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Asaad W, Volos P, Maksimov D, Khavina E, Deviatkin A, Mityaeva O, Volchkov P. AAV genome modification for efficient AAV production. Heliyon 2023; 9:e15071. [PMID: 37095911 PMCID: PMC10121408 DOI: 10.1016/j.heliyon.2023.e15071] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Revised: 03/23/2023] [Accepted: 03/27/2023] [Indexed: 04/04/2023] Open
Abstract
The adeno-associated virus (AAV) is one of the most potent vectors in gene therapy. The experimental profile of this vector shows its efficiency and accepted safety, which explains its increased usage by scientists for the research and treatment of a wide range of diseases. These studies require using functional, pure, and high titers of vector particles. In fact, the current knowledge of AAV structure and genome helps improve the scalable production of AAV vectors. In this review, we summarize the latest studies on the optimization of scalable AAV production through modifying the AAV genome or biological processes inside the cell.
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Peng J, Zou WW, Wang XL, Zhang ZG, Huo R, Yang L. Viral-mediated gene therapy in pediatric neurological disorders. World J Pediatr 2023:10.1007/s12519-022-00669-4. [PMID: 36607547 DOI: 10.1007/s12519-022-00669-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Accepted: 11/27/2022] [Indexed: 01/07/2023]
Abstract
BACKGROUND Due to the broad application of next-generation sequencing, the molecular diagnosis of genetic disorders in pediatric neurology is no longer an unachievable goal. However, treatments for neurological genetic disorders in children remain primarily symptomatic. On the other hand, with the continuous evolution of therapeutic viral vectors, gene therapy is becoming a clinical reality. From this perspective, we wrote this review to illustrate the current state regarding viral-mediated gene therapy in childhood neurological disorders. DATA SOURCES We searched databases, including PubMed and Google Scholar, using the keywords "adenovirus vector," "lentivirus vector," and "AAV" for gene therapy, and "immunoreaction induced by gene therapy vectors," "administration routes of gene therapy vectors," and "gene therapy" with "NCL," "SMA," "DMD," "congenital myopathy," "MPS" "leukodystrophy," or "pediatric metabolic disorders". We also screened the database of ClinicalTrials.gov using the keywords "gene therapy for children" and then filtered the results with the ones aimed at neurological disorders. The time range of the search procedure was from the inception of the databases to the present. RESULTS We presented the characteristics of commonly used viral vectors for gene therapy for pediatric neurological disorders and summarized their merits and drawbacks, the administration routes of each vector, the research progress, and the clinical application status of viral-mediated gene therapy on pediatric neurological disorders. CONCLUSIONS Viral-mediated gene therapy is on the brink of broad clinical application. Viral-mediated gene therapy will dramatically change the treatment pattern of childhood neurological disorders, and many children with incurable diseases will meet the dawn of a cure. Nevertheless, the vectors must be optimized for better safety and efficacy.
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Affiliation(s)
- Jing Peng
- Department of Pediatrics, Clinical Research Center for Chidren Neurodevelopmental disablities of Hunan Province, Xiangya Hospital, Central South University, Changsha, 410008, China
| | - Wei-Wei Zou
- Reproductive Medicine Center, Department of Obstetrics and Gynecology, the First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Xiao-Lei Wang
- Reproductive Medicine Center, Department of Obstetrics and Gynecology, the First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Zhi-Guo Zhang
- Reproductive Medicine Center, Department of Obstetrics and Gynecology, the First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Ran Huo
- State Key Laboratory of Reproductive Medicine, Nanjing Medical University, Nanjing, China
| | - Li Yang
- Department of Pediatrics, Clinical Research Center for Chidren Neurodevelopmental disablities of Hunan Province, Xiangya Hospital, Central South University, Changsha, 410008, China.
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3
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Zaman H, Khan A, Khan K, Toheed S, Abdullah M, Zeeshan HM, Hameed A, Umar M, Shahid M, Malik K, Afzal S. Adeno-Associated Virus-Mediated Gene Therapy. Crit Rev Eukaryot Gene Expr 2023; 33:87-100. [PMID: 37522547 DOI: 10.1615/critreveukaryotgeneexpr.2023048135] [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: 08/01/2023]
Abstract
Choice of vector is the most critical step in gene therapy. Adeno-associated viruses (AAV); third generation vectors, are getting much attention of scientists to be used as vehicles due to their non-pathogenicity, excellent safety profile, low immune responses, great efficiency to transduce non-dividing cells, large capacity to transfer genetic material and long-term expression of genetic payload. AAVs have multiple serotypes and each serotype shows tropism for a specific cell. Different serotypes are used to target liver, lungs, muscles, retina, heart, CNS, kidneys, etc. Furthermore, AAV based gene therapies have tremendous marketing applications that can be perfectly incorporated in the anticipated sites of the host target genome resulting in life long expression of transgenes. Some therapeutic products use AAV vectors that are used to treat lipoprotein lipase deficiency (LPLD) and it is injected intramuscularly, to treat mutated retinal pigment epithelium RPE65 (RPE65) that is introduced to subretinal space, an intravenous infusion to treat spinal muscular atrophy and rAAV2-CFTR vector is introduced into nasal epithelial cells to treat cystic fibrosis. AAV therapies and other such interdisciplinary methodologies can create the miracles for the generation of precision gene therapies for the treatment of most serious and sometimes fatal disorders.
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Affiliation(s)
- Hassan Zaman
- Centre of Excellence in Molecular Biology, University of the Punjab, Lahore, Pakistan
| | - Aakif Khan
- Centre of Excellence in Molecular Biology, University of the Punjab, Lahore, Pakistan
| | - Khalid Khan
- Centre of Excellence in Molecular Biology, University of the Punjab, Lahore, Pakistan
| | - Shazma Toheed
- Centre of Excellence in Molecular Biology, University of the Punjab, Lahore, Pakistan
| | - Muhammad Abdullah
- Centre of Excellence in Molecular Biology, University of the Punjab, Lahore, Pakistan
| | | | - Abdul Hameed
- Centre of Excellence in Molecular Biology, University of the Punjab, Lahore, Pakistan
| | - Muhammad Umar
- Centre of Excellence in Molecular Biology, University of the Punjab, Lahore, Pakistan
| | - Muhammad Shahid
- Division of Molecular Virology and Infectious Diseases, Center of Excellence in Molecular Biology (CEMB), 87-West Canal Bank Road Thokar Niaz Baig, University of the Punjab, Lahore, Pakistan
| | - Kausar Malik
- Centre of Excellence in Molecular Biology, University of the Punjab, Lahore, Pakistan
| | - Samia Afzal
- Center of Excellence in Molecular Biology (CEMB), 87-West Canal Bank Road Thokar Niaz Baig, University of the Punjab, Lahore, Pakistan
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4
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Ebner LJA, Grimm C. AAV Serotypes and Their Suitability for Retinal Gene Therapy. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1415:131-134. [PMID: 37440025 DOI: 10.1007/978-3-031-27681-1_20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/14/2023]
Abstract
Throughout the last 25 years, exceptional progress in retinal gene therapy was achieved. The major breakthrough was realized in 2017 when the FDA approved the adeno-associated virus (AAV)-based gene therapy for treatment of the monogenetic disorder Leber congenital amaurosis type 2 (LCA2). Since then, many therapies for inherited retinal diseases (IRD) reached phase I/II clinical trials, targeting diseases like achromatopsia, choroideremia, retinitis pigmentosa, Stargardt disease, and many more (reviewed in (Trapani and Auricchio, Trends Mol Med 24:669-681, 2018)). Advanced vector and capsid design technologies as well as improved gene transfer and gene editing methods may lead to refined therapies for various eye diseases. Many research departments worldwide focus on optimizing transgene expression by designing novel AAV serotypes. Besides serotype tropism, the method of injection (intravitreal, subretinal, or suprachoroidal) (Han et al., Hum Gene Ther 31:1288-1299, 2020) defines the efficiency outcome along with the use of tissue-specific promotors which play a critical role for cell targeting.
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Affiliation(s)
- Lynn J A Ebner
- Lab for Retinal Cell Biology, Department of Ophthalmology, University Hospital Zurich, University of Zurich, Schlieren, Switzerland.
| | - Christian Grimm
- Lab for Retinal Cell Biology, Department of Ophthalmology, University Hospital Zurich, University of Zurich, Schlieren, Switzerland
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5
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Multinuclear MRI in Drug Discovery. Molecules 2022; 27:molecules27196493. [PMID: 36235031 PMCID: PMC9572840 DOI: 10.3390/molecules27196493] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2022] [Revised: 09/17/2022] [Accepted: 09/29/2022] [Indexed: 11/05/2022] Open
Abstract
The continuous development of magnetic resonance imaging broadens the range of applications to newer areas. Using MRI, we can not only visualize, but also track pharmaceutical substances and labeled cells in both in vivo and in vitro tests. 1H is widely used in the MRI method, which is determined by its high content in the human body. The potential of the MRI method makes it an excellent tool for imaging the morphology of the examined objects, and also enables registration of changes at the level of metabolism. There are several reports in the scientific publications on the use of clinical MRI for in vitro tracking. The use of multinuclear MRI has great potential for scientific research and clinical studies. Tuning MRI scanners to the Larmor frequency of a given nucleus, allows imaging without tissue background. Heavy nuclei are components of both drugs and contrast agents and molecular complexes. The implementation of hyperpolarization techniques allows for better MRI sensitivity. The aim of this review is to present the use of multinuclear MRI for investigations in drug delivery.
