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Ling N, Liu H, Guo J, Liang Z, Zhang Y, Li H, Wu H, Xie T, Yuan Y, Li X, Peng M, Wei X, Liang L, Liu J, Wu W, Ye M. Generation of DNA Aptamers with Functional Activity in Mammalian Cells by Mimicking Retroviruses. Anal Chem 2023. [PMID: 37327388 DOI: 10.1021/acs.analchem.3c00387] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
DNA aptamers are single-stranded DNA oligonucleotide sequences that bind to specific targets with high affinity. Currently, DNA aptamers can be produced only by in vitro synthesis. It is difficult for DNA aptamers to have a sustained impact on intracellular protein activity, which limits their clinical application. In this study, we developed a DNA aptamer expression system to generate DNA aptamers with functional activity in mammalian cells by mimicking retroviruses. Using this system, DNA aptamers targeting intracellular Ras (Ra1) and membrane-bound CD71 (XQ2) were successfully generated in cells. In particular, the expressed Ra1 not only specifically bound to the intracellular Ras protein but also inhibited the phosphorylation of downstream ERK1/2 and AKT. Furthermore, by inserting the DNA aptamer expression system for Ra1 into a lentivirus vector, the system can be delivered into cells and stably produce Ra1 over time, resulting in the inhibition of lung cancer cell proliferation. Therefore, our study provides a novel strategy for the intracellular generation of DNA aptamers with functional activity and opens a new avenue for the clinical application of intracellular DNA aptamers in disease treatment.
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Affiliation(s)
- Neng Ling
- Molecular Science and Biomedicine Laboratory (MBL), State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Biology, College of Chemistry and Chemical Engineering, Aptamer Engineering Center of Hunan Province, Hunan University, Changsha, Hunan 410082, China
| | - Huiming Liu
- Molecular Science and Biomedicine Laboratory (MBL), State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Biology, College of Chemistry and Chemical Engineering, Aptamer Engineering Center of Hunan Province, Hunan University, Changsha, Hunan 410082, China
| | - Junxiao Guo
- Molecular Science and Biomedicine Laboratory (MBL), State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Biology, College of Chemistry and Chemical Engineering, Aptamer Engineering Center of Hunan Province, Hunan University, Changsha, Hunan 410082, China
| | - Zhouliang Liang
- Molecular Science and Biomedicine Laboratory (MBL), State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Biology, College of Chemistry and Chemical Engineering, Aptamer Engineering Center of Hunan Province, Hunan University, Changsha, Hunan 410082, China
| | - Yibin Zhang
- Department of Pathology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China
| | - Hui Li
- Molecular Science and Biomedicine Laboratory (MBL), State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Biology, College of Chemistry and Chemical Engineering, Aptamer Engineering Center of Hunan Province, Hunan University, Changsha, Hunan 410082, China
| | - Hui Wu
- Molecular Science and Biomedicine Laboratory (MBL), State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Biology, College of Chemistry and Chemical Engineering, Aptamer Engineering Center of Hunan Province, Hunan University, Changsha, Hunan 410082, China
| | - Tiantian Xie
- Molecular Science and Biomedicine Laboratory (MBL), State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Biology, College of Chemistry and Chemical Engineering, Aptamer Engineering Center of Hunan Province, Hunan University, Changsha, Hunan 410082, China
| | - Yijun Yuan
- Molecular Science and Biomedicine Laboratory (MBL), State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Biology, College of Chemistry and Chemical Engineering, Aptamer Engineering Center of Hunan Province, Hunan University, Changsha, Hunan 410082, China
| | - Xiahui Li
- Molecular Science and Biomedicine Laboratory (MBL), State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Biology, College of Chemistry and Chemical Engineering, Aptamer Engineering Center of Hunan Province, Hunan University, Changsha, Hunan 410082, China
| | - Menglan Peng
