抗人组织金属蛋白酶抑制剂—1核酶的体外制备和活性鉴定

研究了特异切割人瘢痕组织中组织金属蛋白酶抑制剂 1(tissueinhibitorofmetalloproteinases 1,TIMP 1)的锤头状核酶 ,测定了其体外切割活性。制备特异切割TIMP 1的U6snRNA嵌合型核酶基因克隆。TIMP 1mRNA基因片段克隆至T载体。用体外转录法大量制备以 [α 3 2 P]UTP标记的核酶及靶RNA ,进行体外切割实验。结果表明 :核酶∶底物 =1∶1时 ,活性的U6snRNA嵌合型核酶 (U6Rz35 8)在 5 0℃具有最佳切割活性 ,切割效率为 76 .34% ;37℃时 ,切割效率为 5 5 .2 1%。5 0℃时 ,Km=39.6nmol/L ,kcat=0 .2 1min-1;而点突变型核酶U6Rz35 8m 没有切割活性。制备的U6 Rz35 8有良好的特异切割活性 ,有望在瘢痕成纤维细胞内抑制人TIMP 1的表达。     

细胞周期蛋白D1特异性核酶表达载体的构建及其活性

应用mfold程序对锤头状核酶(ribozyme,Rz)和大鼠细胞周期蛋白(cyclin)D1基因的二级结构进行分析,设计合成锤头状Rz基因,通过RT-PCR扩增获得大鼠细胞周期蛋白D1目的基因,将Rz基因和细胞周期蛋白D1基因分别克隆入载体pGEM-3Zf( )中,体外转录Rz基因和靶基因并进行切割实验;将Rz基因与逆转录病毒载体pLXSN重组得到Rz真核表达载体pLXSN-Rz,将其转染入HSC-T6细胞,G418筛选出阳性细胞克隆,用RT-PCR检测细胞周期蛋白D1基因的表达。结果显示:针对目的基因的832位点设计合成了Rz832,成功获得Rz832基因、细胞周期蛋白D1mRNA的体外转录载体pGEM3Zf-Rz832和pGEM3Zf-cD1,经体外转录出Rz832(105nt)及细胞周期蛋白D1mRNA(1079nt)。体外切割实验证实Rz832能够特异性切割细胞周期蛋白D1mRNA,产生1014nt和65nt的切割产物,切割效率为80%。所构建的pLXSN-Rz832经酶切电泳、PCR鉴定显示,插入的Rz832序列大小约为57bp,与预期结果相同,经测序证实Rz832序列正确。转染pLXSN-Rz832的肝星状细胞(hepaticstellatecells,HSCs)细胞周期蛋白D1mRNA的表达受到明显抑制,仅为对照组的42.22%(t=-193.443,P<0.01),结果表明:Rz832能够在体外特异性切割细胞周期蛋白D1mRNA、并在HSC-T6细胞内有效抑制细胞周期蛋白D1基因的表达。     

锤头状核酶对转化生长因子β1 RNA的体外剪切作用

为研究转化生长因子β1（TGFβ1）在造血调控中的关键作用, 构建针对抗转化生长因子β1的锤头状核酶, 并对它的体外剪切活性进行探讨. TGFβ1 cDNA部分基因片段其克隆入T载体中, ３２Ｐ标记TGFβ1体外转录物, 变性的聚丙烯酰胺凝胶电泳纯化获得靶RNA.计算机设计抗TGFβ1的锤头状核酶, 并把合成的核酶基因片段克隆入pGEM-9Zf(-)中T7启动子的下游, 凝胶电泳纯化回收３２Ｐ标记核酶的体外转录物.在不同条件下进行核酶的剪切反应, 变性PAGE, 放射自显影.活性的Rz445在37℃时具有良好活性, Km为29.55 nmol/L, Kcat为0.1533 min－1, 突变型核酶Rz445m没有剪切活性.制备的Rz445在体外具有良好的特异催化剪切活性, 并有望胞内抑制TGFβ1表达, 从而在干细胞移植中应用.     

