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Objectiveof this work was cloning of the Vibrio cholerae nanH gene as part of a plasmid vector, providing expression of foreign genes under the control of T5 promoter, and construction of a E. coli strain – producer of V. cholerae recombinant neuraminidase.Materials and methods. V. cholerae о1 strain served as a DNA donor, pQE30 – as a vector plasmid. The gene was PCR-amplifi ed, the cloning was carried out by means of conventional methods, performance of recombinants and localization of the required protein was determined based on the results of electrophoresis of cell lysates. Neuraminidase activity was identifi ed by fl uorescence in ultraviolet light after incubation with specifi c substrate (4-methylumbelliferyl-N-acetylneuraminic acid).Results and discussion. Recombinant plasmid pNanH, containing the cloned gene nanH V. cholerae, has been constructed. The gene is inserted into BamHI-PstI sites of the polylinker of pQE30. Expression of the cloned gene in the producer strain E. coli JM103pNanH occurs under the control of T5 promoter after isopropyl-1-thio-β-D-galactopyranoside (IPTG) induction. The strain shows neuraminidase activity. The recombinant NanH protein is accumulated in the producer’s cells in two forms. The fi rst form, with molecular mass (MM) of 89.5 kDa, is an unprocessed protein with the hexahistidine block (6His-tag) at its N-terminus, it is located in inclusion bodies. Its percentage is 5.6–6.6 % of the total cell proteins. The second one, with MM of 83 kDa, is found in the periplasmic space and corresponds to the mature NanH, its percentage being 3.4–3.8 %. The total percentage of both forms is 9–10 % of total cell proteins, which allows to consider the strain E. coli JM103pNanH to be a super-producer of the required protein. The strain may be used for purifi cation of NanH preparations for construction of specifi c diagnostic, therapeutic and pharmaceutical preparations as well as for investigation of the protein as a virulence/persistence factor of the pathogen.

Graphical abstract, DNA cloning remains the primary step before the further investigation of gene function. Restriction enzyme-based cloning methods are still widely used and numerous restriction-free cloning techniques are available as alternatives. Here we describe a PCR-based cloning method named ABC cloning. This method uses PCR to combine three overlapping DNA fragments into a recombinant vector that can be immediately transformed into competent cells. This technique uses only a thermostable DNA polymerase and is more rapid and efficient than previously described methods.

The phosphatidylinositol 3-kinases (PIK3s) are lipid kinases. Mutation in the exon 9 and exon 20 determined as a predictive factor in anti-HER-2 therapy. In some countries, such as Singapore, China, and Peru, PIK3CA exon 9 E545A was reported to produce the highest rate of mutation. In this research, we developed and optimized PIK3CA exon 9 E545A detection methods with intercalating dye SYBR Green I based on the Tm Shift approach by using prepared recombinant plasmid pGEMT-easy PIK3CA exon 9 and PIK3CA exon 9 E545A. Recombinant plasmid was used due to the limited number of samples. Methods: Recombinant plasmid was prepared based on manufactured procedures, and this process was then followed by Tm prediction with Poland software, Tm Shift SYBR Green I development, and its characterization (reproducibility, repeatability, sensitivity, qPCR efficiency, and qPCR amplification), respectively. Result: A method for PIK3CA E545A detection based on TM shift SYBR Green I has been successfully developed. The melting temperature for PIK3CA exon 9 was 78.1 ± 0.1 °C, while that for PIK3CA exon E545A was 80.20 °C. The Tm of mutant was the same as that predicted using Polland Software. The reproducibility of the methods was high, with the coefficient values for inter and intra assays were below 10% with a high sensitivity at 1%, while R2 0.99 and PCR efficiency was 97.75%. Conclusion: The results presented here demonstrate that the PIK3CA exon 9 E545A detection method has a good sensitivity and efficacy assay, which proves that the method has a high diagnostic accuracy in breast cancer. Keywords: SYBR Green I, PIK3CA E545A, Breast cancer, Real time PCR, Recombinant plasmid