- Molecular Science and Biomedicine Laboratory (MBL), State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Biology, College of Chemistry and Chemical Engineering, Aptamer Engineering Center of Hunan Province, Hunan University, Changsha, Hunan 410082, China
| | - Xianhua Wei
- Molecular Science and Biomedicine Laboratory (MBL), State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Biology, College of Chemistry and Chemical Engineering, Aptamer Engineering Center of Hunan Province, Hunan University, Changsha, Hunan 410082, China
| | - Long Liang
- Molecular Biology Research Center and Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410078, China
| | - Jing Liu
- Molecular Biology Research Center and Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410078, China
| | - Wencan Wu
- The Eye Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325027, China
- Oujiang Laboratory (Zhejiang Lab for Regenerative Medicine, Vision and Brain Health), Wenzhou, Zhejiang 325000, China
| | - Mao Ye
- Molecular Science and Biomedicine Laboratory (MBL), State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Biology, College of Chemistry and Chemical Engineering, Aptamer Engineering Center of Hunan Province, Hunan University, Changsha, Hunan 410082, China
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Abstract
Retrons are bacterial genetic elements involved in anti-phage defense. They have the unique ability to reverse transcribe RNA into multicopy single-stranded DNA (msDNA) that remains covalently linked to their template RNA. Retrons coupled with CRISPR-Cas9 in yeast have been shown to improve the efficiency of precise genome editing via homology-directed repair (HDR). In human cells, HDR editing efficiency has been limited by challenges associated with delivering extracellular donor DNA encoding the desired mutation. In this study, we tested the ability of retrons to produce msDNA as donor DNA and facilitate HDR by tethering msDNA to guide RNA in HEK293T and K562 cells. Through heterologous reconstitution of retrons from multiple bacterial species with the CRISPR-Cas9 system, we demonstrated HDR rates of up to 11.4%. Overall, our findings represent the first step in extending retron-based precise gene editing to human cells.
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Affiliation(s)
- Bin Zhao
- Department of Biology, Stanford University, Stanford, California, USA
| | - Shi-An A. Chen
- Department of Biology, Stanford University, Stanford, California, USA
| | - Jiwoo Lee
- Department of Biology, Stanford University, Stanford, California, USA
| | - Hunter B. Fraser
- Department of Biology, Stanford University, Stanford, California, USA
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3
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Heiat M, Ranjbar R, Latifi AM, Rasaee MJ, Farnoosh G. Essential strategies to optimize asymmetric PCR conditions as a reliable method to generate large amount of ssDNA aptamers. Biotechnol Appl Biochem 2017; 64:541-548. [PMID: 27222205 DOI: 10.1002/bab.1507] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2016] [Accepted: 05/20/2016] [Indexed: 12/19/2022]
Abstract
Asymmetric PCR, a simple method to generate single-stranded DNA (ssDNA) aptamers in systematic evaluation of ligand by exponential enrichments rounds, is coupled with limitations. We investigated the essential strategies for optimization of conditions to perform a high-quality asymmetric PCR. Final concentrations of primers and template, the number of PCR cycles, and annealing temperature were selected as optimizing variables. The qualities of visualized PCR products were analyzed by ImageJ software. The highest proportion of interested DNA than unwanted products was considered as optimum conditions. Results revealed that the best values for primers ratio, final template concentration, annealing temperature, and PCR cycles were, respectively, 30:1, 1 ng/μL, 55 °C, and 20 cycles for the first and 50:1, 2 ng/μL, 59 °C, and 20 cycles for other rounds. No significant difference was found between optimized asymmetric PCR results in the rounds of two to eight (P > 0.05). The ssDNA quality in round 10 was significantly better than other rounds (P < 0.05). Generally, the ssDNA product with less dimers, double-stranded DNA (dsDNA), and smear are preferable. The dsDNA contamination is the worst, because it can act as antidote and inhibits aptameric performance. Therefore, to choose the best conditions, the lower amount of dsDNA is more important than other unwanted products.
