32细胞

染色体组蛋白修饰—从保持到多样性一、摘要二、引言三、内容四、结论五、致谢六、参考文献基因信息通过核染色质DNA调节表达和维护处于动态过程中。核小体核心组蛋白N端“尾巴”是主要的翻译后修饰，比如乙酰化作用、甲基化作用、磷酸化作用、泛素化作用、糖基化作用、ADP-核糖化作用、羰基化和sumoylation。这些修饰和DNA甲基化作用一起，控制核小体排列折叠成更高级的结构，调节细胞过程的信号。尽管组蛋白和组蛋白修饰是高度保守的，最近数据显示个别修饰（乙酰化、甲基化、磷酸化）染色体的分布可能是不同的随着细胞周期，在真核生物类群之间或之中也是这样。这意味着阅读组蛋白密码进化趋异是可能的。二、引言特异性抗体是重要的工具，在原位定位组蛋白修饰的不同类型，特异性抗体识别翻译后修饰的氨基酸。组蛋白H3的多样化修饰，明显的修饰在同一组蛋白分子上或者分别在不同的组蛋白分子上都不能被区分。现在，在植物中，我们比较选定的组蛋白修饰的分布随着细胞周期过程中的染色体，这些植物具有不同的基因组大小和报道的非植物真核生物的系统发育对应数据。在细胞周期阶段模型会发生偏离，比如一些乙酰化作用或者磷酸化作用，在突变体（特别的甲基化）或者生物体（乙酰化，甲基化，磷酸化作用）之间被讨论，就潜在功能意义而言，或者被高度关注作为将来工作中一个开放的问题。三、内容1，甲基化的组蛋白-稳定的标记“开放的”核染色质和抑制状态的核染色质a“开放”核染色质结构用甲基化的H3K4（组蛋白H3的4号赖氨酸），H3K36标记b抑制的核染色质结构用甲基化的H3K9，H3K27，H4K20标记2，在不同生物体中特定异染色质组蛋白甲基化染色体的分布常染色体：H3K4H3K36（保守）异染色质：H3K9H3K27Ｈ４Ｋ２０（多变）酵母中H3K9me2（组蛋白H3的9号赖氨酸二甲基化）着丝粒端粒接合型H3K27NDH4K20me1,2,3显著但基因调节中没作用，异染色体形成中能检测到，可能与DNA损伤反应有关在脉胞菌中H3K9me3（组蛋白H3的9号赖氨酸三甲基化）nootherreportH3K9me3alltypes果蝇中H3K9me1,2,H3K27me1,2，H4K20me3显著臂间异染色质H3K9me3，H3K27me3enrichmentatthechromocentrecore鼠中鼠中1，H3K9me3,H3K27me1andH4K20me3preferentiallymarkconstitutiveheterochromatin2，thefacultative（特定的）heterochromatin,representedbytheinactive（没有活性）Xchromosome,ismarkedbyH3K9me2,H3K27me3andH4K20me1Immunostainingwithantibodiesthatdiscriminate（区别）betweenmono-,di-andtrimethylationofspecificlysines(K4,K9,K27andK36ofH3andK20ofH4)IdentifiedH3K9me2typicalnotessential（非必要）拟南芥（160Mbp/1C）Thesedistributionpatternsarenotconservedamongplants.AndreasHoubenetal.studied24plantspecieswithdifferentgenomesizesandfoundthatImmunostainingwithantibodiesagainstH3K4me2exclusively（专门的）labelledeuchromaticregionsinallspeciestested(alsoinmostlytranscriptionallyinactiveB-chromosomes),H3K9me2异染色质的染色中心散布整个核（大基因组）B染色体独立存在于物种染色体组以外的一特殊染色体，广泛存在于生物界。遗传机制是非孟德尔式的。大麦(5100Mbp/1C)H3K27me2拟南芥异染色质的染色中心大麦常染色质的核区域中期染色体末端最强蚕豆(12740Mb/1C)H3K4me1,2,3常染色质H3K9me1,2,H3K27me1,2,3，H4K20me1整个核染色质asistypicalfor‘heterochromatin-specific’marksinplantswithalargegenome1，H3K9me1（组蛋白H3的9号赖氨酸一甲基化）andH3K27me2werelocallyenrichedatdifferentindividualheterochromaticregions(mainlyatweakerGiemsabands）2，H3K27me3waslocallyenrichedeveninregionsnotdefinedasGiemsa-bandedheterochromatin.allmethylationstatesofH3K4arerestrictedtoeuchromatininplants(forH3K36thisissofaronlyknownforArabidopsis).Bycontrast,H3K9me1,2,H3K27me1andH4K20me1areconservedheterochromatinmarksinplantTodate,therearenodataonthechromosomaldistributionofmethylatedH3K14,H3K18andH3K23orthemethylatedterminalargininesofH3andH4inplantsIngeneral,H3K9methylationisahallmarkofconstitutiveheterochromatinconservedfromfissionyeasttomammalsandplants。