急性单核细胞白血病新抗原基因MLAA-34启动子的克隆及其核心区鉴定

目的:克隆急性单核细胞白血病新抗原基因MLAA-34上游启动子序列并检测其活性、鉴定核心区域。方法:PCR扩增MLAA-34基因启动子区全长片段,将其连接至p GL3-Basic载体,克隆重组质粒;构建一系列MLAA-34基因启动子5'侧翼区截短质粒;将含MLAA-34启动子序列的重组质粒及其截短型质粒转染至U937、HEK293细胞,应用双荧光素酶报告基因检测各片段的启动子活性,确定启动子最小活性区域,并通过生物信息学方法分析转录因子结合位点。结果:构建了含有MLAA-34启动子序列的重组质粒及其截短型质粒;与空载体相比,其启动子活性明显增加(P 0. 001)。MLAA-34最小活性区域位于转录起始位点-402 bp至-200 bp之间,其中包含E2F1,MZF-1,SP1,USF2和STAT3等多个转录因子结合位点。结论:成功构建急性单核细胞白血病新抗原基因MLAA-34不同缺失片段的启动子荧光素酶报告基因重组质粒,鉴定出核心启动子区,其中含有多个潜在的转录因子结合序列。     

基于CA杂合启动子基因敲入载体的构建

目的:改造原有的Rosa26基因敲入系统,引入启动能力更强的CA杂合启动子(由鸡actin启动子和SV40增强子融合而成)。方法:运用PCR,限制性内切酶酶切及T4连接酶连接的方法,构建带有CA启动子的基因敲入载体。结果:成功地对原有Rosa26基因敲入系统进行了改造,引入了CA启动子,并且成功构建了mGluR5基因敲入载体。结论:基于CA杂合启动子的基因敲入载体具有更强的启动能力,而且能够在某些特定组织中增强目的基因的表达,为今后研究基因功能及疾病模型小鼠的制备奠定了良好基础。     

小鼠Nestin启动子的克隆及其表达载体的构建

目的:克隆Nestin基因启动子序列,并研究其调控能力。方法:用高保真酶PCR扩增出小鼠Nestin启动子全序列、核心序列,pcDNA3.1质粒双酶切切掉CMV启动子序列,将Nestin基因启动子序列插入到原CMV启动子位置,pEGFP-N1质粒双酶切下EGFP序列,克隆入pcDNA3.1多克隆位点中,重组构建质粒,分别用Nestin启动子全序列和核心序列调控EGFP基因的表达。重组质粒分别转染Nestin+细胞和Nestin-细胞,观察EGFP基因在细胞内的表达情况。结果:成功克隆出Nestin基因启动子全序列和核心序列,经酶切鉴定及测序证实正确。二序列皆能调控EGFP在各种细胞内的表达。结论:Nestin基因启动子全序列和核心序列具有非特异性调控能力。     

构建创伤修复相关基因p21表达载体

目的:构建创伤修复相关基因p21启动子驱动的荧光素酶报告基因表达载体,并评估其稳定性和可靠性.方法:实验于2004-06/08在第三军医大学西南医院烧伤研究所内皮细胞室完成.野生型p21基因启动子全序列经酶切亚克隆入pGL3-basic荧光素酶报告基因载体,重组载体pGL3-p21p转染ECV304细胞,并应用双荧光素酶检测系统检测荧光素酶活性,排除转染过程误差.结果:①目的片段克隆载体与p21基因启动子cDNA序列高度同源.②转染重组载体pGL3-p21p和E47 IPTG诱导细胞荧光素酶活性明显增强,而空载体pGL3-basic的荧光素酶表达处于基础水平,两者比较差异有显著性意义(P＜0.05).结论:构建的野生型p21基因启动子驱动的荧光素酶报告基因载体,转染ECV304细胞后能够表达荧光素酶蛋白,具有稳定和可靠性能.     