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Affiliation(s)
- Mohammad Heiat
- Molecular Biology Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran
| | - Reza Ranjbar
- Molecular Biology Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran
| | - Ali Mohammad Latifi
- Applied Biotechnology Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran
| | - Mohammad Javad Rasaee
- Department of Clinical Biochemistry, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| | - Gholamreza Farnoosh
- Applied Biotechnology Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran
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Reza F, Glazer PM. Therapeutic genome mutagenesis using synthetic donor DNA and triplex-forming molecules. Methods Mol Biol 2015; 1239:39-73. [PMID: 25408401 PMCID: PMC6608751 DOI: 10.1007/978-1-4939-1862-1_4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Genome mutagenesis can be achieved in a variety of ways, though a select few are suitable for therapeutic settings. Among them, the harnessing of intracellular homologous recombination affords the safety and efficacy profile suitable for such settings. Recombinagenic donor DNA and mutagenic triplex-forming molecules co-opt this natural recombination phenomenon to enable the specific, heritable editing and targeting of the genome. Editing the genome is achieved by designing the sequence-specific recombinagenic donor DNA to have base mismatches, insertions, and deletions that will be incorporated into the genome when it is used as a template for recombination. Targeting the genome is similarly achieved by designing the sequence-specific mutagenic triplex-forming molecules to further recruit the recombination machinery thereby upregulating its activity with the recombinagenic donor DNA. This combination of extracellularly introduced, designed synthetic molecules and intercellularly ubiquitous, evolved natural machinery enables the mutagenesis of chromosomes and engineering of whole genomes with great fidelity while limiting nonspecific interactions. Herein, we demonstrate the harnessing of recombinagenic donor DNA and mutagenic triplex-forming molecular technology for potential therapeutic applications. These demonstrations involve, among others, utilizing this technology to correct genes so that they become physiologically functional, to induce dormant yet functional genes in place of non-functional counterparts, to place induced genes under regulatory elements, and to disrupt genes to abrogate a cellular vulnerability. Ancillary demonstrations of the design and synthesis of this recombinagenic and mutagenic molecular technology as well as their delivery and assayed interaction with duplex DNA reveal a potent technological platform for engineering specific changes into the living genome.
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Affiliation(s)
- Faisal Reza
- Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT, 06520-8040, USA
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Sargent RG, Kim S, Gruenert DC. Oligo/polynucleotide-based gene modification: strategies and therapeutic potential. Oligonucleotides 2011; 21:55-75. [PMID: 21417933 DOI: 10.1089/oli.2010.0273] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Oligonucleotide- and polynucleotide-based gene modification strategies were developed as an alternative to transgene-based and classical gene targeting-based gene therapy approaches for treatment of genetic disorders. Unlike the transgene-based strategies, oligo/polynucleotide gene targeting approaches maintain gene integrity and the relationship between the protein coding and gene-specific regulatory sequences. Oligo/polynucleotide-based gene modification also has several advantages over classical vector-based homologous recombination approaches. These include essentially complete homology to the target sequence and the potential to rapidly engineer patient-specific oligo/polynucleotide gene modification reagents. Several oligo/polynucleotide-based approaches have been shown to successfully mediate sequence-specific modification of genomic DNA in mammalian cells. The strategies involve the use of polynucleotide small DNA fragments, triplex-forming oligonucleotides, and single-stranded oligodeoxynucleotides to mediate homologous exchange. The primary focus of this review will be on the mechanistic aspects of the small fragment homologous replacement, triplex-forming oligonucleotide-mediated, and single-stranded oligodeoxynucleotide-mediated gene modification strategies as it relates to their therapeutic potential.
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Affiliation(s)
- R Geoffrey Sargent
- Department of Otolaryngology-Head and Neck Surgery, University of California , San Francisco, California 94115, USA
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Liu Y, Nairn RS, Vasquez KM. Targeted gene conversion induced by triplex-directed psoralen interstrand crosslinks in mammalian cells. Nucleic Acids Res 2009; 37:6378-88. [PMID: 19726585 PMCID: PMC2770658 DOI: 10.1093/nar/gkp678] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Correction of a defective gene is a promising approach for both basic research and clinical gene therapy. However, the absence of site-specific targeting and the low efficiency of homologous recombination in human cells present barriers to successful gene targeting. In an effort to overcome these barriers, we utilized triplex-forming oligonucleotides (TFOs) conjugated to a DNA interstrand crosslinking (ICL) agent, psoralen (pTFO-ICLs), to improve the gene targeting efficiency at a specific site in DNA. Gene targeting events were monitored by the correction of a deletion on a recipient plasmid with the homologous sequence from a donor plasmid in human cells. The mechanism underlying this event is stimulation of homologous recombination by the pTFO-ICL. We found that pTFO-ICLs are efficient in inducing targeted gene conversion (GC) events in human cells. The deletion size in the recipient plasmid influenced both the recombination frequency and spectrum of recombinants; i.e. plasmids with smaller deletions had a higher frequency and proportion of GC events. The polarity of the pTFO-ICL also had a prominent effect on recombination. Our results suggest that pTFO-ICL induced intermolecular recombination provides an efficient method for targeted gene correction in mammalian cells.
