基于EBNA1和oriP的载体在基因治疗中的应用研究进展

非病毒载体用于基因治疗的主要问题是导入靶细胞的效率较低,目的基因表达水平低,疗效持续时间也较短。EBNA1和oriP元件使引入该元件的质粒在真核细胞内保持为游离体、转运入核、转录增强。质粒携带的目的基因能够获得较高的转染效率,高水平、持续的表达。基于EBNA1/oriP的质粒在肿瘤、单基因缺陷先天性疾病、TNF相关的炎性疾病的基因治疗中显示了良好的应用前景。EBNA1/oriP元件用于构建人工染色体,携带目的基因的调控序列,可望实现可调控的基因治疗。     

hMAM启动子／增强子调控表达载体构建和调控作用

目的构建人乳腺珠蛋白（human mammaglobin,hMAM）启动子／增强子调控报告基因表达载体,探讨hMAM启动子／增强子序列在乳腺癌细胞中的特异性调控作用。方法应用PCR技术,从基因组DNA中扩增出hMAM启动子／增强子DNA序列,构建于PGL3报告基因上游,分别转染体外培养的乳腺癌细胞MDA—MB-415、T47D及胃癌细胞7901,分析启动子和增强子序列对乳腺癌细胞的基因表达调控作用。结果酶切图谱分析、DNA序列测定表明成功构建hMAM启动子／增强子调控的表达载体;荧光素酶报告基因检测结果分析表明,hMAM启动子／增强子能够调控报告基因的表达。结论hMAM启动子／增强子,在MDA—MB-415乳腺癌细胞具有调控基因表达的作用;     

EB病毒融合基因重组BCG穿梭质粒的构建及表达

分别以卡介苗(BCG)和EB病毒融合基因cDNA为模板,通过PCR扩增得到139bp的BCG-Ag85B信号肽序列和2291bp的Z2A基因序列。将BCG-Ag85B信号肽序列与大肠杆菌-卡介苗穿梭表达载体pMV261重组,得到重组质粒pMVS。再将EB病毒融合基因序列Z2A亚克隆至pMVS中,得到重组质粒pMVZ2A,电转化导入BCG。SDS-PAGE分析结果表明,构建的重组质粒pMVZ2A经双酶切、PCR扩增及测序鉴定证实,克隆基因BCG-Ag85B信号肽和Z2A正确插入载体pMV261,电转化导入BCG,能够在BCG中分泌表达。     

携带不同数量增强子的嵌合型肝脏特异性启动子的构建及其体外实验研究

通过PCR手段成功获得肝细胞特异性启动子人α1-抗胰蛋白酶启动子hAATp(human α1-antitrypsin promoter,hAATp)及具有增强子功能的肝脏特异的肝调控区HCR (hepatic control region,HCR)。在此基础上,通过分子克隆手段构建获得携带有不同数量的HCR增强子的嵌合型肝脏特异性hAAT启动子,并在下游连入报告基因Luciferase,然后将重组质粒转染人肝癌细胞系HepG2、小鼠肝癌细胞系Hepa1-6、人胚肾细胞系HEK293和人脑星形胶质母细胞瘤细胞系U87-MG,通过检测Luciferase表达活性分析携带不同数量增强子的肝脏特异性启动子的启动活性及其组织特异性。结果表明,携带有3个增强子的嵌合型肝脏特异性启动子活性及特异性最好,为肝脏类疾病的靶向性治疗研究奠定了基础。     

狂犬病病毒CVS-11株全序列测定及其感染性克隆的构建

[目的]测定狂犬病病毒标准攻击毒CVS-11株全基因组序列,构建CVS-11株全长cDNA感染性克隆.[方法]RT-PCR扩增CVS-11株全基因组得到有重叠的12个片段,分别克隆至平端载体pEASY-Blunt,测定CVS-11株全基因组核苷酸序列.用软件DNAMAN分析CVS-11全序列单一性酶切位点,设计引物,分4段扩增CVS-11全基因组,扩增产物经多步酶切、连接逐步插入至真核表达载体pcDNA3.1,获得全长质粒pcDNA3.1-CVS-11.pcDNA3.1-CVS-11与其辅助质粒pcDNA3.1-N、P、L、G共转染NA细胞,经免疫荧光染色、RT-PCR鉴定,拯救得到重组病毒rCVS-11.[结果]CVS-11全基因组序列由11 927个核苷酸组成,编码5个结构蛋白,结构基因排列同已知的其他狂犬病病毒一致.成功构建了CVS-11全长cDNA重组质粒pcDNA3.1-CVS-11和其辅助质粒pcDNA3.1-N、P、L和G.经共转染,成功拯救了重组病毒rCVS-11.[结论]CVS-11株感染性克隆的构建为从分子水平上进一步研究狂犬病病毒奠定了基础.     

