Use of the Tn903 neomycin-resistance gene for promoter analysis in the fission yeast Schizosaccharomyces pombe

Summary The bacterial neo gene from transposon Tn903 (Tn601) was used for dominant transformation of the fission yeast Schizosaccharomyces pombe. It was found that high transformation efficiency was dependent on a high level of promoter activity, mediated by the strong promoter of the Schizosaccharomyces pombe alcohol dehydrogenase gene (adh1), as shown by comparing the efficiency of transformation to G418-resistance, the resistance levels of transformed cells, and the in vitro aminoglycoside phosphotransferase activity. On the other hand, the heterologous promoter of the Saccharomyces cerevisiae alcohol dehydrogenase I gene (adc1) is shown to be a weak promoter in Schizosaccharomyces pombe, though its activity is significantly enhanced in cells grown on glycerol as a carbon source. This system for selection and detection of promoter-active sequences may provide a useful basis for the analysis of promoter elements in fission yeast.     

Repetitive sequences upstream of the pfg27/25 gene determine polymorphism in laboratory and natural lines of Plasmodium falciparum

The structure of the genomic region located upstream of the gametocyte-specific gene pfg27/25 of Plasmodium falciparum was analysed in laboratory lines and field isolates of the parasite. The gene is located in a subtelomeric region of chromosome 13 in parasite clones 3D7 and HB3. Analysis of laboratory lines and field isolates of P. falciparum indicated that polymorphism upstream of pfg27/25 is mainly due to the structure of a repetitive DNA region located at about half a kilobase from the pfg27/25 coding sequence. Different types of repetitive sequences are present in this region, whose copy number is variable in different parasite lines. In addition a GC-rich sequence element contained in this region, which is proposed to be the startpoint of pfg27/25 mRNA, presents either a direct or a reverse orientation in different parasite lines. Genomic deletions upstream of the pfg27/25 gene are also described in two laboratory lines of the parasite, which eliminate two newly identified malaria genes, orf P and orf Gap, from the genome of these parasites. One of them, orf Gap, deleted from the reference parasite clone 3D7, is abundantly expressed as mature mRNA in asexual parasites. PCR analysis on 64 field isolates of P. falciparum indicated that orf P and orf Gap sequences are present in all tested samples of naturally propagating parasites.     

Interaction between mitochondrial DNA and mitochondrial plasmids in Claviceps purpurea: analysis of plasmid-homologous sequences upstream of the IrRNA-gene

Homology of two linear, mitochondrial (mt) Claviceps purpurea plasmids, pC1K1 and pClT5, to the upstream region of the large ribosomal RNA gene in the mtDNA of three strains (W3, T5 and K) has been investigated in detail to explore the widespread phenomenon of homology between mt plasmids and mtDNA in C. purpurea. Sequence comparison indicates that recombination between free plasmids and mtDNA is the cause of the observed homology. The process is similar to the integration of the structurally related adenoviruses into the mammalian genome. As in other fungi, palindromic sequences seem to be involved in this mitochondrial recombination process.     

Nuclear suppressors of mitochondrial chloramphenicol resistance in Baker's yeast: their use for the isolation of novel mutants

Summary Strains that are genotypically sensitive to chloramphenicol and also contain one of the nuclear suppressors of mitochondrial chloramphenicol resistance (Waxman et al. 1979) were constructed. A manganese mutagenesis on such a strain produced chloramphenicol resistant mutants, most of which resulted from mutations in nuclear genes. These mutants may be either dominant or recessive, and they probably do not code for membrane proteins. The few mitochondrial mutants fall into several classes, but all result from mutations in the 21S rRNA gene. The suppressor allele effectively prevents the appearance of the most common group of mitochondrial mutants (those that map at cap1), and thereby enhances the selection of novel mutants in the region.     

