細胞分裂增殖

細胞學說：“Whereacellarises,theremustbeapreviouscell,justasanimalscanonlyarisefromanimalsandplantsfromplants.”

德國病理學家威爾肖Cellproliferationandcontrol

細胞增殖及調控Chapter126weeks12weeks16weeks

I.生物學意義1.細胞增殖(cellproliferation)是細胞生命活動的重要特征之一,是生物繁育的基礎。Redbloodcell120d.1011/d2millionstemcellsdivideeverysecond2.成體生物仍然需要細胞增殖，取代衰老死亡

的細胞，維持個體細胞數(shù)量的相對平衡和機

體的正常功能。

機體創(chuàng)傷愈合、組織再生、病理組織修復等，

都要依賴細胞增殖。DamagedtissuebyUVlightIfdamagedseriouslybyX-ray,mousewilldiewithinseveraldaysII.Thecell-divisioncycle細胞分裂周期

細胞從一次有絲分裂結束到下一次有絲分裂完成所經(jīng)歷的一個有序過程。其間細胞遺傳物質和其他內含物分配給子細胞。Cellcycle1.細胞周期時相

G1

Interphase間期S G2Mphase分裂期細胞沿著G1→S→G2→M→G1周期性運轉，在間期細胞體積增大(生長)，在M期細胞先是核分裂，接著胞質分裂，完成一個細胞周期。不同細胞的細胞周期時間差異很大

Someeukaryoticcellcycletimes

CelltypeEarlyfrogembryocellsYeastcellsIntestinalepithelialcellsHumanlivercellsCell-cycletime

30min 1.5-3h 12h ~1yearWhysodifferent?

S+G2+M的時間變化教小，細胞周期時間長短主要差別在G1期小鼠食管上皮細胞T=115hG1=103h十二指腸上皮細胞T=15hG1=6h2.根據(jù)增殖狀況，細胞分為三類(1).周期細胞Cyclingcells體內連續(xù)分裂的細胞(2).休眠細胞G0cells正常情況下不分裂，一旦受到信號刺激后重新進入細胞周期:livercells,lymphocytes(3).終末分化細胞TerminallyDifferentiatedcellsHighlyspecialized,havelosttheabilitytodivideuntiltheydie.EmbryocellsCyclingcellsTerminalcellsG0cells

?研究細胞周期的方法

ObservewithamcroscopeBrdU-labledepitheliacellsofthezebrafishgut.(Gree:Sphasecells)BrdU-labledRKOcells(Red:Sphasecells),Dr.ZouFD流式細胞儀的應用G1cellsgreater?G1/SprogressioninRKOWTandmiR-21knockoutcellsWTKO3.Synchronizationofcell細胞同步化(1).自然同步化NaturalsynchronizationEarlyembryoinmostinvertebratesandafewvertebrates果蠅胚胎(2).人工同步化SelectedsynchronizationMphaseSG2BlockingDNAsynthesisbyTdR:G1/S

G1

G1/S

M秋水仙素讓細胞停留在M期4.特殊的細胞周期—Earlyembryo30min/cellcycleFrogXenopuslaevisWhysorapidly?NoG1andG2phase,Sphaseisveryshort細胞分裂快,無G1期,G2期非常短,S期也短(所有復制子都激活),

以至認為僅含有S期和M期·無需臨時合成其它物質·子細胞在G1、G2期并不生長，越分裂體積越小1 32 4III.Mphase:1.有絲分裂Mitosis(Nucleardivision)前期Prophase前中期Prometaphase中期Metaphase后期Anaphase末期Telophase(1).前期◆標志前期開始的第一個特征是染色質開始濃縮(condensation)形成有絲分裂染色體(mitoticchromosome）◆第二個特征細胞骨架解聚，有絲分裂紡錘體(mitoticspindle)開始裝配FormationofthecompactedmitoticchromosomeCondensin濃縮素VincentL.etal.,MultiplerolesofCondensins:acomplexstory,BiologyoftheCell,2004,96:201–213Cohesin粘連素Thesisterchromatidsaregluedtogetherbycohesins.AsterMTsinterpolarMTsFormationofthemitoticspindle

Centrosome duplicatedatS, andseparateto formmitotic spindleatthe beginningof prophase

