小鼠pEGFP-Hoxa11真核表达载体的构建及表达

目的 构建和鉴定Hoxa11和EGFP双基因共表达真核载体.方法 采用DNA重组技术,将目的 基因Hoxa11克隆至含有报告基因EGFP的pEGFP-N1真核表达载体中,构建的真核表达载体pEGFP-Hoxa11经PCR,双酶切及基因测序鉴定;转染至CHO细胞,荧光显微镜下观察重组质粒的表达,提取细胞蛋白Western印迹检测蛋白表达.结果 pEGFP-Hoxa11重组质粒构建成功.构建的真核表达载体pEGFP-Hoxa11能在CHO细胞中有效表达.结论 成功构建了共表达Hoxa11和EGFP的真核表达载体,并能在CHO细胞中有效表达.为进一步研究Hoxa11的功能提供实验基础.     

TurboFect介导骨形态发生蛋白2 转染CHO 细胞的研究

目的:构建真核表达载体p IRES-EGFP-BMP-2,通过Turbo Fect转染得到表达BMP-2蛋白的CHO细胞系。方法:利用逆转录PCR方法扩增获得人的BMP-2基因c DNA,克隆入p MD18-T载体,经PCR、酶切和基因测序分析等方法鉴定重组质粒;将BMP-2连入p IRES-EGFP真核表达载体中,经限制性酶切和PCR扩增鉴定重组质粒。以壳聚糖和Turbo Fect分别作为基因载体转染CHO细胞,荧光显微镜检测分析转染结果;G418筛选富集转染阳性细胞。结果:成功的克隆得到了BMP-2基因,酶切鉴定成功构建了p IRES-EGFP-BMP-2质粒。与壳聚糖组相比,Turbo Fect用量为1:1时,细胞阳性率为(31.92±1.31)%,高于壳聚糖的细胞阳性率(6.33±1.53)%。目的基因与Turbo Fect比例为1:2时转染效率为(42.90±1.10)%高于1:1的(28.59±2.38)%和1:3的(37.52±2.14)%。细胞密度调节到5×103 cells/cm2阳性细胞率可达到(44.43±3.23)%。荧光检测可见荧光阳性细胞得到稳定传代。Western Blot检测可见BMP-2蛋白表达。结论:Turbo Fect成功的介导了p IRES-EGFP-BMP-2载体转染CHO细胞,建立了稳定表达BMP-2和EGFP的CHO细胞株。     

CDK2蛋白质分子结构与其入核转运过程关系的初步分析

应用重组技术构建野生型及缺失型CDK2基因的真核表达载体,分别使野生型及缺失型(2DK2蛋白与增强型绿色荧光蛋白(Enhanced-green Fluorescent Protein,EGFP)形成融合蛋白。通过脂质体介导的方法将载体转染人宫颈癌细胞系HeLa和中华仓鼠卵巢细胞系CHO,经过细胞周期同步化处理后于荧光显微镜下观察EGFP的亚细胞定位以示踪野生型及缺失型CDK2基因的表达。结果表明,野生型CDK2基因的表达产物定位于细胞核．而两种缺失型CDK2基因分别编码的CDK2蛋白N-端1～201及98～298多肽均主要定位于细胞质。以上结果提示,CDK2蛋白序列中不含有与核定位直接相关的信号,其入核过程可能是由其N-端1～97及202～298多肽范围内的部分氨基酸共同形成高级结构,并依赖此高级结构与其他含有入核信号的蛋白形成复合物,从而被带动进入细胞核的     

水稻基因APRT的克隆及其与温敏核雄性不育的关系

在拟南芥中腺嘌呤磷酸核糖转移酶基因(APRT)突变导致植株雄性不育.本文首次报道从水稻(Oryza sativa subsp.indica)中克隆了基因APRT(GenBank登录号AY238894),并将其定位于水稻第4染色体的一个BAC克隆(AL606604)的58 000 bp至63 000 bp区域.该基因长4 220 bp(起始密码子至终止密码子),含7个外显子、6个内含子,编码的APRT蛋白长212个氨基酸残基,与其他物种来源的APRT序列存在很高的同源性.与大麦、小麦、拟南芥1型及其2型的该蛋白同源性分别为54.9%、54.9%、49.6%和59.5%.经保守结构域搜索发现该蛋白中存在APRT催化结构域.从DNA、mRNA两个水平分析了该基因与水稻温敏核雄性不育(TGMS)的关系,结果表明:受温度诱导,水稻"安农S-1"APRT基因的表达变化可能与温敏核雄性不育表现型具相关性.     