The use of a double-marker shuttle vector to study DNA double-strand break repair in wild-type and radiation-sensitive mutants of the yeast Saccharomyces cerevisiae

An episomal DNA vector (YpJA18), encoding two selectable recombinant yeast genes (TRP1, URA3), was constructed to assess the fidelity of DNA repair in haploid repair-competent (RAD) wild-type yeast and several radiation-sensitive mutants. Either a DNA double-strand break (DSB) or a double-strand gap of 169 bp (DSG) was introduced by restriction enzymes in-vitro within the coding sequence of the URA3 gene of this vector. To eliminate transfer artefacts, selection was first applied for the undamaged TRP1 gene followed by counter selection for URA3 gene activity, which indicated correct repair of the DSB and DSG. Correct repair of the damaged URA3 gene was found to be about 90% in RAD cells (normalized for the expression of undamaged URA3 in TRP ⁺ transformants). Plasmids isolated from the transformants (URA ⁺ TRP ⁺) carry both unique sites (ApaI and NcoI) within the URA3 gene indicating the precise restitution of the 169-bp gap. An excision-repair-defective rad4-4 mutant repaired these lesions as correctly as RAD cells, whereas the mutants rad50-1, rad51-1 and rad54-1, proven to be defective in DSB repair and mitotic recombination, showed less than 5% correct repair of such lesions. In contrast, a representative of the RAD6 epistasis group of genes, the rev2-1 mutant which is sensitive towards UV and ionizing radiation, had a significantly reduced ability (about 20%) for the correct repair of both DSBs and DSGs.     

Evaluation on the use of beta-lactamase and aminoglycoside modifying enzyme gene sequences as markers for the early detection of antibiotic resistance profile of Pseudomonas aeruginosa

Pseudomonas aeruginosa is one of the major causes of infections including the hospital acquired (Nosocomial) infections. Detection of them and their antibiotic resistance profile by conventional method takes about three days. Recently, DNA based diagnostic methods are being used for the identification of the pathogens. Hence we have tested a rapid and sensitive method using DNA sequences as markers for detecting the presence of three genes coding for the enzymes that inactivate the two most commonly used Anti-pseudomonadal drugs such as beta-lactam antibiotics (Penicillin, and its derivatives) and Aminoglycosides such as Gentamicin, Tobramycin, Amikacin, Streptomycin. The internal region of these genes were used for designing and synthesizing primers and these primers were used in Polymerase Chain Reaction (PCR) to screen for the presence of these genes in the clinical isolates and to label them non-radioactively with Biotin. They in turn were used to detect the presence of the antibiotic resistance genes in the clinical isolates by hybridization. The specificity (ratio of positive results obtained in both methods and the sensitivity (the minimum amount of sample DNA and the labeled probe required for the tests) were evaluated.     

生长抑制因子1基因核定位序列-绿荧光蛋白融合表达载体的构建及表达

目的构建p33^ING1b核定位序列（nuclear locating sequence，NLS）-绿荧光蛋白融合表达载体，将其转染到人胚肺纤维母细胞系MRC-5，建立稳定表达该融合蛋白的细胞模型。方法应用逆转录PCR获得p33^ING1b的NLS序列，然后将NLS序列插入绿荧光蛋白融合表达载体pEGFP-C1的多克隆位点，构建pEGFP-C1-NLS-绿荧光蛋白融合表达载体，再用此载体转染MRC-5细胞系，观察活细胞绿荧光蛋白的亚细胞定位。结果成功构建了pEGFP-C1-NLS-绿荧光蛋白融合表达载体，由该载体表达的绿荧光蛋白-NLS肽段融合蛋白产生的绿色荧光信号全部定位于胞核部位，而空载体转染的细胞表达的绿色荧光蛋白，绿色荧光信号定位于细胞浆中。结论在活细胞内，生理情况下p33^ING1b完全定位于细胞核，并且在其亚细胞定位的转运过程中，NLS肽段起着决定性作用。     

Heterologous gene expression of the glyphosate resistance marker and its application in yeast transformation