Objective of this work was the cloning of Vibrio cholerae hlyA gene in a plasmid vector providing expression of foreign genes under the control of T5 promoter, and construction of E. coli strain – super-producer of Vibrio cholerae recombinant hemolysin. Materials and methods . V. cholerae о1 strain served as a DNA donor, pQE30 – as a vector plasmid. The gene was PCR-amplified, cloning was carried out by means of conventional methods, productivity of recombinants and localization of the required protein was determined based on the results of electrophoresis of cell lysates. Results and conclusions. A recombinant plasmid pHlyA, expressing the cloned hlyA gene of Vibrio cholerae El Tor under the control of T5 promoter after IPTG induction, has been constructed. Carrying this plasmid strain E. coli M15[pREP4]pHlyA is the super-producer of hemolysin: the content of the product in whole cell lysates is up to 13 %, and in inclusion bodies – up to 17 % of the total cell proteins. The product of the cloned gene, in spite of the absence of proteolytic processing and presence of the hexahistidine block (6His-tag) at its N-terminus, possesses hemolytic activity towards sheep erythrocytes. 6His-tag will provide for obtaining a purified preparation on specific sorbents with a view to create diagnosticums as well as to study the significance of hemolysin as a pathogenicity/persistence factor. The advantages of this producer are the high output of the required protein, inability of synthesis of any accessory biologically active substances, short-term period of biomass growing (4–6 h including induction) and possibility of culturing without sticking to the guidelines for work with the agents of particularly dangerous infections.

Objective of the study is to construct recombinant E. coli strain – producer of TcpA protein of cholera agent El Tor, carrying tcpACIRS gene in its genome, and use the strains for antigen production. Materials and methods. Utilized was non-toxigenic genovariant strain of Vibrio cholerae biovar El Tor from the “State Collection of Pathogenic Bacteria” at the premises of RusRAPI “Microbe”, as well as commercial E. coli strains and plasmids for cloning (Invitrogen, USA). Chromosomal DNA from V. cholerae cells was extracted using Charge Smitch gDNA Mini Bacteria Kit applying nucleo-sorption. To extract plasmid DNA from E. coli cells PureLink Quick Plasmid DNA MiniprepKits were used. The presence of tcpACIRS gene was assayed by PCR, using designed through our own efforts primers. DNA fragments were isolated from agarose gel with the help of PCR Clear-Up-System panel. SDS-PAGE was performed according to U.K.Laemmli method. Protein content of samples was measured by M.M.Bradford method. The panel for affinity chromatography was applied for recombinant TcpA protein purification. Results and conclusions. Constructed safe strain of E. coli is the producer of recombinant TcpA protein, basic subunit of toxin-coregulated pilus of adhesion of cholera agent biovar El Tor. The region of tcpA gene of Vibrio cholerae biovar El Tor was cloned as part of vector plasmid pET302 by the restriction sites XhoI-BamHI in E. coli strain BL21(DE3)Star. In the stated design protein biosynthesis is under transcriptional control of phage promoter T7 and induced by isopropyl-s-thiogalactoside (IPTG). Tested were the conditions for optimum TcpA protein production and the layout of its purification using affinity chromatography. It was demonstrated that TcpA is present in cells of intestinal bacterium, both in native form and as inclusion bodies. Overall TcpA protein production amounted to 60 mcg/ml. Obtained purified TcpA protein can be used for studies of its immunogenic and physical-chemical properties, as well as development of immune-diagnostic preparations to evaluate the level of TcpA production in various V. cholerae strains, and identification of antigen composition of cholera vaccine preparations.

Cloning of a DNA fragment into a vector is one of the fundamental techniques in recombinant DNA technology. Recently, an in vitro recombination system for DNA cloning was shown to enable the joining of multiple DNA fragments at once. Interestingly, E. coli potentially assembles multiple linear DNA fragments that are introduced into the cell. Improved protocols for this in vivo cloning have realized a high level of usability, comparable to that by in vitro recombination reactions. However, the mechanism of in vivo cloning is highly controversial. Here, we clarified the fundamental mechanism underlying in vivo cloning and also constructed a strain that was optimized for in vivo cloning. Additionally, we streamlined the procedure of in vivo cloning by using a single microcentrifuge tube., Escherichia coli has an ability to assemble DNA fragments with homologous overlapping sequences of 15 to 40 bp at each end. Several modified protocols have already been reported to improve this simple and useful DNA cloning technology. However, the molecular mechanism by which E. coli accomplishes such cloning is still unknown. In this study, we provide evidence that the in vivo cloning of E. coli is independent of both RecA and RecET recombinases but is dependent on XthA, a 3′ to 5′ exonuclease. Here, in vivo cloning of E. coli by XthA is referred to as in vivo E. coli cloning (iVEC). We also show that iVEC activity is reduced by deletion of the C-terminal domain of DNA polymerase I (PolA). Collectively, these results suggest the following mechanism of iVEC. First, XthA resects the 3′ ends of linear DNA fragments that are introduced into E. coli cells, resulting in exposure of the single-stranded 5′ overhangs. Then, the complementary single-stranded DNA ends hybridize each other, and gaps are filled by DNA polymerase I. Elucidation of the iVEC mechanism at the molecular level would further advance the development of in vivo DNA cloning technology. Already we have successfully demonstrated multiple-fragment assembly of up to seven fragments in combination with an effortless transformation procedure using a modified host strain for iVEC. IMPORTANCE Cloning of a DNA fragment into a vector is one of the fundamental techniques in recombinant DNA technology. Recently, an in vitro recombination system for DNA cloning was shown to enable the joining of multiple DNA fragments at once. Interestingly, E. coli potentially assembles multiple linear DNA fragments that are introduced into the cell. Improved protocols for this in vivo cloning have realized a high level of usability, comparable to that by in vitro recombination reactions. However, the mechanism of in vivo cloning is highly controversial. Here, we clarified the fundamental mechanism underlying in vivo cloning and also constructed a strain that was optimized for in vivo cloning. Additionally, we streamlined the procedure of in vivo cloning by using a single microcentrifuge tube.

