PCR—SSCP与测序技术相结合检测小麦耐盐突变体

根据位于小麦第四同源群上与耐盐有关的gf-2.8基因的编码区序列设计1对引物,分别以两个耐盐突变体及其亲本的总DNA为模板进行PCR扩增,在5个供试材料中均扩增出1条约685bp的目的条带,SSCP电泳显示突变体974915与其他供试材料之间存在差异。测序表明冀麦24和其耐盐突变体8901-17的扩增产物序列与gf-2.8基因的发表序列相同,这表明突变体8901-17的突变位点不在该基因上,而另一耐盐突变体974915的序列中则至少存在2个单碱基突变,有一处突变导致了氨基酸的变化,该突变位点位于gf-2.8基因的保守区域内。     

改进的多片段重叠延伸PCR制作基因多位点突变

为在研究工作中提高制作目标基因多位点突变体的效率,对常规重叠延伸PCR进行适当改进:对于相距较近的两个突变位点,只需设计一对突变引物各自涵盖其中一个位点即可一次突变;对于相距较远的两个位点,可以采用三片段重叠延伸PCR的办法解决;两者结合则可一次性突变多个位点。以制作RBCT的6位点突变体PSM6为例,利用上述策略,设计两对突变引物;采用OE-PCR法,第一轮PCR扩增出三个片段,第二轮PCR同时利用三片段重叠延伸产物作为模板扩增出目标基因突变体,再按常规分子克隆方法将其连入质粒载体。经测序检测,发现得到了预期的目标基因多位点突变体。因此,采用灵活的引物设计策略,结合多片段重叠延伸PCR即可一次性制作基因的多位点突变体,此方案可解决研究工作中大多数多位点突变问题。     

DNA模板中发卡结构对定量PCR扩增的影响

[目的]探究模板引物结合区发卡对定量PCR的影响及优化方法。[方法]用分布连接法构建一系列在模板引物结合区含环大小为5~60 nt,茎长9 bp的DNA模板,考察发卡环部大小、茎干区GC含量对q PCR扩增效率的影响,再针对引物浓度、引物长度及退火温度来优化含发卡结构DNA模板的扩增。[结果]环区为5~40 nt时,其Ct值比对照组高1.3~4.2,对q PCR的抑制作用与环大小成负相关;茎长9 bp发卡结构当GC含量达3 bp以上时会对定量扩增产生明显抑制作用;增加引物长度、提高引物浓度和退火温度可提高发卡模板的扩增效率。[结论]模板引物结合区环大小在40 nt以内,茎长达9 bp的发卡结构对q PCR扩增会产生抑制作用,通过增加引物长度、提高引物浓度和退火温度可缓解此类抑制。     

DNA甲基化敏感位点(CCGG)文库克隆载体的构建

目的:旨在建立一种简便易行的DNA甲基化文库构建载体,用于筛选细胞中具有甲基化敏感性CCGG位点的DNA片段。方法:根据HpaⅡ/MspⅠ酶切体系对甲基化酶敏感性不同的特点,通过在PCR引物中添加CCGG酶切位点的方法,将扩增得到的目的片段连接到无CpG甲基化的质粒载体上。结果:成功构建了含双CCGG位点的pCpGfree-HpaⅡ/MspⅠ-1质粒载体。结论:所构建的pCpGfree-HpaⅡ/MspⅠ-1质粒载体CCGG位点未发生甲基化,故可以用于构建含有甲基化CCGG序列的DNA甲基化文库。     

