L 原核生物的转录调控ppt课件.ppt

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1、SectionL.原核生物的转录调控Housekeepinggenes（看家基因）:expressedconstitutively,essentialforbasicprocessesincellreplicationandgrowth.Induciblegenes（诱导性基因）:expressedonlywhentheyareactivatedbyinducersorcellularfactors.GeneexpressionisregulatedIneukaryoticcells,RNA生成过程mayberegulatedatthestagesofmodification,splici

2、ng,transport,orstability.Inbacteria,anmRNAisinprincipleavailablefortranslationassoonasitissynthesized,andthesestagesofcontrolarenotavailable.真核生物与原核生物表达调控的差异L1TheLacOperon（乳糖操纵子）L2TheTrpOperon（色氨酸操纵子）L3TranscriptionalRegulationbyAlternativeσFactorsL1TheLacOperonL2TheTrpOperonL3Transcriptionalregul

3、ationbyalternativeσFactors操纵子，乳糖操纵子；乳糖阻抑物；诱导；cAMP受体蛋白色氨酸操纵子；色氨酸阻抑物；弱化子；前导RNA结构；前导肽；弱化作用；弱化的重要性Sigmafactor,启动子识别；热休克；枯草杆菌的孢子形成；噬菌体SigmafactorOperonproposedbyJacob&Monad1961In1961,JacobandMonod区别betweentwotypesofsequencesinDNA:sequencesthatcodefortrans-actingproducts（反式作用因子）;andcis-actingsequences（顺

4、式作用序列）thatfunctionexclusivelywithintheDNA.Geneactivityisregulatedbythespecificinteractionsofthetrans-actingproducts(usuallyproteins)withthecis-actingsequences(usuallysitesinDNA).Agene(反式作用products)asequenceofDNAthatcodesfora可传播product.Thisproductmaybeprotein(asinthecaseofthemajorityofgenes)ormaybe

5、RNA(asinthecaseofgenesthatcodefortRNAandrRNAetc.).Thecrucialfeatureisthattheproductdiffusesawayfromitssiteofsynthesistoactelsewhere.一种基因的蛋白质产物，能影响位于基因组另一条染色体上的（或基因组别处的）另一个基因的活性，这种作用叫做反式作用。参与这种反式作用的特定因子叫做反式作用因子，一般指的是蛋白质，它能够通过同顺式作用元件（DNA）之间的相互作用而影响基因的表达。Thecis-actingsequencefunctionsexclusivelyasaDN

6、Asequence在原位,affectingonlytheDNAtowhichitisphysicallylinked.(Insomecases,acis-actingsequencefunctionsinanRNAratherthaninaDNAmolecule,suchasRNAtermintor)影响自身基因表达活性的非编码DNA序列。Operon:aunitofprokarytoicgeneexpressionandregulationwhichtypicallyincludes:1.Structuralgenesforenzymesinaspecificbiosyntheticp

7、athwaywhoseexpressioniscoordinatelycontrolled2.Controlelements,suchasoperatorsequence3.Regulatorgene(s)whoseproductsrecognizethecontrolelements.CanbeencodedbyageneinanotheroperonControlelementStructuralgenes操纵子：是