A simple method for site-directed mutagenesis with double-stranded plasmid DNA

Chromosome painting with library DNA probes specific for all human chromosomes was used to study the chromosomal content of micronuclei (MN) in normal and 5-azacytidine (5-aza-C)-treated lymphocyte cultures. More than 60,000 normal lymphocytes were screened for associated MN after in situ hybridization. At least 50 MN were scored for each probe. With the exception of chromosomes 12 and 19, which did not occur in MN, all other chromosomes were detected in MN at frequencies varying from 1 to 11.5%. Treatment of lymphocyte cultures with 5-aza-C induced preferential exclusion of chromosomes 1 (34%), 9 (32%) and 16 (20%) material in MN, whereas chromosome 8, 10, 12-15 and 21 material was not detected in MN. The results obtained from normal lymphocytes allow for the first time an estimation of the frequency of occurrence of all chromosomes in spontaneously occurring MN in human cells. Data derived from 5-aza-C-treated lymphocytes are furthermore consistent with the view that undermethylation of heterochromatin may be associated with loss of specific chromosomes at metaphase.     

A general method for isolation of high molecular weight DNA from eukaryotes

A new method for isolation of high molecular weight DNA from eukaryotes is presented. This procedure allows preparation of DNA from a variety of tissues such as calf thymus or human placenta and from cells which were more difficult to lyse until now (e.g. Crypthecodinium cuhnii, a dinoflagellate). The DNA obtained in such a way has an average molecular weight of about 200 X 10(6) d and contains very few, if any, single strand breaks.     

Electroporation of, plasmid isolation from and plasmid conservation in Clostridium acetobutylicum DSM 792

Procedures have been developed allowing recombinant DNA work with Clostridium acetobutylicum DSM 792. Electroporation was used to introduce plasmid DNA into exponentially growing clostridial cells and 6 x 10(2) transformants/microgram DNA could be obtained at a time constant of 5.5 ms, 1.8 kV, 50 microF, and 600 omega. The method also allowed the taxonomic group IV strain NI-4082 to be transformed (10(1) transformants/microgram DNA). Plasmid preparation from recombinant clostridia was optimal when a modification of the alkaline lysis method was employed. It was also important to use cells from the mid-logarithmic growth phase. Recombinant strains could be easily preserved as spore suspensions; under all conditions tested plasmids were maintained.     

Flexibility in the boiling method of extracting plasmid DNA directly from cell culture

To investigate the possibility of correcting thrombocytopenia of chronic liver disease, 19 patients (6 male and 13 female) with long-term chronic liver disease and platelet count < or = 85,000/microliters were studied. Either a short-term course (7-20 days) of recombinant human erythropoietin, 4000 U daily SQ (12 patients) or placebo (7 patients) was administered. Treatment was interrupted if the platelets rose to > or = 100,000/microliters or if no significant increase was noted after 14 days. After treatment, platelets increased in the recombinant human erythropoietin group (from a baseline value of 70,000 +/- 11,184 to 101,250 +/- 37,625/microliters), while no difference was noted in the placebo group (70,714 +/- 9928 vs 70,000 +/- 10,231/microliters). The increase in the platelet count in the recombinant human erythropoietin group was significant, both compared to baseline values (paired Student's t-test, t = -3.80, p < 0.005) and to the results of treatment in the placebo group (unpaired Student's t-test, t = 2.71, p < 0.02). Eight out of 12 recombinant human erythropoietin-treated patients (66%) reached > or = 100,000/microliters platelets while four (33%) did not. In comparison to responders, non-responders had a significantly lower baseline platelet count (58,500 +/- 7937 vs 75,750 +/- 7498/microliters, t = -3.69, p = 0.004) and failed more frequently than responders to improve their haematocrit in response to recombinant human erythropoietin (Pearson chi 2 = 4.687, p = 0.03). When treatment was discontinued, the platelet count reverted to baseline in a few weeks. In conclusion, recombinant human erythropoietin treatment transiently corrected mild thrombocytopenia in patients with chronic liver disease.(ABSTRACT TRUNCATED AT 250 WORDS)     

A method for high yield isolation and purification of anti-native DNA antibodies present in lupus sera

Antibodies to nucleic acids may serve as biochemical tools or as probes of cellular function. Particularly important, but also particularly difficult to obtain, is antibody which reacts exclusively with double stranded DNA. We describe here a method for the separation of antibodies to double stranded DNA from SLE serum, using hydroxyapatite to which DNA is adsorbed at a low molarity of phosphate buffer. Having applied the serum to the column we passed it through a continuous gradient of phosphate buffer ranging from 0.005 to 0.5 M. Deoxyribonuclease and magnesium ions were added when the gradient had reached the molarity at which single stranded DNA had already been desorbed and double stranded DNA began to be eluted. The antibody to native DNA that we obtained reacted in complement fixation, counterimmunoelectrophoresis and Farr's assay with native DNA and did not react with single stranded DNA, single and double stranded RNA or with a panel of 24 protein-coupled nucleosides, nucleotides and dinucleotides.     

