瞬时基因表达可溶性的VEGFR2: I-IV

通过RT-PCR的方法从三个月的流产绒毛组织中克隆目的基因VEGFR2 (Vascular endothelial growth factor receptor 2, 血管内皮细胞生长因子受体2) 胞外I-IV区, 连接到真核表达载体上构建了重组表达载体。首先在无血清悬浮培养的HEK293细胞中, 使用报告基因GFP(Green fluorescence protein, 绿色荧光蛋白)优化转染条件, 发现在转染时DNA: PEI=1:2 (W/W)、1.5 mg DNA/106 cells及开始转染4 h内使用无血清、摇床(120 r/min)时可以达到最佳的转染效率和细胞数量。在确定转染条件之后, 将构建的表达载体分别在HEK293细胞、COS-7细胞和CHO-K1细胞中进行瞬时转染表达, 结果发现仅在CHO-K1细胞的培养上清中检测到目的蛋白的表达。瞬时转染CHO-K1细胞至总体积约为1.5 L, 由于目的蛋白的羧基端有8-His标签, 通过Ni2+-IDA柱纯化得到5 mg左右的目的蛋白。     

基于逆转录病毒载体的外源基因表达系统的评价和应用

逆转录病毒表达系统是基因治疗研究和RNA干扰技术广泛采用的外源基因表达系统。文中以增强型绿色荧光蛋白 (EGFP) 基因的表达水平和稳定性为指标,比较逆转录病毒表达载体pQCXIN和pcDNA3.1(+) 表达质粒介导的外源基因在HEK293细胞和CHO-K1细胞的表达效率。病毒感染HEK293细胞和CHO-K1细胞的相对荧光强度 (Relative fluorescence intensity,RFI) 均约为对应的质粒转染细胞的2倍。多轮反复感染逆转录病毒表达载体能有效提高HEK293细胞表达EGFP的效率。HEK293细胞经4轮病毒感染后的RFI值较1次病毒感染HEK293细胞的RFI值约提高2倍。此外,逆转录病毒表达载体介导的外源基因表达的稳定性优于质粒转染的外源基因表达。采用携带人重组活性蛋白C (Recombinant human activated protein C,rhAPC) 基因的pQCXIN和HEK293细胞进一步验证了逆转录病毒载体介导的外源基因表达效率,构建了rhAPC表达水平为10~15 mg/(106 cells·d) 的HEK293细胞系。研究结果表明,逆转录病毒表达系统是有应用价值的介导外源基因在哺乳动物细胞高效表达的技术途径。     

人Cuedc2真核表达载体的构建及其在HEK293细胞中的表达

目的:构建人Cuedc2的真核表达载体,并进行体外验证。方法:提取人卵巢癌细胞总RNA,通过RT-PCR的方法其反转录为cDNA;以之为模板,利用PCR获得Cuedc2的编码区,纯化后克隆入pcDNA3.1myc-his(-),利用菌落PCR及DNA测序进行鉴定。最后,采用瞬时转染的方法,将所构建的重组CUEDC2真核表达载体通过脂质体转染HEK293细胞,48h后通过western blot检测Cuedc2蛋白的表达。结果:Cuedc2编码区cDNA正确地插入真核表达载体pcDNA3.1myc-his(-)中,western blot检测证实其在HEK293细胞中表达,而空载体转染的细胞为阴性,表明所构建的pcDNA3.1myc-his(-)-Cuedc2能够在体外有效表达。结论:本研究成功地克隆了人Cuedc2 cDNA,构建了重组真核表达载体,并在HEK293细胞中有效表达,为进一步研究人Cuedc2的功能及其与肿瘤的关系奠定了实验基础。     

hTEM8-N-RFP融合蛋白真核表达载体的构建及在HEK293F细胞中表达

目的:构建人肿瘤内皮标志物8(hTEM8)胞外区(N端)与红色荧光蛋白(RFP)融合表达载体并在HEK293F细胞中表达,为进一步研究hTEM8的相互作用蛋白及其在肿瘤血管形成过程中的机制奠定实验基础。方法:以质粒pDsRed-Express-C1和重组质粒pcDNA3.1(+)-hTEM8/Fc为模板,PCR扩增RFP和hTEM8-N基因片段,先后插入真核表达载体pcDNA3.1(+)中,构建重组表达载体pcDNA3.1(+)-hTEM8-N-RFP,转染HEK293F细胞,通过荧光显微镜观察融合蛋白在转染细胞中的的表达,并用G418对转染的细胞进行加压筛选,Western blot检测hTEM8-N-RFP融合蛋白在转染细胞中的表达。结果:DNA测序、酶切鉴定的结果显示,表达载体pcDNA3.1(+)-hTEM8-N-RFP构建成功,且序列正确。转染后经荧光显微镜观察到HEK293F细胞中有红色荧光,经加压筛选单克隆后,在荧光显微镜下观察到稳定表达红色荧光的细胞株,Western blot检测到融合蛋白hTEM8-N-RFP在真核细胞HEK293F中获得表达。结论:成功构建了pcDNA3.1(+)-hTEM8-N-RFP真核表达载体,并在HEK293F细胞中表达,为后期研究hTEM8的相互作用蛋白和其生理功能奠定了良好的基础。     