Summary The E. coli aroA gene was inserted between yeast promoter and terminator sequences in different shuttle expression plasmids and found to confer enhanced EPSP synthase activity as well as resistance to glyphosate toxicity. Subsequently, a transformation system using these newly constructed vectors in yeast was characterized. The efficiency of the glyphosate resistance marker for transformation and selection with plasmid pHR6/20-1 in S. cerevisiae laboratory strain SHY2 was found to be relatively high when compared with selection for LEU2 prototrophy. The fate of the recombinant plasmid pHR6/20-1 in the transformants, the preservation of the aroA E. coli DNA fragment in yeast, mitotic stability, EPSP synthase activity, and growth on glyphosate-containing medium have been investigated. As this plasmid also allows direct selection for glyphosate resistant transformants on rich media, the glyphosate resistance marker was used for transforming both S. cerevisiae laboratory strain SHY2 and brewer's yeast strains S. cerevisiae var. uvarum BHS5 and BHS2. In all cases, the vector pHR6/20-1 was maintained as an autonomously replicating plasmid. The resistance marker is, therefore, suitable for transforming genetically unlabeled S. cerevisiae laboratory, wild, and industrial yeast strains.Abbreviations EPSP 5-enolpyruvylshikimate 3-phosphate     

逆转录病毒介导DNA修复蛋白在人骨髓细胞中的表达和抗性研究

目的增强造血细胞对化疗药物的耐药表型,探讨逆转录病毒介导的基因转移效率及耐药基因的特性和在造血细胞保护性基因治疗中的作用和意义.方法应用RT-PCR从人肝组织中获得编码六氧甲基鸟嘌呤-DNA-甲基转移酶(MGMT)cDNA,将其克隆于pGEM-T质粒载体并构建了逆转录病毒载体G1Na-MGMT,应用脂质体LipofectAMINE基因转移法将后者导入GP+E86和PA317病毒包装细胞,以BCNU加压筛选后的阳性克隆上清经乒乓效应后继而感染K562细胞和人造血细胞.应用PCR,Southernblot,RT-PCR,Westernblot及MTT法检测人MGMT基因在细胞中的转移和表达.结果酶切鉴定及DNA测序证实其MGMTcDNA克隆的正确性,脂质体介导方法成功将其导入病毒包装细胞,BCNU加压筛选和乒乓感染法使病毒效价达8.6×106CFU/ml,逆转录病毒载体介导的MGMT基因在K562细胞及人造血细胞中获得有效转移和表达.结论MGMT耐药基因的成功克隆并导入骨髓造血细胞且获高效表达对开展肿瘤基因治疗的临床研究奠定了实验基础.     

肝硬变内HBV DNA及其五种抗原的表达及意义

取２２５例人肝硬变活检组织石蜡切片，检测了ＨＢＶＤＮＡ及其５种抗原。分别用免疫组化ＡＢＣ法检测ＨＢｘＡｇ、ｐｒｅ－Ｓ＿１和ｐｒｅ－Ｓ＿２抗原；用ＰＡＰ法检测ＨＢｓＡｇ和ＨＢｃＡｇ；用原位杂交方法检测ＨＢＶＤＮＡ；用免疫组化、原位杂交双标记方法检测ＨＢＶＤＮＡ和ＨＢｓＡｇ、ＨＢｘＡｇ或ＨＢｃＡｇ。结果显示，阳性检出率ＨＢｓＡｇ为７０．０％（１２８／１８３例），ｐｒｅ－Ｓ＿１抗原为６４．４％（８５／１３２例）、ｐｒｅ－Ｓ＿２抗原为６１．４％（８１／１３２例），ＨＢｘＡｇ为７５．３％（１１３／１５０例），ＨＢｃＡｇ为２２．４％（３９／１７４例），ＨＢＶＤＮＡ为６２．４％（５８／９３例）。双标阳性检出率ＨＢＶＤＮＡ和ＨＢｓＡｇ为３７．３％（１９／５１例），ＨＢＶＤＮＡ和ＨＢｘ－Ａｇ为８６．３％（４４／５１例），ＨＢＶＤＮＡ和ＨＢｃＡｇ为３９．２％（２０／５１例）。ＨＢＶＤＮＡ和ＨＢＶ５种抗原阳性病例中８０％以上均伴有肝细胞不典型增生。这一结果表明，在我国肝硬变的发生发展与ＨＢＶ慢性感染有密切的关系。     