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6
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Robust AAV Genotyping Based on Genetic Distances in Rep Gene That Are Maintained by Ubiquitous Recombination. Viruses 2022; 14:v14051038. [PMID: 35632781 PMCID: PMC9143360 DOI: 10.3390/v14051038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 05/04/2022] [Accepted: 05/09/2022] [Indexed: 02/01/2023] Open
Abstract
Adeno-associated viruses (AAVs) are a convenient tool for gene therapy delivery. According to the current classification, they are divided into the species AAV A and AAV B within the genus Dependoparvovirus. Historically AAVs were also subdivided on the intraspecies level into 13 serotypes, which differ in tissue tropism and targeted gene delivery capacity. Serotype, however, is not a universal taxonomic category, and their assignment is not always robust. Cross-reactivity has been shown, indicating that classification could not rely on the results of serological tests alone. Moreover, since the isolation of AAV4, all subsequent AAVs were subdivided into serotypes based primarily on genetic differences and phylogenetic reconstructions. An increased interest in the use of AAV as a gene delivery tool justifies the need to improve the existing classification. Here, we suggest genotype-based AAV classification below the species level based on the rep gene. A robust threshold was established as 10% nt differences within the 1248 nt genome fragment, with 4 distinct AAV genotypes identified. This distinct sub-species structure is maintained by ubiquitous recombination within, but not between, rep genes of the suggested genotypes.
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7
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Abstract
Although the sequence of the AAV inverted terminal repeat has been known for 40 years, there are still unanswered questions about functions attributable to the terminal 125 nucleotides.
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Affiliation(s)
- Kenneth I Berns
- Department of Molecular Genetics and Microbiology, University of Florida College of Medicine, Gainesville, Florida, USA
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8
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Moço PD, Aharony N, Kamen A. Adeno-Associated Viral Vectors for Homology-Directed Generation of CAR-T Cells. Biotechnol J 2019; 15:e1900286. [PMID: 31642193 DOI: 10.1002/biot.201900286] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Revised: 10/06/2019] [Indexed: 12/19/2022]
Abstract
Immunotherapy with T cells expressing chimeric antigen receptors (CAR) is an emerging and promising treatment against refractory cancers. However, the currently adopted methods of modification of T cells pose a risk of insertional oncogenesis because lentiviral and retroviral vectors integrate the CAR transgene in a semi-random fashion. In addition, this therapy is only available using autologous cells, which create problems in production and limit the access for patients who have their T cells depleted. One modification method that shows the ability to overcome both drawbacks is the knock-in of the CAR simultaneously knocking-out genes that prevent allogeneic therapy, such as the endogenous T cell receptor. In this mini-review, the authors present recent efforts to develop safer universal CAR-T cells. More specifically, the combined application of target-directed nucleases, which create a double-strand break at a specific genome locus, and the delivery of CAR DNA via adeno-associated viral vectors for subsequent integration via homologous recombination and silencing of the targeted gene is focused on.
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Affiliation(s)
- Pablo D Moço
- Department of Bioengineering, McGill University, Montréal, H3A 0E9, Canada
| | - Noga Aharony
- Department of Bioengineering, McGill University, Montréal, H3A 0E9, Canada
| | - Amine Kamen
- Department of Bioengineering, McGill University, Montréal, H3A 0E9, Canada
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9
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Schmelas C, Grimm D. Split Cas9, Not Hairs - Advancing the Therapeutic Index of CRISPR Technology. Biotechnol J 2018; 13:e1700432. [PMID: 29316283 DOI: 10.1002/biot.201700432] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Revised: 12/28/2017] [Indexed: 02/06/2023]
Abstract
The discovery that the bacterial CRISPR/Cas9 system can be translated into mammalian cells continues to have an unprecedented impact on the biomedical research community, as it largely facilitates efforts to experimentally interrogate or therapeutically modify the cellular genome. In particular, CRISPR promises the ability to correct disease-associated genetic defects, or to target and destroy invading foreign DNA, in a simple, efficient, and selective manner directly in affected human cells or tissues. Here, we highlight a set of exciting new strategies that aim at further increasing the therapeutic index of CRISPR technologies, by reducing the size of Cas9 expression cassettes and thus enhancing their compatibility with viral gene delivery vectors. Specifically, we discuss the concept of splitCas9 whereby the Cas9 holo-protein is segregated into two parts that are expressed individually and reunited in the cell by various means, including use of 1) the gRNA as a scaffold for Cas9 assembly; 2) the rapamycin-controlled FKBP/FRB system; 3) the light-regulated Magnet system; or 4) inteins. We describe how these avenues, despite pursuing the identical aim, differ in critical features comprising the extent of spatio-temporal control of CRISPR activity, and discuss additional improvements to their efficiency or specificity that should foster their clinical translation.
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Affiliation(s)
- Carolin Schmelas
- Heidelberg University Hospital, Department of Infectious Diseases/Virology, Cluster of Excellence CellNetworks, BioQuant BQ0030, Im Neuenheimer Feld 267, D-69120, Heidelberg, Germany.,BioQuant, University of Heidelberg, BioQuant BQ0030, Im Neuenheimer Feld 267, D-69120, Heidelberg, Germany
| | - Dirk Grimm
- Heidelberg University Hospital, Department of Infectious Diseases/Virology, Cluster of Excellence CellNetworks, BioQuant BQ0030, Im Neuenheimer Feld 267, D-69120, Heidelberg, Germany.,BioQuant, University of Heidelberg, BioQuant BQ0030, Im Neuenheimer Feld 267, D-69120, Heidelberg, Germany.,German Center for Infection Research (DZIF), Partner site Heidelberg, BioQuant BQ0030, Im Neuenheimer Feld 267, D-69120, Heidelberg, Germany
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10
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Deletion of the B-B' and C-C' regions of inverted terminal repeats reduces rAAV productivity but increases transgene expression. Sci Rep 2017; 7:5432. [PMID: 28710345 PMCID: PMC5511163 DOI: 10.1038/s41598-017-04054-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Accepted: 05/09/2017] [Indexed: 11/30/2022] Open
Abstract
Inverted terminal repeats (ITRs) of the adeno-associated virus (AAV) are essential for rescue, replication, packaging, and integration of the viral genome. While ITR mutations have been identified in previous reports, we designed a new truncated ITR lacking the B-B’ and C-C’ regions named as ITRΔBC and investigated its effects on viral genome replication, packaging, and expression of recombinant AAV (rAAV). The packaging ability was compared between ITRΔBC rAAV and wild-type (wt) ITR rAAV. Our results showed the productivity of ITRΔBC rAAV was reduced 4-fold, which is consistent with the 8-fold decrease in the replication of viral genomic DNA of ITRΔBC rAAV compared with wt ITR rAAV. Surprisingly, transgene expression was significantly higher for ITRΔBC rAAV. A preliminary exploration of the underlying mechanisms was carried out by inhibiting and degrading the ataxia telangiectasia mutated (ATM) protein and the Mre11 complex (MRN), respectively, since the rAAV expression was inhibited by the ATM and/or MRN through cis interaction or binding with wt ITRs. We demonstrated that the inhibitory effects were weakened on ITRΔBC rAAV expression. This study suggests deletion in ITR can affect the transgene expression of AAV, which provides a new way to improve the AAV expression through ITRs modification.
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11
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Chandler RJ, Sands MS, Venditti CP. Recombinant Adeno-Associated Viral Integration and Genotoxicity: Insights from Animal Models. Hum Gene Ther 2017; 28:314-322. [PMID: 28293963 DOI: 10.1089/hum.2017.009] [Citation(s) in RCA: 149] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Currently, clinical gene therapy is experiencing a renaissance, with new products for clinical use approved in Europe and clinical trials for multiple diseases reporting positive results, especially those using recombinant adeno-associated viral (rAAV) vectors. Amid this new success, it is prudent to recall that the field of gene therapy experienced tragic setbacks in 1999 and 2002 because of the serious adverse events related to retroviral and adenoviral gene delivery in two clinical trials that resulted in the death of two patients. In both cases, the toxicity observed in humans had been documented to occur in animal models. However, these toxicities were either undetected or underappreciated before they arose in humans. rAAVs have been tested extensively in animals and animal models of disease, largely without adverse events, except for transient elevation in liver enzymes in some patients. However, a small but growing number of murine studies have documented that adeno-associated viral gene delivery can result in insertional mutagenesis. Herein, the aggregate data are reviewed from multiple murine studies where genotoxicity associated with rAAV treatment has been observed. The data emphasize the need for a proactive position to evaluate the potential risks and possible solutions associated with AAV-mediated gene therapy.
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Affiliation(s)
- Randy J Chandler
- 1 Medical Genomics and Metabolic Genetics Branch, National Human Genome Research Institute, National Institutes of Health , Department of Health and Human Services, Bethesda, Maryland
| | - Mark S Sands
- 2 Department of Internal Medicine, Washington University School of Medicine , St. Louis, Missouri.,3 Department of Genetics, Washington University School of Medicine , St. Louis, Missouri
| | - Charles P Venditti
- 1 Medical Genomics and Metabolic Genetics Branch, National Human Genome Research Institute, National Institutes of Health , Department of Health and Human Services, Bethesda, Maryland
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12
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Dogbevia GK, Marticorena-Alvarez R, Bausen M, Sprengel R, Hasan MT. Inducible and combinatorial gene manipulation in mouse brain. Front Cell Neurosci 2015; 9:142. [PMID: 25954155 PMCID: PMC4404871 DOI: 10.3389/fncel.2015.00142] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Accepted: 03/25/2015] [Indexed: 12/30/2022] Open
Abstract
We have deployed recombinant adeno-associated viruses equipped with tetracycline-controlled genetic switches to manipulate gene expression in mouse brain. Here, we show a combinatorial genetic approach for inducible, cell type-specific gene expression and Cre/loxP mediated gene recombination in different brain regions. Our chemical-genetic approach will help to investigate 'when', 'where', and 'how' gene(s) control neuronal circuit dynamics, and organize, for example, sensory signal processing, learning and memory, and behavior.