Convenient plasmid for extrachromosomal DNA recombination in mouse cells

We constructed a convenient plasmid for DNA recombination assay. The plasmid, pMR1, contains a double prokaryotic terminator to decrease the background and two unique restriction enzyme sites on both sides of the double terminator to allow for easy construction. The assay is capable of selecting the bacterial cells containing recombined plasmid DNA on a selective plate containing ampicillin and chloramphenicol. We adapted pMR1 for V(D)J recombination and homologous recombination and detected both types of recombination in murine PreB cell line. As pMR1 has the double terminator, background on the selective plate decreases effectively and we select only the recombined clones. We consider the vector, pMR1, to be convenient for the analysis of homologous and non-homologous recombinations.     

General method for plasmid construction using homologous recombination

We describe a general method for plasmid assembly that uses yeast and extends beyond yeast-specific research applications. This technology exploits the homologous recombination, double-stranded break repair pathway in Saccharomyces cerevisiae to join DNA fragments. Synthetic, double-stranded "recombination linkers" were used to "subclone" a DNA fragment into a plasmid with > 80% efficiency. Quantitative data on the influence of DNA concentration and overlap length on the efficiency of recombination are presented. Using a simple procedure, plasmids were shuttled from yeast into E. coli for subsequent screening and large-scale plasmid preps. This simple method for plasmid construction has several advantages. (i) It bypasses the need for extensive PCR amplification and for purification, modification and/or ligation techniques routinely used for plasmid constructions. (ii) The method does not rely on available restriction sites, thus fragment and vector DNA can be joined within any DNA sequence. This enables the use of multifunctional cloning vectors for protein expression in mammalian cells, other yeast species, E. coli and other expression systems as discussed. (iii) Finally, the technology exploits yeast strains, plasmids and microbial techniques that are inexpensive and readily available.     

Stability of peptide-condensed plasmid DNA formulations

Low molecular weight homogeneous peptides were used to form peptide/DNA condensates. A peptide possessing 18 lysines was found to protect plasmid DNA from serum endonuclease and sonicative-induced degradation whereas a shorter peptide possessing 8 lysines dissociated in 0.1 M sodium chloride and failed to protect DNA from enzymatic degradation. Peptide-condensed DNA showed no change in the ratio of supercoiled to circular DNA following 100 W sonication for up to 60 s and was able to transfect HepG2 cells with equivalent efficiency as untreated condensed plasmid DNA. Alternatively, uncondensed plasmid DNA was rapidly fragmented by sonication and serum endonucleases and resulted in negligible gene expression following condensation with peptide. Cationic lipid/DNA complexes were only partially effective at stabilizing DNA in serum compared to the complete stabilization afforded by peptide/DNA condensation. These results indicate that the stabilization afforded by condensation with a peptide protects DNA during formulation and preserves its structure in serum. These functions are important to achieve optimal gene expression from a nonviral gene delivery system.     

Development of a multigenic plasmid vector for HCV DNA immunization

OBJECTIVES: The aim of this study was to determine the prevalence of multiple sclerosis in a population in South Hungary. METHODS: The diagnosis was established with the aid of the Poser diagnostic criteria and the degree of physical disability was determined on the Kurtzke expanded disability status scale (EDSS). The present medical state (EDSS score) was determined from outpatient clinical control tests. The prevalence, the average age at onset of the disease and the proportions of the various clinical forms were calculated, and the patients' disability status was estimated. RESULTS: In 1996, the prevalence was 65/100,000, and the incidence from January 1, 1995 through December 31, 1996 was 7/100,000/year. DISCUSSION: During a period of 2 years, the number of diagnosed patients has almost doubled. The disease can be recognized in an early stage with a minimal neurological deficit. The development of the diagnostics necessitates re-examinations with modern diagnostic procedures. During the last 3 years, the general practitioner system has been reorganized, and the working relationships between the clinic and family doctors have developed considerably. A comparison of the present findings with those in other countries with a similar climate revealed very similar prevalence data.     