构建创伤修复相关基因p21表达载体

目的:构建创伤修复相关基因p21启动子驱动的荧光素酶报告基因表达载体,并评估其稳定性和可靠性.方法:实验于2004-06/08在第三军医大学西南医院烧伤研究所内皮细胞室完成.野生型p21基因启动子全序列经酶切亚克隆入pGL3-basic荧光素酶报告基因载体,重组载体pGL3-p21p转染ECV304细胞,并应用双荧光素酶检测系统检测荧光素酶活性,排除转染过程误差.结果:①目的片段克隆载体与p21基因启动子cDNA序列高度同源.②转染重组载体pGL3-p21p和E47 IPTG诱导细胞荧光素酶活性明显增强,而空载体pGL3-basic的荧光素酶表达处于基础水平,两比较差异有显性意义(P＜0.05).结论:构建的野生型p21基因启动子驱动的荧光素酶报告基因载体,转染ECV304细胞后能够表达荧光素酶蛋白,具有稳定和可靠性能.     

小鼠adam10基因启动子克隆和双荧光素酶报告基因系统构建及鉴定

本研究旨在克隆小鼠adam10基因启动子,构建以adam10基因启动子为启动序列的双荧光素酶报告基因系统并分析其活性,为研究adam10基因转录调控提供有效工具。以BALB/c小鼠脑组织为模板,采用PCR方法克隆小鼠adam10基因启动子序列至pCR-Blunt载体,酶切后连接至荧光素酶报告质粒pGL4.10启动子区域,构建重组荧光素酶报告质粒pGL4.10-adam10,采用阳离子脂质体法与阳性对照质粒pGL4.74共转染真核细胞293FT,以离子霉素刺激为刺激组、DMSO为未加干预组,同时以不含启动子的pGL4.10与阳性对照质粒pGL4.74共转染组为阴性对照组,化学发光仪检测荧光强度及比例。结果表明,酶切及测序验证克隆的adam10启动子序列正确且无突变,构建的重组荧光素酶报告质粒pGL4.10-adam10与阳性对照质粒pGL4.74载体成功共转染293FT细胞,pGL4.10-adam10转染细胞后具有转录活性。离子霉素刺激组活性明显高于DMSO组,荧光比值约为DMSO组2倍(P<0.05),阴性对照组不具备转录活性。结论:成功克隆了adam10启动子并构建了重组荧光素酶报告质粒pGL4.10-adam10,离子霉素可增强adam10基因启动子转录活性。     

人核心蛋白聚糖基因靶向肺癌细胞特异性表达载体的构建及其表达

目的构建调控人核心蛋白聚糖基因特异性在肺癌细胞A549内表达的基因表达载体,为进一步应用该基因进行肺癌靶向治疗的研究奠定实验基础。方法应用PCR技术从人外周血基因组中扩增肺癌细胞特异性表达的人分泌型白细胞蛋白酶抑制剂的启动子,利用基因重组技术将该启动子插入真核细胞表达载体pcDNA3.1（＋）,替换该载体的CMV启动子与增强子序列,从而构建成由人分泌型白细胞蛋白酶抑制剂基因的启动子启动基因表达的基因表达载体。将人核心蛋白聚糖基因通过基因重组技术插入到上述载体人分泌型白细胞蛋白酶抑制剂基因启动子的下游。PCR产物通过测序鉴定核苷酸序列。重组载体通过限制性酶切进行鉴定。结果 PCR扩增的人分泌型白细胞蛋白酶抑制剂的启动子片段长度为1 250 bp;该启动子经测序获得的核苷酸序列与Genebank上该基因上游5′末端转录调控区的序列完全一致;重组载体的酶切鉴定结果显示（1）该启动子成功插入到pcDNA3.1（＋）载体,并替换CMV启动子与增强子序列,（2）人核心蛋白聚糖基因成功插入该载体。结论成功构建由人分泌型白细胞蛋白酶抑制剂基因启动子调控人核心蛋白聚糖基因表达载体,该载体实现调控人核心蛋白聚糖基因在肺癌细胞内特异性表达。     