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Affiliation(s)
- Godwin K Dogbevia
- Department of Molecular Neurobiology, Max Planck Institute for Medical Research Heidelberg, Germany ; Institute of Experimental and Clinical Pharmacology and Toxicology, University of Lübeck Lübeck, Germany
| | | | - Melanie Bausen
- Department of Molecular Neurobiology, Max Planck Institute for Medical Research Heidelberg, Germany
| | - Rolf Sprengel
- Department of Molecular Neurobiology, Max Planck Institute for Medical Research Heidelberg, Germany
| | - Mazahir T Hasan
- Department of Molecular Neurobiology, Max Planck Institute for Medical Research Heidelberg, Germany ; NeuroCure Cluster of Excellence, Charité-Universitätsmedizin Berlin, Germany
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13
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Evidence of pervasive biologically functional secondary structures within the genomes of eukaryotic single-stranded DNA viruses. J Virol 2013; 88:1972-89. [PMID: 24284329 DOI: 10.1128/jvi.03031-13] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Single-stranded DNA (ssDNA) viruses have genomes that are potentially capable of forming complex secondary structures through Watson-Crick base pairing between their constituent nucleotides. A few of the structural elements formed by such base pairings are, in fact, known to have important functions during the replication of many ssDNA viruses. Unknown, however, are (i) whether numerous additional ssDNA virus genomic structural elements predicted to exist by computational DNA folding methods actually exist and (ii) whether those structures that do exist have any biological relevance. We therefore computationally inferred lists of the most evolutionarily conserved structures within a diverse selection of animal- and plant-infecting ssDNA viruses drawn from the families Circoviridae, Anelloviridae, Parvoviridae, Nanoviridae, and Geminiviridae and analyzed these for evidence of natural selection favoring the maintenance of these structures. While we find evidence that is consistent with purifying selection being stronger at nucleotide sites that are predicted to be base paired than at sites predicted to be unpaired, we also find strong associations between sites that are predicted to pair with one another and site pairs that are apparently coevolving in a complementary fashion. Collectively, these results indicate that natural selection actively preserves much of the pervasive secondary structure that is evident within eukaryote-infecting ssDNA virus genomes and, therefore, that much of this structure is biologically functional. Lastly, we provide examples of various highly conserved but completely uncharacterized structural elements that likely have important functions within some of the ssDNA virus genomes analyzed here.
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14
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Berns KI. My life with adeno-associated virus: a long time spent studying a short genome. DNA Cell Biol 2013; 32:342-7. [PMID: 23781880 DOI: 10.1089/dna.2013.2120] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
My 45 years of studying the molecular biology of adeno-associated virus are recounted. Additional activities as a mentor, department chair, and medical school administrator are described, as are my activities in the public sphere, which involved national issues related to science policy and medical education.
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Affiliation(s)
- Kenneth I Berns
- Department of Molecular Genetics and Microbiology, University of Florida College of Medicine, Gainesville, Florida 32608, USA.
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15
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Tanyi JL, Chu CS. Dendritic cell-based tumor vaccinations in epithelial ovarian cancer: a systematic review. Immunotherapy 2013; 4:995-1009. [PMID: 23148752 DOI: 10.2217/imt.12.100] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
After decades of extensive research, epithelial ovarian cancer still remains a lethal disease. Multiple new studies have reported that the immune system plays a critical role in the growth and spread of ovarian carcinoma. This review summarizes the development of dendritic cell (DC) vaccinations specific for ovarian cancer. So far, DC-based vaccines have induced effective antitumor responses in animal models, but only limited results from human clinical trials are available. Although DC-based immunotherapy has proven to be clinically safe and efficient at inducing tumor-specific immune responses, its clear role in the therapy of ovarian cancer still needs to be clarified. The relatively disappointing low-response rates in early clinical trials point to the need for the development of more effective and personalized DC-based anticancer vaccines. This article reviews the basic mechanisms, limitations and future directions of DC-based anti-ovarian cancer vaccine development.
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Affiliation(s)
- Janos L Tanyi
- Division of Gynecologic Oncology, Department of Obstetrics & Gynecology, University of Pennsylvania Health System, Philadelphia, PA, USA
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16
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Maintenance of the flip sequence orientation of the ears in the parvoviral left-end hairpin is a nonessential consequence of the critical asymmetry in the hairpin stem. J Virol 2012; 86:12187-97. [PMID: 22933276 DOI: 10.1128/jvi.01450-12] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Parvoviral terminal hairpins are essential for viral DNA amplification but are also implicated in multiple additional steps in the viral life cycle. The palindromes at the two ends of the minute virus of mice (MVM) genome are dissimilar and are processed by different resolution mechanisms that selectively direct encapsidation of predominantly negative-sense progeny genomes and conserve a single Flip sequence orientation at the 3' (left) end of such progeny. The sequence and predicted structure of these 3' hairpins are highly conserved within the genus Parvovirus, exemplified by the 121-nucleotide left-end sequence of MVM, which folds into a Y-shaped hairpin containing small internal palindromes that form the "ears" of the Y. To explore the potential role(s) of this hairpin in the viral life cycle, we constructed infectious clones with the ear sequences either inverted, to give the antiparallel Flop orientation, or with multiple transversions, conserving their base composition but changing their sequence. These were compared with a "bubble" mutant, designed to activate the normally silent origin in the inboard arm of the hairpin, thus potentially rendering symmetric the otherwise asymmetric junction resolution mechanism that drives maintenance of Flip. This mutant exhibited a major defect in viral duplex and single-strand DNA replication, characterized by the accumulation of covalently closed turnaround forms of the left end, and was rapidly supplanted by revertants that restored asymmetry. In contrast, both sequence and orientation changes in the hairpin ears were tolerated, suggesting that maintaining the Flip orientation of these structures is a consequence of, but not the reason for, asymmetric left-end processing.
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17
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Luo Y, Kofod-Olsen E, Christensen R, Sørensen CB, Bolund L. Targeted genome editing by recombinant adeno-associated virus (rAAV) vectors for generating genetically modified pigs. J Genet Genomics 2012; 39:269-74. [PMID: 22749014 DOI: 10.1016/j.jgg.2012.05.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2012] [Accepted: 05/10/2012] [Indexed: 12/22/2022]
Abstract
Recombinant adeno-associated virus (rAAV) vectors have been extensively used for experimental gene therapy of inherited human diseases. Several advantages, such as simple vector construction, high targeting frequency by homologous recombination, and applicability to many cell types, make rAAV an attractive approach for targeted genome editing. Combined with cloning by somatic cell nuclear transfer (SCNT), this technology has recently been successfully adapted to generate gene-targeted pigs as models for cystic fibrosis, hereditary tyrosinemia type 1, and breast cancer. This review summarizes the development of rAAV for targeted genome editing in mammalian cells and provides strategies for enhancing the rAAV-mediated targeting frequency by homologous recombination. We discuss current development and application of the rAAV vectors for targeted genome editing in porcine primary fibroblasts, which are subsequently used as donor cells for SCNT to generate cloned genetically designed pigs and provide positive perspectives for the generation of gene-targeted pigs with rAAV in the future.
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Affiliation(s)
- Yonglun Luo
- Department of Biomedicine, Aarhus University, Wilhelm Meyers Alle 4, DK-8000 Aarhus C, Denmark.
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18
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Kivovich V, Gilbert L, Vuento M, Naides SJ. The putative metal coordination motif in the endonuclease domain of human Parvovirus B19 NS1 is critical for NS1 induced S phase arrest and DNA damage. Int J Biol Sci 2011; 8:79-92. [PMID: 22211107 PMCID: PMC3248650 DOI: 10.7150/ijbs.8.79] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2011] [Accepted: 11/02/2011] [Indexed: 12/14/2022] Open
Abstract
The non-structural proteins (NS) of the parvovirus family are highly conserved multi-functional molecules that have been extensively characterized and shown to be integral to viral replication. Along with NTP-dependent helicase activity, these proteins carry within their sequences domains that allow them to bind DNA and act as nucleases in order to resolve the concatameric intermediates developed during viral replication. The parvovirus B19 NS1 protein contains sequence domains highly similar to those previously implicated in the above-described functions of NS proteins from adeno-associated virus (AAV), minute virus of mice (MVM) and other non-human parvoviruses. Previous studies have shown that transient transfection of B19 NS1 into human liver carcinoma (HepG2) cells initiates the intrinsic apoptotic cascade, ultimately resulting in cell death. In an effort to elucidate the mechanism of mammalian cell demise in the presence of B19 NS1, we undertook a mutagenesis analysis of the protein's endonuclease domain. Our studies have shown that, unlike wild-type NS1, which induces an accumulation of DNA damage, S phase arrest and apoptosis in HepG2 cells, disruptions in the metal coordination motif of the B19 NS1 protein reduce its ability to induce DNA damage and to trigger S phase arrest and subsequent apoptosis. These studies support our hypothesis that, in the absence of replicating B19 genomes, NS1-induced host cell DNA damage is responsible for apoptotic cell death observed in parvoviral infection of non-permissive mammalian cells.
