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1、oncogene&tumor suppressor gene,Department of Biochemistry andmolecular biology Zhang Ying,OVERVIEW,Many genes and factors outside of genes is involved in carcinogenesis.The accumulation of manygenetic changescause cancer other than mutationsof a singlegene bycausing disorders of cell growth and diff
2、erentiation,thecell proliferationout of control.Oncogene,antioncogene,tumor metastasis gene,cell apoptosis,DNA damage and repair,telomerase,microRNA,Relationships of oncogene,tumor suppressor geneand growth factors,The regulation of gene expression andcell proliferation,differentiation is involved i
3、n the mechanism of oncogenesand tumor suppressor genes,Section I Oncogene,Concept of oncogeneViral oncongeneCellular oncogeneThe products of oncongene and its fuction,一、the concept of oncogene,Oncogene:the genes in cells is responsible of controlling cellgrowth,proliferation and differentiation.They
4、 will cause cellularcancerationwhen their structure or expression turns abnormal.All of genes which encode for growth factors,growth factor receptors,signal molecules and transcription factors related to growth.,The writing of oncogene,ras、src、mycv-rasc-ras,Classification of oncogene,1、virus oncogen
5、es,v-onc:the genes existing in virus(mostly,retrovirus)which cause the target cells maligant transformation,such as v-src2、Proto-oncogenes or cellular-oncogene,c-onc:the oncogenes existing in normal genome which are in quiescence or inactive state such as c-myc、c-ras、c-src。Under normal condition,the
6、se genes are in quiescence or low expression state and not only no harmful to cells but also helpful to stain normal function to cells.,The structural comparison of c-src and v-src,二、Virus oncogenesthe oncogene existing in virus genome which does not encode the protein of virurs and is not helpful t
7、o replication but do make host cell Continuous proliferation,Rous Peyton,Rous 肉瘤,the structure of Rous sarcoma virus,1970,Temin and Batimore,reverse transcriptase,1975 Nobel1971,Duesberg,the genome of RSV,1979,H.Varmus and J.M.Bishop found that src is carcinogenesis in RSV,but also found that the ho
8、mologs of src exist in animal cells commonly if the cDNA of src is hybridized with other genome DNA.Result:src stem from normal cell genome.-1989 Nobel Voiceover:that is why such RSV retrovirus induce host cell carcinogenesis.,三、cellular oncogene,(一)the traits of cellular oncogeneUniversality:exists
