8b.Nucleus+and+Chromosomes(曲志才)

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1、Chap8NucleusandChromosomesNucleusofaEukaryoticCellNuclearEnvelopeNuclearPoreComplexChromatinNucleolusandRibosomeBiogenesisNuclearMatrix8.1TheNucleusofaEukaryoticCellTheinnernuclearmembraneTheouternuclearmembraneSurroundedbytwoconcentricmembranes8.1.1OrganizationoftheN

2、ucleuschromosomesnuclearmatrixnucleolinucleoplasmaninterphaseHeLacellnucleusshowingsomeofthemajorcomponentsofthenucleus8.1.2InternalArchitecturecontrasttothecytoplasm,thenucleus:❖notindividuallyenclosedbymembranes❖notvisibleusingconventionallightorelectronmicroscopytech

3、niquesrevisedpictureofnuclearstructureNuclearmatrix:aproteinaceousscaffold-likenetworkNucleolus:thecenterforsynthesisandprocessingofrRNAmolecules8.2TheNuclearEnvelopeTheseparationofacell’sgeneticmaterialfromthesurroundingcytoplasmmaybesinglemostimportantfeaturethatdisti

4、nguisheseukaryotesfromprokaryotes.StructureofthenuclearenvelopeouternuclearmembraneinnernuclearmembranenuclearlaminaperinuclearspacenuclearporenuclearlaminaFunctionofthenuclearenvelopeabarrierbetweenthenucleusandcytoplasm,asadistinctbiochemicalcompartmentsolechannelst

5、hroughthenuclearenvelope8.3NuclearPoreComplexVertebrate:50100proteinsDiameter:120nm,125MDabasketlikeapparatuseightfoldsymmetryCompositionoftheNPCCytoplasmicringNuclearringSpokeCentralplugNuclearenvelopesofXenopusoocytesvisualizedbyfieldemissionin-lensSEMCut-awaymodelof

6、theNPCThree-dimensionalmodelsoftheNPCAstructurewitheightfoldsymmetryTheNPCconsistsofanassemblyofeightspokesarrangedaroundacentralchannelThespokesareconnectedtoringsatthenuclearandcytoplasmicsurfacesElectronmicrographofNPCNLSsdirectnuclearproteinstothenucleusThenucle

7、arproteinsareselectivetrafficacrossthenuclearenvelopefromthecytoplasmtothenucleusTheNLSsincludehistones,DNApolymerases,RNApolymerases,transcriptionfactors,splicingfactorstransportthroughNPC核孔运输特点◆被动运输◆主动运输●信号引导●双向性MoleculartrafficthroughNPC核孔的被动运输Smallmoleculartraffic

8、throughtheNPCbypassivediffusionSmallmoleculesandsomeproteinswithMW<50kDpassfreelyacrossthenuclearenvelopeineit