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Affiliation(s)
- Yaobin Liu
- Department of Carcinogenesis, University of Texas MD Anderson Cancer Center, Science Park-Research Division, Smithville, Texas, USA
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Benimetskaya L, Ayyanar K, Kornblum N, Castanotto D, Rossi J, Wu S, Lai J, Brown BD, Popova N, Miller P, McMicken H, Chen Y, Stein CA. Bcl-2 protein in 518A2 melanoma cells in vivo and in vitro. Clin Cancer Res 2006; 12:4940-8. [PMID: 16914583 DOI: 10.1158/1078-0432.ccr-06-1002] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE Bcl-2 is an apoptotic protein that is highly expressed in advanced melanoma. Several strategies have been employed to target the expression of this protein, including G3139, an 18-mer phosphorothioate oligodeoxyribonucleotide targeted to the initiation region of the Bcl-2 mRNA. This compound has recently completed phase III global clinical evaluation, but the function of Bcl-2 as a target in melanoma has not been completely clarified. To help resolve this question, we have permanently and stably down-regulated Bcl-2 protein and mRNA expression in 518A2 cells by two different technologies and evaluated the resulting clones both in vitro and in vivo. EXPERIMENTAL DESIGN 518A2 melanoma cells were transfected with plasmids engineered to produce either a single-stranded antisense oligonucleotide targeted to the initiation codon region of the Bcl-2 mRNA or a short hairpin RNA also targeted to the Bcl-2 mRNA. In vitro growth, the apoptotic response to G3139, and the G3139-induced release of cytochrome c from isolated mitochondria were evaluated. Cells were then xenografted into severe combined immunodeficient mice and tumor growth was measured. RESULTS In vitro, down-regulation of Bcl-2 expression by either method produced no change either in the rate of growth or in sensitivity to standard cytotoxic chemotherapeutic agents. Likewise, the induction of apoptosis by G3139 was entirely Bcl-2 independent. In addition, the G3139-induced release from isolated mitochondria was also relatively independent of Bcl-2 expression. However, when xenografted into severe combined immunodeficient mice, cells with silenced Bcl-2, using either technology, either failed to grow at all or grew to tumors of low volume and then completely regressed. In contrast, control cells with "normal" levels of Bcl-2 protein expression expanded to be large, necrotic tumors. CONCLUSIONS The presence of Bcl-2 protein profoundly affects the ability of 518A2 melanoma cells to grow as human tumor xenografts in severe combined immunodeficient mice. The in vivo role of Bcl-2 in melanoma cells thus differs significantly from its in vitro role, and these experiments further suggest that Bcl-2 may be an important therapeutic target even in tumors that do not contain the t14:18 translocation.
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Affiliation(s)
- Luba Benimetskaya
- Albert Einstein-Montefiore Cancer Center, Department of Oncology, Montefiore Medical Center, Bronx, New York, USA
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8
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Visser AE, Verschure PJ, Gommans WM, Haisma HJ, Rots MG. Step into the Groove: Engineered Transcription Factors as Modulators of Gene Expression. ADVANCES IN GENETICS 2006; 56:131-61. [PMID: 16735157 DOI: 10.1016/s0065-2660(06)56004-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Increasing knowledge about the influence of dysregulated gene expression in causing numerous diseases opens up new possibilities for the development of innovative therapeutics. In this chapter, we first describe different mechanisms of misregulated gene expression resulting in various pathophysiological conditions. Then, an overview is given of different technologies developed to readjust expression levels of genes. One of the most promising upcoming approaches in this respect is the development of engineered zinc-finger transcription factors. Results obtained from modulating endogenous gene expression using such engineered transcription factors are reviewed in depth. Finally, we address possible pitfalls of using such transcriptional targeting approaches at the "chromatin level." We describe aspects of studies at this level that influence successful DNA binding of engineered transcription factors, thereby affecting gene activity. Engineered transcription factors have great promise as potent therapeutics. Moreover, this technology is expected to yield fundamental knowledge about the organization and function of the genome.