人Notch信号通路中Jagged1基因的克隆与真核表达

[目的]克隆人Notch信号通路中配体Jagged1基因并进行真核表达。[方法]采用RT-PCR的方法从Hela细胞总RNA中获取Jagged1基因,并克隆至携带FLAG标签的真核表达载体pCMV-Tag4。经酶切、PCR和测序鉴定后,将重组质粒Jagged1-pCMV-Tag4瞬时转染HEK 293T细胞,通过Q-PCR和Western blot检测目的蛋白的表达。[结果]成功构建了真核表达质粒Jagged1-pCMV-Tag4并在HEK 293T细胞中瞬时表达。[结论]Jagged1在HEK 293T细胞中实现瞬时表达,为稳定表达和进一步研究Jagged1/Notch信号通路奠定基础。     

重组人CLK1的真核表达及鉴定

目的:合成真核细胞CLK1(Cdc2-like kinase 1)编码基因,构建CLK1/pEGFP-N2真核表达载体并在真核细胞HEK293A中过表达,为CLK1的生物学功能研究奠定基础。方法:从人脐静脉血管内皮细胞中提取总RNA,采用RT-PCR技术用已知引物合成cDNA,将CLK1基因扩增后插入真核细胞表达载体pEGFP-N2,将重组质粒热转化至大肠杆菌感受态Trans 10细胞中获得重组菌株,提取质粒进行酶切鉴定及插入基因测序;将构建的重组质粒转染HEK293A细胞,用Western印迹及免疫荧光检测CLK1的表达水平,同时对其下游的磷酸化SF2/ASF蛋白进行检测。结果:构建了CLK1/pEGFP-N2真核表达载体,将其转染HEK293A细胞后24 h,CLK1蛋白表达水平最高;同时,CLK1过表达后使得下游的SF2/ASF蛋白磷酸化水平升高。结论:构建了人CLK1基因的真核细胞表达载体CLK1/pEGFP-N2,并在HEK293A细胞中过表达,其生物活性也得到了验证。本研究为外源性CLK1基因在真核细胞中过表达提供了一种途径,为CLK1的生物学功能研究奠定了基础,也可为真核细胞其他蛋白表达体系的构建提供借鉴。     

人酪氨酸蛋白激酶Lyn的真核表达、纯化及鉴定

[目的]构建含人酪氨酸蛋白激酶Lyn基因的载体并进行真核表达、纯化和研究其对细胞增殖的影响。[方法]提取人Hela细胞总RNA,用RT-PCR方法获得Lyn基因并克隆至pcDNA3.1(-)载体。经双酶切、PCR和测序方法鉴定后,将重组质粒瞬时转染HEK 293T细胞表达目的蛋白,应用组氨酸标签镍离子螯合磁珠纯化融合蛋白,通过Western Blot检测蛋白的表达及纯化,并用CCK-8法检测过表达Lyn后细胞增殖能力的变化。[结果]成功构建真核表达质粒pcDNA3.1(-)-Lyn并进行瞬时表达和蛋白纯化,CCK-8法检测过表达Lyn的HEK 293T细胞的增殖能力显著性下降(P0.01)。[结论]Lyn在HEK 293T细胞中成功瞬时表达及纯化,并可以使细胞的增殖能力受到明显抑制,为稳定表达和深入研究其生物学功能及作用机制奠定基础。     

