与14-3-3ζ相互作用的蛋白Polo样激酶1的筛选与鉴定

目的:应用酵母双杂交系统筛选与14-3-3ζ相互作用的蛋白,进一步鉴定其与Polo样激酶1(Plk1)相互作用。方法:构建pGBKT7-14-3-3ζ诱饵表达载体,筛选HeLa细胞cDNA文库中与14-3-3ζ相互作用蛋白,进一步通过共转酵母、免疫荧光以及外源性和内源性的细胞免疫共沉淀实验验证两者的相互作用。结果:通过酵母双杂交系统筛选出的阳性相互作用蛋白中包括Plk1,进一步通过共转酵母,外源性和内源性的细胞免疫共沉淀实验证实两者的相互作用,免疫荧光实验证实两者共定位于有丝分裂过程中胞质分裂期的中体。结论:Plk1是高度保守的丝氨酸/苏氨酸蛋白激酶,在中体的成熟,有丝分裂期染色体的分离,胞质分裂以及DNA的损伤应答等环节发挥重要作用,其与14-3-3ζ的相互作用为14-3-3蛋白家族参与有丝分裂(M期)的调控提供了直接证据。     

人PIRH2b与ARF4相互作用的初步研究

目的利用酵母双杂交技术筛选PIRH2b的相互作用蛋白。方法以PIRH2b为诱饵蛋白,利用酵母双杂交技术筛选人胎肝cDNA文库,用GST-pull down验证PIRH2b与ARF4在体外的相互作用,并用绿色荧光蛋白标记PIRH2b,红色荧光蛋白标记ARF4,观察两者在肝癌细胞株Hep3B中的亚细胞定位。结果利用酵母双杂交筛选到一个能与PIRH2b相互作用的蛋白ARF4,GST-pull down验证了两者在体外的相互作用,荧光标记共定位结果显示两个蛋白共定位于Hep3B细胞的核周区域。结论首次发现并证实了PIRH2b与ARF4的相互作用,PIRH2b对ARF4的功能可能有重要影响。     

NSPc1相互作用蛋白的筛查及其与组蛋白乙酰化酶HBO1相互作用的验证

目的 寻找多梳家族(polycomb group)蛋白NSPc1的体内可能的相互作用蛋白.方法 通过酵母双杂交实验筛选与NSPc1相互作用的蛋白.使用Pull-down实验,Co-IP实验以及细胞内荧光共定位实验进一步证实双杂交中发现的相互作用.结果 分别以NSPc1蛋白的全长、N端和C端作为诱饵筛查人3月胎脑cDNA文库,发现N端诱饵可以与组蛋白乙酰化转移酶HBO1相互作用,该相互作用在体内外实验中都得到了验证.结论 组蛋白乙酰化酶HBO1是NSPc1的相互作用蛋白之一,该相互作用可能参与NSPc1对靶基因转录的表观抑制活性的发挥.     

应用酵母双杂交系统筛选人胃黏膜上皮组织SHIP2的相互作用蛋白

目的通过酵母双杂交系统筛选人胃黏膜上皮组织标准均一化cDNA文库,寻找与含Src同源蛋白2肌醇-5-磷酸酶2(SHIP2)相互作用的蛋白。方法利用酵母双杂交系统,以SHIP2的P1(SH2+5-Ptase)和P2(PRD+SAM)段作为诱饵蛋白,筛选出人胃黏膜上皮组织均一化cDNA文库中与SHIP2相互作用的蛋白,并通过免疫共沉淀法进行验证。结果挑选出39个阳性克隆,经测序比对分析,回复性杂交,免疫共沉淀试验验证,最终确定一个与SHIP2相互作用的蛋白抗增殖蛋白1(prohibitin1/PHB)。结论酵母双杂交系统筛选人胃黏膜上皮组织SHIP2的相互作用蛋白PHB。     