Flag标签MORC2-677丝氨酸位点突变载体构建及表达

构建Flag标签pcDNA3.1-MORC2的677丝氨酸位点突变重组质粒并完成在SGC-7901细胞中表达,更好地研究677丝氨酸位点所发生的功能.首先,构建含有KpnⅠ和XhoⅠ酶切位点Flag标签的pcDNA3.1空载体;再以含有KpnⅠ和XhoⅠ酶切位点的pcDNA3.1A-MORC2-WT野生型质粒为模板,在S677突变位点两侧设计重叠突变引物,进行三轮重叠延伸PCR完成定点突变,获得MORC2全长编码序列的S677位点的定点突变体载体(pcDNA3.1A-MORC2-S677A/S677E);再通过KpnⅠ和XhoⅠ酶切把pcDNA3.1A-MORC2-WT/S677A/S677E各载体定向克隆到已构建好的pcDNA3.1-Flag空载体中,酶切鉴定及测序正确后,转染到SGC-7901细胞中,利用Flag–标签抗体,Western blot检测其各突变载体的表达.成功构建了人Flag标签MORC2全长编码序列S677位点突变体真核表达载体并在SGC-7901细胞中获得带Flag标签融合蛋白表达产物,为进一步研究MORC2的功能奠定了基础.     

优化重叠PCR法进行单链抗体基因扩增和点突变

利用重叠PCR技术扩增单链抗体基因或位点突变是抗体文库构建或稳定表达的关键和难点,国内外文献未见其方法学的系统报道.以不同VH、VL和Linker基因为拼接模板进行重叠PCR,针对影响重叠PCR扩增的拼接类型,引物设计,反应条件等进行优化.结果表明两段重叠连接比三段更容易实现,且扩增效果好;引物的互补序列长度一般应大于15 bp,且在18～24 bp 时扩增效果最好;退火温度在52～60℃,Mg2+浓度在1.5～2.5 mM时对拼接的效果影响较小;直接或间接使用拼接模板均可以实现重叠PCR的扩增.利用优化策略,首次构建了抗除虫菊酯的scFv基因文库并引入抗XAC糖蛋白scFv基因的点突变,为除虫菊酯抗体文库构建和抗XAC重组抗体的稳定表达奠定了基础.     

利用微卫星标记分析新疆老面酵头中酿酒酵母遗传多样性

本研究对分离自新疆不同地区老面酵头中433株酿酒酵母进行微卫星标记技术分析,研究新疆老面酵头中酿酒酵母遗传多样性。结果表明,新疆老面酵头中酿酒酵母观测等位基因数为1.396 6–1.8599,平均有效等位基因数为1.0463–1.1082,基因多样性指数为0.0356–0.0850,Shannon指数为0.1583–0.0682,其中,南疆酿酒酵母遗传多样性指数高于北疆。新疆各地域居群具有明显简单重复序列(simple sequence repeat, SSR)基因特征,主要表现为7个类群(XJⅠ–XJⅦ),在6个微卫星位点上具有显著的基因型差异,并在120–160 bp和250–300 bp扩增位点多样性均明显少于参考菌株葡萄酒酵母EC1118。居群XJⅢ、XJⅣ、XJⅥ、XJⅦ在250–400bp扩增位点少于XJⅠ、 XJⅡ、 XJⅤ;XJⅣ、 XJⅤ、XJⅦ丰度明显大于XJⅠ、 XJⅡ、XJⅢ、 XJⅥ和EC1118。XJⅠ、XJⅤ、XJⅥ扩增位点在300–400 bp少于XJⅡ、XJⅢ、XJⅣ、XJⅦ;XJⅠ、XJⅡ丰度比XJⅢ、XJⅣ、XJⅤ、XJⅥ、XJⅦ和EC1118低,...     

