生物化学-原核生物基因表达调控

ResearchInterestsInMyGroupEtiology,Mechanism,Diagnosis,PreventionandTreatmentofBirthDefects,CardiovascularDiseases,BreastCancer,etc.1

RegulationofGeneExpressioninProkaryotes

RegulationofGeneExpressioninEukaryotesDNABasedInformationTechnologyWhatI’llTalkAbout2345ProkaryotesEukaryotes1.Nucleolus;2.Nucleus;3.Ribosome;4.Vesicle;5.Roughendoplasmicreticulum;6.Golgiapparatus;7.Cytoskeleton;8.Smoothendoplasmicreticulum;9.Mitochondrion;10.Vacuole;11.Cytosol;12.Lysosome;13.Centriole6GeneralPrinciplesofGeneExpressionRegulationTheCentralDogmaofMolecularBiologyGeneticinformationfromDNAtoRNAtoProtein.GeneExpression:cellsandvirusesturntheinformationongenesintogeneproducts,whichareproteinsorRNAs.

GeneRegulation:Controlanddeterminewhichgenesareswitchedonandoff,andwhen,howlong,andtowhatextentthegenesareexpressed.7GeneTypesHousekeepingGene

istypicallyaconstitutivegenethatisrequiredforthemaintenanceofbasalcellularfunction,andarefoundinallhumancellsRegulatedGenesaregeneswhoseactivityiscontrolledinresponsetotheneedsofacellororganismsInducibleGenesaregenesturnedoninabacteriumorcellbyasubstance,suchaslactoseoralcoholdehydrogenase.8SevenprocessesthataffectGeneExpression910RegulationofGeneExpressioninProkaryotes11CouplingofTranscriptionandTranslationinBacteria12mRNAIsTranscribed,TranslatedAndDegradedSimultaneouslyinBacteria13GeneClusterAgeneclusterisasetoftwoormoregenesthatservetoencodeforthesameorsimilarproductswhichnecessarytoperformcoordinatedfunction.Becausepopulationsfromacommonancestortendtopossessthesamevarietiesofgeneclusters,theyareusefulfortracingbackrecentevolutionaryhistory.1415OperonsofBacteria

Inbacteria,genesareclusteredintooperons（操纵子）.Anoperonisafunctioningunitofkeynucleotidesequencesincludinganoperator,acommonpromoter,andoneormorestructuralgenes,whichiscontrolledasaunittoproducemRNAintheprocessoftranscription.16TranscriptionunitPromoterisaregulatoryregionofDNAlocatedupstreamofagene,providingacontrolpointforregulatedgenetranscription17ConsensusSequenceforManyE.coliPromotersOptimalPromoterT80A95T45A60A50T96T82G78A65C54A9518TypicalE.coliPromoters19GeneExpressionIsRegulatedbyDNA-BindingProteins

Transcriptionfactor(sequence-specificDNAbindingfactor)isaproteinthatbindstospecificsequencesofDNAandtherebycontrolsthetransfer(ortranscription)ofgeneticinformationfromDNAtoRNA.RNApolymeraseTATAbindingproteinGeneralTranscriptionFactorSpecificTranscriptionFactor20TranscriptionbyRNAPolymeraseinE.coli.21TranscriptionInitiationandElongationbyE.coliRNAPolymerase.22CombineofSpecificProteinandDNAControlstheStartofTranscription23

DNA-bindingdomain(DBD):attachtospecificsequencesofDNA.

Trans-activatingdomain(TAD):containbindingsitesforotherproteins.glutamine-richactivationdomainsproline-richactivationdomainsacidicactivationdomains

Signalsensingdomain(SSD)(ligandbindingdomain)whichsensesexternalsignalsandinresponsetransmitthesesignalstotherestofthetranscriptioncomplexresultinginupordownregulationofgeneexpression.StructureofTranscriptionFactors24HTHiscomposedoftwoαhelicesjoinedbyashortstrandofaminoacids,whichrecognizesandbindstoDNA.OneαhelicesbindstothemajorgrooveofDNA.TheotherαhelixstabilizestheinteractionbetweenproteinandDNA.lacrepressor,CAP,trprepressor,λrepressorhaveHTHmotif.Helix-Turn-Helix(HTH)

25ZincFingerAzincfingerconsistsoftwoantiparallelβstrands,andanαhelix.Thezincioniscrucialforthestability.ZincfingerinteractwiththemajorgrooveofDNAinwhichcasethezincfingersarearrangedaroundtheDNAstrandinsuchawaythattheα-helixofeachfingercontactstheDNA,forminganalmostcontinuousstretchofα-helicesaroundtheDNAmolecule.26cis-actingelement

BAGeneCodingsequenceInitiationPointTrans-actingfactorTranscriptionfactorTFAcis-elementisaregionofDNAorRNAthatregulatestheexpressionofgeneslocatedonthatsamestrand.cis-regulatoryelement

Ａ

transcriptionfactorisaproteinthatbindstospecificsequencesofDNAandtherebycontrolsthetranscriptionofgeneticinformationfromDNAtoRNA.27cGeneaGeneTransregulationCCisregulationmRNA

CProteinCbARNAProteinAA

trans-actingfactorStructuralgene28LactosemetabolisminE.coli29RegAreaCatabolitegeneactivatorprotein（CAP）bindingsitePromoterOperator

StructureGenez:

β-galactosidase

y:

permease

a:transacetylase

zyaOPDNAIIgeneLacOperonLacoperonisrequiredforthetransportandmetabolismoflactoseinE.coli.Lacoperonisregulatedbyglucoseandlactose.Lacoperonisoftenusedastheexampleofprokaryoticgeneregulation.terminator30RepressorgenemRNARepressorProteinIDNAzyaOPpolWithoutlactoseLacOperonIsBlockedByRepressorProtein31mRNARepressorProteinLactoseIDNAzyaOPpolInitiateTranscriptionmRNALactoseAllolactoseβ-galactosidaseLactoseOperonOpensByInducerGalactose32LacOperonHasAWeakPromoter33GlucoseLevelsControlTheLacOperon34++++TranscriptioncAMPishigh,withoutglucose

cAMPislowandhaveglucoseZYAOPDNACAPCAPCAPCAPCAPCAPCAPCAPbindingsite35mRNALowgalactoseGlucoselowcAMPhighGlucosehighcAMPlowRNA-polOOOOＩＩNotranscriptionNotranscriptionLowtranscriptionHighgalactose36RegulationofAraOperon

AraOperoncontainsthreedifferentgenesthatcodeforthreeenzymesneededtoconvertarabinosetoxylulose-5-phosphate.AfourthgenecodesforaraCthatregulateathestructuralgenes.37WhenAraCproteinisdepleted,thearaCgeneistranscribedfromitsownpromoter.Whenarabinoselevelsarelowandglucoselevelshigh,AraCproteinbindstobotharaIandaraO2andbringsthesesitestogethertoformaDNAloop.Theoperonisrepressedinthisstate.AraCproteinalsobindstoara01,repressingfurthersynthesisofAraC.Whenarabinoseispresentandglucoseconcentrationislow,AraCproteinbindsarabinoseandchangesconformationtobecomeanactivator.TheDNAloopisopened,andtheAraCproteinactsinconcertwithCAP-cAMPtofacilitatetranscription.38PrincipalofTrpOperonTrpoperonpromotestheproductionoftryptophanwhenitisn'tpresentintheenvironment.3940TranscriptionalAttenuationintrpOperon41Trp

HighTrpLowTrpmRNAEDCBAOPtrpRRegAreaStructureGeneRNAPolyRNAPoly?PrincipalofTrpOperon42UUUU……UUUU……RegulationArea

StructureGene

trpROPLeaderSeq

AttenuaterAreaUUUU……LeadermRNA1234AttenuaterstructureTerminalcode14aaleaderpeptideAbilitytoformhair-spin：

Seq1/2>Seq2/3>Seq3/4trpcodes

UUUU……MechanismofAttenuation

The3-4structureisatranscriptionterminationsequence,onceitforms,RNApolymerasewilldisassociatefromDNAandtranscriptionwillnotoccur.43UUUU……34UUUU3’34RibosomeLeaderPeptide

LeadermRNAHighTrp125’trpcode

AttenuateristerminaterLeaderDNA

UUUU3’RNAPoly44UUUU……342423UUUU……Ribosome15’trpcode

StructuregeneLeaderDNA

RNAPolyLowTrpTranscriptionSeq3&4can’tformattenuaterLeadermRNA

LeaderPeptide45CooperationofDNAInverstionandRepressionSalmonella46InitiatingTranslationinBacteria47EveryopenreadframehasainitiationcodeAUGandShine-Dalgarno(SD)sequence(AGGAGG)whichhelpsrecruitthe

ribosome

tothemRNAtoinitiate

proteinsynthesis

byaligningtheribosomewiththestartcodon.SDsequence,distancetotranslationinitiationanditslocationaffecttheefficiencyofTranslationInitiation.RegulationofProkaryoticGeneExpressionatTranslationLevel485¢3¢ErythromycinMethylasemRNA1234SDSD(A)NoErythromycinEndingCode1234SDNoTranslation2LeaderPeptide34SDEryrTranslation5¢3¢1234SDSDLeaderPeptideCodingRegion(B)Erythromycin1234SD234SDEryrTranslationRegulationofErythromcinMethylasemRNA49StabilityofmRNADeterminetheAmountofTranslateProduct50

RegulationofmRNAinterferingcomplementaryRNA(micRNA)ontheosmoticpressureinE.ColiHypotonicityHypertonicityOmpRompFgeneONOmpFprotein3'mRNA5'ompCgeneTurnOffONONOFF3'5'micRNA5'3'5'3'3'5'ompCmRNAOmpCAllostericOmpROFFPromoter3'micFgeneOFF3'5'5'3'OmpCProteinTurnOffPromotermicRNAParticipateintheRegulationofProteinSynthesis51SmallRNAintheRegulationofTranslationTn10TransposasemRNA3¢5¢5¢3¢RepressorRNApOUTOriginateTranscript3¢5¢5¢3¢pIN+1+1pOUTpIN5¢3¢3¢5¢3¢5¢5¢3¢3¢5¢5¢3¢+15¢3¢3¢5¢OriginateTranscriptTn10TransposasemRNARepressorRNATranslationInitiationSite52RegulationofGeneExpressioninLambdaPhage

53LysisorLysogen?5455

Exision(Xis):managesexcisionandinsertionofphagegenomeintothehost'sgenome.Intergrate(Int):managesinsertionofphagegenomeintothehost'sgenomeAttached(Att):pointofactionofIntandXisinintegrationandexcisionofthephagegenomeintothehost'sgenomeStructureofLambdaPhagecI:TranscriptioninhibitorcII:Transcriptionactivator

cIII:ProtectscIIfromdegradationbyproteasescro:Controlofrepressor'soperatorN:Antiterminator5657cIIreachesahighconcentrationandturningoncI.cIturnsoffcroandotherearlygeneexpression.PLis