细胞分裂增殖

细胞学说：“Whereacellarises,theremustbeapreviouscell,justasanimalscanonlyarisefromanimalsandplantsfromplants.”

德国病理学家威尔肖Cellproliferationandcontrol

细胞增殖及调控Chapter126weeks12weeks16weeks

I.生物学意义1.细胞增殖(cellproliferation)是细胞生命活动的重要特征之一,是生物繁育的基础。Redbloodcell120d.1011/d2millionstemcellsdivideeverysecond2.成体生物仍然需要细胞增殖，取代衰老死亡

的细胞，维持个体细胞数量的相对平衡和机

体的正常功能。

机体创伤愈合、组织再生、病理组织修复等，

都要依赖细胞增殖。DamagedtissuebyUVlightIfdamagedseriouslybyX-ray,mousewilldiewithinseveraldaysII.Thecell-divisioncycle细胞分裂周期

细胞从一次有丝分裂结束到下一次有丝分裂完成所经历的一个有序过程。其间细胞遗传物质和其他内含物分配给子细胞。Cellcycle1.细胞周期时相

G1

Interphase间期S G2Mphase分裂期细胞沿着G1→S→G2→M→G1周期性运转，在间期细胞体积增大(生长)，在M期细胞先是核分裂，接着胞质分裂，完成一个细胞周期。不同细胞的细胞周期时间差异很大

Someeukaryoticcellcycletimes

CelltypeEarlyfrogembryocellsYeastcellsIntestinalepithelialcellsHumanlivercellsCell-cycletime

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

S+G2+M的时间变化教小，细胞周期时间长短主要差别在G1期小鼠食管上皮细胞T=115hG1=103h十二指肠上皮细胞T=15hG1=6h2.根据增殖状况，细胞分为三类(1).周期细胞Cyclingcells体内连续分裂的细胞(2).休眠细胞G0cells正常情况下不分裂，一旦受到信号刺激后重新进入细胞周期:livercells,lymphocytes(3).终末分化细胞TerminallyDifferentiatedcellsHighlyspecialized,havelosttheabilitytodivideuntiltheydie.EmbryocellsCyclingcellsTerminalcellsG0cells

?研究细胞周期的方法

ObservewithamcroscopeBrdU-labledepitheliacellsofthezebrafishgut.(Gree:Sphasecells)BrdU-labledRKOcells(Red:Sphasecells),Dr.ZouFD流式细胞仪的应用G1cellsgreater?G1/SprogressioninRKOWTandmiR-21knockoutcellsWTKO3.Synchronizationofcell细胞同步化(1).自然同步化NaturalsynchronizationEarlyembryoinmostinvertebratesandafewvertebrates果蝇胚胎(2).人工同步化SelectedsynchronizationMphaseSG2BlockingDNAsynthesisbyTdR:G1/S

G1

G1/S

M秋水仙素让细胞停留在M期4.特殊的细胞周期—Earlyembryo30min/cellcycleFrogXenopuslaevisWhysorapidly?NoG1andG2phase,Sphaseisveryshort细胞分裂快,无G1期,G2期非常短,S期也短(所有复制子都激活),

以至认为仅含有S期和M期·无需临时合成其它物质·子细胞在G1、G2期并不生长，越分裂体积越小1 32 4III.Mphase:1.有丝分裂Mitosis(Nucleardivision)前期Prophase前中期Prometaphase中期Metaphase后期Anaphase末期Telophase(1).前期◆标志前期开始的第一个特征是染色质开始浓缩(condensation)形成有丝分裂染色体(mitoticchromosome）◆第二个特征细胞骨架解聚，有丝分裂纺锤体(mitoticspindle)开始装配FormationofthecompactedmitoticchromosomeCondensin浓缩素VincentL.etal.,MultiplerolesofCondensins:acomplexstory,BiologyoftheCell,2004,96:201–213Cohesin粘连素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，这一过程是由核纤层蛋白磷酸化导致核纤层解体纺锤体微管与染色体的动粒结合，捕捉住染色体每个已复制的染色体有两个动粒，朝相反方向，保证与两极的微管结合；纺锤体微管捕捉住染色体后，形成三种类型的微管(3).中期Metaphase