NMDA受体亚单位NR2D与MOCA相互作用的鉴定

目的:寻找N-甲基-D-天冬氨酸(N-methyl-D-aspartate,NMDA)受体亚单位NR2D的结合蛋白,为探讨NR2D在视网膜兴奋性毒性损伤中的作用提供依据。方法:构建了包含NR2D细胞内C末端的cDNA片段为诱饵质粒,应用酵母双杂交技术筛选小鼠脑cDNA文库,并用免疫共沉淀实验进一步验证NR2D与其结合蛋白之间的相互作用,免疫荧光显微镜观察NR2D和目的蛋白在视网膜中的共表达。结果:酵母双杂交筛选到细胞黏附修饰因子(modifier of cell adhesion,MOCA)为NR2D可能的相互作用蛋白,两者在视网膜有共定位。结论:MOCA能特异结合谷氨酸受体NR2D,这为进一步研究谷氨酸的兴奋性毒性参与视网膜退行性变的机制奠定了实验基础。     

甲型H3N2流感病毒截短型PB1-F2蛋白与宿主蛋白的相互作用的初步研究

目的利用酵母双杂交技术研究甲型H3N2流感病毒截短型PB1-F2蛋白与人类宿主蛋白的相互作用,为该病毒蛋白的功能研究和致病机制提供理论依据。方法以本实验室分离和鉴定的甲型H3N2流感病毒A／Guangdong／7028／2010为模版,构建pGBKT7-PB1-F2重组载体,利用Y2HGold酵母双杂交系统,从人类通用cDNA文库中筛选与其相互作用的蛋白。结果成功构建含诱饵蛋白基因的pGBKT7-PB1-F2重组载体,转化酵母自激活和毒性实验显示为阴性：酵母双杂交实验显示Y2HGold和Y187酵母的结合率为5．22％,符合实验要求;经筛选和验证后,得到3个与截短型PB1-F2蛋白有相互作用的阳性克隆,分别为钾／钠ATP酶B1亚基、热休克蛋白40和白介素-2受体1亚基。结论初步推断截短型H3N2流感病毒PB1-F2蛋白可能影响流感病毒在宿主细胞中的复制功能和凋亡调控。     

酵母双杂交文库筛选及N型钙离子通道与BART相互作用的初步分析

目的应用酵母双杂交技术筛选N型钙离子通道相关蛋白,并对候选蛋白BART(binder of arltwo)进行初步分析。方法用N型钙离子通道α1亚基C端630个氨基酸残基肽段(Calcium channel630a-mino acids,CaCh630)作为探针,运用酵母双杂交技术筛选出与之相互作用的基因。通过PCR扩增并克隆候选基因BART,然后分别构建带有红色荧光蛋白标签的表达载体pDsRed-BART和带绿色荧光蛋白标签的pEGFP-CaCh630,共转染海马神经元后,用激光共聚焦扫描显微镜观察这两个外源蛋白在细胞中的定位情况。结果应用酵母双杂交技术筛选出6个相关基因,体外共转染试验发现BART和CaCh630分子在海马神经元内有共定位现象,进一步证明其可能存在相互作用。结论BART可能在维持钙离子通道细胞骨架中定位起重要作用。     

酵母双杂交筛选与单剪接型2.2 kb乙型肝炎病毒剪接特异性新蛋白相互作用的肝细胞蛋白

目的 筛选与单剪接型2.2 kb乙型肝炎病毒(HBV)剪接特异性新蛋白相互作用的肝细胞蛋白.方法 PCR扩增单剪接型2.2 kb HBV剪接特异性新基因TPss并克隆于诱饵载体pGBKT7,在证实TPss蛋白不具有自激活作用的前提下,以酵母双杂交系统筛查与TPss蛋白相互作用的肝细胞蛋白,进而通过哺乳动物细胞双杂交实验验证候选肝细胞蛋白与TPss蛋白在Huh7和HepG2肝细胞中的相互作用.结果 构建酵母双杂交诱饵载体pGBKT7-TPss,Western blot显示其在酵母中表达TPss蛋白.酵母双杂交筛选及哺乳动物细胞双杂交证实TPss蛋白可与4种肝细胞蛋白相互作用,即组织蛋白酶B、微粒体环氧化物水解酶、组织蛋白酶D与纤维蛋白原γ链.结论 TPss可与多种肝细胞蛋白相互作用.     