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Affiliation(s)
- Violetta Kivovich
- Pennsylvania State College of Medicine/ Milton S. Hershey Medical Center, Hershey, PA, USA
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19
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Chiriva-Internati M, Mirandola L, Kast WM, Jenkins MR, Cobos E, Cannon MJ. Understanding the Cross-Talk between Ovarian Tumors and Immune Cells: Mechanisms for Effective Immunotherapies. Int Rev Immunol 2011; 30:71-86. [DOI: 10.3109/08830185.2011.561507] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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20
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Wang J, Faust SM, Rabinowitz JE. The next step in gene delivery: molecular engineering of adeno-associated virus serotypes. J Mol Cell Cardiol 2010; 50:793-802. [PMID: 21029739 DOI: 10.1016/j.yjmcc.2010.10.017] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2010] [Revised: 10/12/2010] [Accepted: 10/13/2010] [Indexed: 12/29/2022]
Abstract
Delivery is at the heart of gene therapy. Viral DNA delivery systems are asked to avoid the immune system, transduce specific target cell types while avoiding other cell types, infect dividing and non-dividing cells, insert their cargo within the host genome without mutagenesis or to remain episomal, and efficiently express transgenes for a substantial portion of a lifespan. These sought-after features cannot be associated with a single delivery system, or can they? The Adeno-associated virus family of gene delivery vehicles has proven to be highly malleable. Pseudotyping, using AAV serotype 2 terminal repeats to generate designer shells capable of transducing selected cell types, enables the packaging of common genomes into multiple serotypes virions to directly compare gene expression and tropism. In this review the ability to manipulate this virus will be examined from the inside out. The influence of host cell factors and organism biology including the immune response on the molecular fate of the viral genome will be discussed as well as differences in cellular trafficking patterns and uncoating properties that influence serotype transduction. Re-engineering the prototype vector AAV2 using epitope insertion, chemical modification, and molecular evolution not only demonstrated the flexibility of the best-studied serotype, but now also expanded the tool kit for molecular modification of all AAV serotypes. Current AAV research has changed its focus from examination of wild-type AAV biology to the feedback of host cell/organism on the design and development of a new generation of recombinant AAV delivery vehicles. This article is part of a Special Section entitled "Special Section: Cardiovascular Gene Therapy".
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Affiliation(s)
- Jinhui Wang
- Thomas Jefferson University Center for Translational Medicine, Philadelphia, PA 19107, USA
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21
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McAlister VJ, Owens RA. Substitution of adeno-associated virus Rep protein binding and nicking sites with human chromosome 19 sequences. Virol J 2010; 7:218. [PMID: 20825662 PMCID: PMC2944168 DOI: 10.1186/1743-422x-7-218] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2010] [Accepted: 09/08/2010] [Indexed: 01/23/2023] Open
Abstract
Background Adeno-associated virus type 2 (AAV2) preferentially integrates its DNA at a ~2 kb region of human chromosome 19, designated AAVS1 (also known as MBS85). Integration at AAVS1 requires the AAV2 replication (Rep) proteins and a DNA sequence within AAVS1 containing a 16 bp Rep recognition sequence (RRS) and closely spaced Rep nicking site (also referred to as a terminal resolution site, or trs). The AAV2 genome is flanked by inverted terminal repeats (ITRs). Each ITR contains an RRS and closely spaced trs, but the sequences differ from those in AAVS1. These ITR sequences are required for replication and packaging. Results In this study we demonstrate that the AAVS1 RRS and trs can function in AAV2 replication, packaging and integration by replacing a 61 bp region of the AAV2 ITR with a 49 bp segment of AAVS1 DNA. Modifying one or both ITRs did not have a large effect on the overall virus titers. These modifications did not detectably affect integration at AAVS1, as measured by semi-quantitative nested PCR assays. Sequencing of integration junctions shows the joining of the modified ITRs to AAVS1 sequences. Conclusions The ability of these AAVS1 sequences to substitute for the AAV2 RRS and trs provides indirect evidence that the stable secondary structure encompassing the trs is part of the AAV2 packaging signal.
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Affiliation(s)
- Victor J McAlister
- Laboratory of Molecular and Cellular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland 20892, USA
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22
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Grimm D, Pandey K, Nakai H, Storm TA, Kay MA. Liver transduction with recombinant adeno-associated virus is primarily restricted by capsid serotype not vector genotype. J Virol 2007; 80:426-39. [PMID: 16352567 PMCID: PMC1317553 DOI: 10.1128/jvi.80.1.426-439.2006] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
We and others have recently reported highly efficient liver gene transfer with adeno-associated virus 8 (AAV-8) pseudotypes, i.e., AAV-2 genomes packaged into AAV-8 capsids. Here we studied whether liver transduction could be further enhanced by using viral DNA packaging sequences (inverted terminal repeats [ITRs]) derived from AAV genotypes other than 2. To this end, we generated two sets of vector constructs carrying expression cassettes embedding a gfp gene or the human factor IX (hfIX) gene flanked by ITRs from AAV genotypes 1 through 6. Initial in vitro analyses of gfp vector DNA replication, encapsidation, and cell transduction revealed a surprisingly high degree of interchangeability among the six genotypes. For subsequent in vivo studies, we cross-packaged the six hfIX variants into AAV-8 and infused mice via the portal vein with doses of 5 x 10(10) to 1.8 x 10(12) particles. Notably, all vectors expressed comparably high plasma hFIX levels within a dose cohort over the following 6 months, concurrent with the finding of equivalent vector DNA copy numbers per cell. Partial hepatectomies resulted in approximately 80% drops of hFIX levels and vector DNA copy numbers in all groups, indicating genotype-independent persistence of predominantly episomal vector DNA. Southern blot analyses of total liver DNA in fact confirmed the presence of identical and mostly nonintegrated molecular vector forms for all genotypes. We conclude that, unlike serotypes, AAV genotypes are not critical for efficient hepatocyte transduction and can be freely substituted. This corroborates our current model for AAV vector persistence in the liver and provides useful information for the future design and application of recombinant AAV.
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Affiliation(s)
- Dirk Grimm
- Department of Pediatrics and Genetics, School of Medicine, Stanford University, Room G305, 300 Pasteur Drive, Stanford, CA 94305, USA
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23
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Kosmider B, Wells RD. Double-strand breaks in the myotonic dystrophy type 1 and the fragile X syndrome triplet repeat sequences induce different types of mutations in DNA flanking sequences in Escherichia coli. Nucleic Acids Res 2006; 34:5369-82. [PMID: 17012280 PMCID: PMC1636463 DOI: 10.1093/nar/gkl612] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The putative role of double-strand breaks (DSBs) created in vitro by restriction enzyme cleavage in or near CGG*CCG or CTG*CAG repeat tracts on their genetic instabilities, both within the repeats and in their flanking sequences, was investigated in an Escherichia coli plasmid system. DSBs at TRS junctions with the vector generated a large number of mutagenic events in flanking sequences whereas DSBs within the repeats elicited no similar products. A substantial enhancement in the number of mutants was caused by transcription of the repeats and by the absence of recombination functions (recA-, recBC-). Surprisingly, DNA sequence analyses on mutant clones revealed the presence of only single deletions of 0.4-1.6 kb including the TRS and the flanking sequence from plasmids originally containing (CGG*CCG)43 but single, double and multiple deletions as well as insertions were found for plasmids originally containing (CTG*CAG)n (where n = 43 or 70). Non-B DNA structures (slipped structures with loops, cruciforms, triplexes and tetraplexes) as well as microhomologies are postulated to participate in the recombination and/or repair processes.
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Affiliation(s)
| | - Robert D. Wells
- To whom correspondence should be addressed. Tel: +1 713 677 7651; Fax: +1 713 677 7689;
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24
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Yoon-Robarts M, Blouin AG, Bleker S, Kleinschmidt JA, Aggarwal AK, Escalante CR, Linden RM. Residues within the B' motif are critical for DNA binding by the superfamily 3 helicase Rep40 of adeno-associated virus type 2. J Biol Chem 2004; 279:50472-81. [PMID: 15371437 DOI: 10.1074/jbc.m403900200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have recently published the crystal structure of the adeno-associated virus type 2 superfamily 3 (SF3) helicase Rep40. Although based on its biochemical properties it is unlikely that Rep40 plays a central role as a replicative helicase the involvement of this motor protein in DNA packaging has recently been demonstrated. Here we focused our attention on residues that fall within and adjacent to the B' motif of SF3 helicases that directly interact with single-stranded DNA during translocation of the motor protein. In vitro, alanine substitution at positions Lys-404 or Lys-406 abrogated the ability of the protein to interact with single-stranded DNA as demonstrated by electrophoretic mobility shift assay and fluorescence anisotropy, and accordingly these mutants could not unwind a partially duplex DNA substrate. Despite this loss of helicase activity, basal ATPase activity in these mutants remained intact. However, unlike the wild-type protein, K404A and K406A ATPase activity was not stimulated by DNA. As predicted, disruption of motor activity through interference with DNA binding resulted in an inability of Rep40 to package adeno-associated virus DNA in a tissue culture-based assay. Taken together, we characterized, for the first time in an SF3 helicase family member, residues that are directly involved in single-stranded DNA binding and that are critical for the Rep motor activity. Based on our findings we propose B' as the signature motif of SF3 helicases that is responsible for the complex interactions required for the coupling of DNA binding and ATP hydrolysis.