携带绿色荧光报告基因的EBV-LMP1真核表达载体构建与鼻咽癌细胞中的表达

潜伏膜蛋白1(LMP1)是由EB病毒编码的致瘤蛋白,众多研究表明LMP1蛋白可通过NF-κB、p38 MAPK、c-JNK等多条重要信号通路引起鼻咽癌细胞的生物学行为改变。我们从EB病毒阳性的B95-8狨猴淋巴瘤细胞中克隆EB病毒LMP1 c DNA,构建携带绿色荧光基因的真核表达质粒p IRES2-Zs-Green1-LMP1,通过脂质体转染的方法将质粒导入鼻咽癌细胞株CNE1、CNE2中,利用质粒所携带的绿色荧光蛋白表达粗略计算转染的效率,通过免疫细胞化学(ICC)、RT-PCR、Western-Blot检测该质粒的表达。本实验室所构建的p IRES2-Zs-Green1-LMP1表达质粒能在鼻咽癌细胞内表达LMP1蛋白,为后续的实验研究奠定基础。     

EB病毒早期蛋白P54的原核表达及其免疫原性的研究

PCR法获得编码EB病毒早期蛋白P54的基因BMRFl,序列分析后亚克隆入原核表达载体pET30a。表达质粒pET30a-BMRF1在大肠杆菌BL21(DE3)菌株中经IPTG诱导后表达了P54抗原,SDS—PAGE表明其相对分子质量为51000;采用镍离子亲和柱纯化重组蛋白。Western印迹结果表明纯化蛋白免疫BALB／c小鼠后产生了P54特异性抗体。间接免疫荧光表明免疫血清可以识别激活的Raji细胞中表达的P54蛋白。以上结果表明构建了原核表达质粒pET30a-BMRF1并在大肠杆菌细胞中成功表达EB病毒早期蛋白P54,表达蛋白具有很好的抗原性和免疫原性。     

家蝇卵黄蛋白基因启动子区的克隆与活性分析

从家蝇基因组文库中分离到含约1．7kb5’上游区的家蝇卵黄蛋白-1基因组基因序列,根据其5’上游序列,PCR扩增出大小不同的4个启动子片段,分别插入到切除了CMV启动子的pCMV-GFP质粒中的绿色荧光蛋白报告基因上游,构建了pMYP1-GFP、pMYP2-GFP、pMYP3-GFP和pMYP4-GFP4个重组质粒。另将 684／ 7、 1165／ 7这两个启动子片段用SpeⅠ和HindⅢ双酶切,去除包含CAAT／TATA盒的 302／ 7序列区后,分别构建了pMYP5-GFP和pMYP6-GFP两个重组质粒。通过电转移实验和荧光检测表明。 684／ 7、 1165／ 7、 1616／ 7这3个启动子片段具有转录活性,而 684／ 7启动子片段的转录活性最强, 296／ 7、 684／ 302、 1165／ 302这3个启动子片段无转录活性。上述实验结果表明。 302／ 7序列区为启动子的核心部分。 302到 1616之间存在调控性启动子或增强子等其他一些顺式元件。细胞转染实验证实,6种启动子片段在BHK-21和Sf9细胞中都未表现出可检测的转录活性,说明家蝇卵黄蛋白基因启动子具有组织或细胞特异性。     

TRIM25及其缺失突变体真核表达载体的构建及表达

目的:扩增先天性免疫中具有重要功能的泛素连接酶TRIM25及其不同结构域的cDNA,构建带有不同标签的融合蛋白载体并进行细胞表达。方法:以TRIM25 cDNA为模板,PCR扩增不同结构域cDNA,扩增产物及载体经酶切、连接后,转化大肠杆菌DH5α,挑克隆,提取重组质粒后酶切鉴定、测序,将测序正确的重组质粒转染293细胞,用Western印迹对融合蛋白的表达进行鉴定。结果:TRIM25、Two-BOX结构域、SPRY结构域以正确读框插入Flag-pcDNA3.0,TRIM25以正确读框插入pCMV-Myc,RING结构域、CDD结构域、Two-BOX结构域以正确读框插入pEGFP-c1,上述重组质粒能够在293细胞中表达。结论:构建了TRIM25及其突变体的重组表达质粒并获得表达,为研究不同RNA病毒通过与TRIM25作用抑制宿主功能提供了基础。     