重组人骨桥蛋白在哺乳动物细胞中的表达、纯化和活性研究

旨在运用哺乳动物表达载体的瞬时转染技术,转染人类胚胎肾细胞(Human Embryonic Kidney 293E,HEK293E),分泌性表达和纯化带His标签的重组人骨桥蛋白(Recombinant Human Osteopontin,rhOPN),并研究其促结肠癌以及非小细胞肺癌细胞增殖功能。合成和构建OPN融合6×His标签重组蛋白的表达载体pcDNA3.1-OPN,利用聚醚酰亚胺(Polyetherimide,PEI)瞬时转染法将pcDNA3.1-OPN转染到HEK293E细胞中,并用镍亲和层析柱对rhOPN进行纯化。SDS-PAGE电泳和Western Blot被用来检测纯化后的rhOPN蛋白在凝胶上的迁移率和纯度。此外,ELISA方法被用于测定rhOPN与抗OPN抗体间的结合能力,并用CCK-8(Cell Counting Kit-8)方法初步研究rhOPN蛋白对结肠癌及非小细胞肺癌细胞增殖的影响。结果显示,通过将pcDNA3.1-OPN瞬时转染HEK293E细胞,成功表达和纯化出纯度达95%的rhOPN,且rhOPN可以被抗OPN抗体很好的识别。rhOPN被证实在36μg/ml浓度时即可显著促进体外培养的HT29细胞增殖,在20μg/mL时能够促进体外培养的非小细胞肺癌H1299及HCC827细胞增殖。运用哺乳动物细胞瞬时转染技术,在HEK293E细胞中成功表达并纯化出高纯度的rhOPN蛋白,并发现rhOPN可以显著促进结肠癌及非小细胞肺癌细胞增殖,具有良好的生物学活性。     

CHO-K1细胞中基因瞬时转染的条件优化

目的:以CHO-K1细胞为宿主基因瞬时转染条件的优化.方法:以GFP(Green Fluorescence Protein)为报告基因,考察了DNA∶PEI比例、DNA用量及血清的加入对CHO-K1细胞的转染效率和细胞数目的影响.结果:DNA∶PEI=1∶2(w/w)、2 gDNA/106 cells时,转染结果最优;血清的加入可降低细胞转染效率.结论:在CHO-K1细胞中进行瞬时转染的最佳条件为DNA∶PEI=1∶2(w/w)、2 gDNA/106 cells,及血清的加入抑制细胞转染.     

比格犬ERβ1293基因真核载体的构建及其在HEK293T细胞中的表达和定位

目的 观察比格犬Myc 标签ERβ1293重组真核表达载体在HEK293T细胞中的表达及定位.方法 以pEGFP-N1-ERβ1293重组真核表达载体为模板,PCR保真酶扩增得到ERβ1293基因编码区全长.Myc标签ERβ1293重组真核载体瞬时转染HEK293T细胞,运用蛋白质印迹技术（Western blotting）和间接免疫荧光技术（indirect immunofluorescence,IF）鉴定pcDNA3.1-Myc-ERβ1293在HEK293T细胞中的表达和定位情况.结果 成功构建pcDNA3.1-Myc-ERβ1293重组真核表达载体,转染至HEK293T细胞中.Western blotting检测有蛋白条带表达,共聚焦显微镜下观察IF处理后的转染细胞,荧光定位于细胞质.结论 前期实验得到比格犬ERβ剪切异构体ERβ1293编码区序列,缺失第四外显子,导致其与配体结合能力减弱或消失,因此目的 基因编码蛋白定位在细胞中发生变化.     

Investigation of relationship between EBNA-1 expression level and specific foreign protein productivity in transient gene expression of HEK293 cells

In an attempt to determine the relationship between the Epstein–Barr virus nuclear antigen-1 (EBNA-1) expression level and specific foreign protein productivity (q_p), EBNA-1-amplifed HEK293 cells, which achieved a higher EBNA-1 expression level than that achieved by HEK293E cells, were established using dihydrofolate reductase (dhfr)-mediated gene amplification. Compared with a control culture in a null pool, Fc-fusion protein production by transient transfection in the EBNA-1-amplified pool showed a significant improvement. q_p was linearly correlated with the EBNA-1 expression level in the transient transfection of EBNA-1-amplified clones, as indicated by the correlation coefficient (R² = 0.7407). The Fc-fusion protein production and q_p in a transient gene expression-based culture with EBNA-1-amplified HEK293 cells, E-amp-68, were approximately 2.0 and 3.2 times, respectively, higher than those in a culture with HEK293E cells. The increase in q_p by EBNA-1 amplification mainly resulted from an enhancement in the amount of replicated DNA and level of mRNA expression but not an improved transfection efficiency. Taken together, it was found that EBNA-1 amplification could improve the therapeutic protein production in an HEK293 cell-based transient gene expression system.     