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Affiliation(s)
- Miran Yoon-Robarts
- Department of Gene and Cell Medicine, Mount Sinai School of Medicine, New York, NY 10029, USA
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25
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Hamilton H, Gomos J, Berns KI, Falck-Pedersen E. Adeno-associated virus site-specific integration and AAVS1 disruption. J Virol 2004; 78:7874-82. [PMID: 15254160 PMCID: PMC446113 DOI: 10.1128/jvi.78.15.7874-7882.2004] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Adeno-associated virus (AAV) is a single-stranded DNA virus with a unique biphasic lifestyle consisting of both a productive and a latent phase. Typically, the productive phase requires coinfection with a helper virus, for instance adenovirus, while the latent phase dominates in healthy cells. In the latent state, AAV is found integrated site specifically into the host genome at chromosome 19q13.4 qtr (AAVS1), the only animal virus known to integrate in a defined location. In this study we investigated the latent phase of serotype 2 AAV, focusing on three areas: AAV infection, rescue, and integration efficiency as a function of viral multiplicity of infection (MOI); efficiency of site-specific integration; and disruption of the AAVS1 locus. As expected, increasing the AAV MOI resulted in an increase in the percentage of cells infected, with 80% of cells infected at an MOI of 10. Additional MOI only marginally effected a further increase in percentage of infected cells. In contrast to infection, we found very low levels of integration at MOIs of less than 10. At an MOI of 10, at which 80% of cells are infected, less than 5% of clonal cell lines contained integrated AAV DNA. At an MOI of 100 or greater, however, 35 to 40% of clonal cell lines contained integrated AAV DNA. Integration and the ability to rescue viral genomes were highly correlated. Analysis of integrated AAV indicated that essentially all integrants were AAVS1 site specific. Although maximal integration efficiency approached 40% of clonal cell lines (essentially 50% of infected cells), over 80% of cell lines contained a genomic disruption at the AAVS1 integration locus on chromosome 19 ( approximately 100% of infected cells). Rep expression by itself and in the presence of a plasmid integration substrate was able to mediate this disruption of the AAVS1 site. We further characterized the disruption event and demonstrated that it resulted in amplification of the AAVS1 locus. The data are consistent with a revised model of AAV integration that includes preliminary expansion of a defined region in AAVS1.
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Affiliation(s)
- Henry Hamilton
- Molecular Biology Program, Weill Medical College of Cornell University, New York, NY 10021, USA
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26
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Marcadier JL, Pearson CE. Fidelity of primate cell repair of a double-strand break within a (CTG).(CAG) tract. Effect of slipped DNA structures. J Biol Chem 2003; 278:33848-56. [PMID: 12807901 DOI: 10.1074/jbc.m304284200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
At least 15 human diseases are caused by the instability of gene-specific (CTG).(CAG) repeats. The precise mechanism of instability remains unknown, though bacterial and yeast models have suggested a role for aberrant repair of double-strand breaks (DSBs). Using an established primate DSB repair system, we have investigated the fidelity of repair of a DSB within a (CTG).(CAG) repeat tract. DSB repair substrates were generated from plasmids that are stably replicated in their circular form, permitting us to highlight the effects of DSB repair on repeat stability and minimize the contribution of replication. DSBs were introduced into repeat-containing plasmids using a unique BsmI site, such that the entire repeat tract comprised one free end of the linearized plasmid. Substrates containing 17, 47, and 79 repeats, in either their linear duplex form or containing slipped structures (out-of-register interstrand mispairings at repeat sequences), were transiently transfected into primate cells. Linearized plasmids with repeats were repaired with mildly reduced efficiency, while the presence of slipped structures considerably reduced repair efficiency. The repaired products were characterized for alterations within the repeat tract and flanking sequence. DSB repair induced predominantly repeat deletions. Notably, a polarized/directional deletion effect was observed, in that the repetitive end of the DSB was preferentially removed. This phenomenon was dramatically enhanced when slipped structures were present within the repeat tract, providing the first evidence for error-prone processing of slipped-strand structures. These results suggest the existence of primate nuclease activities that are specific for (CTG).(CAG) repeats and the structures they form.
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Affiliation(s)
- Julien L Marcadier
- Department of Molecular & Medical Genetics, University of Toronto, Ontario M5A 1X8, Canada
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27
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Bossis I, Chiorini JA. Cloning of an avian adeno-associated virus (AAAV) and generation of recombinant AAAV particles. J Virol 2003; 77:6799-810. [PMID: 12768000 PMCID: PMC156192 DOI: 10.1128/jvi.77.12.6799-6810.2003] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Recent studies have proposed that adeno-associated viruses (AAVs) are not evolutionarily linked to other mammalian autonomous parvoviruses but are more closely linked to the autonomous parvoviruses of birds. To better understand the relationship between primate and avian AAVs (AAAVs), we cloned and sequenced the genome of an AAAV (ATCC VR-865) and generated recombinant AAAV particles. The genome of AAAV is 4,694 nucleotides in length and has organization similar to that of other AAVs. The entire genome of AAAV displays 56 to 65% identity at the nucleotide level with the other known AAVs. The AAAV genome has inverted terminal repeats of 142 nucleotides, with the first 122 forming the characteristic T-shaped palindromic structure. The putative Rep-binding element consists of a tandem (GAGY)(4) repeat, and the putative terminal resolution site (trs), CCGGT/CG, contains a single nucleotide substitution relative to the AAV(2) trs. The Rep open reading frame of AAAV displays 50 to 54% identity at the amino acid level with the other AAVs, with most of the diversity clustered at the carboxyl and amino termini. Comparison of the capsid proteins of AAAV and the primate dependoviruses indicate that divergent regions are localized to surface-exposed loops. Despite these sequence differences, we were able to produce recombinant AAAV particles carrying a lacZ reporter gene by cotransfection in 293T cells and were able to examine transduction efficiency in both chicken primary cells and several cell lines. Our findings indicate that AAAV is the most divergent AAV described to date but maintains all the characteristics unique to the genera of dependovirus.
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Affiliation(s)
- Ioannis Bossis
- Gene Therapy and Therapeutics Branch, National Institue of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland 20892, USA
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28
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Ding C, Urabe M, Bergoin M, Kotin RM. Biochemical characterization of Junonia coenia densovirus nonstructural protein NS-1. J Virol 2002; 76:338-45. [PMID: 11739698 PMCID: PMC135713 DOI: 10.1128/jvi.76.1.338-345.2002] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Junonia coenia densovirus (JcDNV) is an autonomous parvovirus that infects the larvae of the common buckeye butterfly, Junonia coenia. Unlike vertebrate parvoviruses, the genes encoding the structural protein and nonstructural (NS) proteins of JcDNV are in opposite orientations; thus, each strand contains a sense and antisense open reading frame (ORF). The promoter at map position 93 controls expression of NS ORFs 2, 3, and 4, which encode three NS proteins, NS-1, NS-2, and NS-3. These proteins are likely to be involved in viral DNA replication, among other functions. In contrast to the nonstructural proteins of the vertebrate parvoviruses, the NS proteins of the Densovirinae have not been characterized. Here, we describe biochemical properties of the NS-1 protein of JcDNV. The NS-1 ORF was cloned in frame with the Escherichia coli malE gene, which encodes the bacterial maltose binding protein (MBP). Using electrophoretic mobility shift and DNase I protection assays, we identified the region of the JcDNV terminal sequence that is recognized specifically by the MBP-NS-1 fusion protein. The site consists of (GAC)4 and is located on the A-A' region of the terminal palindrome. In addition, the MBP-NS-1 fusion protein catalyzes the cleavage of single-stranded DNA (ssDNA) substrates derived from the JcDNV putative origin of replication, primarily at two sites in the motif 5'-G*TAT*TG-3'. One cleavage site is between the thymidine dinucleotide at positions 92 and 93 and the other site corresponds to thymidine at nucleotide 95; both sites are on the complementary strand of the sequence assigned GenBank accession number A12984. Cleavage of ssDNA is dependent on the presence of a divalent metal cofactor but does not require nucleoside triphosphate hydrolysis. Parvovirus NS proteins contain the phylogenically conserved Walker A- and B-site ATPase motifs. These sites in JcDNV NS-1 diverge from the consensus, yet despite these atypical motifs our analyses support that MBP-NS-1 has ATP-dependent helicase activity. These results indicate that JcDNV NS-1 possesses activities common to the superfamily of rolling-circle replication initiator proteins in general and the parvovirus replication proteins in particular, and they provide a basis for comparative analyses of the structure and function relationships among the parvovirus NS-1 equivalents.
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Affiliation(s)
- Chuantian Ding
- Laboratory of Biochemical Genetics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892-1654, USA
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29
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Yoon M, Smith DH, Ward P, Medrano FJ, Aggarwal AK, Linden RM. Amino-terminal domain exchange redirects origin-specific interactions of adeno-associated virus rep78 in vitro. J Virol 2001; 75:3230-9. [PMID: 11238849 PMCID: PMC114116 DOI: 10.1128/jvi.75.7.3230-3239.2001] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The unique ability of adeno-associated virus type 2 (AAV) to site-specifically integrate its genome into a defined sequence on human chromosome 19 (AAVS1) makes it of particular interest for use in targeted gene delivery. The objective underlying this study is to provide evidence for the feasibility of retargeting site-specific integration into selected loci within the human genome. Current models postulate that AAV DNA integration is initiated through the interactions of the products of a single viral open reading frame, REP, with sequences present in AAVS1 that resemble the minimal origin for AAV DNA replication. Here, we present a cell-free system designed to dissect the Rep functions required to target site-specific integration using functional chimeric Rep proteins derived from AAV Rep78 and Rep1 of the closely related goose parvovirus. We show that amino-terminal domain exchange efficiently redirects the specificity of Rep to the minimal origin of DNA replication. Furthermore, we establish that the amino-terminal 208 amino acids of Rep78/68 constitute a catalytic domain of Rep sufficient to mediate site-specific endonuclease activity.