A total of ~38.6 million mortalities occur due to liver cancer annually, worldwide. Although a variety of therapeutic methods are available, the efficacy of treatment at present is extremely limited due to an increased risk of malignancy and inherently poor prognosis of liver cancer. Gene therapy is considered a promising option, and has shown notable potential for the comprehensive therapy of liver cancer, in keeping with advances that have been made in the development of cancer molecular biology. The present study aimed to investigate the synergistic effects of the abilities of the hemagglutinin neuraminidase protein of Newcastle disease virus (NDV), the pro-apoptotic factor apoptin from chicken anaemia virus, and the interferon-γ inducer interleukin-18 (IL-18) in antagonizing liver cancer. Therefore, a recombinant DNA plasmid expressing the three exogenous genes, VP3, IL-18 and hemagglutinin neuraminidase (HN), was constructed. Flow cytometry, acridine orange/ethidium bromide staining and analysis of caspase-3 activity were performed in H22 cell lines transfected with the recombinant DNA plasmid. In addition, 6-week-old C57BL/6 mice were used to establish a H22 hepatoma-bearing mouse model. Mice tumor tissue was analyzed by immunohistochemistry and scanning electron microscopy. The results of the present study revealed that the recombinant DNA vaccine containing the VP3, IL-18 and HN genes inhibited cell proliferation and induced autophagy via the mitochondrial pathway in vivo and in vitro.

Background To develop a new 18 high-risk human papillomavirus (HR HPV) detection and genotyping assay, which is important to evaluate the risk degree of HR HPV for causing cancers. Methods All 18 HR HPV and β-globin relative DNA fragments were synthesized and cloned to a plasmid pUC57 to obtain their recombinant plasmids. Based on the matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) platform, each of the 18 HR HPV genotypes were investigated using their constructed recombinant plasmids. The new 18 HR HPV genotyping assay was tested using 356 clinical specimens and the results were compared to ones detected by the Roche Cobas 4800 HPV assay (Cobas). The discrepant results between two assays were resolved by sequencing and genotyping methods. Results The new 18 HR HPV MALDI-TOF MS genotyping assay was developed using HPV recombination plasmids. The sensitivity was 103 to 102 copies/reaction for the all 18 HR HPV. This new developed HR HPV genotyping test was used to detect the clinical specimens. When the results on clinical samples detected by the new MALDI-TOF MS HPV test were compared with ones detected by the Roche Cobas 4800 HPV assay in terms of 14 HR HPV, the concordance was 80.1% (kappa coefficient, 0.60; 95% confidence interval [CI], 0.52–0.69). The discrepant results were resolved by sequencing and genotyping and suggests that the developed HR HPV assay is more sensitive and specific. Conclusions The new developed 18 HR HPV detection method based on MALDI-TOF MS platform is a high-throughput assay for the all 18 HR HPV genotypes and a powerful complement to current detection methods. Electronic supplementary material The online version of this article (10.1186/s12885-019-6036-z) contains supplementary material, which is available to authorized users.