相思豆毒蛋白—a A链在大肠杆菌中的表达及体外生物活性的测定

用RT PCR方法克隆了相思豆毒蛋白 aA链 (ABRaA)的cDNA编码序列 ,并将其重组到原核表达质粒 pET2 8b中。成熟的ABRaA在大肠杆菌中得到高效表达 ,可溶性重组蛋白质的获得率达 4mg/L培养物 ,而且具有较好的纯度。重组蛋白质体外生物活性的测定结果表明 ,其对兔网织红细胞裂解液的体外蛋白质生物合成具有较强的抑制作用 ,IC50 为 0 .0 8nmol/L ,与天然ABRaA的 (0 .0 6nmol/L)相差不大 ;重组ABRaA蛋白表现出较强的N 糖苷酶活性 ,其可切割大鼠肝脏核糖体 2 8SrRNA的A4 32 4位点 ,释放出一条约 4 2 0nt的小片段RNA。这些结果提示重组的ABRaA具有有效的生物活性 ,可以作为一种潜在的肿瘤化疗药物而用于制备免疫毒素。     

重组酿酒酵母腺苷激酶的表达、纯化和鉴定

腺苷激酶 (adenosinekinase ,AK)是控制细胞中腺苷浓度的一种关键酶 ,在许多细胞和组织中发挥着重要的生理效应子作用。从酿酒酵母 (Saccharomycescerevisiae)中克隆了腺苷激酶基因 (ak) ,并将其接入大肠杆菌pET16b表达质粒中进行表达。重组蛋白质经部分纯化后 ,测定其酶动力学常数 ,结果表明该酶对腺苷的Km 值为 (3.5± 0 .2 ) μmol L ,对ATP的Km 值为(10 0 .0± 11.0 ) μmol L ,对腺苷的kcat值为 (15 30± 2 0 )min- 1 ,对ATP的kcat值为 (14 4 8± 2 5 )min- 1 。该酶对其他核苷和脱氧核苷的Km 值测定数据表明 ,从酵母中克隆得到的该重组腺苷激酶具有较高的底物特异性。     

家蝇抗性和敏感品系中的乙酰胆碱酯酶动力学研究(英文)

本文对家蝇抗性和敏感品系中的乙酰胆碱酯酶 (AChE)的催化特性进行了研究。抗性品系中AChE水解ATCh和BTCh的Vmax分别为 4578.50和 1 71 6.0 8;而敏感品系的Vmax则为 1 884.75和864.72nmol/min/mgprotein ;Vmax的比率 (R/S)对ATCh是 2 .2 6倍 ;对BTCh则是 1 .74倍。AChE的Km 值在敏感品系中分别是 0 .0 69和 0 .0 34;而在抗性品系中则分别是 0 .1 56和 0 .0 59mmol/L ;Km 的比率 (R/S)对ATCh是 2 .43倍 ;对BTCh则是 1 .98倍。此外 ,我们还用eserine作为滴定剂测定了AChE的转换数kcat和酶特异性常数kcat/Km,抗性品系中的AChEkcat值均比敏感品系的要高 ;而kcat/Km 值与此相反。本文着重分析了抗性品系与敏感品系间AChE的催化特性以及对残杀威、灭多威、对氧磷的敏感度差异 ,研究结果表明抗性品系中的AChE性质有可能发生变化。同时还观察到某些杀虫剂能增强抗性品系AChE的活力 ,我们认为这种“增强反应”可能与家蝇对有机磷或氨基甲酸酯类杀虫剂的抗性发展有关     