InNeurospora（脉孢霉）andmammals,H3K9me3isenrichedatsilentlociInDrosophilaandplants,H3K9me1,2isenrichedatheterochromatin.Inmetazoaandplants，H3K27methylationhasonlybeenreportedInmammals,H3K27me1occursatcentromericheterochromatinInDrosophilaandArabidopsis,heterochromatinalsocontainsH3K27me2InDrosophila,mammalsandplants，ubiquitous（普遍存在）H4K20methylationiscorrelatedwithheterochromatinInfliesandmammals，H4K20me3isheterochromatinspecificInArabidopsis，H4K20me1isheterochromatinspecificContrarytothesituationinmetazoa,theconstitutiveheterochromatininArabidopsisischaracterizedbymono-anddimethylationmarksonly.ThisissurprisingbecauseN-terminaltrimethylatedlysinesareconsideredtobemorerobustthanmono-anddimethylatedones3，H3K9-去甲基化：在植物中CG甲基化结果和CNG甲基化的先决条件Inmammals,DNAmethylationismainlyrestrictedtosymmetrical（对称的）CGSequencesInplants,methylationoccursatCG,CNG(N=anynucleotide)andCHH(H=A,CorT)sequencesTheArabidopsisgenomecontainsthreeclassesofDNAmethyltransferasesMET1（染色质甲基化酶）isconsideredtobethemaintenanceDNAmethyltransferaseNullallelemutantsofMET1resultedinacompletelossofCGmethylationPlant-specificCNGmethylationiscatalysed（催化）byCMT3（染色质甲基化转移酶3)，CMT3alsocontrolstheasymmetric（不对称）CHHmethylationinalocus-specificmannerDRM1（域重新甲基化转移酶）andDRM2areresponsibleformaintainingCHHmethylationandfordenovomethylationImmunostainingwithantibodiesagainstH3K9me2labelledtheheterochromaticchromocentresoftheDNAhypomethylation（低甲基化）(partialloss-of-function)mutantmet1lessstronglythanthoseofwildtype,eveninnucleiofF1ofbackcrossComparabledatawerefoundforamutantofthechromatinremodellingfactorDDM1(DECREASEINDNAMETYLATION1).However,thedistributionofH3K27me1,2isnotinfluencedbyDNAmethylationatCGsites.TogetherwiththelossofH3K9me2inanArabidopsisnullmutantofMET1,theseobservationssuggestthatDNAmethylationatCGsequencesdirectsH3K9-dimethylationatthechromocentres.Thealteration（修饰）inDNAmethylationisaccompaniedbyarelaxationoftheheterochromaticchromocentresIncontrastwiththemethylationatCGsites,methylationoutsideCGhasnoeffectonhistonemethylation,buthistonemethylationinturndirectsDNAmethylationatCNGsitesMutantsoftheH3K9me2-specifichistonemethyltransferase（甲基转移酶）KRYPTONITE(KYP=SUVH4)andoftheDNAmethyltransferaseCMT3resultinalossofcytosine(胞嘧啶)methylationatCNGsitesGiventhattheCMT3（染色质甲基转移酶）chromodomainbindstoH3peptides（多肽类）onlywhenK9andK27aremethylated,AndersLindrothetal.proposedthatmethylatedH3K9andH3K27arebothrequiredtorecruit（招集）CMT3totargetloci.Studyingthefunctionalinteractionofthehistonemethyltrans