pcDNA3.1(-)-Bcr-Abl及pcDNA 3.1(-)-Bcr-Abl T3151突变质粒真核表达载体的构建

目的:将Bcr-Abl及Bcr-Abl T3151突变克隆入pcDNA3.1(-)真核表达载体,为研究靶向降解受体型酪氨酸激酶BCR-Abl,抑制肿瘤细胞生长提供研究基础.方法:pcDNA3.1 (-)-Bcr-Abl质粒构建:分别设计引物,通过分段PCR将BCR-ABL克隆入pcDNA3.1(-).首先通过PCR扩增出Bcr-a片段,将其克隆入pcDNA3.1(-)的NheⅠ/XhoⅠ之间;接着将PCR扩增出的Abl-c片段克隆入KpnⅠ/ HindⅢ之间,最后XhoⅠ/KpnⅠ双酶切pGD210,将酶切下片段插入pcDNA3.1(-)的相应位点即可.酶切鉴定及测序正确后,转染293T细胞,Western blot验证质粒的表达.pcDNA 3.1(-)-Bcr-Abl T3151的突变质粒:首先设计引物,第一步以pcDNA3.1(-)-BCR/ABL为模板,以Abl-c-u和ba-M1为引物扩增出A-1:560 bp.第二步,相同模板,以ba-M2和ba-M-down为引物扩增出A-2:870 bp.第三步,以扩增出的A-1和A-2为模板,以Abl-c-u和ba-M-down为引物,扩增出1434 bp的片段A-l+2,以Bcl和Kpn Ⅰ分别酶切pcDNA3.1 (-)-BCR/ABL以及A-1+2,将突变后的A-l+2置换入pcDNA3.1 (-)-BCR/ABL.结果:PCR结果显示3.1(-)-Bcr-Abl及3.1 (-)-Bcr-Abl T3151突变质粒条带大小符合,重组质粒经酶切鉴定和测序结果正确,转染后可见融合蛋白的表达.结论:成功构建pcDNA3.1 (-)-Bcr-Abl及pcDNA 3.1(-)-Bcr-Abl T3151的真核表达载体,并且转染293T细胞后证实其能够正确表达,为后续研究奠定了基础.     

结合单酶切位点的融合PCR技术对SCN1A基因的定点诱变

目的:利用结合单酶切位点的融合PCR技术对癫痫相关基因SCN1A进行定点突变。方法:首先设计两对引物PF1/PR1和PF2/PR2,PF1和PR2均位于突变位点最近的单酶切位点处,而突变位点设计在第一对反向引物(PR1)和第二对正向引物上(PF2)。通过重叠延伸法两次PCR扩增:第一次用PF1/PR1和PF2/PR2分开扩增,以扩增产物作模板,PF1/PR2作引物进行融合PCR,得到的扩增产物即含有所需要的突变位点,最后将扩增片段克隆入pMD18-T载体,经测序筛选阳性克隆。结果:DNA测序表明SCN1A基因所编码的第946位密码子由精氨酸(Arg)突变为组氨酸(His),再通过酶切和连接反应将重组质粒上的突变片段替换SCN1A表达质粒上的对应片段,成功构建了SCN1A突变载体。结论:与现在常用的长距离PCR定点诱导突变相比较,结合单酶切位点的融合PCR定点突变技术具备扩增距离短的优点,大大降低了自发突变的概率,适合于大肠杆菌中易自发突变的较大载体的定点诱变。     

邻近多位点基因突变的组合大引物PCR策略(英文)

报道了一种新的组合多位点突变策略,通过单管中三阶段聚合酶链式反应(PCR)得以实现。在第一阶段,PCR扩增出多位点突变大引物,然后在第二阶段延伸大引物,在第三阶段获得全长突变基因序列。基于退火温度与热循环参数的组合大引物反应的优化,三个阶段中退火温度差异小(低于10°C),成功扩增出多位点突变基因序列和比邻突变序列。是一种简单、高效的多位点突变方法。     

乙肝病毒核心抗原基因在大肠杆菌中的表达

根据乙型肝炎病毒(HBV)DNA全基因组克隆pHBV-NC的酶切图谱,分别用限制性内切酶HincⅡ-AvaⅠ和BgLⅡ剪切pHBV—NC_1-DNA,获得了两种不同长度HBV核心抗原基因片段:HBcAgⅠ片段和HBcAgⅡ片段。用带有P_R启动子的质粒pCQV2和带有Lac启动子的质粒pUR222与HBcAgⅠ段和HBcAgⅡ片段连接,分别转化到大肠杆菌中,获得了三种不同的表达菌株,命名为pHBcAgⅠ、pHBcAgⅡ和pLcAgⅡ,并对其核心抗原的表达量做了比较。     