白念珠菌FLO8基因高表达菌株构建及鉴定

目的 :构建白念珠菌FLO8基因高表达菌株。方法 :将白念珠菌FLO8基因插入p CP20质粒载体ADH1启动子后,通过聚合酶链反应(polymerase chain reaction,PCR)将ADH1-FLO8-Lox P-ARG4-Lox P-ADE2片段扩增,并通过同源重组技术将该片段整合至SN152的ADE2位点。结果:通过测序鉴定FLO8基因高表达质粒载体构建成功;通过同源重组及实时反转录PCR验证表明FLO8基因整合到SN152菌株的ADE2位点并且表达量增高。结论:以p CP20质粒为载体,通过同源重组等技术,可高效构建白念珠菌FLO8基因高表达菌株。     

人ID4基因表达调控启动子及其亚克隆荧光素酶报道重组子的构建

本研究旨在克隆ID4基因启动子及上游调控序列,并构建一系列启动子亚克隆-pGL3Basic荧光素酶报道重组子,以探讨ID4基因表达调控机制。方法与结果:以ID4基因cDNA全长作为探针,在NCBI的人类基因组数据库中搜索并下载ID4基因转录起始位点上游5′侧翼区约2242bp及下游5′非翻译区212bp的基因组序列;利用TESS和Genomax等在线启动子分析软件进行启动子及上游调控元件的特征分析,据此设计PCR引物,采用分段扩增法,获得了2条长度分别为1 829bp和784bp的产物片段,分别插入pGEM-T载体,转化至TOP10感受态大肠杆菌,筛选阳性菌落;继之先后应用KpnI/NheI、KpnI/EcoRI对获得的2个pGEMT重组载体及pGL3Basic荧光素酶报道重组载体进行双酶切,用T4DNA连接酶连接,转化至TOP10感受态大肠杆菌,筛选阳性菌落,成功构建了人ID4基因启动子-pGL3Basic荧光素酶报道重组子;经KpnI/NheI双酶切和测序鉴定,获得了与GenBank相应序列一致、长度为2 459bp的目的片段;以此片段为模板,相隔400bp左右设计了5对3′端平齐、5′端不同的PCR引物,进行半巢式PCR扩增,获得5条长度分别为2 112bp、1 703bp、1 290bp、784bp和496bp片段,回收纯化后分别插入pGEM-T载体,转化至TOP10感受态大肠杆菌,筛选阳性菌落;继之用KpnI/NheI对获得的5个pGEMT重组载体及pGL3Basic荧光素酶报道载体双酶切,T4DNA连接酶连接,转化至TOP10感受态大肠杆菌,筛选阳性菌落,经KpnI/NheI双酶切和测序鉴定。结论:成功克隆了长度为2.5kb的ID4基因启动子及上游表达调控序列,构建了一系列ID4启动子亚克隆-pGL3-Basic荧光素酶报道重组子。     

携带Egr-1启动子和Endostatin基因的腺病毒穿梭质粒构建及鉴定

目的构建含辐射敏感启动子Egr-1和人内皮抑素（endostatin）基因的腺病毒穿梭质粒pshuttle-Egr1-Endo-statin。方法利用RT-PCR方法从人胎肝中扩增出人endostatin cDNA序列，从T-Egr1质粒中扩增出Egr-1基因序列，并将它们连接到pMD19T质粒进行测序，利用基因重组技术构建含有辐射诱导启动子Egr-1的腺病毒穿梭质粒pshuttle-Egrl-Endostafin。结果经测序证实，获得的人endostatin基因和Egr-1基因与GenBank公布的完全一致，表明克隆人帆．dostatin基因和Egr-1启动子成功，并经鉴定证实含有辐射诱导启动子Egr-1的腺病毒穿梭质粒pshuttle-Egr1-Endostatin构建正确。结论本实验成功克隆了人endostatin基因和Egr-1启动子并构建了含辐射敏感启动子的腺病毒穿梭质粒pshtntle-Egr1-Endostatin。     

