案例細胞生物學(xué)11nucleus

AnimalcellChapter11Animalcell王芳WangDepartmentofMedicalGeneticsandCell:Nucleusisthemostimportantandlargestorganelle,theprincipalfeaturethatdistinguisheseukaryoticfromprokaryoticcellsThemainfunctionforthestorageandreplicationofgeneticmaterial,transcriptionofRNA,(geneexpression–translation,localizedtothecytosm)Theshape,numberandsizeofShape:Number:one(almost),many(skeletalmuscle),none(matureredblood)Size:diameter---Nuclearmorphologywiththecellcycleandthephysiologicalstatecanbedividedintointerphaseandmitoticphase

Theinterphasenucleusofaeukaryotic sm:FluidoftheNuclearenvelope（核膜）2.Transportthroughnuclearporecomplex（核孔）5.Chromosome（ 7.Nuclearmatrix（核基質(zhì)

Nuclear1Structureofthenuclearouternuclearmembrane innernuclearmembrane perinuclearspace nuclearporecomplexnuclear

envelopeisbynuclearandiswiththe structure:adensefilamentousmeshwork;composedoflaminsMostm liancells,containfourdifferentlamins,designatedA,B1,B2,andCnuclear

supportandfixedthenuclearofnuclearenvelopenuclear

Nuclearporecomplex Nuclearporesarefoundatpointsofcontactbetweentheinnerandouternuclearmembranes

Modelofthenuclearporesabout

40nm

Thespokesareconnectedtoringsatthenuclearandcytosmicsurfaces,andthespoke-ringassemblyisanchoredwithinthenuclearenvelopeatsitesoffusionbetweentheinnerandouternuclearmembranes2 smicface smicface thenumberofnuclearporesrelatedtothecelltypeandmetabolicstateFunctionsofthe

Transportofnuclearpore Passivediffusion:Smallmolecules(diametersofapproximay9nm)Transportedbyaselective,(diameterofmorethan25nm,lessthan120nm)Bidirectionaltraffichistones,DNApolymerases,RNAfactors,splicingfactors,andmanyothers.Theseproteinsaretargetedtothenucleusbyspecificaminoacidsequences,callednuclearlocalizationsignals,thatdirecttheirtransportthroughthenuclearporecomplexTheTantigen(SV40)nuclearlocalizationsignalisasinglestretchofaminoacids.Incontrast,thenuclearlocalizationsignalofnucleosmin(aproteininvolvedinchromatinassembly)isbipartite,consistingofaLys-Argsequence,followedbyaLys-Lys-Lys-Lyssequencelocatedtenaminoacidsfartherdownstream3NuclearLocalizationSignal(A)ThenormalT-antigenprotein containsthelysine-richsequence localizationsignal(athreonineindicatedandisimportedtoitssiteof recingalysine)remainsintheactioninthenucleus,asindicatedby nucleartransportProteinimportthroughthenuclearporecomplexRoleRoleoftheranproteininnuclear4NuclearRNAandprotein (heterogeneousribonucleoprotein,hnRNP)→信使RNP(mRNP)→輸出

ProteinexportthroughnuclearporesnRNAexportand

5MolecularchaperonesChaperonediscoveryand―chaperonewasfirstusedbyRonLaskeyandhiscolleaguestodescribeaprotein smin核質(zhì)蛋白)thatisrequiredfortheassembly(裝配ofnucleosomes(核小體)fromhistones(組蛋白)andDNA.Chaperones:actascatalyststhat

1991年Ellis等人提出Molecularchaperones:分子內(nèi)伴侶(intromolecular

11.3.2functionsof參與細胞器和細胞核結(jié)構(gòu)的發(fā)6ActionofActionofchaperonesduringActionsofchaperonesGroEL,GroESofE.coliinproteinActionActionofchaperonesduringproteinActionofchaperonesin.2functionsof應(yīng)激反應(yīng)heat- 11.4Chromatinisfilamentsintheinterphasenucleus,consistsofDNAandprotein.Chromosomeisashortrod-likestructureinmitoticcells,formedbythehelixofchromatinheightly.7