Background Silent information regulator 2 (SIR2) proteins are a family of NAD + -dependent protein deacetylases that are considered potential targets for anti-parasitic agents. In this study, we cloned and characterized SIR2A of the protozoan parasite Eimeria tenella (EtSIR2A) and investigated its protective efficacy as a DNA vaccine. Methods The EtSIR2A gene encoding 33.37 kDa protein from E. tenella second-generation merozoites was cloned, and recombinant EtSIR2A protein (rEtSIR2A) was produced in an Escherichia coli expression system. The rEtSIR2A was used to immunize rabbits. Anti-rEtSIR2A antibodies were used to determine the immunolocolization of EtSIR2A in the parasite by immunofluorescence assay (IFA). Transcript and protein expression of EtSIR2A in different development stages of E. tenella were observed by quantitative real-time PCR (qPCR) and western blot (WB) analysis, respectively. The recombinant plasmid pCAGGS-EtSIR2A was constructed and its efficacy against E. tenella infection in chickens was evaluated. Results qPCR and WB analysis revealed EtSIR2A expression was developmentally regulated at both the mRNA and protein levels. EtSIR2A mRNA levels were higher in unsporulated oocysts than at other developmental stages, including sporulated oocysts, sporozoites and second-generation merozoites. In contrast, EtSIR2A protein expression levels were highest in second-generation merozoites, moderate in unsporulated oocysts and sporulated oocysts and lowest in sporozoites. Immunostaining with anti-rEtSIR2A antibody indicated that EtSIR2A was mainly located in the cytoplasm of sporozoites and second-generation merozoites, and was strongly expressed during first stage schizogony. Animal-challenge experiments demonstrated that immunization with pCAGGS-EtSIR2A significantly increased average body-weight gain, and decreased mean lesion score and oocyst output in chickens. Conclusions These results suggest that EtSIR2A may play an important role in parasite cell survival and may be an effective candidate for the development of new vaccines against E. tenella infection in chickens. Electronic supplementary material The online version of this article (doi:10.1186/s13071-016-1871-0) contains supplementary material, which is available to authorized users.

Background Molecular cloning is an essential step in biological engineering. Methods involving megaprimer-based PCR of a whole plasmid are promising alternatives to the traditional restriction-ligation-based molecular cloning. Their widespread use, however, is hampered by some of their inherent characteristics, e.g., linear amplification, use of self-annealing megaprimers and difficulty with performing point insertion of DNA. These limitations result in low product yield and reduced flexibility in the design of a genetic construct. Result Here, we present a novel technique of directional cloning, which overcomes these problems yet retaining the simplicity of whole-plasmid amplification. QuickStep-Cloning utilizes asymmetric PCRs to create a megaprimer pair with 3′-overhangs, and hence, facilitates the subsequent exponential whole-plasmid amplification. QuickStep-Cloning generates nicked-circular plasmids, thereby permitting direct bacterial transformation without DNA ligation. It allows DNA fragment integration into any plasmid at any position, in an efficient, time- and cost-effective manner, without tedious intermediate DNA gel purification, modified oligonucleotides, specialty enzymes and ultra-competent cells. The method is compatible with competent E. coli cells prepared using the conventional calcium chloride method. Conclusion QuickStep-Cloning expands the versatility of megaprimer-based cloning. It is an excellent addition to the cloning toolbox, for the benefit of protein engineers, metabolic engineers and synthetic biologists. Electronic supplementary material The online version of this article (doi:10.1186/s13036-015-0010-3) contains supplementary material, which is available to authorized users.

Experimental studies have shown that dental pulp tissue has potential to regenerate dentine in response to adverse stimuli, such as caries and associated operative procedures. However, the potential of dental pulp regeneration seems to be limited by regenerative capacity of the cell involved. In this study, we report the effect of transfection of a recombinant plasmid containing human BMP-2 gene in proliferation and differentiation of dental pulp tissue in vitro. The regenerative capacity was analyzed by ALP production and calcium content. Results showed that the transfected dental pulp cell was able to differentiate into the odontoblast phenotype, indicating the presence of odontoblast progentitor cells in dental pulp tissue.

Ultrashort pulsed laser ablation in liquids represents a powerful tool for the generation of pure gold nanoparticles (AuNPs) avoiding chemical precursors and thereby making them especially interesting for biomedical applications. However, because of their electron accepting properties, laser-generated AuNPs might affect biochemical properties of biomolecules, which often adsorb onto the nanoparticles. We investigated possible effects of such laser-generated AuNPs on biological functionality of DNA molecules. We tested four differently sized and positively charged AuNPs by incubating them with recombinant eGFP-C1-HMGB1 DNA expression plasmids that code for eGFP fusion proteins and contain the canine architectural transcription factor HMGB1. We were able to show that successfully transfected mammalian cells are still able to synthesize and process the fusion proteins. Our observations revealed that incubation of AuNP with the plasmid DNA encoding the recombinant canine HMGB1 neither prevented the mediated uptake of the vector through the plasma membrane in presence of a transfection reagent nor had any effect on the transport of the synthesized fusion proteins to the nuclei. Biological activity of the recombinant GFP-HMGB1 fusion protein appears to have not been affected either, as a strong characteristic protein accumulation in the nucleus could be observed. We also discovered that transfection efficiencies depend on the size of AuNP. In conclusion, our data indicate that laser-generated AuNPs present a good alternative to chemically synthesized nanoparticles for use in biomedical applications.