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Affiliation(s)
- M Yoon
- Institute for Gene Therapy and Molecular Medicine, New York, New York 10029, USA
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30
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Abstract
The single-stranded adeno-associated virus type 2 (AAV) genome is flanked by terminal repeats (TRs) that fold back on themselves to form hairpinned structures. During AAV DNA replication, the TRs are nicked by the virus-encoded Rep proteins at the terminal resolution site (trs). This origin function apparently requires three sequence elements, the Rep binding element (RBE), a small palindrome that comprises a single tip of an internal hairpin within the TR (RBE'), and the trs. Previously, we determined the sequences at the trs required for Rep-mediated cleavage and demonstrated that the trs endonuclease reaction occurs in two discrete steps. In the first step, the Rep DNA helicase activity unwinds the TR, thereby extruding a stem-loop structure at the trs. In the second step, Rep transesterification activity cleaves the trs. Here we investigate the contribution of the RBE and RBE' during this process. Our data indicate that Rep is tethered to the RBE in a specific orientation during trs nicking. This orientation appears to align Rep on the AAV TR, allowing specific nucleotide contacts with the RBE' and directing nicking to the trs. Accordingly, alterations in the polarity or position of the RBE relative to the trs greatly inhibit Rep nicking. Substitutions within the RBE' also reduce Rep specific activity, but to a lesser extent. Interestingly, Rep interactions with the RBE and RBE' during nicking seem to be functionally distinct. Rep contacts with the RBE appear necessary for both the DNA helicase and trs cleavage steps of the endonuclease reaction. On the other hand, RBE' contacts seem to be required primarily for TR unwinding and formation of the trs stem-loop structure, not cleavage. Together, these results suggest a model of Rep interaction with the AAV TR during origin nicking through a tripartite cleavage signal comprised of the RBE, the RBE', and the trs.
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Affiliation(s)
- J R Brister
- Department of Molecular Genetics and Microbiology and Powell Gene Therapy Center, College of Medicine, University of Florida, Gainesville, Florida 32610, USA
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31
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Abstract
Adeno-associated virus (AAV) vectors were shown capable of high efficiency transduction of both dividing and nondividing cells and tissues. AAV-mediated transduction leads to stable, long-term transgene expression in the absence of apparent immune response. These properties and the broad host range of AAV vectors indicate that they constitute a powerful tool for gene therapy purposes. An additional potential benefit of AAV vectors is their ability to integrate site-specifically in the presence of Rep proteins which can be expressed transiently, thus limiting their suspected adverse effects. The major restrictions of AAV as vectors are their limited genetic capacity and strict packaging size constraint of less than 5 kb. Another difficulty is the labor-intensive and expensive procedure for the production and packaging of recombinant AAV vectors. The major benefits and drawbacks of AAV vectors and advances made in the past 3 years are discussed.
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Affiliation(s)
- J Tal
- Department of Virology, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
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32
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Tsunoda H, Hayakawa T, Sakuragawa N, Koyama H. Site-specific integration of adeno-associated virus-based plasmid vectors in lipofected HeLa cells. Virology 2000; 268:391-401. [PMID: 10704347 DOI: 10.1006/viro.1999.0122] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Adeno-associated virus (AAV) integrates specifically into a site (AAVS1) on human chromosome 19q13.3-qter. Similarly, there is accumulating evidence that this site-specific integration occurs by transfection of AAV-based plasmid vectors. In order to further define the process of plasmid integration events, we constructed some AAV plasmids, introduced them into HeLa cells by lipofection, and isolated chromosomal integrants. One of such plasmids, pTH-5, contained the rep and neomycin-resistant (neo(r)) genes flanked by the 5'- and 3'-inverted terminal repeats of AAV and the hygromycin-resistant (hyg(r)) gene located in the plasmid backbone. Southern blot analysis revealed that among 36 G418-resistant (G418(r)) clones isolated, 22 (61%) showed site-specific integration into AAVS1. Further structural and functional analyses on the expression of the hyg(r) gene in the site-specific clones and the LacZ gene in clones generated with plasmid pTH-2 indicated that, together with the AAV sequence, the plasmid backbone was integrated into the AAVS1 site and thus the neo(r) and hyg(r) genes remained linked at high frequencies in the targeted integrants compared with random integrants. Sequence analysis of integration junctions between pTH-5 and AAVS1 revealed that the junctions occurred in the p5 promoter region of the plasmid while mainly in the partial cDNA coding region of the AAVS1 site. We also found that plasmid pTH-1 linearized in the backbone before lipofection gave a significantly lower frequency of site-specific integration (26%) than the circular form (60%). This finding may support the involvement of the double-stranded, circular form of infected AAV in the integration process. Our results may help to understand the process and mechanism of site-specific integration of lipofected AAV plasmid vectors.
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Affiliation(s)
- H Tsunoda
- Kihara Institute for Biological Research, Graduate School of Integrated Science, Yokohama City University, Maioka-cho 641-12, Totsuka-ku, Yokohama, 244-0813, Japan
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Abstract
In contrast to other gene delivery systems, adeno-associated virus vectors show long term gene expression without immune response or toxicity. New production methods have increased vector titers and eliminated adenovirus contamination, thereby facilitating effective in vivo use. These advancements will expedite additional animal model studies providing validation for use of this vector in human clinical trials.
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Affiliation(s)
- J E Rabinowitz
- Human Gene Therapy Center, University of North Carolina at Chapel Hill 27599-7352, USA.
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34
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Yang CC, Xiao X, Zhu X, Ansardi DC, Epstein ND, Frey MR, Matera AG, Samulski RJ. Cellular recombination pathways and viral terminal repeat hairpin structures are sufficient for adeno-associated virus integration in vivo and in vitro. J Virol 1997; 71:9231-47. [PMID: 9371582 PMCID: PMC230226 DOI: 10.1128/jvi.71.12.9231-9247.1997] [Citation(s) in RCA: 131] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The human parvovirus adeno-associated virus (AAV) is unique in its ability to target viral integration to a specific site on chromosome 19 (ch-19). Recombinant AAV (rAAV) vectors retain the ability to integrate but have apparently lost this ability to target. In this report, we characterize the terminal-repeat-mediated integration for wild-type (wt), rAAV, and in vitro systems to gain a better understanding of these differences. Cell lines latent for either wt or rAAV were characterized by a variety of techniques, including PCR, Southern hybridization, and fluorescence in situ hybridization analysis. More than 40 AAV-rAAV integration junctions were cloned, sequenced, and then subjected to comparison and analysis. In both immortalized and normal diploid human cells, wt AAV targeted integration to ch-19. Integrated provirus structures consisted of head-to-tail tandem arrays with the majority of the junction sequences involving the AAV inverted terminal repeats (ITRs). No complete viral ITRs were directly observed. In some examples, the AAV p5 promoter sequence was found to be fused at the virus-cell junction. Data from dot blot analysis of PCR products were consistent with the occurrence of inversions of genomic and/or viral DNA sequences at the wt integration site. Unlike wt provirus junctions, rAAV provirus junctions mapped to a subset of non-ch-19 sequences. Southern analysis supported the integration of proviruses from two independent cell lines at the same locus on ch-2. In addition, provirus terminal repeat sequences existed in both the flip and flop orientations, with microhomology evident at the junctions. In all cases with the exception of the ITRs, the vector integrated intact. rAAV junction sequence data were consistent with the occurrence of genomic rearrangement by deletion and/or rearrangement-translocation at the integration locus. Finally, junctions formed in an in vitro system between several AAV substrates and the ch-19 target site were isolated and characterized. Linear AAV substrates typically utilized the end of the virus DNA substrate as the point of integration, whereas products derived from AAV terminal repeat hairpin structures in the presence or absence of Rep protein resembled AAV-ch-19 junctions generated in vivo. These results describing wt AAV, rAAV, and in vitro integration junctions suggest that the viral integration event itself is mediated by terminal repeat hairpin structures via nonviral cellular recombination pathways, with specificity for ch-19 in vivo requiring additional viral components. These studies should have an important impact on the use of rAAV vectors in human gene therapy.
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MESH Headings
- Base Sequence
- Cell Line, Transformed
- Chromosome Mapping
- Chromosomes, Human, Pair 19
- Chromosomes, Human, Pair 2
- Cloning, Molecular
- DNA, Viral
- Dependovirus/genetics
- HeLa Cells
- Humans
- Molecular Sequence Data
- Nucleic Acid Conformation
- Proviruses/genetics
- Recombination, Genetic
- Repetitive Sequences, Nucleic Acid
- Sequence Analysis, DNA
- Virus Integration
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Affiliation(s)
- C C Yang
- Gene Therapy Center and Department of Pharmacology, University of North Carolina at Chapel Hill, 27599-7352, USA
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35
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Brunstein J, Astell CR. Analysis of the internal replication sequence indicates that there are three elements required for efficient replication of minute virus of mice minigenomes. J Virol 1997; 71:9087-95. [PMID: 9371565 PMCID: PMC230209 DOI: 10.1128/jvi.71.12.9087-9095.1997] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Prior analysis of minigenomes of minute virus of mice carried out by our laboratory indicated that sequences within the region of nucleotides 4489 to 4695, inboard of the 5' palindrome, are required for efficient DNA replication of the virus and are the site of specific interactions with unidentified factors present in a host cell nuclear extract (P. Tam and C. R. Astell, Virology 193:812-824, 1993; P. Tam and C. R. Astell, J. Virology 68:2840-2848, 1994). In order to examine this region in finer detail, a comprehensive library of linker-scanning mutants spanning the region was tested for the ability to support replication of minigenome constructs and for the ability to interact with host cell factors. Three short discrete sequence elements critical for replication competence were observed. Binding of host cell nuclear factors was localized to four sites, with two major complexes each appearing to have two binding sites within the region. All factor binding sites were found to be directly adjacent to or overlapping with sequence elements contributing to replication competence, and evidence suggesting a correlation between factor binding and minigenome replication is presented. A possible model is proposed for function of a viral origin within the region of the internal replication sequence which addresses the still-unresolved problem of how parvoviruses overcome the thermodynamic energy barrier involved in the rearrangement of the 5'-terminal palindrome from an extended form to a hairpin conformation.