阿维菌素起始酰基转移酶的底物特异性

[背景]阿维菌素起始酰基转移酶(AveAT0)能够以2-甲基丁酰-辅酶A (coenzyme A,CoA)和异丁酰-CoA作为起始单元分别合成"a"系列或"b"系列的阿维菌素。[目的]探究AveAT0对两种底物的偏好性并进行改造。[方法]通过与识别不同底物的起始酰基转移酶(loading acyltransferases,AT0s)进行序列比对,找到AveAT0底物结合重要的氨基酸,利用活性位点定点突变的方法得到对底物偏好性改变的特定突变体。以2-甲基丁酰-CoA、异丁酰-CoA的类似物2-甲基丁酰-N-乙酰半胱氨(N-acetylcysteamine,SNAC)和异丁酰-SNAC为底物,用Ellman测试法检测释放SNAC的游离巯基(sulfhydryl,SH),测定AveAT0及其突变体的动力学常数,以此表征AveAT0及其突变体的底物偏好性。[结果]AveAT0对2-甲基丁酰SNAC的Km值为0.4 mmol/L,kcat值为14.1 min^-1,kcat/Km为32.1 L/(mmol·min);对异丁酰-SNAC的Km值为0.8 mmol/L,kcat值为6.4 min^-1,kcat/Km为7.5 L/(mmol·min)。选定的突变位点为V224M、Q149L、L121M。按顺序累积突变后发现三突变株AveAT0 V224M/Q149L/L121M对两个底物的偏好性区别最大,对2-甲基丁酰SNAC的Km值为0.8 mmol/L,kcat值为5.4 min^-1,kcat/Km为6.9 L/(mmol·min);对异丁酰-SNAC的kcat/Km为0.1 L/(mmol·min)。[结论]研究发现了AveAT0识别底物过程中的关键氨基酸,为改造阿维菌素聚酮合酶酰基转移酶提供了依据。     

特异切割12-脂加氧酶mRNA的核酶体外活性及动力学研究

根据锤头状核酶(Ribozyme)的作用模式,设计、合成并克隆了特异性切割12-脂加氧酶(12-LO)mRNA的核酶基因。以合成的25个核苷酸长的12-脂加氧酶RNA片段为底物与转录的核酶RNA一起保温检测其体外切割活性。实验结果表明,在37℃保温时,核酶在体外对12脂加氧酶具有较高的特异切割活性,其Km值为1300 nmol/L,其kcat值为0.083/min,在50℃保温时,核酶具有很高的切割活性,其kcat值为0.31/min。     

HPV-16早期基因E1在果蝇细胞S2中的表达和鉴定

目的:在果蝇S2细胞中表达人乳头瘤病毒16型(HPV-16)E1。方法:PCR扩增HPV-16 E1全长,将PCR产物连接至pMD18-T并测序鉴定,继而将HPV-16 E1构建至果蝇表达载体pMT/Bip/V5-HisA中。大量提取pMT/Bip/V5/His-E1重组表达载体并与筛选质粒pCoBlast共转染果蝇S2细胞,经杀稻瘟菌素(Blasticidin S)筛选获得具有抗性的稳定转染S2细胞。提取稳转S2细胞基因组DNA,PCR鉴定S2细胞中整合的E1。以终浓度为5μmol/L CdCl2诱导表达,收集上清进行SDS-PAGE及Western blot鉴定。结果:双酶切及测序结果显示HPV-16 E1基因已克隆人重组质粒pMT/Bip/V5-E1,PCR和Western blot结果表明HPV-16 E1基因已整合至果蝇S2细胞基因组并稳定表达。结论:获得HPV-16 E1转染的果蝇S2细胞株,该细胞株可持续稳定表达E1蛋白。     

抗肿瘤细胞多药抗性基因MDR1和MRP1双靶位自剪切核酶的合成及其在体外活性研究

多药耐药基因MDR1和 (或 )MRP1过度表达是引起肿瘤细胞对化疗药物产生多重耐药性的重要原因 .在以往研究抗MDR1基因的核酶 (196MDR1 Rz)的基础上 ,合成了针对MRP1基因 2 10和 730编码子的核酶 (2 10MRP1 Rz ,730MRP1 Rz) ,同时利用RNA二级结构分析程序mfold 3 0设计合成了一种双靶位自剪切核酶体系 (Coat) .将 196MDR1 Rz和 2 10MRP1 Rz基因同时载入到该体系中 ,建立了抗MDR1 MRP1双靶位核酶 .在无细胞体系中对上述核酶进行的生物活性实验表明 ,2 10MRP1 Rz与 730MRP1 Rz相比能够更有效地切割底物 ;载入Coat的抗MDR1和MRP1核酶均能得以有效释放 ,同时切割各自的靶RNA序列 ,切割效率与单靶位核酶一致 ;串联核酶的先后顺序不影响切割活性     

Effect of ribozyme against transforming growth factorbeta1 on biological character of activated HSCs