Nucleotide-sequence analysis indicates that a DNA plasmid in a diseased isolate of Ophiostoma novo-ulmi is derived by recombination between two long repeat sequences in the mitochondrial large subunit ribosomal RNA gene

The nucleotide sequence of a mitochondrial plasmid (2234 bp) in a diseased isolate of Ophiostoma novo-ulmi, and sequences of the mitochondrial DNA that overlap and flank the plasmid end-points, have been determined. The plasmid was shown to be derived from the O. novo-ulmi mitochondrial large subunit ribosomal RNA gene and contained most of intron 1, the whole of exon 2, and probably the first part of intron 2. Within intron 1 there is an open reading frame with the potential to encode a 323 amino-acid polypeptide which contained dodecapeptide sequences typical of RNA maturases and DNA endonucleases. The endpoints of the plasmid in the mtDNA were located within two 90-bp direct imperfect repeat sequences, one of which comprised the last 7 bp of exon 1 and the first 83 bp of intron 1 whilst the other comprised the last 7 bp of exon 2 and the first 83 bp of intron 2. It is proposed that the Ld plasmid was generated by intramolecular recombination between these two repeats with the crossover point probably within the last 15 bp.     

Suppression of tyrosinase gene expression by bromodeoxyuridine in Syrian hamster melanoma cells is not due to its incorporation into upstream or coding sequences of the tyrosinase gene

5-Bromodeoxyuridine (BrdU), a thymidine analog, suppresses melanogenesis in Syrian hamster melanoma cells. Tyrosinase, which is the key enzyme for the synthesis of melanin, is suppressed by exposure to BrdU, and the drop in enzyme activity is correlated with a drop in tyrosinase mRNA level. In order to investigate whether suppression of tyrosinase mRNA by BrdU is due to BrdU substitution into coding sequences or upstream sequences of the tyrosinase gene, we carried out stable and transient transfection assays with constructs containing either the human tyrosinase cDNA sequence under the control of a nontyrosinase promoter or a chloramphenicol acetyltransferase (CAT) reporter gene under the control of 5 flanking sequences of the mouse tyrosinase gene. When the plasmid containing the tyrosinase cDNA was stably transfected into mouse fibroblasts, tyrosinase activity in the transfectants was not suppressed by BrdU. Since BrdU would be incorporated into the tyrosinase cDNA integrated in these transfectants, the results suggest that BrdU suppression of tyrosinase gene expression is not due to its incorporation into coding sequences of the tyrosinase gene. When plasmids with tyrosinase regulatory sequences were transfected into melanoma cells for transient expression assays, CAT gene expression was suppressed by BrdU. Because the CAT plasmids do not contain a mammalian origin of replication and should not replicate under the conditions of transient transfection, BrdU would not be incorporated into the DNA of those plasmids. Therefore, these results suggest that the suppression of tyrosinase gene expression by BrdU also is not due to the incorporation of BrdU into upstream sequences of the tyrosinase gene.     

Detection of sequence variants in the gene for human type II procollagen (COL2A1) by direct sequencing of polymerase chain reaction-amplified genomic DNA.

The direct sequencing of the human type II procollagen (COL2A1) gene from polymerase chain reaction (PCR)-amplified genomic DNA is described. Thirty-two regions of the COL2A1 gene were asymmetrically amplified with intron primers which were specifically chosen to amplify a region spanning 500 to 800 bp of sequence encoding one or more exons and their accompanying intervening sequences. Primers for dideoxynucleotide sequencing of the PCR products were then designed to provide complete exon sequence information and to insure that intron:exon splice junction sequence data would be obtained. Amplification and sequencing reactions were performed on an automated workstation to facilitate the handling of multiple DNA templates. The procedure allowed efficient sequencing of over 25,000 bp of each allele of the COL2A1 gene per diploid genome. We used this method for the comparative analyses of COL2A1 sequences in DNA isolated from the blood of 42 unrelated individuals and we identified 21 neutral sequence variants in the gene. The sequence variations were confirmed by independent assays, including restriction enzyme digestion. The sequence variants described here will be important for identifying haplotypes of the type II procollagen gene that will be useful in defining a genetic etiology for diseases of cartilaginous tissues.     