应用逆转录聚合酶链反应法扩增类胰岛素生长因子Ⅱ基因

利用酸性异硫氰酸胍-酚-氯仿一步法从人胚胎组织中提取总RNA,经Oligo(dT)纤维柱分离纯化出mRNA。用逆转录与聚合酶链反应相结合的RT-PCR法,扩增出人类胰岛素生长因子Ⅱ(IGFⅡ)的cDNA片段,在限制性内切酶Sma Ⅰ存在的连接体系中,将扩增出的cDNA片段克隆进PUC12的Sma Ⅰ位点处。经限制性内切酶EcoR Ⅰ、Sal Ⅰ、Eco47Ⅲ酶切鉴定其方向。以重组质粒的双链DNA为模板,用末端终止法测定其全部核苷酸顺序,证实其核苷酸编码的IGFⅡ在氨基酸顺序上与文献报道的相同。     

Site-directed mutagenesis by combination of homologous recombination and DpnI digestion of the plasmid template in Escherichia coli

A rapid site-directed mutagenesis strategy using homologous recombination and DpnI digestion of the template in Escherichia coli is described. Briefly, inverse polymerase chain reaction amplification of the entire circular plasmid was performed by mutagenic primers with overlapping sequences ( approximately 15 bp) for generating PCR products with approximately 15 bp of homology on the terminal ends. On direct transformation of the amplified PCR products into restriction endonuclease DpnI-expressing E. coli BUNDpnI, homologous recombination occurs in E. coli while the original templates are removed via DpnI digestion in vivo, thus yielding clones harboring mutated circular plasmids. Nearly 100% efficiency was attained when this strategy was used to modify DNA sequences.     

Site-specific mutagenesis method which completely excludes wild-type DNA from the transformants.

A highly efficient site-specific mutagenesis method has been devised to exclude wild-type DNA from incorporation into the transformed cells. Two complementary oligonucleotides, corresponding to a target sequence of a DNA molecule and containing an insertion mutation which created an endonuclease restriction site, were synthesized. By using the wild-type DNA molecule flanked by two restriction sites on each side of the target region as a template, the two oligonucleotide primers were extended, enriched, and isolated. The extended products, in turn, were used as templates in a polymerase chain reaction to obtain a mutagenized double-stranded DNA fragment which was conveniently cloned into plasmids by using the flanking restriction sites. Escherichia coli cells transformed by these plasmids were subject to large-scale analysis. One hundred percent of the transformants examined by colony hybridization, restriction enzyme analysis, and DNA sequencing were found to contain the mutant DNA sequence.     

Site-specific mutagenesis method which completely excludes wild-type DNA from the transformants.

A highly efficient site-specific mutagenesis method has been devised to exclude wild-type DNA from incorporation into the transformed cells. Two complementary oligonucleotides, corresponding to a target sequence of a DNA molecule and containing an insertion mutation which created an endonuclease restriction site, were synthesized. By using the wild-type DNA molecule flanked by two restriction sites on each side of the target region as a template, the two oligonucleotide primers were extended, enriched, and isolated. The extended products, in turn, were used as templates in a polymerase chain reaction to obtain a mutagenized double-stranded DNA fragment which was conveniently cloned into plasmids by using the flanking restriction sites. Escherichia coli cells transformed by these plasmids were subject to large-scale analysis. One hundred percent of the transformants examined by colony hybridization, restriction enzyme analysis, and DNA sequencing were found to contain the mutant DNA sequence.     