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Affiliation(s)
- Astrid E Visser
- Department of Molecular Genetics, Leiden Institute of Chemistry, University of Leiden, 2300 RA Leiden, The Netherlands
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9
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Silverman SK. In vitro selection, characterization, and application of deoxyribozymes that cleave RNA. Nucleic Acids Res 2005; 33:6151-63. [PMID: 16286368 PMCID: PMC1283523 DOI: 10.1093/nar/gki930] [Citation(s) in RCA: 215] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Over the last decade, many catalytically active DNA molecules (deoxyribozymes; DNA enzymes) have been identified by in vitro selection from random-sequence DNA pools. This article focuses on deoxyribozymes that cleave RNA substrates. The first DNA enzyme was reported in 1994 and cleaves an RNA linkage. Since that time, many other RNA-cleaving deoxyribozymes have been identified. Most but not all of these deoxyribozymes require a divalent metal ion cofactor such as Mg2+ to catalyze attack by a specific RNA 2′-hydroxyl group on the adjacent phosphodiester linkage, forming a 2′,3′-cyclic phosphate and a 5′-hydroxyl group. Several deoxyribozymes that cleave RNA have utility for in vitro RNA biochemistry. Some DNA enzymes have been applied in vivo to degrade mRNAs, and others have been engineered into sensors. The practical impact of RNA-cleaving deoxyribozymes should continue to increase as additional applications are developed.
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Affiliation(s)
- Scott K Silverman
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, IL 61801, USA.
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Tan XX, Actor JK, Chen Y. Peptide nucleic acid antisense oligomer as a therapeutic strategy against bacterial infection: proof of principle using mouse intraperitoneal infection. Antimicrob Agents Chemother 2005; 49:3203-7. [PMID: 16048926 PMCID: PMC1196239 DOI: 10.1128/aac.49.8.3203-3207.2005] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Antisense oligodeoxynucleotides (ODNs) and their analogs have been successfully utilized to inhibit gene expression and bacterial growth in vitro or in cell culture. In this study, acpP-targeting antisense peptide nucleic acid (PNA) and its peptide conjugate were tested as potential antibacterial agents in two groups of experiments using a mouse model. In the first group, Escherichia coli mutant strain SM101 with a defective outer membrane was used to induce bacteremia and peritonitis in BALB/c mice by intraperitoneal (i.p.) injection. The resulting bacteremia was fatal within 48 h. A single i.p injection of 5 nmol (or more) of PNA administered 30 min before bacterial challenge significantly reduced the bacterial load in mouse blood. Reductions in serum concentrations of the proinflammatory cytokines tumor necrosis factor alpha, interleukin-1beta (IL-1beta), IL-6, and IL-12 were also observed. PNA treatment was effective in rescuing 100% of infected animals. In the second group, bacteremia in BALB/c mice was induced by i.p. injection of E. coli wild-type strain K-12. The infected mice were treated by a single intravenous injection of peptide-PNA conjugate 30 min after bacterial challenge. Treatment with the peptide-PNA conjugate significantly reduced the K-12 load, with modest reduction in cytokine concentrations. The conjugate treatment was also able to rescue up to 60% of infected animals. This report is the first demonstration of ODNs' antibacterial efficacy in an animal disease model. The ability of PNA and its peptide conjugate to inhibit bacterial growth and to prevent fatal infection demonstrates the potential for this new class of antibacterial agents.
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Affiliation(s)
- Xin-Xing Tan
- Cytogenix, Inc., 3100 Wilcrest Drive, Suite 140, Houston, TX 77042, USA.
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McMicken HW, Bates PJ, Chen Y. Antiproliferative activity of G-quartet-containing oligonucleotides generated by a novel single-stranded DNA expression system. Cancer Gene Ther 2004; 10:867-9. [PMID: 14712312 DOI: 10.1038/sj.cgt.7700652] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Recently, a novel single-stranded DNA (ssDNA) expression system that can generate intracellularly ssDNA or oligodeoxynucleotide (ODN) molecules has been developed. Previous studies showed that this ssDNA expression system is capable of generating DNA enzyme ODNs and triplex-forming oligodeoxynucleotides (TFOs) in cells. In this study, we constructed an ssDNA expression vector that can generate a G-quartet-containing ODNs, GRO29A, in cells. Similar to synthetic ODNs, vector-generated GRO29As were shown to have significant antiproliferative activities in a number of cancer cell lines. These results further demonstrate the potential application of ssDNA expression system in gene target validation and drug development.
