分子生物學(xué)英文版課件：chapter18-regulation of gene expression

RegulationofgeneexpressionChapter18BasedontheNationalplanningtextbook，8thedition,2013Section1

Basicconceptionandcharactersofgeneexpression

TheprocessinwhichgenewastranscribedintoRNAandtranslatedintoprotein.

Ortheprocessinwhichthefunctionalproductwasproduced.(includingthetranscriptionofrRNAandtRNA)DNA→mRNA→Protein(orDNA→RNA)

Ⅰ.Geneexpression:

*Temporalspecificity(Stagespecificity)Notallgenesareexpressedallthetime.Inthehumangenomeonlyafractionareexpressedatanygiventime.example:alphafetalprotein,AFP

inlivercancercells,AFPisactivated*Spatialspecificity(cellortissuespecificity)forspecifictissue,somegeneproductshavefunctions,presenceinverylargeamounts.Othergeneproductsareneededinmuchsmalleramounts.

example:expressionofinsulinⅡ.Specificityofgeneexpression:Ⅲ.Themodesofgeneexpression:1.Constitutivegeneexpression(housekeepinggene):

*expressinginalmostallcells*expressinginalllifeperiod*influencedlessbytheenvironmentalchanges

*housekeepinggeneisconstitutivelyexpressed*onlyinfluencedbypromoterandRNApolymerasehousekeepinggenes:

Somegeneproductsarerequiredallthetime,andtheirgenesareexpressedatconstantlevelinallthecellsofaspeciesororganism.

Manyofthegenesforenzymesthatcatalyzestepsincentralmetabolicpathways.constitutivegeneexpression:

Constant,unregulatedexpressionofthegenes.ItisonlyregulatedbypromoterandRNApol.KeytermInductionorrepression:turnedon/offbyenvironmentalevents,Somegeneproductsriseanddecreaseinresponsetomolecularsignals.

*induciblegenes:increasedbyinducers

theprocessofincreasingexpressionofthegeneiscalledinduction.example:TheexpressionofgenesencodingDNArepairenzymes

*repressiblegenes:decreasedbyrepressors

thedecreaseingeneexpressioniscalledrepression.Example:theenzymescatalyzingtryptophanbiosynthesis.2.Inductionandrepressionofgeneexpression:3.CoordinategeneexpressionThegenesthatassociatefunctionallyareregulatedtoexpresstogether.Example:genesforenzymesandtransportproteinsparticipatingin

thesamemetabolismpathway(suchastheenzymesforglycolysis)Ⅳ.multiplelevelsandcomplexityofgeneexpressionregulation:GeneactivationInitiationoftranscriptionPosttranscriptionalprocessingTranslationPosttranslationalmodification①②③1.adaptingtotheenvironmentalchanges.2.maintainingthegrowth,development,

differentiationandreproductionoforganisms.

*Byswitchinggenesonoroff,cellscanpreventresourcesfrombeingwasted.*RegulationcanoccuratseverallevelsⅤ.Regulationofgeneexpressionisthebasesofgrowthanddevelopment:

Section2

RugulationofgeneexpressioninProkaryotes

1.notmanyrepetitivesequences.2.thestructuregenescodedforproteinsarecontinuousandusuallyonecopy(exceptforrRNA)3.Theratio(about50%)ofstructuregenesismuchthanthatofeukaryote.4.somestructuregenesareclusteredtoaoperon.FeaturesofgenomeinprokaryotesThegenomeofprokaryotesisclosedsuperhelixdoublestrandsDNA.

Operonincludesregulatorysequenceandstructuregene:

Ⅰ.

OperonisthebasicunitoftranscriptregulationinprokaryoteStructuralgenesA，B，CFigure.Anoperon.GenesA,B,andCaretranscribedononepolycistronicmRNA.Typicalregulatorysequencesincludebindingsitesforproteinsthateitheractivateorrepresstranscriptionfromthepromoter.Operon:

consistsofmorethan2codingsequences,promoter,operatorandotherregulatorysequencesclusteredinthegenome.Structuralgenes:codeforproteins.Thestructuralgenesaregroupedtogether.Promoter:RNApolymerasebindingsite,Operator:

repressorbindingsite,overlappingwithpromoterandinitiationsiteKeytermOperonisgeneralinprokaryotePolycistron:Inprokaryote,severalstructuregenesareclusteredtogether,onlyonemRMNAmoleculeisproducedintranscription,andseveralpeptidesaretranslatedfromthisonemRNA.ThismRNAiscalledpolycistron.Theconsensussequenceofpromoter:determinetheactivityofgenetranscription.Prokaryoticpromoterconsensussequence:ConsensussequenceformanyE.colipromoters(Strong/weakpromoter)PromoterandRNApolymeraseactivatyPromotersthatexactlymatchtheconsensussequencegenerallyhavethehighestaffinity

forRNApolymeraseandthehighestfrequencyoftranscriptioninitiation.Forhousekeepinggenes,theinteractionofRNApolymeraseandpromoteristheonlyfactoraffectingtranscriptioninitiation.regulatingproteinsingeneexpressionspecificfactors:

alterthespecificityofRNApolymeraseforagivenpromoterorsetofpromoters;Repressors(negativeregulation):bindtotheoperator,blockingaccessofRNApolymerasetothepromoter;blockinggenetranscription.