Transfection of partially purified plasmid DNA for high level transient protein expression in HEK293-EBNA cells

One of the major constraints to performing large-scale transfections of cultured mammalian cells for the transient expression of recombinant proteins is the production of large quantities of purified plasmid DNA. In this report partially purified plasmid DNA was prepared by a method that combines alkaline lysis of E. coli with standard precipitation techniques. The efficiency of calcium phosphate-DNA co-precipitate formation with crude DNA was similar to that observed for pure DNA, but precipitate formed with crude DNA also contained RNA. The transfection of adherent and suspension-adapted HEK293-EBNA cells with partially purified pEGFPN1 resulted in levels of transient GFP expression equivalent to those achieved with pure DNA. In addition, the co-transfection of 1-200 ml cultures of suspension-adapted HEK293-EBNA cells with two different plasmids encoding the heavy and light chain genes of anti-human RhD IgG1, respectively, yielded similar IgG titers with pure and partially purified plasmid DNA. Finally, it was observed that suspension-adapted cells were more tolerant to the presence of RNA in the plasmid preparations than were adherent cells. These findings are relevant to the field of DNA transfection, including applications ranging from high-throughput screening to large-scale transient protein expression.     

人P2X7真核表达载体的构建及稳定转染细胞株的建立

目的：构建人P2X7基因的真核表达载体,并通过转染获得稳定表达P2X7分子的HEK293细胞株。方法：以人脑组织P2X7cDNA为模板扩增出P2X7基因,插入到真核表达载体pEGFP-N1中,构建重组质粒pEGFP-N1/P2X7。用X-fect试剂盒将重组质粒转染HEK293细胞,通过G418辅助荧光筛选建立稳定表达P2X7-EGFP细胞株。经流式细胞仪、Western blot和激光共聚焦显微镜检测,了解人P2X7在HEK293细胞中的表达水平及细胞内定位。结果：重组质粒pEGFP-N1/P2X7构建正确,建立了稳定表达人P2X7的HEK293细胞系。Western blot和流式细胞仪检测证实,P2X7在HEK293细胞系中成功表达,激光共聚焦显微镜检测显示P2X7-EGFP定位在细胞膜上。结论：重组载体pEGFP-N1/P2X7构建成功并建立了稳定表达人P2X7的HEK293细胞系,为进一步研究P2X7离子通道结构和功能奠定基础。     

三重表达肺结核DNA疫苗在细胞水平的检测

目的 检测共表达siRNA、抗原基因与hIL-12的新型肺结核DNA疫苗在人胚肾293细胞中表达。方法 在已构建含有靶向抗调亡基因Mcl-1L的siRNA、结核分枝杆菌抗原基因Ag85B-ESAT6 (PVAE)、hIL-12的新型肺结核DNA疫苗pVAX-siRNA-PVAE-IL-12基础之上,将抗原基因与增强型绿色荧光蛋白（EGFP）基因融合,得到真核表达重组质粒pVAX1-siRNA-PVAE-EGFP-hIL12。并将siRNA单元用靶向EGFP基因的siEGFP代替,得到pVAX1-siEGFP-PVAE-EGFP-hIL12重组表达载体。用重组质粒转染人胚肾细胞293,分别观察融合抗原基因与siEGFP的表达。以ELISA测定培养细胞上清中hIL-12的表达。结果 经酶切鉴定和测序证实肺结核DNA疫苗改造成功。转染细胞中检测到绿色荧光,证实抗原表达。对照组检测到siEGFP的表达。转染48 h后检测出细胞上清中hIL-12的量为1571.63 pg/mL;72 h后检测出细胞上清中hIL-12的量为2392.25pg/mL。结论 已构建的肺结核质粒DNA疫苗能在真核细胞中有效表达siRNA、抗原基因与hIL-12。为进一步研究该DNA疫苗抗肺结核的免疫治疗和基因治疗效果打下基础。     

牙龈卟啉单胞菌HA2基因和白细胞介素IL-15基因重组质粒的构建

构建抗牙龈卟啉单胞菌的牙周炎基因疫苗p VAX1-HA2、pVAX1-HA2/IL-15,体外检测其在293T细胞的表达。以HA2基因(牙龈卟啉单胞菌牙龈素—血凝素基因编码区的核心功能区)为目的基因与IL-15基因为免疫佐剂构建真核表达质粒,用Lip2000介导瞬时转染293T细胞,RT-PCR检测目的基因mRNA水平及酶联免疫吸附试验检测IL-15蛋白表达水平。重组质粒p VAX1-HA2、pVAX1-HA2/IL-15经酶切及DNA测序鉴定构建正确,转染的293T细胞能够检测到目的基因的表达,也可以检测到IL-15蛋白的表达。说明我们成功构建了真核共表达质粒pVAX1-HA2和p VAX1-HA2/IL-15,为下一步研制抗牙龈卟啉单胞菌DNA疫苗奠定了基础。     