携带EGFP基因的戊型肝炎病毒重组质粒的构建及其感染性的验证

为了构建携带增强型绿色荧光蛋白(Enhanced green fluorescent protein,EGFP)基因的戊型肝炎病毒(Hepatitis E virus,HEV)重组质粒,转染人肺癌细胞A549细胞验证其感染性,PCR法分两段扩增HEV全基因组序列和EGFP基因序列,将EGFP报告基因插入到HEV ORF2基因下游,并克隆到体外转录表达载体pGEM-7Zf(+)上。然后利用脂质体转染法将重组质粒转入A549细胞,24h后在荧光显微镜下观察EGFP的表达;转染72h后,利用免疫荧光法检测HEV ORF2蛋白的表达。转染7d后将发生病变的A549细胞收集作为接种物,接种A549细胞验证携带EGFP的HEV-EGFP重组病毒的感染性。结果显示经酶切和测序鉴定携带EGFP的HEV重组表达质粒pGEM-HEV-EGFP构建成功;EGFP基因与HEV在A549细胞中可融合表达;携带EGFP的HEV重组表达质粒转染A549细胞7d后出现病变,并且连续传代3代仍具有感染性。本研究成功构建了携带EGFP的HEV全基因组重组质粒pGEM-HEV-EGFP,并成功感染A549细胞,为进一步研究HEV的复制机制及致病机理奠定基础。     

CHO/dhfr-细胞定点整合高效表达系统的建立

为了克服随机整合建立高表达细胞株时“位置效应”所带来的不可预知的后果,我们尝试建立基于定点整合的CHO高效表达系统。首先设计一个新的高效筛选载体pMCEscan。该载体含有报告基因(k2tPA)、扩增基因(dhfr)、重组酶识别序列(FRT)及筛选基因(neo),且neo基因的表达经过系统的弱化,确保能够对基因组中的整合位点进行大规模的高效筛选。然后利用该载体转染CHO/dhfr-细胞并进行大规模筛选以获得足够多的阳性克隆,并对阳性克隆进行系统分析,筛选出报告基因表达水平高、单拷贝且扩增效果好的克隆,此克隆被认为筛选载体整合入CHO细胞基因组中转录热点(Hotspot)区域,从而获得了能够实现外源基因在基因组中定点整合和有效表达的CHO/dhfr-细胞系。随后利用位点特异性重组系统(FLP-FRT)将外源基因定点整合到Hotspot区域,以实现外源基因在CHO细胞基因组中的定点整合及高效表达。并利用该细胞系实现了k2tPA的高表达,表达量达到17.1μg/106cell.24h。该研究致力于CHO细胞基因组中高表达位点的寻找和确认,建立基于定点整合的哺乳动物细胞高效表达系统。     

新疆南部和田羊、卡拉库尔羊、多浪羊MSTN基因的真核表达

旨在构建新疆南部4个地方品种(品系)绵羊,即平原型和田羊(HP)、山区型和田羊(HS)、卡拉库尔羊(KL)和多浪羊(DL)的肌生成抑制素(myostatin,MSTN)基因与增强型绿色荧光蛋白(EGFP)的融合表达质粒并在真核细胞中表达。从4种绵羊骨骼肌中提取总RNA,逆转录获得c DNA,PCR扩增MSTN后与p MD18-T载体连接构建重组质粒并测序分析,然后将MSTN(HP、HS、DL和KL)基因插入到融合表达载体p EGFP-N1中,构建真核融合表达重组质粒p EGFP-N1-MSTN,在细胞铺满80%时用脂质体法转染到CHO中,观察EGFP与MSTN蛋白在CHO细胞内融合表达的绿色荧光。结果显示,平原型和田羊、山区型和田羊、卡拉库尔羊和多浪羊MSTN的ORF序列都是1 125 bp(不含终止密码子),编码375个氨基酸;与Gen Bank中MSTN序列比较,与田羊(HS、HP)没有差异;卡拉库尔羊有2个碱基差异,造成2个氨基酸变异;多浪羊有6个碱基的差异,造成4个氨基酸变异。成功构建EFGP和MSTN共表达重组质粒并在真核细胞CHO中得以表达。     