Optimization of the Gal4-UAS system in an Anopheles gambiae cell line

The development of the bipartite Gal4-UAS system in Anopheles gambiae would improve the functional characterization of genes in this important malaria vector. Towards this aim, we used Gal4 driver plasmids to successfully activate expression of the reporter gene, luciferase, from UAS responder plasmids when cotransfected into an An. gambiae cell line. To optimize Gal4-regulated gene expression in mosquitoes, we compared the efficiency of a series of alternative Gal4 transactivators to drive reporter gene expression from responder plasmids incorporating different numbers of tandemly arrayed Gal4 binding sites or upstream activation sequences (UAS). The results indicated that the native Gal4 is only weakly active in these cells. Modified forms of Gal4, including those carrying minimal VP16 activation domains, as well as a deleted form of Gal4, give up to 20-fold greater activity than the native protein, when used in conjunction with a responder plasmid having 14 UAS repeats. The identification of Gal4-UAS vectors that are efficiently expressed in a mosquito cell line should facilitate the transfer of this versatile expression system to An. gambiae, and potentially to other insects of medical importance.     

Investigation of red blood cells from alpha1,3-galactosyltransferase-knockout pigs for human blood transfusion

BACKGROUND: Pigs are a potential source of red blood cells (RBCs) for transfusion into humans, but the pre‐sence of galactose‐α1,3‐galactose (Gal) epitopes on their surface, against which humans have anti‐Gal, has been perceived as a major barrier. α1,3‐Galactosyltransferase gene‐knockout pigs, which do not express Gal epitopes on RBCs (Gal–/–), have recently become available. STUDY DESIGN AND METHODS: In vitro, RBCs from Gal–/– pigs were exposed to sera from naïve humans or baboons or from baboons previously sensitized to pig antigens; immunoglobulin binding was measured by flow cytometry, and cytotoxicity, by a hemolytic assay. In vivo, relatively small numbers of Gal–/– RBCs were transfused into two nonsensitized untreated baboons. The survival of pig RBCs was detected by flow cytometry. RESULTS: In vitro, binding of immunoglobulin (Ig) M from naïve human or baboon sera was detected to Gal–/– RBCs but was significantly less than to Gal+/+ RBCs; IgG binding to Gal–/– RBCs was absent or minimal. Sera had minimal cytotoxicity to Gal–/– RBCs compared to Gal+/+ RBCs. Sensitized baboon sera demonstrated much higher IgG binding to Gal–/– RBCs and increased cytotoxicity, but again these were less than to Gal+/+ RBCs. In vivo, the transfusion of relatively small volumes of Gal–/– RBCs was followed by detection of the cells in the baboon's blood for only 5 minutes. CONCLUSION: Pig RBCs are rapidly phagocytosed from the primate circulation by a mechanism not involving anti‐Gal.     

Pathogenesis of shigella diarrhea. XI. Isolation of a shigella toxin- binding glycolipid from rabbit jejunum and HeLa cells and its identification as globotriaosylceramide

A glycolipid that specifically binds shigella toxin was isolated from both HeLa cells and rabbit jejunal mucosa and identified as globotriaosylceramide (Gb3) by its identical mobility on HPTLC to authentic erythrocyte Gb3. Toxin also bound to a band tentatively identified as alpha-hydroxylated Gb3. In addition, toxin bound to P1 antigen present in group B human erythrocyte glycolipid extracts. The common feature of the three binding glycolipids is a terminal Gal alpha 1----4Gal disaccharide linked beta 1----4 to either Glc or GlcNAc. Globoisotriaosylceramide, which differs from Gb3 only in possessing a Gal alpha 1----3Gal terminal disaccharide, and LacCer, which lacks the terminal Gal residue of Gb3, were incapable of binding the toxin. Binding was shown to be mediated by the B subunit by the use of isolated toxin A and B subunits and monoclonal subunit-specific antibodies. Gb3-containing liposomes competitively inhibited the binding of toxin to HeLa cell monolayers but did not inhibit toxin-induced cytotoxicity. These studies show an identical carbohydrate-specific glycolipid receptor for shigella toxin in gut and in HeLa cells. The toxin B subunit that mediates this binding has also been shown to recognize a glycoprotein receptor with different sugar specificity. Thus, we have demonstrated that the same small (Mr 6,500) B subunit polypeptide has two distinctive carbohydrate-specific binding sites. The Gal alpha 1----4Gal disaccharide of the glycolipid toxin receptor is also recognized by the Gal-Gal pilus of uropathogenic E. coli. This suggests the possibility that the pilus and toxin B subunit contain homologous sequences. If this is true, it may be possible to use the purified Gal-Gal pilus to produce toxin-neutralizing antibodies.     