9、 in biological widely;conservatism:The gene sequencewas highly homologous in the process of evolution Importance:the expression protein regulate cell proliferation,differentiation and apoptosisprecisely Harmfulness:the variation of structure and numbers make cell carcinogenesis,the oncogenes existin
10、g in normal genome which are in quiescence or inactive state such as c-myc、c-ras、c-src。Under normal condition,these genes are in quiescence or low expression state and not only no harmful to cells but also helpful to stain normal function to cells.,family member action locationsrc家族:src、abl、fgr、fes、
11、TPK活性 膜内侧或跨膜 yes、fps、lck、kek、(酪氨酸蛋 fym、lyn、tkl 白激酶)ras家族:H-ras、K-ras、N-ras G蛋白(P21)膜内侧 myc家族:c-myc、N-myc、L-myc 结合蛋白 核内 jun、fos 转录因子(AP-1)核内 sis家族:仅sis P28(类PDGF)胞外 myb家族:myb、myb-ets 核蛋白(转录因子)核内,1.Based on family,(二)the classfication of cellular oncogene,2、based on function and location,类 别 名 称 定 位 生
12、物学功能生长因子 c-sis 分泌到胞外 血小板源生长因子生长因子受体 c-erb B 细胞膜 表皮生长因子受体 c-fms 细胞膜 集落刺激因子-1受体 c-trk 细胞膜 神经生长因子受体胞内传递蛋白 c-src、c-abl 细胞质 酪氨酸蛋白激酶 c-raf、c-mos 细胞质 Ser/Thr蛋白激酶 c-ras 细胞膜 GTP/GDP结合蛋白转录调节因子 c-myc 细胞核内 DNA结合蛋白 c-jun、c-fos 细胞核内 转录因子(AP-1)c-erb A 细胞核内 甾体激素受体类蛋白,四、activation of oncogene,Activation factors:onco
13、gene is activated andabnormal expressed under some conditions such as virus infection,exposure to chemical carcinogenor ionizing radiation,leading to cell malignanttransformation and carcinogenesis.Different cellular oncogenes under different condition can be activated by different pathway and becom
14、e active oncogene.The results of oncogene activation will be(1)The expression productis abnormal or truncated(2)the products are normal but excessive(3)new products appearActivation mechanism:Gene mutation,gene amplification,chromosomal rearrangements,variation of oncogene methylation gene overexpre
15、ssionetc.,(一)point mutation,The proto-oncogenesare point mutated by exposure of radiationand carcinogens,the amino acid or the structure of protein is changed and the protein is in continuous active state,which lead to carcinogenesis.1982,MITUniversity,National CancerInstitute and Columbia Universit
16、y:human bladdercancer results from the point mutation of c-H-ras H-ras normal cells GGC(12Gly)turmor cells GTC(12Val),the protein of mutated ras is locked in active state,GDP,GDP,GTP,GTP,Pi,Inactive Ras protein,The inputsignalstimulate GDP-GTP switch,Output signal,the protein of mutated ras is locke
17、d in active state,active Ras protein,GTPase activating protein,GAP,(二)Gene Amplication,Gene structure itself is normal,but because a part of chromosome is replicated excessively,the gene copies increase and the products overexpress.Tumor occur Breast cancer erb-B2 Small cell lung cancer myc family n