所有染色体排列到赤道板(MetaphasePlate)上，标志着细胞分裂已进入中期(4).后期Anaphase排列在赤道面上的染色体的姐妹染色单体分离产生向极运动AnaphaseA:后期A，动粒微管去装配变短，染色体产生两极运动AnaphaseB:极间微管长度增加，两极之间的距离逐渐拉长，介导染色体向极运动(5).末期Telophase◆染色单体到达两极，即进入了末期（telophase）,到达两极的染色单体开始去浓缩◆核膜开始重新组装◆Golgi体和ER重新形成并生长◆核仁也开始重新组装，RNA合成功能逐渐恢复,有丝分裂结束2.胞质分裂Cytokinesis(Cytoplasmdivision)(1).Inanimalcells蛙受精卵的卵裂培养细胞的胞质分裂Contractilering有丝分裂收缩环分裂沟形成的时间和位置至关重要Thesiteofformationofthecleavageplane(2).Inplantcells与动物细胞胞质分裂不同的是，植物细胞胞质分裂是因为在细胞内形成新的细胞膜和细胞壁而将细胞分开SummaryTwoidenticaldaughtercells如何保证遗传物质准确分配给子细胞？3.Meiosis减数分裂减数分裂是细胞仅进行一次DNA复制，随后进行两次分裂，染色体数目减半的一种特殊的有丝分裂MeiosisMitosis减数分裂的意义◆确保世代间遗传的稳定性；◆增加变异机会，确保生物的多样性，增强生物适应环境变化的能力。◆减数分裂是生物有性生殖的基础，是生物遗传、生物进化和生物多样性的重要基础保证。III.Controlofcellcycle1.检验点和它们的功能Cell-cyclecontrolsystem:

本质就是周期性激活的蛋白激酶（cyclicallyactivatedProteinskinases）2.MPF:促进细胞从G2期到M期的转换成熟促进因子（Maturation-promotingfactor），有丝分裂促进因子（Mitosis-promotingfactor)细胞融合实验和染色体的提前凝集MphaseHeLacellwithaPtK2cell,1974,Humangenetik23:437非洲爪蟾卵母细胞成熟过程MasuiandMarkert’sexperiments(J.Exp.Zool.177:142,1971)注射实验表明：孕酮诱导卵母细胞成熟；成熟卵细胞质中，含有卵母细胞成熟的因子，称做MPF。MPF的活性与细胞周期的关系Inthemid-1970sasapostdocstudyingthefissionyeastS.pombe.Nursefoundcdc2裂殖酵母中几个温度敏感的cdc基因的隐性突变使得裂殖酵母在周期中不能进入M期,由于生长没有停止,所以比正常的酵母长很多。这些基因中的一个显性突变,命名为cdc2。cdc2DNormalcdc2-Cdc2encodesaproteinkinasewith34kDwhoseactivityisrequiredforcellstoenterMphase.(p34cdc2)MPF是一种使多种底物蛋白磷酸化的蛋白激酶；由M期Cyclin-Cdk(Cyclin-dependentproteinkinase)形成的复合物。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

一位教授在实验室分离得到两株突变酵母，cdc25-和wee1-,但忘了标记这两株酵母分别是什么突变。根据细胞周期调控的相关知识，你只需用一台光学显微镜观察野生型、突变型酵母的增殖形态，便可轻易给这位教授解决这个难题。野生型突变株1突变株2(1)突变株1和突变株2分别是什么突变？为什么？(2)两株突变酵母的哪一周期时相发生了改变？这一时相是变 长还是变短？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:促使细胞通过G1checkpointG1/S-cyclins:在G1末结合Cdks促使细胞DNA复制S-cyclins:结合S-Cdk启动DNA复制M-cyclins:

促使细胞进入mitosisCyclin-CdkVertebratesBuddingYeastG1cyclinDCdk4,6Cln3Cdk1G1/SSMcyclinECdk2 cyclinACdk2 cyclinBCdk1

Cln1,2Cdk1 Clb5,6Cdk1Clb1,2,3,4Cdk1Cdk1:cdc2invertebratesandfissionyeast, cdc28inbuddingyeastVariouscyclin-Cdkcomplexesareregulatedby:(1)在不同时相各种Cyclins的合成与降解(2)Cyclin-Cdk复合物被不同Kinase和Phosphatase作用6.Inhibitionofcellcycleprogress细胞至少可通过两种机制阻止细胞周期的运转(1)BindingofCdkinhibitorproteins(CKIs/CDIs)(2)Turno