Identification of an active disaccharide unit of a glycoconjugate receptor for pneumococci attaching to human pharyngeal epithelial cells

Glycoconjugates containing the disaccharide unit GlcNAc beta 1 leads to 3Gal beta were suggested as receptors for pneumococci adhering to human pharyngeal epithelial cells. The receptor activity was detected both by inhibition of adhesion by an excess of free oligosaccharide and by induction or increase of adhesion after coating of target cells with glycolipid. Studies with free natural and synthetic oligosaccharides identified the disaccharide GlcNAc beta 1 leads to 3Gal beta as one critical binding site. The specificity of recognition was shown inter alia by the lack of inhibitory activity of GlcNAc beta 1 leads to 4Gal beta, which differs only in the linkage of the two sugars. Specific interference with pneumococcal adhesion by administration of soluble receptor sugar may improve our understanding of the role of adhesion in vivo.     

Rat and human colonic mucins bind to and inhibit adherence lectin of Entamoeba histolytica.

Establishment of adherence by Entamoeba histolytica is mediated by a 170-kD Gal/GalNAc inhibitable lectin and is required for cytolysis and phagocytosis of mammalian target cells. We studied the biochemical mechanisms of the in vitro interaction between rat and human colonic mucins and axenic E. histolytica trophozoites. Crude mucus prevented amebic adherence to Chinese hamster ovary (CHO) cells by up to 70%. Purification of the colonic mucins by Sepharose 4B chromatography, nuclease digestion, and cesium chloride gradient centrifugation resulted in a 1,000-fold enrichment of the inhibitory mucins. Purified rat mucin inhibited amebic adherence to and cytolysis of homologous rat colonic epithelial cells. Oxidation and enzymatic cleavage of rat mucin Gal and GalNAc residues completely abrogated mucin inhibition of amebic adherence. The binding of rat 125I-mucin to amebae was galactose specific, saturable, reversible, and pH dependent. A monoclonal antibody specific for the 170-kD amebic Gal/GalNAc lectin completely inhibited the binding of rat 125I-mucin. Rat mucin bound to Affigel affinity purified the amebic lectin from conditioned medium. Colonic mucin glycoproteins act as an important host defense by binding to the parasite's adherence lectin, thus preventing amebic attachment to and cytolysis of host epithelial cells.     

Structural biology of carbohydrate xenoantigens

Transplantation of organs across species (xenotransplantation) is being considered to overcome the shortage of human donor organs. However, unmodified pig organs undergo an antibody-mediated hyperacute rejection that is brought about by the presence of natural antibodies to Galα(1,3)Gal, which is the major carbohydrate xenoantigen. Genetic modification of pig organs to remove most of the Galα(1,3)Gal epitopes has been achieved, but the human immune system may still recognize residual lipid-linked Galα(1,3)Gal carbohydrates, new (cryptic) carbohydrates or additional non-Galα(1,3)Gal carbohydrate xenoantigens. The structural basis for lectin and antibody recognition of Galα(1,3)Gal carbohydrates is starting to be understood and is discussed in this review. Antibody binding to Galα(1,3)Gal carbohydrates is predicted to primarily involve end-on insertion of the terminal αGal residue, but it is possible that groove-type binding can occur, as for some lectins. It is likely that similar antibody and lectin recognition will occur with other non-Galα(1,3)Gal xenoantigens, which potentially represent new barriers for pig-to-human xenotransplantation.     