犬细小病毒可视化LAMP检测方法的建立

目的:建立犬细小病毒(CPV)可视化环介导等温扩增(LAMP)检测方法。方法:比对77个不同犬细小病毒全基因组数据,从中找出一段433 bp的高度保守序列作为检测对象,通过基因合成得到含该序列的质粒,制备1×10~3、1×10~2、1×10~1拷贝/μL的质粒作为标准品,并设计一套能扩增这段序列的LAMP引物。结果:首先采用实时荧光定量LAMP扩增,确定了设计的引物能够扩增质粒标准品,最低检测浓度为1×10~1拷贝/μL;然后用pH敏感指示剂中性红进行可视化LAMP扩增检测,肉眼观察到扩增反应液变为紫红色即判断为阳性,最低检测浓度同样为1×10~1拷贝/μL;随后采用实时荧光定量LAMP和可视化LAMP测试50份犬细小病毒疑似临床DNA样品,检测出阳性样品35个,与国标诊断结果完全吻合;将阳性样品扩增后测序,经比对,确定为犬细小病毒序列;对金黄色葡萄球菌、宋内志贺菌、坂崎肠杆菌、单增李斯特菌、大肠杆菌DNA进行扩增,结果均为阴性,证明了该方法的特异性。结论:建立了高度特异和灵敏的犬细小病毒可视化LAMP检测方法。     

Plasmids with easily excisable cat gene cartridges

New cat-cassette-containing vectors based on kanamycin-resistance-encoding plasmids, pHSG298/299, were constructed. They were designed to facilitate the subcloning of the promoterless cat gene into frequently used plasmids, including those with an ampicillin-resistance marker. In plasmids pCAT10-pCAT40, the cat gene cartridges are flanked by polylinker sequences and can be excised by double digestion with pairs of appropriate restriction enzymes. Translation stop condons in all three reading frames are located upstream from the AUG start codon of the pCAT40 cartridge; the latter can also be excised by a single digestion with the enzymes, SalI, PstI, or HindIII.     

Identification of protein-binding sites in the hepatitis B virus enhancer and core promoter domains.

We have investigated the role of liver-specific trans-acting factor(s) in the regulation of hepatitis B virus (HBV) gene expression. A recorder plasmid (pEcoAluCAT; HBV nucleotides 1 through 1878) was constructed containing the HBV enhancer and the promoter region of the pregenomic RNA, which was ligated to the bacterial chloramphenicol acetyltransferase (CAT) gene. Upon transfecting this plasmid into various cell lines, the CAT gene was expressed only in cells of liver origin. Moreover, competition cotransfections with pEcoAluCAT and plasmids containing HBV enhancer sequences in human hepatoblastoma-derived HepG2 cells indicated the presence of titratable trans-acting factor(s) in these cells. Gel mobility shift assays using HBV enhancer and core promoter domains confirmed the existence of sequence-specific DNA-binding proteins in liver cell nuclear extract which bound to these regions. These binding sites encompass 17- and 12-nucleotide palindromes in the HBV enhancer and core promoter domains, respectively, when mapped by the methylation interference assay.     

Retroviral vectors containing putative internal ribosome entry sites: development of a polycistronic gene transfer system and applications to human gene therapy.