三種DNA構(gòu)型中,溝的特征在遺傳信息表達過程中起關(guān)鍵作用,調(diào)控蛋白都是通過其分子上氨基酸側(cè)鏈與溝中堿基對兩側(cè)潛在的氫原子供體(=NH)或受體(O和N)形成氫鍵而識別DNA遺傳信息的。另外,Z型DNA同細胞 有定的關(guān)系。DNA1.uniquesequence:1~5copiesin12.repetitivesequence:over10copiesin1

ARS(AutonomousReplicatingCEN(centromericThecentromereisaspecializedregionofthechromosomethat ysacriticalroleinensuringthecorrectdistributionof duplicatedchromosomestodaughter中度重復(fù)序列：10～10copies(組蛋白rRNA等高度重復(fù)序列：>105

during omericThesequencesattheendsofeukaryoticchromosomes,called rolesinchromosomereplicationand

8 (artificialchromosome)

Yeastartificial.2ThenatureandtypeofThehistonesaresmallproteinscontainingahighproportionofbasicaminoacids(arginineandlysine)thatfacilitatebindingtothenegativelychargedDNAfivemajortypes--H1,H2A,H2B,H3,andH4.highlyconservative高度保守染色質(zhì)中的組蛋白與DNAThefunctionof核小體 顆粒的組蛋白lhistone:H2、H2B、H3和H4,作用與DN組裝成核小體 顆粒

雖然組蛋白分子的氨基酸序列是高度保守基化、磷酸化，以及ADP核糖化等。作用：中和正電荷或使側(cè)鏈帶負電荷，9 11.4.3ThetypesandnatureoftheCategories：>500sequence-specificDNA-binding

參與的構(gòu)建;幫助DNA分子有利于DNA的和的轉(zhuǎn)錄 帶負電荷，屬酸性蛋白質(zhì)；常常磷鋅指結(jié)構(gòu)基序(模體）(zinc鋅指結(jié)構(gòu)基序(模體）(zincThezincionofeachfingeriscoordinatedtotwocysteinesandtwohistidines.有兩種主要的鋅指結(jié)構(gòu)∶Cys2/His2helixmotif)一個螺旋為識別螺旋(recognitionhelix),負另一個螺旋沒有堿基特異性,與DNA亮氨酸拉鏈基序(Theleucinezippermotif)containsfourorfiveleucineresiduesspacedatintervalsofsevenaminoacids,resultingintheirhydrophobicsidechainsbeingexposedatonesideofahelicalregion.TheTheleucinezipperThismotifischaracterizedbytwo-helicalsegmentsseparatedbyaninterveningloop.它與螺旋-轉(zhuǎn)角-螺旋結(jié)構(gòu)的差別在于∶兩旋-環(huán)-螺旋結(jié)構(gòu)位于兩個多肽之間時，這Thehelix-loop-helix(HLH)Thehelix-loop-helix(HLH)反式作用因子(trans-actingThey(蛋白質(zhì)因子)canaffecttheexpressionofgeneslocatedonotherchromosomeswithinthecell.順式作用元件(cis-actingTheyaffecttheexpressionofonlylinkedgenesonthesameDNAmolecule.包括啟動子、增andcis-acting11.4.4Heterochromatinandtheinterphasenucleusofaeukaryoticreturnstoadispersedstateduringinterphase(structure—30-nmfibersandloopedhastranscriptionalsynthesizesintheearlysyntheticphaseliesinthelight-stainingregionsamongheterochromatinorinteriorofthenucleolus.