Controlled biodistribution of galactosylated liposomes and incorporated probucol in hepatocyte-selective drug targeting.

Two types of galactosylated liposomes containing cholesten-5-yloxy-N-(4-((1-imino-2-beta-D-thiogalactosyle thyl)amino)b utyl)formamide (Gal-C4-Chol) as a homing device were prepared to study the biodistribution of liposomal carriers and the incorporated drug. Distearoylphosphatidylcholine (DSPC)/cholesterol (Chol)/Gal-C4-Chol (60:35:5) (Gal DSPC), DSPC/Chol (60:40) (DSPC), egg yolk phosphatidylcholine (eggPC)/Chol/Gal-C4-Chol (60:35:5) (Gal eggPC), and eggPC/Chol (60:40) (eggPC) liposomes labeled with [(3)H]cholesteryl hexadecyl ether (CHE) were tested and [(14)C]probucol, with a partition coefficient between octanol and water (PC(oct)) of 10(10.8), was selected as a model drug with lipophilicity suitable for liposomal incorporation. After intravenous injection of the combination of [(14)C]probucol and [(3)H]liposomes, the liver uptake of [(3)H]CHE was the highest in Gal DSPC liposomes, followed by Gal egg PC liposomes, egg PC liposomes, and DSPC liposomes in that order. [(14)C]Probucol incorporated in Gal DSPC liposomes exhibited lower liver uptake than [(3)H]CHE, suggesting that substantial release from liposomes had taken place. In contrast, [(14)C]probucol incorporated in Gal eggPC liposomes was more stably incorporated under in vivo conditions. Co-administration with galactosylated bovine serum albumin significantly inhibited the liver uptake of [(14)C]probucol in both types of galactosylated liposomes, suggesting that the hepatic uptake of liposomes should be mediated by asialoglycoprotein receptors being [(14)C]probucol incorporated in them.     

Ethanol destabilizes liver Gal beta l, 4GlcNAc alpha2,6-sialyltransferase, mRNA by depleting a 3'-untranslated region-specific binding protein

Asialoconjugates are viable biomarkers for alcohol abuse. We previously showed that chronic ethanol feeding down-regulated liver Gal beta l, 4GlcNAc alpha2,6-sialyltransferase (ST6Gal l) mRNA by destabilizing it. Since RNA-binding proteins are known to stabilize many eukaryotic mRNAs by interacting with the 3'-untranslated region (UTR), we have delineated the possible mechanism by which ethanol destabilizes ST6Gal l mRNA. Using (32)P-labeled RNA probes generated from a 2.7-kb 3'-UTR of ST6Gal l mRNA, we identified a liver cytosolic 41-kDa specific binding protein that interacts with its 3'-UTR domain and protects it from degradation in normal rat liver but disappears after chronic ethanol treatment. Mapping of the binding region revealed that four RNA probes of 80-base pair (bp) length spanning the 304 bp of the 3'-UTR of ST6Gal l mRNA showed equal binding intensity. The corresponding cDNA sequences for the four 80-bp RNA probes share the 13-bp consensus sequence. Mutagenesis analysis identified that four nucleotides, AG and TC, among the consensus sequences were critical for the RNA-protein interaction. Therefore, 5'-CAGCCTCCTCCCT-3' serves as a cis-element critically involved in this interaction. The RNA-protein complex formation progressively decreased with increasing dietary ethanol, resulting in its virtual disappearance with 36% of the dietary calories as ethanol. Concomitantly, the same ethanol diet decreased sialic acid index of plasma apolipoprotein J by 45% (p < 0.05). Thus, depletion of a binding protein that specifically interacts with its 3'-UTR region of ST6Gal l mRNA may account for its destabilization and consequent appearance of asialoconjugates as alcohol biomarkers.