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Lestienne P, Pourquier P, Bonnet J. Elongation of oligonucleotide primers forming a triple helix on double-stranded DNA templates by purified DNA polymerases. Biochem Biophys Res Commun 2004; 311:380-5. [PMID: 14592425 DOI: 10.1016/j.bbrc.2003.10.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Current knowledge on the replication of DNA involves enzymatic steps of DNA strand separation upon helicase activity, thus enabling the exposed bases of the single-stranded DNA to direct the polymerization of complementary nucleotides through Watson-Crick base pairing rules by DNA-dependent DNA polymerases. Here, we report that oligonucleotide primers (9-11 nt long) bound to the double-stranded DNA, can be elongated by the T7 and by the Thermus thermophilus DNA polymerases and by the Escherichia coli Klenow fragment. A perfectly base-paired DNA cannot be used as a template, but a single A/A mismatch located even 5 bp upstream from the theoretical 3'-end of the oligonucleotide primer is sufficient for DNA elongation by these first two enzymes, while five are required for the Klenow fragment. Elongation products from templates containing A/A mismatches at different positions revealed similar patterns independently of the positions of the A/A mismatches. The sequencing of the elongated products revealed that both purine and pyrimidine are incorporated at the pyrimidine-purine-pyrimidine transitions of the template strands, probably because of a shift of the primers on the double helix template. These data confirm that prokaryotic DNA polymerases may accommodate transiently three DNA strands in their catalytic centre. They also show for the first time that replication can occur on double-stranded DNA in the absence of DNA helicase, when mismatches are present in the vicinity of the triple helix initiation complex.
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Affiliation(s)
- Patrick Lestienne
- Institut Bergonié, Laboratoire de Pharmacologie des Agents Anticancéreux., FRE 2618 CNRS, 229, cours de l'Argonne, 33076 Bordeaux Cedex, France.
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Uil TG, Haisma HJ, Rots MG. Therapeutic modulation of endogenous gene function by agents with designed DNA-sequence specificities. Nucleic Acids Res 2003; 31:6064-78. [PMID: 14576293 PMCID: PMC275457 DOI: 10.1093/nar/gkg815] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Designer molecules that can specifically target pre-determined DNA sequences provide a means to modulate endogenous gene function. Different classes of sequence-specific DNA-binding agents have been developed, including triplex-forming molecules, synthetic polyamides and designer zinc finger proteins. These different types of designer molecules with their different principles of engineered sequence specificity are reviewed in this paper. Furthermore, we explore and discuss the potential of these molecules as therapeutic modulators of endogenous gene function, focusing on modulation by stable gene modification and by regulation of gene transcription.
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Affiliation(s)
- Taco G Uil
- Department of Molecular Cell Biology, Leiden University Medical Center, Leiden, The Netherlands
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14
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Chen Y, McMicken HW. Intracellular production of DNA enzyme by a novel single-stranded DNA expression vector. Gene Ther 2003; 10:1776-80. [PMID: 12939644 DOI: 10.1038/sj.gt.3302068] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A set of single-stranded DNA (ssDNA) expression vectors, which can generate intracellularly any ssDNA or oligodeoxynucleotide (ODN) molecules, have been developed in our laboratory. Studies from our laboratory as well as our collaborators demonstrated that these ssDNA expression vectors are capable of producing: (1) 10-23 DNA enzyme for downregulating c-raf kinase gene expression and (2) triplex-forming oligodeoxynucleotide (TFO) for inducing genomic recombination. We report here the construction of a new version of ssDNA expression vector. A beta-galactosidase (beta-gal) reporter gene was used as a test target so that the alteration of gene expression can be easily measured using beta-gal activity assay. We designed a 10-23 DNA enzyme molecule that specifically cleaves beta-gal mRNA at protein translation starting site (ATG). Using a cell-free RNA cleavage assay, we confirmed that this DNA enzyme molecule could effectively cleave beta-gal RNA. However, a single substitution from T to G in the catalytic domain of this DNA enzyme molecule abolished its RNA cleavage activity. We also constructed an expression vector that can generate DNA enzyme molecules in cells. A549 lung carcinoma cells were cotransfected with both DNA enzyme expression vector and the beta-gal reporter gene. Compared to the cells that were transfected with the mutated DNA enzyme expression vector, significant reduction of beta-gal gene expression (up to 76%) was observed in the cells transfected with DNA enzyme expression vector as indicated by the protein expression level as well as its enzyme activity. These results further suggest that the ssDNA expression vector has potential applications in the study of gene function and target validation.