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Affiliation(s)
- J Brunstein
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of British Columbia, Vancouver, Canada
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36
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Chiorini JA, Yang L, Liu Y, Safer B, Kotin RM. Cloning of adeno-associated virus type 4 (AAV4) and generation of recombinant AAV4 particles. J Virol 1997; 71:6823-33. [PMID: 9261407 PMCID: PMC191963 DOI: 10.1128/jvi.71.9.6823-6833.1997] [Citation(s) in RCA: 182] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
We have cloned and characterized the full-length genome of adeno-associated virus type 4 (AAV4). The genome of AAV4 is 4,767 nucleotides in length and contains an expanded p5 promoter region compared to AAV2 and AAV3. Within the inverted terminal repeat (ITR), several base changes were identified with respect to AAV2. However, these changes did not affect the ability of this region to fold into a hairpin structure. Within the ITR, the terminal resolution site and Rep binding sites were conserved; however, the Rep binding site was expanded from three GAGC repeats to four. The Rep gene product of AAV4 shows greater than 90% homology to the Rep products of serotypes 2 and 3, with none of the changes occurring in regions which had previously been shown to affect the known functions of Rep68 or Rep78. Most of the differences in the capsid proteins lie in regions which are thought to be on the exterior surface of the viral capsid. It is these unique regions which are most likely to be responsible for the lack of cross-reacting antibodies and the altered tissue tropism compared to AAV2. The results of our studies, performed with a recombinant version of AAV4 carrying a lacZ reporter gene, suggest that AAV4 can transduce human, monkey, and rat cells. Furthermore, comparison of transduction efficiencies in a number of cell lines, competition cotransduction experiments, and the effect of trypsin on transduction efficiency all suggest that the cellular receptor for AAV4 is distinct from that of AAV2.
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Affiliation(s)
- J A Chiorini
- Molecular Hematology Branch, National Heart Lung and Blood Institute, Bethesda, Maryland 20892, USA
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37
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Fan PD, Dong JY. Replication of rep-cap genes is essential for the high-efficiency production of recombinant AAV. Hum Gene Ther 1997; 8:87-98. [PMID: 8989998 DOI: 10.1089/hum.1997.8.1-87] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Adenoassociated virus (AAV) has been developed as a vector for gene transfer because of its advantageous features: it is nonpathogenic, naturally replication-defective; it infects growth-arrested cells, and can transfer the therapeutic gene without co-delivery of any viral genes. However, a major obstacle in conducting systematic studies of AAV-mediated gene transfer in animal models is the difficulty of obtaining large quantities of recombinant virus. Recent development of AAV packaging cell lines has simplified the procedure of producing recombinant AAV (rAAV). However, the efficacy of producing large quantities of rAAV with these cell lines is yet to be demonstrated. In this study we have analyzed the difference between the replication of wild-type AAV and the production of rAAV. Using a combined single-plasmid system that carries both an AAV vector and the rep-cap genes, we have demonstrated that the AAV vector replicates to high number of copies whereas the rep-cap sequences remain unamplified in the virus-producing cells, When the copy number of rep-cap genes was increased by varying the vector/rep-cap ratio in the transfection mixture, the titer of rAAV increased proportionally. Thus, the titer of rAAV is limited by the low copy number of the rep-cap genes that results in an insufficient expression of the Rep and Cap proteins. We have also shown that generation of double-stranded replicating form of the vector DNA is accompanied by an amplified transgene expression. We propose that the increased gene expression from the accumulating double-stranded viral DNA is likely to be the mechanism by which wild-type AAV produces a large number of particles necessary to package the self-replicating AAV genomes. We conclude that mimicking this amplified expression of rep-cap genes may provide the key to produce high titers of rAAV.
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Affiliation(s)
- P D Fan
- Department of Laboratory Medicine, University of California, San Francicso 94143-0724, USA
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38
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Bishop BM, Santin AD, Quirk JG, Hermonat PL. Role of the terminal repeat GAGC trimer, the major Rep78 binding site, in adeno-associated virus DNA replication. FEBS Lett 1996; 397:97-100. [PMID: 8941722 DOI: 10.1016/s0014-5793(96)01149-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The adeno-associated virus (AAV) terminal repeats (TR) are cis required, and the AAV encoded Rep78 protein is trans required, for AAV DNA replication. The Rep78 protein recognizes and interacts with at least three regions within the TR DNA. The major binding site, with the highest affinity for Rep78 binding, is within the TR stem (nt 36-16) and includes the 'core' GAGC trimer (GAGC3, nt 33-22; Fig. 2) sequence. In this study mutations were made within the GAGC trimer and these mutants assayed for their ability to allow for AAV double stranded (ds DNA, prepackaging DNA replication), and single stranded DNA (ss DNA, due to virion packaging) replication. Here, it is shown that when the two inside GAGC motifs are mutated, with only motif no. 1 left intact (see Fig. 2), the resulting AAV (mutA) genome was significantly defective for both ds DNA (17% of wild type) and ss DNA (9%). If the TRs contained only the two outside motifs intact (mutB), motifs no. 1 and 2, the AAV genome had a significant but reduced level of both ds (50%) and ss (34%) DNA replication. Finally, if only the middle motif no. 2 was mutated, with motifs no. 1 and 3 left intact (mutC), the resulting DNA replication for both ds and ss forms was essentially wild type (80% that of wild type). These data suggest that the GAGC trimer plays a role in AAV DNA replication, and that GAGC motif no. 3 is the most important of the three motifs for both ds and ss DNA replication.
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Affiliation(s)
- B M Bishop
- Department of Obstetrics, University of Arkansas for Medical Sciences, Little Rock 72205, USA
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39
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Ryan JH, Zolotukhin S, Muzyczka N. Sequence requirements for binding of Rep68 to the adeno-associated virus terminal repeats. J Virol 1996; 70:1542-53. [PMID: 8627673 PMCID: PMC189976 DOI: 10.1128/jvi.70.3.1542-1553.1996] [Citation(s) in RCA: 98] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
We have used reciprocal competition binding experiments with mutant substrates and chemical modification interference assays to precisely define the sequences within the adeno-associated virus (AAV) terminal repeat (TR) that are involved in site-specific binding to the AAV Rep protein. Mutagenesis experiments were done with a 43-bp oligonucleotide which contained the Rep binding element (RBE) within the A stem of the TR. Experiments in which two adjacent base pairs of the RBE were substituted simultaneously with nucleotides that produced transversions identified a 22-bp sequence (CAGTGAGCGAGCGAGCGCGCAG) in which substitutions measurably affected the binding affinity. Although the 22-bp RBE contains the GAGC motifs that have been found in all known Rep binding sites, our results suggest that the GAGC motifs alone are not the only sequences specifically recognized by Rep. The effects of substitutions within the 22-bp sequence were relatively symmetrical, with nucleotides at the periphery of the RBE having the least effect on binding affinity and those in the middle having the greatest effect. Dinucleotide mutations within 18 (GTGAGCGAGCGAGC) of the 22 bp were found to decrease the binding affinity by at least threefold. Dinucleotide mutations within a 10-bp core sequence (GCGAGCGAGC) were found to decrease binding affinity by more than 10-fold. Single-base substitutions within the 10-bp core sequence lowered the binding affinity by variable amounts (up to fivefold). The results of the mutagenesis analysis suggested that the A-stem RBE contains only a single Rep binding site rather than two or more independent sites. To confirm the results of the mutant analysis and to determine the relative contribution of each base to binding, chemical modification experiments using dimethyl sulfate and hydrazine were performed on both the linear A-stem sequence and the entire AAV TR in both the flip and flop hairpinned configurations. Interference assays on the linear A stem identified the 18-bp sequence described above as essential for binding. G, C, and T residues on both strands contributed to binding, and the interference pattern correlated well with the results of the mutagenesis experiments. Interference assays with complete hairpinned TR substrates also identified the 18-bp sequence as important for binding. However, the interference patterns on the two strands within the RBE and the relative contributions of the individual bases to binding were clearly different between the hairpinned substrates and the linear A-stem binding element. Interference assays also allowed us to search for residues within the small internal palindromes of the TR (B and C) that contribute to binding. The largest effect was seen by modification of two T residues within the sequence CTTTG. This sequence was present in the same position relative to the terminal resolution site (trs) in both the flip and flop orientations of the TR. In addition, the interference pattern suggested that the remaining bases within the CTTTG motif as well as other bases within the B and C palindromes make contacts with the Rep protein, albeit with lower affinities. Regardless of whether the TR was in the flip or flop orientation, most of the contact points were clustered in the small internal palindrome furthest away from the trs. We also determined the relative binding affinity of linear substrates containing a complete RBE with hairpinned substrates and found that linear substrates bound Rep less efficiently. Our results were consistent with our previous model that there are three distinct elements within the hairpinned AAV TR that contribute to binding affinity or to efficient nicking at the trs: the A-stem RBE, the secondary structure element which consists of the B and C palindromes, and the trs.
