分子生物学第十一章 riboswitch_movie.ppt

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1、RiboswitchRegulationofGeneExpressionRiboswitchesarepresentinuntranslatedregionsofmRNAs.Theirpurposeistoregulategeneexpressioninresponsetobindingsmallmoleculemetabolites.Riboswitchesaredefinedbytwomaincriteria:Direct(protein-free)bindingofmetabolitetoRNAMetabolite-dependentregulationofgenesThismo

2、viedemonstratesthemoleculareventscommontomostbacterialriboswitches.Resourcesarelistedattheendofthemovie.PartI:GeneRegulationbyaTypicalRiboswitchBacterialriboswitchesarepresentinthe5´untranslatedregionofmRNAs.Transcriptionisregulatedbythegenepromoterandtranscriptioninitiationfactors…RNApolymerase

3、initiatestranscription.TheRNAfoldsintramolecularlyinlocalregionsofcomplementarity,presumably,whiletranscriptionisproceeding.Alonguntranslatedleaderisproducedfirst.NascentRNARNApolymeraseDNAtemplateRNApolymeraseCase1:Cellularconcentrationofmetaboliteistoolowtooccupytheriboswitchbindingsite.Transc

4、riptionand…3421RNApolymeraseUUUUUAUGRNApolymeraseCase1:Cellularconcentrationofmetaboliteistoolowtooccupytheriboswitchbindingsite.TranscriptionandintramolecularRNAfoldingcontinue.34213421UUUUUAUGCase1:Cellularconcentrationofmetaboliteistoolowtooccupytheriboswitchbindingsite.Translationisinitiated

5、.RibosomeTypicallythenewmRNAcodesforabiosyntheticortransportproteinthatraisestheintracellularlevelofthemetabolite.Generegulation(nextcase)isaccomplishedbyvariationsintheinteractionsoftheregionshighlightedinorange.TranscriptionandintramolecularRNAfoldingcontinue.3421Case2:Cellularconcentrationofm

6、etabolite(X)ishigh.Intramolecularfoldingcanleadtoanalternateconformation.RNApolymeraseproducesthelonguntranslatedleaderregion.Thealternateriboswitchconformationisstablewhenmetaboliteisbound.XXXXXRNApolymeraseXNascentRNADNAtemplateCase2:Cellularconcentrationofmetabolite(X)ishigh.Intramolecularfol

7、dingcanleadtoanalternateconformation.RNApolymeraseproducesthelonguntranslatedleaderregion.Thealternateriboswitchconformationisstablewhenmetaboliteisbound.XXXXXXTranscriptioncontinues.UUUUURNApolymerase3421Case2:Cellularconce