High-performance membrane chromatography of supercoiled plasmid DNA

Membrane adsorbers are well established in protein chromatography. The present paper investigated for the first time the behavior of polynucleotides on these stationary phases, taking a 7.2-kb predominantly supercoiled plasmid as example. Gradient and isocratic elution was studied. In contrast to protein high-performance membrane chromatography (HPMC), isocratic elution is possible in DNA chromatography. In the case of gradient elution, much higher salt concentrations can be used in the starting buffer. Under optimized conditions, both approaches led to a splitting of the single plasmid peak into three maximums, which corresponded to the three-albeit isolated-bands in the agarose gel. Presumably the three fractions were supercoiled, nicked, and open circular plasmid DNA. Linearization of the plasmid lowered the adsorption energy, and the linearized plasmid eluted earlier than the nonlinearized one. The HPMC experiments were compared to similar ones performed using a conventional packed-bed anion-exchange column (BioScale Q2, 7 x 52 mm, 10-micron porous particles) and a novel monolithic-type anion-exchange column (UNO Q1, 7 x 35 mm). The results and characteristic differences observed in these experiments were interpreted in the light of the newly developed theory of HPMC.     

Lipitoids--novel cationic lipids for cellular delivery of plasmid DNA in vitro

To determine whether or not the erythrophore originates from xanthophores in the dorsal skin of the brown frog, Rana ornativentris, we morphologically examined the differentiation and migration of the two chromatophore types and their pigmentary organelle formation. At an early tadpole stage, three kinds of chromatophores, xanthophores, iridophores, and melanophores, appeared in the subdermis, whereas the erythrophore did so just before the foreleg protrusion stage. By the middle of metamorphosis, most chromatophores other than erythrophores had migrated to the subepidermal space. Erythrophores, which appeared late in the subdermis, proliferated actively there during metamorphosis and finished moving into the subepidermal space by the completion of metamorphosis. Carotenoid vesicles and pterinosomes within the erythrophores and xanthophores showed several significant differences in structure. In xanthophores, carotenoid vesicles were abundant throughout life, whereas those in erythrophores decreased in number with the growth of the frogs. The fibrous materials contained in the pterinosomes were initially scattered but soon formed a concentric lamellar structure. In erythrophores, the lamellar structure began to form at the periphery of the organelles but at the center in xanthophores. In addition, the pterinosomes of erythrophores were uniform in size throughout development, while those of xanthophores showed a tendency to become smaller after metamorphosis. The pterinosomes of xanthophores were significantly larger than those of erythrophores. These findings suggest that an erythrophore is not a transformed xanthophore, although they resemble each other closely in many respects.     

A serum-resistant cytofectin for cellular delivery of antisense oligodeoxynucleotides and plasmid DNA

Development of antisense technology has focused in part on creating improved methods for delivering oligodeoxynucleotides (ODNs) to cells. In this report, we describe a cationic lipid that, when formulated with the fusogenic lipid dioleoylphosphatidyliethanolamine, greatly improves the cellular uptake properties of antisense ODNs, as well as plasmid DNA. This lipid formulation, termed GS 2888 cytofectin, (i) efficiently transfects ODNs and plasmids into many cell types in the presence or absence of 10% serum in the medium, (ii) uses a 4- to 10-fold lower concentration of the agent as compared to the commercially available Lipofectin liposome, and (iii) is > or = 20-fold more effective at eliciting antisense effects in the presence of serum when compared to Lipofectin. Here we show antisense effects using GS 2888 cytofectin together with C-5 propynyl pyrimidine phosphorothioate ODNs in which we achieve inhibition of gene expression using low nanomolar concentrations of ODN. This agent expands the utility of antisense ODNs for their use in understanding gene function and offers the potential for its use in DNA delivery applications in vivo.     