18、euroblastoma N-mycThe copies is related to progress、prognosis and metastasis(1)When the amplified DNA is inserted into one of the chromosomes,it is termed homogeneous staining regions(HSR)(2)the amplified DNA are sometimes visible on a chromosome spread as a separate DNA fragments,referrred to as”do
19、uble minutes(DM)”,Gene Amplification:Neuroblastoma,HSRDM,(三)chromosome gene translocation and rearrangements,chromosome gene translocation and rearrangements make some proto-oncogene to near to stong promoter or enhancer.Mostly,Found in thebloodsystem tumors The head of a gene is joined to the tail
20、of another gene because of chromosome rearrangements and a new fusion protein produces.The fusion protein promotes cell transformation and induce carcinogenesis,Example:Burkit lymphoma,c-myc in chromosome 8 move to chromosome 14,IgH,strong enhancer,Immunoglobulin gene,Chromosome 14,Chromosome 8,c-my
21、c does not express,c-myc基因,E,E,c-myc over expresses,translocation,Burkitts Lymphoma,Chronic Myelogenous Leukemia,Reciprocal translocation between long arms of 22 22),PHILADELPHIA CHROMOSOME(Ph1)MUTATION AND ACTIVATION OF oncogeneabl to bcr=hybrid gene with tyrosine kinase activity,Chronic Myelogenou
22、s Leukemia,bcr-abl gene product,the Philadelphia(Ph)chromosome,Ideogram and banded chromosomes showing the normal chromosomes 9 and 22 plus the two derivating chromosomes resulting from the t(9;22)(q34;q11),The Ph chromosome was the first consistent abnormality noted in a human cancer,arising from a
23、 reciprocal translocation,t(9;22)(q34;q11.2),and molecularly by the fusion of the proto-oncogene ABL,located on the long arm of chromosome 9,with the BCR gene of chromosome 22,known as the breakpoint cluster region(bcr).,DNA甲基化状态的改变可导致基因结构和功能的异常,是细胞癌变过程中重要一步。在真核细胞中最重要的甲基化碱基是C,通常发生在双核苷酸区域(CpG岛)。某些癌基因
24、低甲基化和抑癌基因的高甲基化改变是细胞癌变的一个重要特征。,(四)oncogenes methylation,甲基化的功能意义:抑制基因表达,维护染色体完整性,调节DNA重组。抵御外来入侵的寄生DNA。低甲基化易致基因组中重复子同源重组,而导致基因组的不稳定性增加。,mutations at promoter controlling gene expression基因表达是指基因的转录与翻释以及它们的调控。基因表达水平的改变是细胞癌变的早期事件,过量表达与细胞的异常增生有关Met、c-ErbB2、ras,(五)基因过量表达(overexpression of oncogenes),与人类肿瘤相
25、关的特征性基因有三种,H-ras、K-ras和N-ras,分别定位于11、12、1号染色体,前二者是大鼠肉瘤病毒的转化基因,后者是从人神经母细胞瘤中分离得到,(一)ras基因家族,常见癌基因,共有特征,(1)基因组中均含4个编码的外显子和1个5端非编码外显子.(2)外显子所编码的蛋白为188-189个氨基酸残基,分子量为21KD即P21蛋白,具有高度特异性和同源性,尤其在氨基酸序列的前80个氨基酸残基中,几乎无种属间差别,具有高度保守性。,Model of Action of ras Gene,(1)P21ras位于细胞膜内侧,以软脂酸共价键形式固定于脂质双层膜的内表面(2)对GTP和GDP具