Development of a Chinese hamster ovary cell line for recombinant adenovirus-mediated gene expression

Recombinant human adenovirus (rhAd) has been used extensively for functional protein expression in mammalian cells including those of human and nonhuman origin. High-level protein production by rhAd vectors is expected in their permissive host cells, such as the human embryonic kidney 293 (HEK293) cell line. This is attributed primarily to the permissiveness of HEK293 to rhAd infection and their ability to support viral DNA replication by providing the missing El proteins. However, the HEK293 cells tend to suffer from cytopathic effect (CPE) as a result of virus replication. Under these circumstances, the host cell function is compromised and the culture viability will be reduced. Consequently, newly synthesized polypeptides may not be processed properly at posttranslational levels. Therefore, the usefulness of HEK293 cells for the expression of complex targets such as secreted proteins could be limited. In the search for a more robust cell line as a production host for rhAd expression vectors, a series of screening experiments was performed to isolate clones from Chinese hamster ovary-K1 (CHO-K1) cells. First, multiple rounds of infection of CHO-K1 cells were performed utilizing an rhAd expressing GFP. After each cycle of infection, a small population of CHO cells with high GFP levels was enriched by FACS. Second, individual clones more permissive to human adenovirus infection were isolated from the highly enriched subpopulation by serial dilution. A single clone, designated CHO-K1-C5, was found to be particularly permissive to rhAd infection than the parental pool and has served as a production host in the successful expression of several secreted proteins.     

G418抗性HEK293细胞的培育

目的　培育具有G418抗性的HEK2 93细胞 ,用于建立猪内源性反转录病毒感染人HEK2 93细胞的模型。方法　通过脂质体转染的方法 ,将含有neo基因的质粒pIRESneo导入HEK2 93细胞中 ,利用G418的选择特性 ,对转染细胞进行压力筛选 ,并对其进行了PCR鉴定。结果　经 6 0 0 μg ml的G418压力筛选后 ,获得了抗性细胞克隆。抗性细胞的形态和生长速度与筛选前细胞没有差异 ,特异性核苷酸引物检测抗性细胞基因组DNA ,可以扩增出对应的核苷酸片段。结论　成功地培育了G418抗性HEK2 93细胞 ,为建立猪内源性反转录病毒感染人HEK2 93细胞的模型奠定了基础。     

Transient gene expression in mammalian cells grown in serum-free suspension culture

In order to establish a simple and scaleable transfection system we have used the cationic polymer polyethylenimine (PEI) to study transient transfection in HEK293 and 293(EBNA) cells grown in serum-free suspension culture. The transfection complexes were made directly within the cell culture by consecutively adding plasmid and PEI (direct method). Alternatively, the DNA-PEI transfection complexes were prepared in fresh medium (1/10 culture volume) and then added to the cells (indirect method). The results of this study clearly show that the ratio of PEI nitrogen to DNA phosphate is very important for high expression levels. The precise ratio is dependent on the DNA concentration. For example, using 1 μg/ml DNA by the indirect method, the ratio of optimal PEI:DNA was about 10–13:1. However, the ratio increases to 33:1 for 0.1–0.2 μg/ml DNA. By testing several different molecular weights of the polycationic polymer we could show that the highest transfection efficiency was obtained with the PEI 25 kDa. Using PEI 25 kDa the indirect method is superior to the direct addition because significantly lower DNA concentrations are needed. The expression levels of the soluble human TNF receptor p55 are even higher at low DNA compared to 1 μg/ml plasmid. The EBV-based pREP vectors gave better transient gene expression when used in 293(EBNA) cells compared to HEK293 cells in suspension culture. No differences in expression levels in the two cell lines were observed when the pC1 (CMV)-TNFR was used. In conclusion, PEI is a low-toxic transfection agent which provides high levels of transient gene expression in 293(EBNA) cells grown in serum-free suspension culture. This system allows highly reproducible, cost-effective production of milligram amounts of recombinant proteins in 2–5 l spinner culture scale within 3–5 days. Fermentor scale experiments, however, are less efficient because the PEI-mediated transient tranfection is inhibited by conditioned medium. This revised version was published online in July 2006 with corrections to the Cover Date.