人CD46启动子真核表达载体的构建

为了构建人CD46（hCD46）启动子指导目的基因表达的真核表达载体,提取HeLa细胞基因组DNA,用PCR扩增出hCD46基因的启动子区域,序列分析结果表明其与GenBank中hCD46基因5’端某片段的同源性为99.9％。用此启动子替换pcDNA3EGFP中的CMV启动子,并在hCD46启动子和EGFP基因之间插入兔β-球蛋白基因第二内含子（RGI）,得到的重组表达载体转染CHO和SP2/0两种鼠源细胞,流式细胞术检测表明CHO细胞EGFP的表达量高于SP2/0细胞,表达特性与人体CD46相似;RGI可以增强EGFP的表达量,但不改变其表达的组织特异性,提示克隆的hCD46启动子可以用于研制模拟人体CD46基因表达特性的转基因小鼠。     

抗病毒基因MxA真核表达载体的构建及在鸡细胞中的表达

将人抗病毒蛋白基因MxA与携带增强型绿色荧光蛋白(EGFP)基因的真核表达质粒重组后构建MxA基因真核表达载体pEGFP-C1-MxA.经PCR和酶切方法鉴定后,重组质粒在脂质体介导下转染鸡成纤维细胞和睾丸组织原代细胞,通过荧光观察,RT-PCR及细胞免疫组化检测目的基因的表达.结果表明,MxA基因片段已经被克隆到pEGFP-C1表达载体,成功构建了MxA基因真核表达载体pEGFP-C1-MxA.经该重组质粒转染后的鸡细胞的胞质中呈现颗粒状分布的绿色荧光,RT-PCR扩增出EGFP和MxA基因的特异性片断,免疫组化结果显示EGFP报告基因在细胞内的阳性表达,并表现出MxA的表达特征,间接证明了MxA可在鸡细胞中表达.MxA基因真核表达载体的成功构建以及在鸡细胞中的表达为进一步研究MxA基因在抗禽病毒性疾病中的应用打下了基础.     

基于CRISPR/Cas9基因编辑技术的EGFP基因定点整合表达

目的:利用CRISPR/Cas9基因编辑技术,实现EGFP基因在CHO细胞ACTB基因座位置定点整合和表达,建立基于CRISPR/Cas9技术的外源基因定点整合和表达技术。方法:根据CHO细胞β-actin(ACTB)基因起始密码子区基因序列,设计相应CRISPR/Cas9系统,同时构建含有ACTB同源臂和EGFP基因的同源供体载体(donor vector),通过脂质体转染法同时转染CRISPR/Cas9和供体载体,流式分选EGFP阳性细胞,分析基因编辑技术在EGFP基因定点整合和表达方面的可行性。结果:构建了能有效切割CHO细胞ACTB基因的CRISPR/Cas9系统,筛选到EGFP定点整合至ACTB基因座并有效表达的细胞,ACTB基因缺失后由于γ-actin代偿性表达增强,ACTB缺失细胞形态和生长未受影响。结论:单纯依靠基因编辑技术可以实现1 kb以内的基因同源置换,但效率较低,如实现更大片段的外源基因置换,需借助其它实验技术。     

Effect of amplification ofdhfr andlac Z genes on growth and β-galactosidase expression in suspension cultures of recombinant CHO cells

Studies were conducted to characterize the effect of gene amplification and foreign gene expression on recombinant CHO cell growth. Chinese hamster ovary (CHO) cells were transfected with an expression vector containing the gene for dihydrofolate reductase (dhfr) and the gene for human β-interferon (β-IFN) or thelac Z gene which codes for β-galactosidase (β-gal). The recombinant genes in these CHO cells were amplified stepwise by growth in 0, 10⁻⁷, and 10⁻⁶ M methotrexate (MTX), and the β-gal expressing cells were adapted to suspension culture. Flow cytometric methods (FCM) were used to measure the distribution of amplifieddhfr gene content and foreign β-gal gene expression in the cell populations. A biochemical assay for β-gal was also used. Beta-gal expression was found to increase with increasing gene amplification. The growth rate of recombinant CHO cells at 10⁻⁷ M MTX was found to be 20% lower than that of recombinant CHO cells in MTX-free medium, and the cell growth rate at 10⁻⁶ M MTX was 20% lower than that of recombinant CHO cells at 10⁻⁷ M MTX. There was no effect of 10⁻⁵ M MTX on the growth of CHO-DG44 (dhfr-) cells. The reduction of growth rate in recombinant CHO cells is therefore thought to be mainly due to the effect ofdhfr and foreign gene amplification and increased β-galactosidase expression.     