酵母双杂交技术筛选NECL1胞内区的结合蛋白

目的 筛选人源膜表面黏附分子NECL1蛋白胞内区相互作用蛋白。 方法 构建含人NECL1蛋白胞内区氨基酸编码序列的诱饵质粒pGBKT7-NECL1C,对人胎脑cDNA文库进行酵母双杂交筛选。用GST pull down实验进行体外蛋白相互作用的验证。结果 酵母双杂交阳性克隆测序后显示共存在9段不同序列（存在重复克隆）。比对氨基酸序列得到5个可能相互作用蛋白。通过GST pull down 实验验证了其中两个蛋白与NECL1胞内区的相互作用。结论 应用酵母双杂交系统,获得了一些候选的NECL1胞内区相互作用蛋白。     

hCDC4 variation in osteosarcoma

The hCDC4 gene (also known as Fbw7 or Archipelago) encodes an F-box protein that is responsible for targeting cyclin E for Skp1-cullin-F box protein (SCF) ubiquitination and proteosomal degradation. Disruption of this pathway has been associated with chromosomal instability and aneuploidy in several cancer cell lines and primary tumors. This study aimed to examine whether hCDC4 mutations contribute to aneuploidy in osteosarcoma. We analyzed 147 primary high-grade osteosarcoma specimens and 6 osteosarcoma cell lines. The protein truncation test (PTT) and single-strand conformation polymorphism (SSCP) analysis with subsequent sequencing were performed to detect alterations of the hCDC4 gene. All specimens exhibited the same PTT pattern of normal bands with less intense common bands. Two shifts were detected by SSCP, and subsequent DNA analysis identified one in-frame three-base GAG (424-426) deletion and one silent nucleotide substitution (C1261T). We conclude that somatic hCDC4 mutations are infrequent in osteosarcoma, and are unlikely to play an important role in aneuploidy of this tumor.     

Cyclin E gene (CCNE) amplification and hCDC4 mutations in endometrial carcinoma

Cyclin E overexpression occurs in a subset of endometrial carcinomas (ECs), but the molecular mechanisms underlying this alteration remain to be established. The present study has analysed amplification of the cyclin E gene (CCNE) and mutation in hCDC4, the gene coding for the F-box protein, which tags phosphorylated cyclin E for proteosomal degradation, to ascertain whether these alterations might be responsible for cyclin E overexpression in ECs. Cyclin E and p53 expression was studied by immunohistochemistry in eight atypical endometrial hyperplasias (AEHs), 51 endometrioid endometrial carcinomas (EECs), and 22 non-endometrioid endometrial carcinomas (NEECs). CCNE amplification was analysed by fluorescence in situ hybridization (FISH). Mutations in exons 2-11 of the hCDC4 gene were screened by PCR-SSCP-sequencing. Finally, the polymorphic marker D4S1610 was used to assess loss of heterozygosity (LOH) in the hCDC4 gene. Cyclin E overexpression was found in 26/81 (32%) cases and was associated with the histological type of the lesion, since it was not found in any AEHs but was present in 27% of EECs and 54.5% of NEECs (p=0.035). Cyclin E overexpression was associated with histological grade (p=0.011) and p53 immunostaining in EECs (p=0.033). CCNE amplification was found in 6 of 37 (16%) ECs examined. There was a significant association between CCNE amplification and the histological type of the lesion, since five (83%) of the six cases with amplification were NEECs (p=0.008). One EEC harboured an hCDC4 mutation: a CGA to CAA (Arg/Gln) change at codon 479. In addition, D4S1610 LOH was found in 7 of 23 (30%) informative cases analysed, but no correlation with cyclin E overexpression was found. However, the tumour with hCDC4 mutation also showed LOH. This is the first study demonstrating that cyclin E overexpression is associated with gene amplification in ECs, these alterations being more frequent in NEECs. Although hCDC4 exhibits a low mutation frequency in ECs overexpressing cyclin E, it seems to function as a tumour suppressor gene that is involved in endometrial carcinogenesis.     

