenosylmethionine)RiboswitchSecondaryStructureinthemRNAListeriamonocyogenesSmallRegulatoryRNAs•1981,theFirstsRNA–Reg

7、ulationofColE1PlasmidReplication•1984,theFirstChromosomallyEncodedsRNA–MicF,InhibitstheTranslationofOmpF•From2001-now,~80sRNAhavebeenverified(E.coliGenome:4,639,221bp,4,377genes)SmallRegulatoryRNAs•Cis-EncodedBasePairingsRNAs•Trans-EncodedsRN