(1)remainscompactedduringinterphase(2)stainsmore(3)haslittleorno(4)synthesizeinthelatesyntheticphase(5)lieintheperipheryofthenucleusandaroundthenucleolusDividedintotwoconstitutiveremainsinthecompactedstateinallcellsatalltimeshasnotranscriptional omere,centromerehasbeenspecificallyinactivatedduringphasesofanorganism’si.e.X

chemicalcomponentofcontentisstable2、histone：conservedbasicprotein,fiveclasses:H1,H2A,H2B,H3,H4synchronizedwithDNAsynthesis,involvedintheconstructionof、nonhistone：acidicproteinlessmanykinds,synthesizethroughthewholecellcycle,involvedintheregulationofgeneexpression、RNAlinkerNucleosomeH1nucleosomecorelinkerNucleosomeH1nucleosomecore(thelowestlevelofH1H1nucleosomecore（octamerhistone：H2A、H2B、H3、H4DNAwrapped1.65turns,146bp）NucleaseNucleasedigestion(Ratliver核小核小組蛋白的賴氨酸乙?；Ｐ?1.5Chromosomeisaformofthegeneticmaterialinthecelldivision,isthechromatinformationwithmulti-stagecompressionpackaging,isahigh-levelstructureofthechromatin.FromDNAto核小體絲(nucleosomeFrom核小體絲to螺線管From螺線管to超螺線管From超螺線管8400 Electronmicrographsofchromatin？Isolatedfrominterphasenucleus30nmChromatinunpacked,showthescanningelectronmicrographofamitotic30nm30nmloop(30nmChromosomeachromatidconsistsof1062nm2nm–11nmnucleosome–30nm––Metaphasechromosomechromosomescaffold(withoutDNAandDNA（withoutDNA（without Themainstructureofthe primaryconstriction(主縊痕):姐妹染重復(fù)的DNA序列； kinetochore(著絲點，動粒):主縊痕兩條染色

secondaryconstriction(次縊痕其它縊痕 核仁組織區(qū)(nucleolarorganizingregion， salite(隨體):通過次縊痕的染色質(zhì)絲與染 組

有帶、帶、帶、帶、Giant (polytene概念：DNA次 子 源 而 Polytene

它是一個二價體,含4條染色單體。它Theinterphasenucleusofaeukaryotic nuclear 11.611.6TheNucleolus(‘tinynucleus”)isareticularfibrogranularstructureinthenucleusthatisspecializedfortranscriptionofribosomalRNAanditspackagingintopre-ribosomalsubunits.ThegenesforribosomalRNAarehighlyamplifiedandlocatedonfivedifferentchromosomes(13,14,15,21,22)calledthenucleolarorganizingregions(NOR).rDNAgenesconcentratedwithinthenumerousfibrillarcentersthenucleolus.rRNAisbelievedtobetranscribedatthebordersoffcandthedensefibrillarcomponentdfc,致密纖維組分whereribosomalproteinsassociatetoformpre-ribosomalRNPparticles.Progressiveprocessingofthepre–rRNPparticlesoccurswithinthegranularcomponent(gc,顆粒區(qū))wherematureribosomalsubunitsarereleasedfortransportintothe Fibrillar

Nucleolusisthefactoryofsynthesisofribosome，the ceofrRNA(5SrRNAexcluded)transcription,processingandribosomalsubunitassemblyCodefor(in18s,28s,5.8slocatedonfivedifferentchromosomes(13,14,15,21,ProcessingOfProcessingOfPre-The45Spre-rRNAtranscrptcontainsexternaltranscribedspacers(ETS)atbothendsandinternaltranscrbedspacers(ITS)betweentheand28SrRNAs.Thepre-rRNAisprocessedviaaseriesofhumanpre-rRNA)toyieldthematurerRNAspecSynthesisandprocessingof5s5srRNAsareencodedbyalargenumbergenes(Human,2000)5srRNAgenearelocatedoutsidethe5srRNAsaretranscibedbyRNApolyrRNAs:RNApolyrRNArRNAgenesaretandemlyarrayedinThemassiverRNAtranscriptionisillustratedby―Christmastree‖structurescomposedofrepeatingnascentrRNPstrandsthatgrowinassemblylinefashionalongtherDNAtranscriptionunits.AssemblyOf（synthesize（synthesizeinthecytosm）528rRNAgenelarge SmallgranularThenucleolusdisappearsduringNucleolarfusionofhumanfibroblastinhumanHelahumanHela11.7NuclearSomedebateoveritsSkeleton–maintainsshapeofScaffold–loopsofAnchorsRNAprocessing/Theconceptofthenuclearmatrixwasproposedin1975onthebasisofexperimentsi