Transforming growth factorbeta1 (TGFbeta1) is considered to be the principal contributor to liver fibrosis. So in this study the ribozymes against TGFbeta1 were designed. The in vitro cleavage activities of the ribozymes were assayed through incubation of (32)p-labeled target RNAs and (32)p-labeled ribozymes in different conditions. HSC-T6 cells were transfected with the eukaryotic constructs encoding ribozyme and disable ribozyme, then the stable cell clones were used to evaluate its antifibrotic characteristic through the effect of ribozyme on biological character of activated hepatic stellate cells (HSCs). The results demonstrated that two ribozymes (Rz803 and Rz1395) could cleave target RNAs into expected products effectively, Rz803 possessed better cleavage activity in vitro. Stable transfection of Rz803 into activated HSCs reduced TGFbeta1 expression in mRNA and protein level efficiently. The further studies demonstrated that Rz803 reduced deposition of collagen I, suppressed HSC proliferation, but had no effect on HSC activation in transfected HSC-T6 cells. Therefore, it indicated that Rz803 could reverse the character of activated HSCs by down-regulating TGFbeta1 expression efficiently and diminishing TGFbeta1 signaling underlying activation of hepatic stellate cells. As the consequence, it would provide a potential therapeutic approach for liver fibrosis.     

抗HPV11E2核酸的计算机设计

借助计算机软件分析,设计出能特异性切割HPV11型644nt型644ntE2mNA的核酶。遵循Symons锤头状核酶结构和GUX剪切位点原则,靶序列存在32个剪切位点,通过计算机软件分析核酶的最佳剪切位点,并对底物及核酶的二级结构进行预测及进行相应基因生物学功能和基因同源性分析,筛选出2个锤头结构核酶。针对这两位点设计的核酶分别命名为RZ277和RZ3281。计算机分析显示,两核酶与底物切点两翼碱基形成锤头状结构,切点所在基因序列具有相对松驰的二级结构,位于该基因重要生物功能区内,是核酶的理想攻击区域,通过基因库检索,在已知人类基因中排除了与上述两核酶切点两翼碱基有基因同源性序列的可能性。并非所有的GUX位点（X：C、U、A）或CUX均可作为核酶的最佳剪切切割反应,为下一步将核酶用于细胞内和体内试验打下基础。     

抗HPV11 E2核酶的计算机设计

 借助计算机软件分析 ,设计出能特异性切割HPV11型 6 4 4ntE2mRNA的核酶 (ribozyme) .遵循Symon′s锤头状核酶结构和GUX剪切位点原则 ,靶序列存在 32个这样的剪切位点 .通过计算机软件分析出核酶的最佳剪切位点 ,并对底物及核酶的二级结构进行预测及进行相应基因生物学功能和基因同源性分析 ,筛选出 2个锤头结构核酶 .针对这两位点设计的核酶分别命名为RZ2 777和RZ32 81.计算机分析显示 ,两核酶与底物切点两翼碱基形成锤头状结构 ,切点所在基因序列具有相对松弛的二级结构 ,位于该基因重要生物功能区内 ,是核酶的理想攻击区域 .通过基因库检索 ,在已知人类基因排除了与上述两核酶切点两翼碱基有基因同源性序列的可能性 .将两核酶用于体外剪切实验取得了良好的实验结果 ,认为借助计算机分析可帮助尽快从多个剪切位点选择出最适核酶     

Allosteric regulation of a ribozyme activity through ligand-induced conformational change.

An allosteric ribozyme has been designed using the hammerhead ribozyme as the active site and aflavin-specific RNA aptamer as a regulatory site. We constructed six variants with a series of base pairs in the linker region (stem II). Under single turnover conditions, kinetic studies were carried out in the absence and presence of flavin mononucleotide (FMN). Interestingly, FMN addition did not influence the cleavage rate of constructs with a 5-6 bp linker but stimulated the catalytic activity of those bearing a shorter linker. In particular, the apparent k cat of Rz3 increases by approximately 10-fold upon addition of saturating amounts of FMN. To determine the rate constants( K m4and k cat), the ribozyme regulated most effectively by FMN was further investigated. FMN mainly affected the k cat value, reflecting the rate limiting conformational change step of the overall cleavage reaction, depending on helix formation in stem II. Probably, FMN influences the orientation of structures necessary for the cleavage reaction through stem II formation. The result of chemical modification revealed that binding of FMN to the aptamer domain induced the helix formation in stem II required for catalytic activity. Therefore, a specific FMN-mediated allosteric interaction seems to promote a conformational alteration from an open to a closed structure in stem II. The concept of conformational modification in the allosteric effect is consistent with other allosteric enzymes, suggesting that such a conformational change is a fundamental feature of allosteric enzymes in biological systems.     

