Lecture_8__Gene_Regulation_in_Eukaryotes

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1、LectureEightGeneRegulationineukaryotes原核生物基因组结构特点●基因组很小，大多只有一条染色体●结构简炼●存在转录单元多顺反子●有重叠基因真核基因组结构特点V真核基因组结构庞大3×109bp、染色质、核膜V单顺反子V基因不连续性断裂基因（interruptedgene）、内含子(intron)、外显子(exon)V非编码区较多多于编码序列(9:1)V含有大量重复序列EukaryotesHaveLargeComplexGeneomes•Thehumangenomeisabout3x109basepairsor≈1

2、mofDNA•Becausehumansarediploid,eachnucleuscontains6.3x109basepairsor≈2mofDNA•Thatisalottopackintoalittlenucleus!OnlyaSubsetofGenesisExpressedatanyGivenTime•Ittakeslotsofenergytoexpressgenes•Thusitwouldbewastefultoexpressallgenesallthetime•Bydifferentialexpressionofgenes,cells

3、canrespondtochangesintheenvironment•Differentialexpression,allowscellstospecializeinmulticelledorganisms.•Differentialexpressionalsoallowsorganismstodevelopovertime.ControlOfExpressionInEukaryotes•Someofthegeneralmethodsusedtocontrolexpressioninprokaryotesareusedineukaryotes,

4、butnothingresemblingoperonsisknown.•Eukaryoticgenesarecontrolledindividuallyandeachgenehasspecificcontrolsequencesprecedingthetranscriptionstartsite•Inadditiontocontrollingtranscription,thereareadditionalwaysinwhichexpressioncanbecontrolledineukaryotesSimilarityofregulationbe

5、tweeneukaryotesandprokaryote1.Principlesarethesame:signals,activatorsandrepressors,recruitmentandallostery（变构）,cooperativebinding2.Expressionofagenecanberegulatedatthesimilarsteps,andtheinitiationoftranscriptionisthemostpervasivelyregulatedstep.Differenceinregulationbetweeneu

6、karyotesandprokaryote1.Pre-mRNAsplicingaddsanimportantstepforregulation.2.Theeukaryotictranscriptionalmachineryismoreelaboratethanitsbacterialcounterpart.3.Nucleosomesandtheirmodifiersinfluenceaccesstogenes.4.Manyeukaryoticgeneshavemoreregulatorybindingsitesandarecontrolledby

7、moreregulatoryproteinsthanarebacterialgenes.ControlofGeneExpressionCytoplasmNuclearPackagingporesDegradationDNATranscriptionTransportationRNARNAModificationProcessingRibosoDegradationetc.mmRNAGAAAAAAGGeAAAAAAAAAAAAExportTranslationNucleusLogicalExpressionControlPoints•DNApack

8、agingIncreasingcost•TranscriptionThelogicalplace•RNAprocessingtocont