26、有高度亲和力,并有同源性GTP酶的活性.生化性质与G蛋白非常类似,提示ras蛋白可能也具有信号传导通路的作用,但目前尚未发现ras蛋白作用的特异受体和靶细胞.,(二)myc基因家族及其表达产物,c-myc定位于第8号染色体的8q24区,其编码产物为439个氨基酸残基的蛋白质。N-myc定位于第2号染色体的2p23-p24区,其产物为456个氨基酸残基蛋白质。L-myc定位于第1号染色体的1p32区,编码产物为364个氨基酸残基的蛋白质。,蛋白产物定位于核内,为核转录调节因子,能够与特殊的DNA顺序结合发生肿瘤时,myc基因家族成员可发生染色体基因易位、基因扩增以及表达过度。,Myc-activ
27、ated mechanisms of action,(三)erb家族,表达产物:细胞骨架蛋白在细胞运动、分裂、信息传递、能量转换、代谢调控以及维持细胞形态方面具有重要作用。,人erb-B编码的蛋白与EGF受体相似,是“掐头”的EGF受体,这个“截短”受体和其配体-表皮生长因子长期结合,从而可永远向细胞内传导促进生长的信号。,与野生型受体相比,跨膜区域无变化,但受体的两端变短,尤其是全部细胞外结构区域都被删除。,The ErbB signalling network,c-erbB-2/HER2/neu,Molecular diagnosis of breast cancer.a|Immunohi
28、stochemistry and b|fluorescence in situ hybridization(FISH)analysis of ErbB2 in human breast cancer.Immunohistochemistry was performed using HercepTest and FISH using a PathVysion ErbB2 DNA probe kit.The ErbB2 gene is seen as red fluorescence and the chromosome-17 centromeric-satellite probe as gree
29、n fluorescence.,(四)c-Met,染色体7q31,编码190KD跨膜糖蛋白,链(50KD)在胞外,链(145KD)含胞外配体结合区、跨膜区、胞内酪氨酸激酶区。蛋白表达位于腺样结构细胞的边缘。肝细胞因子(HGF)或离散因子(SF)作为c-Met受体的配体,形成HGF/SF-c-Met内分泌信号系统。配体结合可使受体酪氨酸激酶磷酸化,促进细胞有丝分裂、细胞动力和向腺上皮的形态分化扩增和过表达肠型胃癌基因重排:1号chr的易位启动子区(tpr)与c-Met gene 5区融合形成tpr-met gene。在浅表性胃炎、萎缩性胃炎、肠化和胃癌组织中均存在tpr-met mRNA高表达。
30、,(五)Bcl-2,从B细胞淋巴瘤中鉴定出来,由染色体t(14;18)(q32;q21)易位而激活,导致易位细胞中Bcl-2表达失控。,Proliferation:Malignancy,P53:Molecular Policeman,Bcl-2,(六)Mdm-2,位于12q13-14。进化保守基因,高表达时现癌基因功能基因产物是90kDa的蛋白质,氨基酸序列分析发现具有一个核定位信号和两个锌指蛋白,提示是一种DNA结合蛋白,具有转录调节作用.Mdm-2蛋白可与p53&Rb蛋白结合而使其功能失活。基因产物可和wtp53和mtp53结合,起到对p53的负调节作用。抑制p53介导的反式激活,阻止p5
31、3抑制细胞增殖和诱导细胞凋亡的功能,解除细胞G1期的阻滞并重新进入细胞周期。mdm2癌基因已在多种肿瘤中发现其突变与扩增,而且mdm2突变与P53突变不共存,mdm2扩增与肿瘤转移密切相关,(七)细胞周期素(Cyclins)/细胞周期素依赖性激酶(Cyclin-Dependant Kinases,CDK),第二节 抑癌基因(anti-oncogenes,tumor suppressor genes),抑癌基因的基本概念抑癌基因作用机制Rb基因“控制细胞周期的重要基因”p53基因“基因组卫士”,一、抑癌基因的基本概念,概念:是一类抑制细胞过度生长、增殖从而遏制肿瘤形成的基因。它的丢失或失活与肿瘤
32、的发生有关。反之,其被导入或激活可抑制细胞的恶性表现。发现:1986年,美国加州大学的Geiser等用正常细胞与肿瘤细胞杂交实验发现并提出抑癌基因,正常细胞与肿瘤细胞杂交实验,正常细胞,融合,非肿瘤型杂交细胞,(正常,但不稳定),传代,肿瘤细胞,肿瘤细胞,11号染色体某片段丢失,导入第11号染色体丢失片段,细胞转变为正常,抑癌基因的产物是抑制细胞增殖,促进细胞分化,和抑制细胞迁移,因此起负调控作用,通常认为抑癌基因的突变是隐性的。判断抑癌基因的3个标准:1)正常组织中存在并表达2)恶性组织中突变而失活3)该基因的野生型导入该基因缺陷的恶性组织中能部分或全部抑制其恶性表型,review,常见的抑
33、癌基因,基 因 定 位 相关肿瘤 作 用跨膜受体类:DCC 18q21 结直肠癌 编码表面糖蛋白(细胞粘附分子)PTCH 9q22.3 HEDGEHOG受体胞质调节因子或结构蛋白:APC 5p21 结直肠癌 可能编码G蛋白 NF1 7q12.2 神经纤维瘤 GTP酶激活剂 NF2 22q 神经鞘膜瘤、脑膜瘤 连接膜与细胞骨架转录因子和转录调节因子:P53 17P 多种肿瘤 编码P53蛋白(转录因子)Rb 13q14 视网膜母细胞瘤、骨 编码P105Rb1蛋白(转录因子)肉瘤、肺癌、乳癌 DPC4 18q21.1 胰腺癌 TGF-调节的MAD相关蛋白 MADR2 18q21 结直肠癌 TGF-调
34、节的MAD相关蛋白 VHL 3P 小细胞肺癌、宫颈瘤 转录调节蛋白 WT1 11P13 肾母细胞瘤 编码锌指蛋白(转录因子)细胞周期因子:P16 9p21 黑色素瘤 编码P16蛋白,CDK 4,6抑制剂 P15 9p21 交质母细胞瘤 编码P15蛋白,CDK 4,6抑制剂 P21 6q21 前列腺癌 编码P21蛋白,CDK 2,3,4,6抑制剂,抑癌基因失活机制:,1.抑癌基因纯合型缺失 2.二个等位基因中的一个缺失,另一个等位基 因突变(LOH)化学致癌物、病毒等引起体细胞中的基因突变 3.基因突变导致抑癌基因失活 4.基因5端CPG岛胞嘧啶(C-5)高度甲基化,抑制抑 癌基因的转录 5.癌