Recombinant retroviral vectors producing multicistronic mRNAs were constructed. Picornavirus putative internal ribosome entry sites (IRES) were used to confer cap-independent translation of an internal cistron. Internal cistrons were engineered by ligation of various lengths of the IRES of encephalomyocarditis (EMC) virus or polio virus to the E. coli chloramphenicol acetyltransferase (CAT) gene. The IRES/CAT fusions were introduced into retroviral vectors 3' to the translation stop codon of the neomycin phosphotransferase (NEO) gene, and the molecular constructs transfected into retroviral vector packaging lines. Retroviral vector producer cells efficiently express the internal CAT gene product only when the full length IRES is used. Both the EMC/CAT and polio/CAT retroviral vectors produced high titer vector supernatant capable of productive transduction of target cells. To test the generality of this gene transfer system, a retroviral vector containing an IRES fusion to the human adenosine deaminase (ADA) gene was constructed. Producer cell supernatant was used to transduce NIH/3T3 cells, and transduced cells were shown to express NEO, and ADA. Novel three-gene-containing retroviral vectors were constructed by introducing the EMC/ADA fusion into either an existing internal-promoter-containing vector, or a polio/CAT bicistronic vector. Producer cell clones of the three-gene vectors synthesize all three gene products, were of high titer, and could productively transduce NIH/3T3 cells. By utilizing cap-independent translation units, IRES vectors can produce polycistronic mRNAs which enhance the ability of retroviral-mediated gene transfer to engineer cells to produce multiple foreign proteins.     

Stability of CAT gene transcript depends on the 3'-end structure

To determine the involvement of 3'-end structure of mRNA in the regulation of gene expression in eukaryotic cell, a series of pSCAT plasmids was constructed with chloramphenicol acetyltransferase (CAT) gene and the 3'-regulatory elements from various eukaryotic genes. As a result of determination of the CAT activities and the mRNA level generated from these plasmids, both results were well correlated. Furthermore, the treatment of transfected cells with phorbol ester (TPA) revealed that the polyadenylated CAT mRNAs form some genes were stabilized, in contrast, the mRNAs bearing 3'-end structure of histone or C-myc genes were not.     

Foot-and-mouth disease virus 2A oligopeptide mediated cleavage of an artificial polyprotein.

We describe the construction of a plasmid (pCAT2AGUS) encoding a polyprotein in which a 19 amino acid sequence spanning the 2A region of the foot-and-mouth disease virus (FMDV) polyprotein was inserted between the reporter genes chloramphenicol acetyl transferase (CAT) and beta-glucuronidase (GUS) maintaining a single, long open reading frame. Analysis of translation reactions programmed by this construct showed that the inserted FMDV sequence functioned in a manner similar to that observed in FMDV polyprotein processing: the CAT2AGUS polyprotein underwent a cotranslational, apparently autoproteolytic, cleavage yielding CAT-2A and GUS. Analysis of translation products derived from a series of constructs in which sequences were progressively deleted from the N-terminal region of the FMDV 2A insertion showed that cleavage required a minimum of 13 residues. The FMDV 2A sequence therefore provides the opportunity to engineer either whole proteins or domains such that they are cleaved apart cotranslationally with high efficiency.     

麻疹病毒全长cDNA构建及其感染性的研究

为发展新型疫苗和改造目前使用的麻疹病毒疫苗,以麻疹病毒疫苗株为模板,构建了具有感染性的麻疹病毒cDNA克隆.用RT-PCR分6段扩增出麻疹病毒全长基因,通过酶切、拼接构建麻疹病毒疫苗株CC-47的全长正链cDNA序列,并精确地置于T7启动子控制下与丁型肝炎病毒核酶序列之前.克隆麻疹病毒CC-47株蛋白N、P、L编码区质粒并置于T7启动子控制下,用4个质粒共转染哺乳动物细胞,在表达T7 RNA聚合酶的重组痘苗病毒VTF7-3的作用下进行病毒拯救.经免疫荧光、PCR等方法检测证实,获得了具有感染性的麻疹病毒.所拯救的病毒在哺乳动物细胞连续传3代后,仍能检出病毒抗原和核酸.     

Complete characterization of the gene coding for the Epstein-Barr virus major membrane antigen gp 220/340 and selective expression of a secreted form of gp 220

The gene which encodes the Epstein-Barr gp 220/340 was inserted into a eukaryotic expression vector. A cDNA clone corresponding to the mature mRNA coding for gp 220 was isolated from an Epstein-Barr virus cDNA library and inserted in the same expression vector, enabling us to identify the precise location of the intron within the gp 220/340 coding sequence. The recombinant plasmids direct the expression of membrane proteins detected by immunofluorescence experiments using an anti-gp 220/340 monoclonal antibody in transfected human cells. The region of the gp 220/340 gene encoding the domain for membrane anchorage was removed from the two recombinant plasmids and the sequence containing the intron produced secreted forms of both truncated gp 220 and gp 340 whereas only the former was obtained with the intronless sequence.