竞争性RT-PCR法及对大肠杆菌acrA基因mRNA表达水平的定量研究

建立了用于检测大肠杆菌(Escherichia coli)ATCC25922的acrA基因mRNA表达水平的定量竞争性RT-PCR(QC-RT-PCR)体系。PCR合成目标片段的突变型片段(321bp)作为内标准模板(Internal standard,IS),与目标片段一致的片段(389bp)作为目标模板(Target standard,TS),优化两种模板共扩增体系;梯度稀释IS与等量大肠杆菌cDNA样本共扩增,扫描电泳条带,软件分析数据。结果表明,引物设计合适,以IS和TS为模板实现共扩增,产物(321bp和389bp)通过1.5%琼脂糖凝胶电泳有效分离;梯度稀释IS与cDNA共扩增产物出现亮度梯度电泳条带;获得一元回归曲线y=-0.345+0.097x(相关系数r=0.959,标准差s=0.05997)。该研究成功构建内标准模板,优化的共扩增PCR体系实现了对大肠杆菌ATCC25922中acrA基因mRNA表达水平的检测,具有简便、高效、敏感度高等优点。     

快捷的定点突变效率近100%的大引物PCR方法

报道了一种新的PCR突变方法,它不需要纯化大引物或设计特别的旁侧引物．利用一个诱变引物和两个测序引物(T_m≤58℃)作为旁侧引物．第一轮PCR产物12.5 μl直接加入到50 μl的第二轮PCR反应体系作为模板和大引物,在开始第二轮PCR反应时,增加在68℃退火温度下进行10个循环的不对称PCR,这一步骤大大提高了通过600 bp或800 bp大引物所导致的突变效率．结果表明,该方法的产物能够达到高保真、97%～98%的突变效率和高产率．     

用富集文库克隆人胰岛素基因组基因

通过构建可富集人胰岛素基因的λ噬菌体文库,克隆了人胰岛素基因组基因．首先从中国人血液白细胞中提取到人基因组ＤＮＡ,用ＥｃｏＲⅠ和ＢｇｌⅡ对基因组ＤＮＡ进行全酶切,经０．４％琼脂糖凝胶电泳,特异回收９．５ｋｂ左右的ＤＮＡ片段．将该片段与λＥＭＢＬ３／ＢａｍＨⅠ臂连接,构建成一个特殊的人基因组λ噬菌体文库（富集文库）,效价为２×１０４．同时采用ＰＣＲ方法及用引物Ⅰ：５′ＧＧＡＣＡＧＧＣＴＡＣＡＴＣＡＧＧＡＡＧＡＧＧ３′,引物Ⅱ：５′ＣＴＧＣＧＴＣＴＡＡＴＴＧＣＡＧＴＡＧＴＴＣ３′,从人基因组ＤＮＡ中扩增出一段含胰岛素基因的１．３６ｋｂＤＮＡ片段,做为放射性标记探针,对文库进行了噬菌斑原位杂交筛选,从１×１０４个噬菌斑中筛选到一个含人胰岛素基因组基因的阳性克隆,并进一步完成了亚克隆和该基因１７３２ｂｐＤＮＡ序列的测定．结果该基因的１７３２ｂｐＤＮＡ序列包括部分５′端和３′端与国外发表的人胰岛素α型等位基因的序列相同     

Markers for species-specific detection of bacteria from Bacillus cereus group

rpoB and gyr genes (and their fragments) of chromosomal DNA of bacteria from Bacillus cereus group - B. anthracis, B. cereus, and B. thuringiensis - which are the potential markers for their genotyping were sequenced and phylogenetic trees were constructed. Sets of primers for species-specific detection of B. anthracis, B. cereus, and B. thuringiensis by multiplex polymerase chain reaction were designed. Also primers sets, which allow to differentiate strains of B. anthracis with various plasmid profiles (containing both plasmids (pXO1+, pXO2+), and without one (pXO1+, pXO2- or pXO1-, pXO2+) or both plasmids (pXO1-, pXO2-), determining pathogenic characteristics of the strains, were developed. For multiplex PCR primer sets were optimized on the annealing temperature of primers and amplicon length. Itwas shown that phylogenetic tree can be applied as an indicator of reliability and accuracy of taxonomical classification of microorganisms' species and subspecies. Comparison of pXO1 and pXO2 plasmid sequences of B. anthracis showed that these plasmids contain 18 and 4 palindrome sequences respectively which can potentially form thermodynamically stable hairpin-loop structures.