35、蛋白的作用,Knudsons两次打击论,抑癌基因在细胞信号传导的通路的多个层次发挥作用,跨膜受体:PTCH基因 DCC基因胞浆调节或结构蛋白:NF1 PTEN APC NF2等转录因子或转录调节因子:p53 WT1 RB1 VHL等细胞周期因子:p16 p21 p15等DNA损伤修复蛋白:MSH2 MLH1 PMS2 ATM BRCA1 BRCA2等,二、抑癌基因作用机制,(一)Rb基因“控制细胞周期的重要基因”,视网膜母细胞瘤是由Rb基因失活所致。基因结构:200kb,27外显子,2.7kb mRNA,编码928残基,分子量为105kDa的蛋白(P105-Rb)P105-Rb功能:参与调节E
36、2F等多种转录因子来控制细胞周期,影响细胞增殖和分化P105-Rb活性调节:高磷酸化无活性型和非或低磷酸化活性型,由Cyclin-CDK来调节;被多种病毒蛋白结合抑制(如:SV40大T抗原,腺病毒E1A蛋白,人乳头瘤病毒E7蛋白),retinoblastoma,Pathogenesis of Retinoblastoma,靶蛋白中包括一组E2F转录因子,它们所激活转录的靶基因其产物是S期所必须的。和RB结合后E2F的激活转录能力受到抑制,表明RB可以阻遏那些依赖E2F的基因表达。通过这种途径RB可直接阻止细胞进入S期。RB-E2F的复合体也可直接阻遏某些靶基因。E2F从RB上解离以后这些基因才
37、能表达。,不同程度磷酸化后,都可使p105活性缺乏或完全消失。非磷酸化的Rb可防止细胞增殖,当DNA肿瘤病毒抗原结合了非磷酸化的Rb时,Rb的活性就受到抑制,使细胞转化为无限增殖状态,形成肿瘤。,pRb蛋白作用示意图,myc,myb,cdc2 DNA聚合酶 胸苷激酶,二氢叶酸还原酶,pRb,CYCA,CDK2,RB pathway and function,RB-E2F,1、p53基因的发现 曾错误把P53基因定为癌基因 因当初从肿瘤细胞分离得到的P53基因如同myc基因一样,能和ras基因协同转化胚胎成纤维细胞,又依据癌基因为细胞显性表型的原则而被定癌基因,后发现实为其突变型。1989年,才
38、确认为“抑癌基因”。p53基因与人类50%的肿瘤有关。P53基因突变型在血液系统肿瘤、膀胱癌、肝癌、肺癌、结肠癌以及口腔癌等的细胞中发现。,(二)p53基因“基因组卫士”,2、p53的结构 基因:20kb,11外显子,mRNA:2.5kb,编码393氨基酸残基,分子量为53kDa的多肽链。,p53蛋白中央核心区结合特定的DNA序列,N未端序列有转录活化的功能,C未端可使p53蛋白自身形成二聚体或四聚体。,3、p53的功能,p53是细胞内重要的转录因子,调节p21、GADD45、BAX等基因的转录表达来实现其功能。当射线或其它因素引起DNA损伤时,p53蛋白就被激活,执行如下功能:调节细胞周期、
39、促进DNA损伤修复:如果细胞处于G1期,p53蛋白通过p21蛋白抑制cdk活性,封闭细胞周期关卡,使细胞生长停止,并激活GADD45,加速DNA修复。诱导细胞凋亡:如果细胞已经处于S期,p53蛋白促进相关细胞凋亡蛋白基因(bax等)表达,启动细胞凋亡。,P53 蛋白作用示意图,GADD45,P21,CDK2,4,6,BAX等,生长停止,DNA修复,细胞凋亡,p53&Mdm2,p21又是p53下游的转录激活产物,其上游调节区含有p53的结合位点,可抑制细胞周期素(cyclin D)/细胞周期素依赖性激酶(CDK)的底物磷酸化,导致G1期阻滞,使细胞在进入S期之前有充足的时间进行损伤DNA的修复。
40、Cyclin D-CDK4复合体正常情况下可促进Rb蛋白磷酸化,低磷酸化或非磷酸化的Rb与E2F(通过G1限制点必需的转录因子)结合。Rb磷酸化可导致E2F的游离和释放,并使E2F转位至核,诱发多种基因的蛋白转录,进而促使细胞进入S期.,4、p53的功能特点,在复制和转录水平上抑制细胞增殖P53可被一些癌基因产物结合而失活(如:SV40大T抗原,腺病毒E1B蛋白,HPV E6蛋白)P53突变具有显性失活的效应。,5、P53突变与肿瘤,P53基因与人类50%的肿瘤有关,人类肿瘤中P53突变主要在高度保守区内,以175、248、249、273、282位点突变最高,不同种类肿瘤不同,The p53
41、family,p53 family members pathways,(三)细胞周期因子,p21(cip1/wAF1),p27(Kip1)和p15/p16(ink4)合称为Cki蛋白,它们结合在cdk-cyclin二聚体上,使其失活。如在静止期通过这种途径阻止RB的磷酸化,使细胞周期不能进入S期。,主要几种Cyclin-CDK细胞周期复合物,P16基因,P16基因又叫MTS(multiple tumor suppressor)基因,是一种细胞周期中的基本基因,直接参予细胞周期的调控,负调节细胞增殖及分裂 一、P16基因结构及表达 P16基因定位于人染色体9p21,8.5Kb由2个内含子及3外显
42、子组成,第1外显子由126bp组成,第2外显子由307bp组成,第3外显子bp组成.P16基因是细胞周期中的一种基本基因二、P16基因的表达产物及功能P16基因编码产物是P16蛋白,定位于细胞核内,为细胞周期素依赖激酶CDK4及CDK6抑制物,通过结合CDK4或CDK6而抑制Cyclin D-CDK4/CDK6复合物,阻止细胞分裂、增生,突变型p16蛋白无此抑制活性,细胞分裂失控,导致癌变。,三、P16基因与肿瘤 P16基因已在多种肿瘤中发现缺失,突变 Kamb等已经从肺癌、乳腺癌、皮肤癌、膀胱癌、肾癌、卵巢癌、淋巴瘤等中检测出50%以上P16纯合子缺失,在黑色素瘤中还检出无义错义,移码突变.