Golgi,ERetc. dispersetoformvesicles;kinetochoreassembly(2).前中期Prometaphase核膜破裂成小的膜泡，這一過程是由核纖層蛋白磷酸化導致核纖層解體紡錘體微管與染色體的動粒結合，捕捉住染色體每個已復制的染色體有兩個動粒，朝相反方向，保證與兩極的微管結合；紡錘體微管捕捉住染色體后，形成三種類型的微管(3).中期Metaphase

所有染色體排列到赤道板(MetaphasePlate)上，標志著細胞分裂已進入中期(4).后期Anaphase排列在赤道面上的染色體的姐妹染色單體分離產(chǎn)生向極運動AnaphaseA:后期A，動粒微管去裝配變短，染色體產(chǎn)生兩極運動AnaphaseB:極間微管長度增加，兩極之間的距離逐漸拉長，介導染色體向極運動(5).末期Telophase◆染色單體到達兩極，即進入了末期（telophase）,到達兩極的染色單體開始去濃縮◆核膜開始重新組裝◆Golgi體和ER重新形成并生長◆核仁也開始重新組裝，RNA合成功能逐漸恢復,有絲分裂結束2.胞質分裂Cytokinesis(Cytoplasmdivision)(1).Inanimalcells蛙受精卵的卵裂培養(yǎng)細胞的胞質分裂Contractilering有絲分裂收縮環(huán)分裂溝形成的時間和位置至關重要Thesiteofformationofthecleavageplane(2).Inplantcells與動物細胞胞質分裂不同的是，植物細胞胞質分裂是因為在細胞內形成新的細胞膜和細胞壁而將細胞分開SummaryTwoidenticaldaughtercells如何保證遺傳物質準確分配給子細胞？3.Meiosis減數(shù)分裂減數(shù)分裂是細胞僅進行一次DNA復制，隨后進行兩次分裂，染色體數(shù)目減半的一種特殊的有絲分裂MeiosisMitosis減數(shù)分裂的意義◆確保世代間遺傳的穩(wěn)定性；◆增加變異機會，確保生物的多樣性，增強生物適應環(huán)境變化的能力。◆減數(shù)分裂是生物有性生殖的基礎，是生物遺傳、生物進化和生物多樣性的重要基礎保證。III.Controlofcellcycle1.檢驗點和它們的功能Cell-cyclecontrolsystem:

本質就是周期性激活的蛋白激酶（cyclicallyactivatedProteinskinases）2.MPF:促進細胞從G2期到M期的轉換成熟促進因子（Maturation-promotingfactor），有絲分裂促進因子（Mitosis-promotingfactor)細胞融合實驗和染色體的提前凝集MphaseHeLacellwithaPtK2cell,1974,Humangenetik23:437非洲爪蟾卵母細胞成熟過程MasuiandMarkert’sexperiments(J.Exp.Zool.177:142,1971)注射實驗表明：孕酮誘導卵母細胞成熟；成熟卵細胞質中，含有卵母細胞成熟的因子，稱做MPF。MPF的活性與細胞周期的關系Inthemid-1970sasapostdocstudyingthefissionyeastS.pombe.Nursefoundcdc2裂殖酵母中幾個溫度敏感的cdc基因的隱性突變使得裂殖酵母在周期中不能進入M期,由于生長沒有停止,所以比正常的酵母長很多。這些基因中的一個顯性突變,命名為cdc2。cdc2DNormalcdc2-Cdc2encodesaproteinkinasewith34kDwhoseactivityisrequiredforcellstoenterMphase.(p34cdc2)MPF是一種使多種底物蛋白磷酸化的蛋白激酶；由M期Cyclin-Cdk(Cyclin-dependentproteinkinase)形成的復合物。MPF=CDK1=p34cdc2+cyclinBIn1982,NurseandhiscolleaguesfoundthatCDC2wasidenticalinfunctiontoCDC28frombuddingyeast,S.cerevisiaeHartwellfoundcdc28TimHuntfoundcyclinin1983WhenthegelwasdevelopedonFriday23July1982,Ifoundthatthestrongestbandearlyonsuddenlygotverymuchweakerataboutthetimewhentheeggswereabouttodivideintwo.Thiswasastunning,startlingdiscovery.“35S-Met:FertilizedeggsFromTimandhiscolleagues

