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1、8885d_c28_1081-11192/12/042:28PMPage1081mac76mac76:385_reb:chapter28REGULATIONOFGENEEXPRESSION28.1PrinciplesofGeneRegulation1082protein—hemoglobin—inerythrocytes.Giventhehigh28.2RegulationofGeneExpressioninProkaryotes1092costofproteinsynthesis,regulationofgeneexpressionisessent
2、ialtomakingoptimaluseofavailableenergy.28.3RegulationofGeneExpressioninEukaryotes1102Thecellularconcentrationofaproteinisdeter-minedbyadelicatebalanceofatleastsevenprocesses,eachhavingseveralpotentialpointsofregulation:Thefundamentalproblemofchemicalphysiologyandofembryologyist
3、ounderstandwhytissuecellsdonotall1.SynthesisoftheprimaryRNAtranscriptexpress,allthetime,allthepotentialitiesinherentintheir(transcription)genome.2.PosttranscriptionalmodificationofmRNA—FrançoisJacobandJacquesMonod,3.MessengerRNAdegradationarticleinJournalofMolecularBiology,1961
4、4.Proteinsynthesis(translation)5.Posttranslationalmodificationofproteins6.Proteintargetingandtransportfthe4,000orsogenesinthetypicalbacterialOgenome,ortheperhaps35,000genesinthehuman7.Proteindegradationgenome,onlyafractionareexpressedinacellatanygiventime.Somegeneproductsarepre
5、sentinverylargeTheseprocessesaresummarizedinFigure28–1.Weamounts:theelongationfactorsrequiredforproteinhaveexaminedseveralofthesemechanismsinprevioussynthesis,forexample,areamongthemostabundantchapters.PosttranscriptionalmodificationofmRNA,byproteinsinbacteria,andribulose1,5-bi
6、sphosphateprocessessuchasalternativesplicingpatterns(seecarboxylase/oxygenase(rubisco)ofplantsandphotosyn-Fig.26–19b)orRNAediting(seeBox27–1),canaffecttheticbacteriais,asfarasweknow,themostabundantwhichproteinsareproducedfromanmRNAtranscriptenzymeinthebiosphere.Othergeneproduct
7、soccurinandinwhatamounts.Avarietyofnucleotidesequencesmuchsmalleramounts;forinstance,acellmaycontaininanmRNAcanaffecttherateofitsdegradation(p.onlyafewmoleculesoftheenzymesthatrepairrare1020).ManyfactorsaffecttherateatwhichanmRNADNAlesions.Requirementsforsomegeneproductsistrans
8、latedintoaprotein,aswellastheposttransla-changeovertim