Target sequence-specific inhibition of HIV-1 replication by ribozymes directed to tat RNA.

The structural motif formed between a hammerhead ribozyme and its substrate consists of three RNA double helices in which the sequence 5' to the XUY is termed helix I and the sequence 3' to the XUY helix III. Two hammerhead ribozymes targeted to the tat gene of HIV-1SF2 were designed to study target specificity and the potential effect of helix I mismatch on ribozyme efficacy both in vitro and in vivo. The first ribozyme (Rz1) targeted to the 5' splicing region of the tat gene was designed to cleave GUC*A. In HIV-1IIIB the A is changed to a G. The second ribozyme (Rz2) was targeted to the translational initiation region of the tat gene which is highly conserved among a variety of HIV-1 isolates, including both HIV-1SF2 and HIV-1IIIB. In vitro cleavage studies demonstrated that Rz1 efficiency cleaved HIV-1SF2 substrate RNA, but not HIV-1IIIB, presumably due to the base change from A to G. In contrast, Rz2 cleaved HIV-1SF2 or HIV-1IIIB substrate with equal efficiency. Both ribozymes were cloned into the 3' untranslated region of the neomycin gene (neo) within the pSV2neo vector and transfected into the SupT1 human CD4+ T cell line. Following selection, stable transfectants were challenged with either HIV-1SF2 or HIV-1IIIB virus. While Rz1-expressing cells were significantly protected from HIV-1SF2 infection, they exhibited no protection when infected with HIV-1IIIB virus. In contrast, Rz2 was effective in inhibiting the replication of both HIV-1SF2 and HIV-1IIIB in SupT1 cells. Expression of both ribozymes in these cells was demonstrated by Northern analysis. RT-PCR sequencing analysis confirmed the respective HIV-1 target sequence integrity. These data demonstrate the importance of the first base pair distal to the XUY within helix I of the hammerhead structure for both in vitro and in vivo ribozyme activities and imply that the effectiveness of the anti-HIV-1 ribozymes against appropriate target sequences is due to their catalytic activities rather than any antisense effect.     

Catalytic antisense RNAs produced by incorporating ribozyme cassettes into cDNA.

A simple strategy is described for the generation of catalytic hammerhead-type ribozymes (Rz) that can be used as highly specific endoribonucleases to cleave a particular target RNA. The technique requires that a cloned cDNA fragment is available which encodes at least a part of the target RNA. About 25 different restriction recognition sequences can be utilized to incorporate specifically designed DNA cassettes into the cDNA. Besides some nucleotides which are specific for a certain restriction site, the DNA cassettes contain a sequence corresponding to the catalytic domain of the hammerhead Rz and, optionally, selectable marker genes, that are removable. The resulting recombinant DNA constructs permit the in vitro and in vivo synthesis of novel 'catalytic antisense RNAs' or 'antisense Rz (Az)', which combine two features: (i) they bind like antisense RNA to their specific substrate RNA, and (ii) they cleave their target as hammerhead Rz do. The utility of the strategy to generate Rz was demonstrated experimentally by incorporating a synthetic SalI-specific DNA ribozyme (Rz) cassette into a unique SalI site of a cloned cDNA fragment of plum pox virus (PPV), which is a single-stranded positive sense plant RNA virus, belonging to the group of potyviruses. The resulting Az constructs delivered Az that were directed against the PPV (+) or (-) RNA, respectively, which cleaved their corresponding target RNAs in the expected manner. Besides the synthetic Rz cassette, a comparable SalI-specific Rz cassette, that had been prepared from a specifically designed plasmid and that contained the tet gene inserted into the sequence of the catalytic domain of the Rz, was also incorporated into the SalI site of the PPV cDNA.(ABSTRACT TRUNCATED AT 250 WORDS)