An efficient expression system was constructed for C-EGF, a fusion protein made of a fragment of the cell-binding domain of human fibronectin (FN) bound with epidermal growth factor (EGF), C-EGF was produced in Escherichia coli HB101 cells carrying the recombinant plasmid pCE102 as inclusion bodies, which were solubilized and refolded after purification. C-EGF had both cell-adhesive and EGF activities, so it might be more effective than EGF in therapeutic applications. This fusion system would be useful for the construction of a recombinant drug delivery system for cells that have fibronectin receptors (integrins).

Yingchih Wang,1,* Li Mo,2,* Wenbin Wei,1 Xuehui Shi1 1Beijing Tongren Eye Center, Capital Medical University, Beijing, People's Republic of China; 2Department of Ophthalmology, The 180th Hospital of PLA, Quanzhou, People's Republic of China *These authors contributed equally to this work Abstract: Human uveal melanoma is the most common primary intraocular tumor, and brachytherapy is one of the most common and effective treatment strategies. In order to find a safer and more effective way to increase the radio sensitivity of the tumor, we tried to use the dendrimer nanoparticle performing coexpression gene radiotherapy. In this study, we constructed recombinant DNA plasmids (early growth response-1 tumor necrosis factor-α [pEgr1-TNFα], pEgr1 thymidine kinase [TK], and pEgr1-TNFα -TK) according to the Egr1 promoter sequence. The sequences of human TNFα and herpes simplex virus (HSV) TK that were published by GenBank. Agarose gel electrophoresis and DNA sequencing had proven that we constructed the double-gene recombined plasmids pEgr1-TNF-TK correctly, as well as the plasmids pEgr1-TNFα and pEgr1-TK. The dendrimer nanoparticles combined with plasmid DNA as dendriplexes were verified with agarose gel electrophoresis and observed by transmission electron microscopy (TEM) and scanning electron microscopy to define size and shape. Zeta potential was measured using a Zetasizer analyzer. Optimal size and neutral zeta-potential characteristics of dendriplexes were achieved for the transfection studies. DNase I examination proved that the dendriplexes could protect plasmid DNA for at least 6 hours. The recombinant plasmids were transfected with dendrimer nanoparticles into the human choroidal melanoma OCM-1 cell line, followed by exposure to iodine-125 (125I) after transfection. After transfection with dendrimer nanoparticles and the irradiation of 125I, the gene expressions of TNFα and HSV1-TK were significantly increased at the protein level by enzyme-linked immunosorbent assay and Western blot analysis in OCM-1 cells. The cellular morphology of OCM-1 cells altering was observed by TEM, and a decrease in cell proliferation was revealed in cell-growth curves. Flow cytometry of annexin V/propidium iodide double-dyeing apoptosis and caspase-3 fluorescence staining showed that this treatment method could turn transfected OCM-1 cells into apoptosis and necrosis by the effects of the gene expression. This study indicated that the dendrimer nanoparticles with coexpression of TNF-α and HSV1-TK gene therapy are effective and safe and can provide us with a novel strategy to treat human uveal melanoma in the future. Keywords: recombinant plasmid, human uveal melanoma, gene radiotherapy, gene expression, dendrimer nanoparticle

Mycobacterium tuberculosis 6-kDa early secretory antigenic target (ESAT-6) is a dominant target antigen for cell-mediated immunity in the early phase of tuberculosis. The fms-like tyrosine kinase 3 ligand (FL) that induces potent immune response has been used as an adjuvant in vaccine development. In this study, a new recombinant plasmid (pIRES-epitope-peptides-FL) encoding three T cell epitopes of ESAT-6 and FL was constructed, and the immunogenicity of the DNA vaccine was assessed in C57BL/6 mice immunized with the plasmid DNA vaccine. Additionally, a strategy of intramuscular injection with the DNA vaccine (prime) and intranasal administration of the epitope peptides (boost) was employed to induce higher immune reaction of the mice. The results showed that mice vaccinated with the recombinant plasmid DNA vaccine and boosted with the peptides not only increased the levels of Th1 cytokines (IFN-γ and IL-12), the number of IFN-γ(+) T cells and activities of cytotoxic T lymphocytes as well as IgG, but also enhanced protection against Mycobacterium tuberculosis challenge. In conclusion, these data indicate that the novel recombinant pIRES-epitope-peptides-FL plasmid is a useful DNA vaccine for preventing Mycobacterium tuberculosis infection.