細(xì)胞分裂增殖

細(xì)胞學(xué)說：“Whereacellarises,theremustbeapreviouscell,justasanimalscanonlyarisefromanimalsandplantsfromplants.”

德國(guó)病理學(xué)家威爾肖Cellproliferationandcontrol

細(xì)胞增殖及調(diào)控Chapter126weeks12weeks16weeks

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

的細(xì)胞，維持個(gè)體細(xì)胞數(shù)量的相對(duì)平衡和機(jī)

體的正常功能。

機(jī)體創(chuàng)傷愈合、組織再生、病理組織修復(fù)等，

都要依賴細(xì)胞增殖。DamagedtissuebyUVlightIfdamagedseriouslybyX-ray,mousewilldiewithinseveraldaysII.Thecell-divisioncycle細(xì)胞分裂周期

細(xì)胞從一次有絲分裂結(jié)束到下一次有絲分裂完成所經(jīng)歷的一個(gè)有序過程。其間細(xì)胞遺傳物質(zhì)和其他內(nèi)含物分配給子細(xì)胞。Cellcycle1.細(xì)胞周期時(shí)相

G1

Interphase間期S G2Mphase分裂期細(xì)胞沿著G1→S→G2→M→G1周期性運(yùn)轉(zhuǎn)，在間期細(xì)胞體積增大(生長(zhǎng))，在M期細(xì)胞先是核分裂，接著胞質(zhì)分裂，完成一個(gè)細(xì)胞周期。不同細(xì)胞的細(xì)胞周期時(shí)間差異很大

Someeukaryoticcellcycletimes

CelltypeEarlyfrogembryocellsYeastcellsIntestinalepithelialcellsHumanlivercellsCell-cycletime

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

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

?研究細(xì)胞周期的方法

ObservewithamcroscopeBrdU-labledepitheliacellsofthezebrafishgut.(Gree:Sphasecells)BrdU-labledRKOcells(Red:Sphasecells),Dr.ZouFD流式細(xì)胞儀的應(yīng)用G1cellsgreater?G1/SprogressioninRKOWTandmiR-21knockoutcellsWTKO3.Synchronizationofcell細(xì)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(xì)胞停留在M期4.特殊的細(xì)胞周期—Earlyembryo30min/cellcycleFrogXenopuslaevisWhysorapidly?NoG1andG2phase,Sphaseisveryshort細(xì)胞分裂快,無G1期,G2期非常短,S期也短(所有復(fù)制子都激活),

以至認(rèn)為僅含有S期和M期·無需臨時(shí)合成其它物質(zhì)·子細(xì)胞在G1、G2期并不生長(zhǎng)，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(biāo)志前期開始的第一個(gè)特征是染色質(zhì)開始濃縮(condensation)形成有絲分裂染色體(mitoticchromosome）◆第二個(gè)特征細(xì)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(dǎo)致核纖層解體紡錘體微管與染色體的動(dòng)粒結(jié)合，捕捉住染色體每個(gè)已復(fù)制的染色體有兩個(gè)動(dòng)粒，朝相反方向，保證與兩極的微管結(jié)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(biāo)志著細(xì)胞分裂已進(jìn)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(yùn)動(dòng)AnaphaseA:后期A，動(dòng)粒微管去裝配變短，染色體產(chǎn)生兩極運(yùn)動(dòng)AnaphaseB:極間微管長(zhǎng)度增加，兩極之間的距離逐漸拉長(zhǎng)，介導(dǎo)染色體向極運(yùn)動(dòng)(5).末期Telophase◆染色單體到達(dá)兩極，即進(jìn)入了末期（telophase）,到達(dá)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(zhǎng)◆核仁也開始重新組裝，RNA合成功能逐漸恢復(fù),有絲分裂結(jié)束2.胞質(zhì)分裂Cytokinesis(Cytoplasmdivision)(1).Inanimalcells蛙受精卵的卵裂培養(yǎng)細(xì)胞的胞質(zhì)分裂Contractilering有絲分裂收縮環(huán)分裂溝形成的時(shí)間和位置至關(guān)重要Thesiteofformationofthecleavageplane(2).Inplantcells與動(dòng)物細(xì)胞胞質(zhì)分裂不同的是，植物細(xì)胞胞質(zhì)分裂是因?yàn)樵诩?xì)胞內(nèi)形成新的細(xì)胞膜和細(xì)胞壁而將細(xì)胞分開SummaryTwoidenticaldaughtercells如何保證遺傳物質(zhì)準(zhǔn)確分配給子細(xì)胞？3.Meiosis減數(shù)分裂減數(shù)分裂是細(xì)胞僅進(jìn)行一次DNA復(fù)制，隨后進(jìn)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(jī)會(huì)，確保生物的多樣性，增強(qiáng)生物適應(yīng)環(huán)境變化的能力。◆減數(shù)分裂是生物有性生殖的基礎(chǔ)，是生物遺傳、生物進(jìn)化和生物多樣性的重要基礎(chǔ)保證。III.Controlofcellcycle1.檢驗(yàn)點(diǎn)和它們的功能Cell-cyclecontrolsystem:

本質(zhì)就是周期性激活的蛋白激酶（cyclicallyactivatedProteinskinases）2.MPF:促進(jìn)細(xì)胞從G2期到M期的轉(zhuǎn)換成熟促進(jìn)因子（Maturation-promotingfactor），有絲分裂促進(jìn)因子（Mitosis-promotingfactor)細(xì)胞融合實(shí)驗(yàn)和染色體的提前凝集MphaseHeLacellwithaPtK2cell,1974,Humangenetik23:437非洲爪蟾卵母細(xì)胞成熟過程MasuiandMarkert’sexperiments(J.Exp.Zool.177:142,1971)注射實(shí)驗(yàn)表明：孕酮誘導(dǎo)卵母細(xì)胞成熟；成熟卵細(xì)胞質(zhì)中，含有卵母細(xì)胞成熟的因子，稱做MPF。MPF的活性與細(xì)胞周期的關(guān)系Inthemid-1970sasapostdocstudyingthefissionyeastS.pombe.Nursefoundcdc2裂殖酵母中幾個(gè)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(jìn)入M期,由于生長(zhǎng)沒有停止,所以比正常的酵母長(zhǎng)很多。這些基因中的一個(gè)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(fù)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(shí)驗(yàn)室分離得到兩株突變酵母，cdc25-和wee1-,但忘了標(biāo)記這兩株酵母分別是什么突變。根據(jù)細(xì)胞周期調(diào)控的相關(guān)知識(shí)，你只需用一臺(tái)光學(xué)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(gè)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(shí)相發(fā)生了改變？這一時(shí)相是變 長(zhǎng)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(xì)胞通過G1checkpointG1/S-cyclins:在G1末結(jié)合Cdks促使細(xì)胞DNA復(fù)制S-cyclins:結(jié)合S-Cdk啟動(dòng)DNA復(fù)制M-cyclins:

促使細(xì)胞進(jìn)入mitosisCyclin-CdkVertebratesBuddingYeastG1cyclinDCdk4,6Cln3Cdk1G1/SSMcyclinECdk2 cyclinACdk2 cyclinBCdk1

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