Occurrence of insertion sequences within the genomes and Tn1546-like elements of glycopeptide-resistant enterococci isolated in Brazil, and identification of a novel element, ISEfa5

Insertion sequences (IS) occur widely within the Tn1546-like elements responsible for VanA glycopeptide resistance in enterococci from several countries. As such insertions can be used as epidemiological markers and for studying horizontal transfer of gene clusters, we investigated the distribution of IS6770, IS1542, IS1216V, IS1476, and IS1251 elements in 26 VanA Enterococcus faecium and 21 VanA Enterococcus faecalis from Brazil. PCR, using genomic DNA as a template, indicated that most of the isolates contained IS6770 (97%), IS1216V (87%) and IS1476 (72%) elements. IS1251 was also detected, but at a higher frequency in E. faecium (80%) than in E. faecalis (14%). None of the isolates harboured IS1542. Only two of 47 isolates had IS elements within their Tn1546-like elements; one possessed IS1251 between vanS and vanH, as reported in the United States; another possessed a novel IS element, designated ISEfa5, located between vanX and vanY. This novel element was found in the genomic DNA of 25 (96%) E. faecium and 11 (52%) E. faecalis. In stability studies, no IS-mediated changes were detected in the Tn1546-like elements of 25 vancomycin-resistant enterococci (VRE) monitored over 11 months. These results suggest that the occurrence of IS in Brazilian isolates is similar to that reported in American isolates, but that these elements occur rarely within the vanA gene clusters. As patterns of IS carriage did not correlate with the PFGE type of the VRE, the prevalence of IS elements in genomic DNA of VRE is not a useful epidemiological marker. However, the presence of IS-modified Tn1546-like elements, which appear to be rare in Brazil, could be a useful molecular marker in local epidemiological studies to monitor the evolution and horizontal transmission of VanA elements.     

Cloning by genetic complementation and restriction mapping of the yeast HEM1 gene coding for 5-aminolevulinate synthase

Summary We have cloned the structural gene HEM1 for 5-aminolevulinate (ALA) synthase from Saccharomyces cerevisiae by transformation and complementation of a yeast hem1–5 mutant which was previously shown to lack ALA synthase activity (Urban-Grimal and Labbe Bois 1981) and had no immunodetectable ALA synthase protein when tested with yeast ALA synthase antiserum. The gene was selected from a recombinant cosmid pool which contained wild-type yeast genomic DNA fragments of an average size of 40 kb. The cloned gene was identified by the restauration.of growth on a non fermentable carbon source without addition of exogenous ALA. Sub cloning of partial Sau3A digests and functional analysis by transformation allowed us to isolate three independent plasmids, each carrying a 6 kb yeast DNA fragment inserted in either orientation into the single BamHI site of the vector pHCG3 and able to complement hem1–5 mutation. Analysis of the three plasmids by restriction endonucleases showed that HEM1 is contained within a 2.9 kb fragment. The three corresponding yeast trans formants present a 1, 2.5 and 16 fold increase in ALA synthase activity as compared to the wild-type strain. The gene product immunodetected in the transformant yeast cells has identical size as the wild-type yeast ALA synthase and its amount correlates well with the increase in ALA synthase activity.     