Kozak序列(+4G)对携带EGFP标签的人淀粉样前体蛋白751在CHO细胞中表达的影响

目的:观察Kozak序列(+4G)对稳定转染的人淀粉样前体蛋白(hAPP751)-EGFP融合真核表达载体在CHO细胞中表达的影响,为APP的水解代谢研究提供细胞模型。方法:分别将含Kozak序列(+4G)和不含Kozak序列的hAPP751全长基因片段亚克隆入pEGFP-N1表达载体,得到pEGFP-hAPP751(+4G)和pEGFP-hAPP751重组质粒,转染CHO细胞,通过G418筛选稳定转染细胞株,再用倒置荧光显微镜挑取绿色荧光强的细胞进行亚克隆,并观察融合蛋白的表达强度和细胞定位,最后用EGFP抗体通过Western印迹检测融合蛋白。结果:PCR、酶切和测序证明将含Kozak序列(+4G)和不含Kozak序列的hAPP751全长基因片段分别连入了真核表达载体pEGFP-N1中;荧光显微镜下观察pEGFP-hAPP751(+4G)稳定转染细胞的细胞膜和细胞质产生较强的绿色荧光,其中在细胞质中成不均匀颗粒状分布,Western印迹检测到相对分子质量约156 000的融合表达蛋白,与预期相符;pEGFP-hAPP751转染细胞,其绿色荧光十分微弱且在整个细胞均匀分布,Western印迹检测到相对分子质量约26 000的EGFP,但检测不到预期的hAPP751-EGFP融合表达蛋白。结论:Kozak序列(+4G)可以明显促进hAPP751的表达,获得稳定转染且高水平融合表达hAPP751-EGFP的细胞株。     

Reconstitution of an episomal mouse aprt gene as a consequence of recombination.

Summary When a functional murine adenine phosphoribosyltransferase (aprt) gene linked to bovine papilloma virus (BPV) DNA is transfected into Aprt^– L cells, the cells are rendered Aprt^– and the aprt gene persists as an episome.Cotransfection with two BPV vectors, one containing the 5 half of the aprt gene and the other the 3 half of the gene, that share about 300 by of common sequence in intron 2, produces Aprt⁺ cells with functional aprt as an episome. Southern blot analysis of low molecular weight DNA derived from Hirt extracts revealed the regeneration of a diagnostic Smal fragment, consistent with establishment of an episome with functional aprt that was reconstituted as a consequence of recombination. To establish cells with an episomal target for recombination, BPV vectors containing a G418 resistance marker and either the 5 half or 3 half of aprt were transfected into Aprt^– L cells. Stably transfected cells, selected by their growth in G418, were in turn transfected with DNA containing the other half of the aprt gene. Following selection of Aprt⁺ cells, Southern blot and polymerase chain reaction (PCR) analysis of low molecular weight DNA confirmed the presence of a complete episomal aprt gene. The region of DNA shared by the episomal aprt fragment and the transfected aprt half was sequenced after PCR amplification of the reconstituted, episomal gene and was found to be wild type. The region of overlap that serves as the substrate for recombination lies entirely within an intron and can, therefore, tolerate nucleotide substitutions and deletions. The absence of such errors in the sequences examined is consistent with recombination events that are not error prone.     

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。     

Mutagenicity testing in mammalian cells: I. Derivation of a chinese hamster ovary cell line heterozygous for the adenine phosphoribosyltransferase and thymidine kinase loci

As a first step in the development of a multiple-marker, mammalian cell mutagenesis assay system, we have isolated a Chinese hamster ovary (CHO) cell line that is heterozygous for both the adenine phosphoribosyltransferase (aprt) and thymidine kinase (tk) loci. Presumptive aprt^+/? heterozygotes with intermediate levels of APRT activity were selected from unmutagenized CHO cell populations on the basis of resistance to low concentrations of the adenine analog, 8-azaadenine. A functional aprt^+/? heterozygote with ～50% wild-type APRT activity was subsequently used to derive sublines that were also heterozygous for the tk locus. Biochemical and genetic characterization of one such subline, CHO-AT3-2, indicated that it was indeed heterozygous at both the aprt and tk loci. CHO-AT3-2 cells permitted single-step selection of mutants resistant to 8-azaadenine or 5-fluorodeoxyuridine, allowing quantitation and direct comparison of mutation induction at the autosomal aprt or tk loci, as well as in the gene involved in ouabain resistance or at the X-linked, hypoxanthine-guanine phosphoribosyltransferase (hgprt) locus. Significant dose-dependent increases in mutation frequency were observed for all 4 genetic markers after treatment of CHO-AT3-2 cells with ethyl methanesulfonate.     