Ubiquitination of p27 is regulated by Cdk-dependent phosphorylation and trimeric complex formation

The cellular abundance of the cyclin-dependent kinase (Cdk) inhibitor p27 is regulated by the ubiquitin-proteasome system. Activation of p27 degradation is seen in proliferating cells and in many types of aggressive human carcinomas. p27 can be phosphorylated on threonine 187 by Cdks, and cyclin E/Cdk2 overexpression can stimulate the degradation of wild-type p27, but not of a threonine 187-to-alanine p27 mutant [p27(T187A)]. However, whether threonine 187 phosphorylation stimulates p27 degradation through the ubiquitin-proteasome system or an alternative pathway is still not known. Here, we demonstrate that p27 ubiquitination (as assayed in vivo and in an in vitro reconstituted system) is cell-cycle regulated and that Cdk activity is required for the in vitro ubiquitination of p27. Furthermore, ubiquitination of wild-type p27, but not of p27(T187A), can occur in G1-enriched extracts only upon addition of cyclin E/Cdk2 or cyclin A/Cdk2. Using a phosphothreonine 187 site-specific antibody for p27, we show that threonine 187 phosphorylation of p27 is also cell-cycle dependent, being present in proliferating cells but undetectable in G1 cells. Finally, we show that in addition to threonine 187 phosphorylation, efficient p27 ubiquitination requires formation of a trimeric complex with the cyclin and Cdk subunits. In fact, cyclin B/Cdk1 which can phosphorylate p27 efficiently, but cannot form a stable complex with it, is unable to stimulate p27 ubiquitination by G1 extracts. Furthermore, another p27 mutant [p27(CK-)] that can be phosphorylated by cyclin E/Cdk2 but cannot bind this kinase complex, is refractory to ubiquitination. Thus throughout the cell cycle, both phosphorylation and trimeric complex formation act as signals for the ubiquitination of a Cdk inhibitor.     

联合靶向阻断miR-29b/92b/106b抑制胃癌细胞生长及迁移

目的:本研究旨在寻找胃癌转移相关微小RNA(microRNA,miRNA,miR),揭示其对胃癌细胞生物学功能的影响,并探讨联合阻断候选miRNA在胃癌治疗中的临床应用价值。方法:收集发生淋巴结转移及无转移患者的胃癌标本各3例,采用miRNA表达芯片筛选转移相关的候选miRNA;将锁核酸修饰的候选miRNA的反义寡核苷酸转染BGC-823胃癌细胞株,运用CCK-8法、流式细胞术、划痕实验及Transwell迁移实验分析候选miRNA抑制前后胃癌细胞生物学功能的变化;构建多西环素诱导多重靶向候选miRNA的裸鼠移植瘤模型,观察联合靶向阻断候选miRNA后,肿瘤细胞体内生长情况。结果:miRNA表达芯片发现miR-29b、miR-92b及miR-106b在发生淋巴结转移患者的胃癌组织最高,并将它们确定为胃癌转移相关候选miRNA;分别在BGC-823细胞中抑制上述miRNA,可导致细胞活力减弱,凋亡诱导增加,迁移能力显著下降(P 0. 05);同时,体内联合阻断miR-29b/92b/106b,裸鼠移植瘤的形成较对照组显著减少。结论:miR-29b、miR-92b及miR-106b与胃癌细胞的迁移有关,联合阻断上述miRNA可明显抑制胃癌细胞体内外生长。这3个miRNA可能作为潜在的治疗靶点。     

Role of toxin functional domains in anthrax pathogenesis

We investigated the role of the functional domains of anthrax toxins during infection. Three proteins produced by Bacillus anthracis, the protective antigen (PA), the lethal factor (LF), and the edema factor (EF), combine in pairs to produce the lethal (PA+LF) and edema (PA+EF) toxins. A genetic strategy was developed to introduce by allelic exchange specific point mutations or in-frame deletions into B. anthracis toxin genes, thereby impairing either LF metalloprotease or EF adenylate cyclase activity or PA functional domains. In vivo effects of toxin mutations were analyzed in an experimental infection of mice. A tight correlation was observed between the properties of anthrax toxins delivered in vivo and their in vitro activities. The synergic effects of the lethal and edema toxins resulted purely from their enzymatic activities, suggesting that in vivo these toxins may act together. The PA-dependent antibody response to LF induced by immunization with live B. anthracis was used to follow the in vivo interaction of LF and PA. We found that the binding of LF to PA in vivo was necessary and sufficient for a strong antibody response against LF, whereas neither LF activity nor binding of lethal toxin complex to the cell surface was required. Mutant PA proteins were cleaved in mice sera. Thus, our data provide evidence that, during anthrax infection, PA may interact with LF before binding to the cell receptor. Immunoprotection studies indicated that the strain producing detoxified LF and EF, isogenic to the current live vaccine Sterne strain, is a safe candidate for use as a vaccine against anthrax.