Activators(positiveregulation):

bindnearapromoter,enhancingtheRNApolymerase-promoterinteraction,enhancingthetranscriptionactivity.1.Lacoperonstructure:

*structuregenes:Z,Y,Aencodingβ-galactosidase,permease,

transacetylaserespectively*promoter:RNApolbindingsite*operator:repressorbindingsite*CAPsite:CAPbindingsite*regulatorygeneI:

encodinglac

repressorproteinregulatoryregionⅡ.LacoperonisatypicalinducibleregulationThestructureofthelac

operonDNALacZLacYLacAStructuralgenesOperatorPromoterCAPsiteRegulatoryregionsRepressorRNApolcAMPLacIRepressorCAPOperon

2.Thenegativeregulationofrepressor:

mediatedbytheinteractionofrepressorandoperator,andinducedbyinducer(半乳糖,異丙基硫代半乳糖苷

(IPTG)

)

3.ThepositiveregulationofCAP:mediatedbytheinteractionofCAP(catabolitegeneactivatorprotein,CAP)andCAPsite,andinducedbycAMP

CAP:homodimer,containingDNAbindingregionand

cAMPbindingregionPositiveandnegativeregulationofthelac

operon4.Thecoordinationofnegativeandpositiveregulation

a)Glucosepresent(cAMPlow),nolactoseb)Glucosepresent(cAMPlow),lactosepresentc)Noglucose(cAMPhigh),lactosepresent

①thepresenceoflactose:toinactivatetherepressor

②the

absenceorlowconcentrationofglucose

toincreasethecAMPconcentrationandfacilitateCAPbinding.StronginductionofLacoperonrequirestwoconditions:Conclusion:Rhofactor-dependent

polyCRhofactor-independent

stemandlooppolyUAttenuationofTrpAntiterminationⅢ.Regulationoftranscriptiontermination

bindtotargetsiteofmRNAautogenouscontrol:regulatoryproteinsblocktheribosomerecognizingthetranslationinitiationsite

2.antisenseRNAcontrol:antisenseRNAblockribosmebindingwithmRNAⅣ.TheregulationattranslationlevelinprokaryotesConclusion:RegulationofprokaryotesatthreelevelsthebeginningoftranscriptionterminaloftranscriptiontranslationSection4

Regulationofgeneexpressionineukaryotes

1.Genomeisbig:human3×109

bp,25,000genes(1%)2.Codingsequenceisonly10%ofgenome.3.Discontinuousgene:intronandexon,splicing4.Monocistron:onegene→onemRNA→onepolypeptide5.DNAbindswithprotein,formingchromatin.6.NucleusDNAandmitochondriaDNAI.FeaturesofgeneexpressionineukaryotesFig.18-5multiplelevelsandcomplexityofgeneexpressionineukaryote1.ActivatedchromatinareSensitivetonuclease(DNaseⅠ,

hypersensitivesites):Ⅱ.Chromatinstructureandgeneexpressionregulationineukaryote2.ChangesofhistoneproteininactivatedChromatin:AcetylationMethylationphosphorylation（a）組蛋白與DNA組成的核小體；（b）組蛋白的氨基端伸出核小體，形成組蛋白尾巴；（c）四種組蛋白組成的八聚體histoneproteinanditschemicalmodification組蛋白氨基酸殘基位點(diǎn)修飾類型功能H3Lys-4methylationactivationH3Lys-9methylation染色質(zhì)濃縮H3Lys-9methylationDNA甲基化所必需H3Lys-9acetylationactivationH3Ser-10phosphorylationactivationH3Lys-14acetylation防止Lys-9的甲基化H3Lys-79methylation端粒沉默H4Arg-3methylationH4Lys-5acetylationassemblyH4Lys-12acetylationassemblyH4Lys-16acetylationassemblyH4Lys-16acetylationFlyXactivationEffectofHistonemodification

3.MethylationlevelofGpCislandislow

GpCisland:GCismorethan60%,300-3000bp,usuallyinpromoteror1stextronofgene.DNAmethyltransferase:

methyltransferasecatalyzesthemethylationofC.Ⅲ.

Cis-actingelementsarekeyregulationsitesineukaryotes1.Cis-actingelements:

arethespecificDNAsequencesregulatingthemselvesgeneexpression.TheyarethesitesbindingRNA-polandtranscriptionfactors.including

promotor,enhancer,silencerKeytermEukaryoticcis-actingelementConsensussequenceformanyEukaryoticpromotersGCboxCAATboxTATAboxEukaryoticcis-actingelements:

promoterEnhancerSilencer

promoterinitiationsite+TATAbox(+GCbox+CAATbox)TATAbox

locatedat-30~-25

bpTFⅡDbindingsitedeterminingtheinitiationsiteandinitiationfrequency2.enhancer:consistsofseveralfunctionalelements;apartfromtranscriptionalinitiationsite;enhancingtheactivityofpromoter;determiningthetemporalandspatialspecificity;functioningindifferentdirectionanddistanceonupstreamordownstream.

Keyterm

ThestructureofeukaryoticgenesCharactersofenhancer：iscis-actingelement;Bindingsiteofthetissuespecifictranscriptionfactor;functioningindifferentdirection(upstreamordownstream);functioningindistance;Promoterisrequired.3.Silencer:negativeregulatorysequence,inhibitingtranscriptionSimilarwithenhancertranscriptionfactors

isalsocalledtrans-actingfactorsbindingcis-actingelementtheregulatoryproteinsmodulatethebindingofRNApolymerasetothepromoteroraffectpolymerasefunction.Ⅳ.TranscriptionfactorsarekeymoleculesoftranscriptionregulationCis-regulationandtrans-regulationTransactingproteinCis-actingprotein(necessaryforRNApol

bindingpromoters)KeytermTrans-actingfactor:Theyaretheproteinfactorsthatcaninteractwiththecis-actingelementsofothergene,andcontrolthetranscriptionofothergene.

1.Generaltranscriptionfactors(necessaryforindividualgenetranscription)transcriptionactivators:enhan