Protection against tuberculosis by a plasmid DNA vaccine

BACKGROUND: Incidence of smooth muscle tumors is increased in patients with human immunodeficiency virus infection and organ transplant recipients. Smooth muscle tumors in immunocompromised patients often occur in unusual locations and exhibit evidence of latent infection by clonal, presumably tumorigenic, Epstein-Barr virus (EBV). OBJECTIVE: To investigate the presence of EBV latent infection in smooth muscle tumors in patients with acquired immunodeficiency syndrome and in immunocompetent patients. DESIGN: Twenty-two extrauterine, extraintestinal smooth muscle and myofibroblastic tumors were reviewed pathologically, and clinical charts were screened. Tumors were malignant (15 patients), benign (6 patients), and borderline (1 patient). Tissue specimens were investigated for latent EBV infection by latent membrane protein immunocytochemistry and EBV-encoded RNA in situ hybridization. SETTING: University Hospital of the University of Nancy, France. PATIENTS: Patients were 18 adults and four children. Two adults had acquired immunodeficiency syndrome. Both had low-grade leiomyosarcomas located in adrenal gland. Moreover, in patient 1, leiomyosarcoma was multifocal in pericardium and lymph node; in lymph node, muscle tumor was adjacent to nodal and skin Kaposi's lesions. RESULTS: In both patients with acquired immunodeficiency syndrome and leiomyosarcoma, latent infection by EBV could be demonstrated in tumor cells, contrasting with absence of detectable EBV infection in adjacent non-neoplastic tissues and nearby Kaposi's lesions. Latent infection by EBV could not be demonstrated in smooth muscle and myofibroblastic tumors in immunocompetent patients. CONCLUSIONS: Latent EBV infection is associated with smooth muscle cell tumors in immunocompromised patients, but not in immunocompetent patients.     

The influence of DNA sequence on the immunostimulatory properties of plasmid DNA vectors

To determine the influence of DNA sequence on immunostimulatory properties of vaccine vectors, we tested the induction of in vitro and in vivo immune responses by plasmids modified to contain extended runs of dG sequences. Studies with oligonucleotides indicate that dG sequences can directly stimulate B cells as well as enhance the activity of immunostimulatory CpG motifs because of interaction with the macrophage scavenger receptor (MSR); this receptor can bind a variety of polyanions including dG sequences. To modify vectors, we introduced stretches of 20-60 dG residues into the pCMV-beta and pSG5rab.gp vectors and measured the ability of these plasmids to induce IL-12 and IFN-gamma production by murine splenocytes. The induction of in vivo antibody responses to rabies glycoprotein was also assessed with the pSG5rab.gp vectors. In in vitro cultures, cytokine production induced by plasmids with and without dG sequences was similar. Furthermore, the addition of dG sequences to pSG5rab.gp vectors failed to enhance the anti-rabies glycoprotein response to immunization. To assess further mechanisms by which plasmids stimulate macrophages, we measured the effects of MSR ligands on in vitro cytokine induction. In in vitro cultures, poly(G), dG30, and fucoidan inhibited IL-12 induction by plasmids. IL-12 induction was also inhibited by mammalian DNA but was unaffected by polyanions that are not MSR ligands. Together, these results suggest that the addition of 20 to 60-base dG sequences to plasmids does not significantly affect their properties as immunostimulators or vaccines. Furthermore, these results suggest that MSR ligands can block cytokine induction by plasmid DNA whether or not the plasmid contains extended runs of dG.     

Monomolecular collapse of plasmid DNA into stable virus-like particles

Cationic lipids are being widely used for cell transfection in vitro. The lipid/DNA complexes, however, tend to aggregate into large and polydisperse particle mixtures; this hampers their use in vivo. Cationic detergents, on the contrary, do not mediate cell transfection per se, yet are capable of condensing individual DNA molecules into discrete entities. We have taken (only) the interesting features of both types of amphiphiles for the two-step formation of stable core particles reminiscent of viruses. Individual anionic plasmid molecules were cooperatively collapsed with a carefully tailored cationic cysteine-based detergent. The resulting 23-nm particles were then simply "frozen" by spontaneous aerobic dimerization of the cysteine-detergent into a cystine-lipid on the template DNA. The population of spherical particles is monodisperse and stable over days, in physiological conditions. Together with a negative surface potential, these properties should ensure good tissue dissemination and escape from the blood stream after i.v. injection.     

脂质体介导质粒DNA细胞转染的优化研究

Objective:The development of gene carriers for efficient gene delivery into cells has attracted growing attention in recent years. The aim of this study was to achieve a better outcome of AAV-293 cells transfection by plasmid DNA.Methods:We studied the optimal condition for higher efficiency of cationic lipid-mediated cell transfection. Four experimental groups were set. Plasmid DNA and liposome were mixed in each groups at different ratios (μg :μL), 1:2.5,1:3.5,1:4.0 and 1:5.0, respectively. LacZ gene functioned as reporter gene, measuring the transfection efficiency of the four groups using the method of X-gal staining. Results:When the ratio was 1:3.5, the cell transfection rate was the highest. While the ratio of 1:2.5recommended by product manual achieve the lowest transfection rate. Their difference had statistical significance. Conclusion:In order to obtain a higher transfection efficiency, optimization on conditions of the ratio of plasmid DNA to liposome is necessary in cell transfection.