16min60min80min120minCyclin:inseaurchineggsthatisdestroyedateachcleavagedivision.Cell33:389-396,1983Whatistherelationshipbetweencyclinsorcdc2andMPF?MPFpurification:1988(Xenopusegg)MPF=32kD+45kDMPFhasproteinkinaseactivityCdc2AntibodyCyclinBMphaseCyclin-Cdk(MPF)(Cyclin-dependentproteinkinase)(2)ActivationofMPFBycyclinByphosphataseandKinaseActiveMPFactivateMPFagain(3)FunctionsofMPF:G2—MtransitionM-Cdk

?inducetheassemblyofthemitoticspindle

?triggerchromosomecondensation???nuclearenvelopebreakdown?cytoskeletonrearrangement?reorganizationofGolgi,ERAlloftheseprocessesarethoughttobetriggeredwhenM-CdkphosphorylatesspecificproteinsM-Cdkdoesnotactalong.ThePolo-likekinaseandtheAurorakinasealsomakeimportantcontributionstothecontrolofearlymitoticevents.ActivationofPolo-likekinasesandAurorakinasesdependsonM-Cdk

一位教授在實驗室分離得到兩株突變酵母，cdc25-和wee1-,但忘了標記這兩株酵母分別是什么突變。根據(jù)細胞周期調控的相關知識，你只需用一臺光學顯微鏡觀察野生型、突變型酵母的增殖形態(tài)，便可輕易給這位教授解決這個難題。野生型突變株1突變株2(1)突變株1和突變株2分別是什么突變？為什么？(2)兩株突變酵母的哪一周期時相發(fā)生了改變？這一時相是變 長還是變短？3.Howtocontroltheseparationofchromosomes?TheAPC/Ctriggerssister-chromatidseperationandthecompletionofmitosisAPC/C(anaphase-promotingcomplex,orcyclosome):ubiquitinligasefamilyActiveAPCSpindleattachmentcheckpoint

Secruin Cdc20 Inactiveseparase UbiquitinsystemActiveseparase

InactiveAPCCohesinG2MetaphaseAnaphaseM-CdkUnattachedchromosomesblocksister-chromatidseperationTheinapproriatelyattachedkinetochoressomehowgenerateadiffusiblesignalthatbindCdc20-APC/Cacitivity.Severalproteins,includingMad2arerecruitedtounattachedkinetochores,andcanbindandinhibiteCdc20-APC/CMad2proteinsonunattachedkinetochores,JCB1998(mammaliancell,stainingwithanti-Mad2)Mad2-cdc20-APCM-cyclininactivion:controlofproteolysis byCdc20-APC.CellexistfrommitosisChildrenwithDownsyndrome.Thediseaseiscausedbytrisomy21,meaningtheirbodies'cellshaveanextrachromosome214.G1checkpointMechanismscontrollingcell-cycleentryandS-phaseinitiationinanimalcellsTheRbproteinsitselfwasidentifiedoriginallythroughstudiesaninheritedeyecancerinchildren,retinoblastoma.5.Thediversityofcyclin-CdkcomplexG1-cyclins:促使細胞通過G1checkpointG1/S-cyclins:在G1末結合Cdks促使細胞DNA復制S-cyclins:結合S-Cdk啟動DNA復制M-cyclins:

促使細胞進入mitosisCyclin-CdkVertebratesBuddingYeastG1cyclinDCdk4,6Cln3Cdk1G1/SSMcyclinECdk2 cyclinACdk2 cyclinBCdk1

Cln1,2Cdk1 Clb5,6Cdk1Clb1,2,3,4Cdk1Cdk1:cdc2invertebratesandfissionyeast, cdc28inbuddingyeastVariouscyclin-Cdkcomplexesareregulatedby:(1)在不同時相各種Cyclins的合成與降解(2)Cyclin-Cdk復合物被不同Kinase和Phosphatase作用6.Inhibitionofcellcycleprogress細胞至少可通過兩種機制阻止細胞周期的運轉(1)BindingofCdkinhibitorproteins(CKIs/CDIs)(2)Turno