43、表明P16参予各种组织的肿瘤形成.因此检测P16基因的突变与缺失,是判断肿瘤性质及预后的一项重要指标.,(四)DNA损伤修复蛋白,BRCA1:基因全长100kb含23个外显子,22个内含子,1个单一长开放阅读框架,编码1863个氨基酸,220KD核内磷酸化蛋白,有锌指区,提示可调节基因表达。肿 瘤:家族性乳腺癌和卵巢癌 功 能:DNA结合区:转录调控 与Rad51相互作用,修复双链DNA断裂BRCA2:13q21编码3418个氨基酸 肿 瘤:男女性乳腺癌,胰腺癌等 功 能:有DNA结合区:转录调控 与Rad51相互作用,修复双链DNA断裂,BRCA1 and BRCA2,BRCA1 funct
44、ions Transcription factor:involved in the regulation of oestrogen receptor activity and related to the control of oestrogeninduced proliferation of breast tissue.DNA repair:homologous recombination and repair of transcription-coupled oxidation-induced DNA damage.Cell-cycle checkpoint control:interac
45、ts with RB,ESF1 and p53.Chromatin remodelling.BRCA1 domains The RING-finger domain is a proteinprotein-interaction domain,and binds BRCA1-associated RING domain 1(BARD1).The carboxy-terminal BRCT domain is necessary for BRCA1s function in DNA repair and transcriptional activation.The highlighted mut
46、ations(denoted by*)are the two common founder mutations found in Ashkenazi Jews.,BRCA1 and BRCA2,BRCA2 functions DNA repair:homologous recombination.Cell-cycle checkpoint control:interacts with p53.Chromatin remodelling.BRCA2 domains Exon 11 contains both the ovarian cancer cluster region(OCCR)and e
47、ight BRC repeats,which are required for binding to RAD51.Mutations in this region are associated with a greater risk of ovarian cancer and a lower risk of breast cancer than are mutations outside this region.The highlighted mutations(denoted by*)are the common founder mutations found in Ashkenazi Je
48、ws and in Iceland.,Factors that modify risk of breast or ovarian cancer,NCOA3.Nuclear receptor coactivator 3(also known as amplified in breast cancer 1,AIB1)RAD51 is involved in the repair of doublestrand DNA breaks,and interacts with both BRCA1 and BRCA2.TAMOXIFEN.One of a group of antioestrogenic
49、drugs.Acts by blocking oestrogen signalling by binding to the oestrogen receptor.HRAS.A non-coding polymorphism of the VNTR(variable number of tandem repeats)type is situated one kilobase downstream of the HRAS proto-oncogene on chromosome 11.,PTEN/MMAC1/TEP1,PTEN(phosphate and tension homology dele
50、ted on chromosome 10,PTEN)又称为MMACI(mutated in multiple advanted cancer1)和TEPI(TGF-regulated and epithelial cell-enriched phosphatase)PTEN:10q23.3 9个外显子 编码403个氨基酸 兼有酪氨酸磷酸酶(PTP)和双重特异性磷酸酶(DSP)结构模体,可以使磷酸化的Tyr、Ser、Thr都去磷酸化,抑制肿瘤发生、发展。PI 3.4.5 P3 PI-4.5 P2,PTEN,PTEN与细胞骨架蛋白中的张力蛋白(tensin)和辅助蛋白(auxilin)具有同源性。