人组织激肽释放酶基因在哺乳动物细胞中的表达

克隆人胰腺组织激肽释放酶基因 (hKK) ,构建融合荧光蛋白基因的真核表达载体 ,在CHO细胞中表达 ,为开发激肽释放酶基因工程产品以及开展基因治疗高血压研究奠定了基础。提取人胰腺组织总RNA后 ,RT PCR扩增KK ,构建中间载体KSKK。从KSKK中切出激肽释放酶基因 ,插入真核表达载体pEGFP C2 ,构建出激肽释放酶带有荧光蛋白报告基因的表达载体pEGC KK ,测序分析后转染CHO细胞 ,荧光显微镜观察激肽释放酶基因表达。并进行SDS PAGE及Westernblot分析。成功克隆激肽释放酶基因 ,并在CHO细胞获得表达 ,克隆的人组织激肽释放酶基因可用于激肽释放酶基因工程产品开发以及基因治疗研究。     

Identification of a potent MAR element from the human genome and assessment of its activity in stably transfected CHO cells

Low‐level and unstable transgene expression are common issues using the CHO cell expression system. Matrix attachment regions (MARs) enhance transgene expression levels, but additional research is needed to improve their function and to determine their mechanism of action. MAR‐6 from CHO chromosomes actively mediates high and consistent gene expression. In this study, we compared the effects of two new MARs and MAR‐6 on transgene expression in recombinant CHO cells and found one potent MAR element that can significantly increase transgene expression. Two MARs, including the human CSP‐B MAR element and DHFR intron MAR element from CHO cells, were cloned and inserted downstream of the poly(A) site in a eukaryotic vector. The constructs were transfected into CHO cells, and the expression levels and stability of eGFP were detected by flow cytometry. The three MAR sequences can be ranked in terms of overall eGFP expression, in decreasing order, as follows: human CSP‐B, DHFR intron MAR element and MAR‐6. Additionally, as expected, the three MAR‐containing vectors showed higher transfection efficiencies and transient transgene expression in comparison with those of the non‐MAR‐containing vector. Bioinformatics analysis indicated that the NFAT and VIBP elements within MAR sequences may contribute to the enhancement of eGFP expression. In conclusion, the human CSP‐B MAR element can improve transgene expression and its effects may be related to the NFAT and VIBP elements.     

腺病毒载体介导PDX-1在骨髓间充质干细胞中的表达

为研究PDX-1基因在骨髓间充质干细胞中的表达情况及生物学功能的发挥,构建了含PDX-1基因的重组腺病毒载体. 酶切PDX-1基因并连入穿梭质粒pAdTrack-CMV.用电穿孔法使穿梭质粒pAdTrack-CMV-PDX-1与病毒骨架质粒pAdEasy-1在大肠杆菌BJ5183中同源重组.利用脂质体介导重组腺病毒载体转染293细胞,包装出完整的腺病毒.分离、培养、扩增骨髓间充质干细胞.用重组腺病毒感染间充质干细胞.用荧光显微镜、RT-PCR、免疫荧光染色等方法检测PDX-1、胰岛素基因及蛋白质的表达,用放射免疫分析法检测转基因细胞分泌胰岛素情况.结果表明:通过测序、PCR、酶切等鉴定PDX-1基因已正确插入穿梭质粒中,并与病毒骨架质粒重组.重组腺病毒滴度为6.3×10⁷ PFU/ml.通过荧光显微镜观察证实重组腺病毒可高效感染骨髓间充质干细胞,经RT-PCR、免疫荧光染色证实转染pAd-PDX-1后培养7天的细胞中有PDX-1及胰岛素基因的表达.这些转基因的细胞向胞外分泌的胰岛素量为(15.21±3.50) mIU/L.