结核分枝杆菌Ag85A基因DNA疫苗的构建及其联合人IL-12表达质粒诱导的小鼠细胞免疫应答观察

目的:构建编码结核分枝杆菌Ag85A分泌蛋白重组真核表达质粒,研究其与hIL-12联合免疫小鼠后的细胞免疫应答。方法:(1)构建质粒:采用PCR法从H37Rv菌株中扩增Ag85A编码基因,用限制性内切酶消化后,插入克隆载体PMD20-T中,经酶切鉴定与序列测定证实后,以亚克隆法构建于真核表达载体PCDNA3.1的相应酶切位点。(2)动物实验:50只C57BL/6N小鼠随机分为:①Ag85A基因疫苗+hIL-12质粒组(联合免疫组);②重组Ag85A基因疫苗组;③卡介苗BCG组(阳性对照);④空载体组(阴性对照);⑤PBS组(空白对照)。基因疫苗、空载体和PBS经肌内注射法免疫各组小鼠,每隔3周免疫1次,共免疫3次,BCG组经尾部皮下注射1×106CFU BCG免疫1次,约0.3 ml/只。第三次免疫小鼠后28天,处死各组小鼠,分离脾细胞,ELISA法检测脾细胞培养上清液中IFNγ-、IL-2、IL-4水平;乳酸脱氢酶释放法检测脾细胞杀伤活性;分离的脾细胞经TB-PPD刺激后,XTT比色法检测脾淋巴细胞增殖活性。结果:(1)成功构建结核分枝杆菌Ag85A基因DNA疫苗。(2)联合免疫组能诱导较强烈的抗原特异性Th1型细胞免疫应答,免疫小鼠脾细胞培养上清液IFN-r和IL-2水平显著高于Ag85A基因疫苗组,与BCG组相当,IL-4分泌减少;特异性CTL杀伤活性明显增强;淋巴细胞增殖活性也明显高于其他组别。结论:hlL-12表达质粒能够增强结核分枝杆菌Ag85A基因DNA疫苗所诱导的小鼠免疫应答。     

Cloning of the Trichoderma reesei pyrG gene and its use as a homologous marker for a high-frequency transformation system

Summary The Trichoderma reesei orotidine-5-phosphate decarboxylase gene was isolated by heterologous hybridization with the corresponding Neurospora gene as a probe. A 2.7 kb SalI fragment, which exclusively hybridized to the Neurospora gene, was subcloned in pGEM-5Zf(+). This subclone was termed pFG1 and was used to transform a Trichoderma reesei pyrG^- negative mutant to PYR⁺. The transformation frequency in this homologous system was up to 12000 transformants per g DNA. About one-fifth of the transformants tested were abortive. Perfect mitotic stability was found in half of the non-abortive transformants, correlating with vector integration at homologous and ectopic loci. In the unstable transformants the transforming DNA appears to be present in the form of extrachromosomal elements.     

The host range of the pKD1-derived plasmids in yeast

Summary pKDI is a 2-like circular plasmid found in the yeast Kluyveromyces drosophilarum that can also stably replicate in Kluyveromyces lactis. We have found a short intergenic region in this genome that appears to be functionally neutral; that is, the introduction of foreign sequences into the single EcoRI restriction site located near one of the inverted repeats did not affect the high stability of the natural plasmid. By introducing a G418 resistance gene at this site, we constructed an autonomous recombinant plasmid. Since this vector did not require cir ⁺ hosts for its stable maintenance, it could be used to examine the transformation host range of pKD1 among all the species belonging to the genus Kluyveromyces. Both species closely related to K. drosophilarum as well as a few other species that are very different in chromosomal GC % could be transformed to yield highly stable transformant clones.     

Cloning of the Aspergillus oryzae 5-aminolevulinate synthase gene and its use as a selectable marker

The hemA gene encoding 5-aminolevulinate synthase, the first enzyme in heme biosynthesis, was cloned from Aspergillus oryzae and evaluated as a selectable marker for the transformation of filamentous fungi. Deletion of the hemA gene resulted in a lethal phenotype that could be rescued either by the supplementation of culture media with 5-aminolevulinic acid (ALA) or by transformation with the wild-type hemA gene, but not by growth on rich media, nor by the addition of exogenous heme. Transformation of a hemA deletion strain with the hemA gene linked to a lipase expression cassette yielded ALA prototrophs expressing lipase. The hemA gene can therefore be used as a selectable marker for the transformation of A. oryzae. Received: 16 March 2000 / Accepted: 18 July 2000