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Affiliation(s)
- Y Chen
- CytoGenix, Inc., Houston, TX 77099, USA
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15
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Potaman VN. Applications of triple-stranded nucleic acid structures to DNA purification, detection and analysis. Expert Rev Mol Diagn 2003; 3:481-96. [PMID: 12877387 DOI: 10.1586/14737159.3.4.481] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Regions of double-stranded (duplex) DNA with purine bases predominantly in one strand and pyrimidine bases in the other may bind oligonucleotides of an appropriate sequence to form triple-stranded (triplex) structures. Oligonucleotide analogs and mimics, such as peptide nucleic acid, may also form stable complexes with duplex DNA. Triplex formation enables the specific targeting of duplex domains. The principles of triplex structures and recent developments in the gene therapeutic and biotechnological applications are briefly reviewed. Adaptations of triplex methodology to molecular diagnostics (DNA purification, detection and analysis) are reviewed in greater detail.
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Affiliation(s)
- Vladimir N Potaman
- Institute of Biosciences & Technology, Texas A&M University Health Sciences Center, Houston 77030-3303, USA.
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16
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Abstract
A novel expression vector system has been developed that can intracellularly generate any single-stranded DNA (ssDNA) molecule, such as a triplex-forming oligonucleotide (TFO), antisense oligodeoxynucleotide (ODN) and DNA enzyme, by our laboratory at CytoGenix, Inc. 'Proof of concept' studies from our laboratory as well as our collaborators' indicate that this ssDNA expression vector system is capable of producing, intracellularly, antisense ODNs, DNA enzymes or TFOs for the purpose of downregulating gene expression or inducing targeted genome modification. This technology provides new research tools and has potential applications in gene target validation and drug development.
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Affiliation(s)
- Yin Chen
- CytoGenix, Inc., 9881 S. Wilcrest Drive, Houston, TX 77099, USA.
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Abstract
The nature of DNA, the sequence of the human genome and our increased understanding of the genetic basis of many inherited and acquired disorders have made the possibility of curing diseases a reality. The modulation of a host's genome is now the ultimate goal in the treatment of genetic diseases. Historically, gene therapy recognized two very different approaches: gene replacement or augmentation and gene repair. Gene repair precisely targets and corrects the chromosomal mutation responsible for a genetic and/or acquired disorder. Many recent advances have been made in this area of research.
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Affiliation(s)
- Betsy T Kren
- Department of Medicine, University of Minnesota Medical School MMC 36, Mayo Building A536, 420 Delaware Street, Minneapolis, MN 55455, USA
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Opalinska JB, Gewirtz AM. Nucleic-acid therapeutics: basic principles and recent applications. Nat Rev Drug Discov 2002; 1:503-14. [PMID: 12120257 DOI: 10.1038/nrd837] [Citation(s) in RCA: 384] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The sequencing of the human genome and the elucidation of many molecular pathways that are important in disease have provided unprecedented opportunities for the development of new therapeutics. The types of molecule in development are increasingly varied, and include antisense oligonucleotides and ribozymes. Antisense technology and catalytic nucleic-acid enzymes are important tools for blocking the expression of abnormal genes. One FDA-approved antisense drug is already in the clinic for the treatment of cytomegalovirus retinitis, and other nucleic-acid therapies are undergoing clinical trials. This article reviews different strategies for modulating gene expression, and discusses the successes and problems that are associated with this type of therapy.
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Affiliation(s)
- Joanna B Opalinska
- Department of Hematology, Pommeranian Academy of Medicine, Ul Rybacka 1, 71-252 Szczecin, Poland
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19
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Chen Y. 10th International Conference on gene therapy of cancer: 13 - 15 December 2001, San Diego, CA, USA. Expert Opin Biol Ther 2002; 2:443-5. [PMID: 11955281 DOI: 10.1517/14712598.2.4.443] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
This annual meeting was organised by R Sobol and A Deisseroth (Sidney Kimmel Cancer Center, San Diego, CA, USA) and K Scanlon (Keck Graduate Institute, Claremont, CA, USA). The meeting covered a wide range of topics in cancer gene therapy and included five sessions. The topics were: (1) Tumour suppressors/apoptosis/antisense-ribozymes/angiogenesis; (2) Vector systems; (3) Therapy sensitisation/'suicide' gene therapy; (4) Haematopoietic gene transfer; and (5) Poster/discussion sessions. The following meeting highlights have focused mainly on the recent progress in antisense/ribozyme-based approaches useful for cancer gene target validation and drug development.
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Affiliation(s)
- Yin Chen
- CytoGenix, Inc., 9881 S. Wilcrest Drive, Houston, TX 77584, USA.
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