分子生物学第十一章riboswitchmov

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

2、entregulationofgenesThismoviedemonstratesthemoleculareventscommontomostbacterialriboswitches.Resourcesarelistedattheendofthemovie.PartI:GeneRegulationbyaTypicalRiboswitchBacterialriboswitchesarepresentinthe5´untranslatedregionofmRNAs.Transcriptionisregulatedbythegenepro

3、moterandtranscriptioninitiationfactors…RNApolymeraseinitiatestranscription.TheRNAfoldsintramolecularlyinlocalregionsofcomplementarity,presumably,whiletranscriptionisproceeding.Alonguntranslatedleaderisproducedfirst.NascentRNARNApolymeraseDNAtemplateRNApolymeraseCase1:Ce

4、llularconcentrationofmetaboliteistoolowtooccupytheriboswitchbindingsite.Transcriptionand…3421RNApolymeraseUUUUUAUGRNApolymeraseCase1:Cellularconcentrationofmetaboliteistoolowtooccupytheriboswitchbindingsite.TranscriptionandintramolecularRNAfoldingcontinue.34213421UUUUUA

5、UGCase1:Cellularconcentrationofmetaboliteistoolowtooccupytheriboswitchbindingsite.Translationisinitiated.RibosomeTypicallythenewmRNAcodesforabiosyntheticortransportproteinthatraisestheintracellularlevelofthemetabolite.Generegulation(nextcase)isaccomplishedbyvariationsin

6、theinteractionsoftheregionshighlightedinorange.TranscriptionandintramolecularRNAfoldingcontinue.3421Case2:Cellularconcentrationofmetabolite(X)ishigh.Intramolecularfoldingcanleadtoanalternateconformation.RNApolymeraseproducesthelonguntranslatedleaderregion.Thealternateri

7、boswitchconformationisstablewhenmetaboliteisbound.XXXXXRNApolymeraseXNascentRNADNAtemplateCase2:Cellularconcentrationofmetabolite(X)ishigh.Intramolecularfoldingcanleadtoanalternateconformation.RNApolymeraseproducesthelonguntranslatedleaderregion.Thealternateriboswitchco

8、nformationisstablewhenmetaboliteisbound.XXXXXXTranscriptioncontinues.UUUUURNApolymerase3421Case2:Cellularconce