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Affiliation(s)
- J H Ryan
- Department of Molecular Genetics and Microbiology, College of Medicine, University of Florida, Gainesville 32610, USA
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40
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Affiliation(s)
- K I Berns
- Department of Microbiology, Hearst Microbiology Research Center, Cornell University Medical College, New York 10021, USA
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41
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Chiorini JA, Yang L, Safer B, Kotin RM. Determination of adeno-associated virus Rep68 and Rep78 binding sites by random sequence oligonucleotide selection. J Virol 1995; 69:7334-8. [PMID: 7474165 PMCID: PMC189665 DOI: 10.1128/jvi.69.11.7334-7338.1995] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
To further define the canonical binding site for the P5-promoted Rep proteins of the adeno-associated virus, a modified random oligonucleotide selection procedure was performed, using purified recombinant Rep protein. These results may explain the effects of Rep on cellular gene expression.
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Affiliation(s)
- J A Chiorini
- Molecular Hematology Branch, NIH/NHLBI, Bethesda, MD 20892-1654, USA
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42
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Clark KR, Voulgaropoulou F, Fraley DM, Johnson PR. Cell lines for the production of recombinant adeno-associated virus. Hum Gene Ther 1995; 6:1329-41. [PMID: 8590738 DOI: 10.1089/hum.1995.6.10-1329] [Citation(s) in RCA: 202] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Adeno-associated virus (AAV) is a replication-defective parvovirus that is being developed as a vector for human gene transfer. However, a major obstacle to commonplace usage of AAV vectors is the production of recombinant virions (rAAV) in sufficient quantities for not only human trials, but also for preclinical studies of basic biology, toxicology, and efficacy. Unfortunately, current methods for large-scale production are cumbersome and expensive. We have developed a simplified method for generating rAAV by establishing neomycin-resistant cell lines containing copies of the AAV rep-cap genes and a rAAV vector. After infection with adenovirus, these cell lines are shown to produce infectious rAAV in relatively high titer. This method eliminates the need for exogenous DNA transfection and scale-up procedures are limited only by the normal constraints of growing cells in culture.
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Affiliation(s)
- K R Clark
- Children's Hospital Research Foundation, Columbus, OH, USA
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43
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Chiorini JA, Wiener SM, Owens RA, Kyöstió SR, Kotin RM, Safer B. Sequence requirements for stable binding and function of Rep68 on the adeno-associated virus type 2 inverted terminal repeats. J Virol 1994; 68:7448-57. [PMID: 7933128 PMCID: PMC237187 DOI: 10.1128/jvi.68.11.7448-7457.1994] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Replication of the palindromic inverted terminal repeats (ITRs) of adeno-associated virus type 2 requires several functions of the viral nonstructural Rep proteins. These include binding to the ITR, nicking of the double-stranded replication intermediate at the terminal resolution site (trs), and then strand displacement and synthesis from the nick. This report demonstrates the ability of both recombinant fusion maltose-binding protein (MBP)-Rep68 delta produced in Escherichia coli and wild-type (wt) Rep68 to bind to a linear truncated form of the ITR, delta 57 ITR, with similar affinity as to the wt hairpin ITR. A dissociation constant for MBP-Rep68 delta of approximately 8 x 10(-10) M was determined for the wt ITR and delta 57 ITR probes. Truncation of delta 57 ITR to generate delta 28 ITR, which retains the GCTC repeat motif but not the trs, bound at least 10 times less efficiently than delta 57 ITR. Extension of delta 28 ITR with nonspecific sequence restored the ability of MBP-Rep68 delta to bind to delta 28 ITR. Thus, high-affinity binding would appear to require stabilization by flanking sequence as well as the intact GCTC repeat motif. Cleavage of the delta 57 ITR probe with DdeI, which truncates the flanking sequence and was previously shown to inhibit binding by Rep68, also inhibited the binding of MBP-Rep68 delta. The requirements for stable binding were further defined with a series of oligonucleotide probes which spanned the region protected by MBP-Rep78 in DNase I footprinting. The binding activity of either MBP-Rep68 delta or wt Rep68 to hairpin ITR or delta 57 ITR was indistinguishable. However, the binding activity of MBP-Rep68 delta to DNA does not appear to correlate with trs endonuclease activity. The nicking and covalent linkage of MBP-Rep68 delta to the nonhairpin delta 57 ITR was approximately 100-fold less efficient than its linkage to a hairpin-containing ITR. Therefore, although the hairpin portion of the ITR does not appear to play a role in recognition and stabilization of MBP-Rep68 delta binding, its presence does affect the trs cleavage activity of the protein.
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Affiliation(s)
- J A Chiorini
- Molecular Hematology Branch, National Heart, Lung, and Blood Institute, Bethesda, MD 20892-1654
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44
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Batchu RB, Kotin RM, Hermonat PL. The regulatory rep protein of adeno-associated virus binds to sequences within the c-H-ras promoter. Cancer Lett 1994; 86:23-31. [PMID: 7954351 DOI: 10.1016/0304-3835(94)90176-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The large rep gene products (rep68 and rep78) of adeno-associated virus (AAV) are pleiotropic effector proteins which not only play a critical role in AAV DNA replication and in the trans-regulation of AAV promotor elements, but are also known for their onco-suppressive functions. We have previously demonstrated that the large AAV rep protein will strongly inhibit expression from the c-H-ras promoter, but not the murine osteosarcoma virus long terminal repeat (MSV-LTR) promoter. To investigate the possibility that rep may physically bind to these promoter sequences, specifically to GCTC motifs, we conducted electrophoretic mobility shift assays (EMSA) with a maltose binding protein-rep chimeric protein, MBP-rep68 delta, and synthetic double stranded DNA substrates of sequences selected from the c-H-ras and MSV-LTR promoters, as well as with the AAV TR. We find that MPB-rep68 delta bound the AAV TR DNA sequence (three motifs) most strongly, followed by the selected c-H-ras DNA sequence (two noninterfering motifs), and most poorly to the MSV-LTR DNA (one motif). These data are consistent with our previous study and suggest a direct mechanism of action for AAV rep inhibition of the c-H-ras promoter. Furthermore, the results suggest that the number of GCTC motifs, when closely associated, affect the affinity of rep binding. Finally, we find that MBP-rep68 delta also binds to the c-H-ras oligomer substrates which have secondary hairpin structures.
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Affiliation(s)
- R B Batchu
- Department of Obstetrics and Gynecology, University of Arkansas for Medical Science, Little Rock 72205
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45
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McCarty DM, Pereira DJ, Zolotukhin I, Zhou X, Ryan JH, Muzyczka N. Identification of linear DNA sequences that specifically bind the adeno-associated virus Rep protein. J Virol 1994; 68:4988-97. [PMID: 8035498 PMCID: PMC236440 DOI: 10.1128/jvi.68.8.4988-4997.1994] [Citation(s) in RCA: 125] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
We have used baculovirus-expressed Rep68 that has been purified to homogeneity to reexamine the binding properties of the Rep protein. We find that Rep68 is capable of binding to a linear DNA sequence that is contained within a 25-bp sequence of the A stem of the adeno-associated virus (AAV) terminal repeat proximal to the B and C palindromes. This has been shown conclusively by demonstrating that Rep68 could specifically bind to a synthetic oligonucleotide containing the 25-bp region in the absence of the other sequences within the terminal repeat. Rep78 was also capable of binding the A stem recognition element, as demonstrated by the fact that a DNA affinity column containing the 25-bp sequence can be used to purify Rep78. The ability to recognize the linear DNA sequence within the A stem provides a mechanism by which the Rep protein can be oriented on the terminal repeat so that only the correct strand is cut at the terminal resolution site (trs site) during terminal resolution. In addition, computer analysis suggests that sequences similar to the A stem element are present within the three AAV promoter regions. Electrophoretic mobility shift experiments clearly demonstrate that the p5 promoter contains a Rep binding sequence. DNase protection experiments indicate that the Rep binding sequence within the p5 promoter is located between the YY1 initiator sequence and the TATA binding site. This position immediately suggests a mechanism by which the Rep protein could act as a repressor or a transactivator of p5 transcription by interacting with either YY1 or TBP. In addition, gel shift experiments suggest that the p19 promoter also contains a Rep binding site. The presence of Rep binding sites upstream of both promoters suggests that these sites may be involved in coordinate regulation of AAV transcription. In addition, we have identified a heterologous Rep binding sequence within pBR322 DNA. A comparison of the sequences within the A stem, p5, and pBR322 binding sites suggests that a repeating GAGC motif is at least part of the Rep recognition sequence. In the accompanying report (D. M. McCarty, J. H. Ryan, S. Zolutukhin, X. Zhou, and N. Muzyczka, J. Virol. 68:4998-5006, 1994), we examine the relative affinity of Rep to the A stem site and the complete terminal repeat. Finally, we also have reexamined the ability of Rep68 and Rep78 to cut at the trs site in substrates that do not contain the B and C palindromes or any apparent secondary structure.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- D M McCarty
- Department of Microbiology, School of Medicine, University at Stony Brook, New York 11794
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46
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Kotin RM. Prospects for the use of adeno-associated virus as a vector for human gene therapy. Hum Gene Ther 1994; 5:793-801. [PMID: 7981305 DOI: 10.1089/hum.1994.5.7-793] [Citation(s) in RCA: 194] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Affiliation(s)
- R M Kotin
- Molecular Hematology Branch, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892
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47
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Snyder RO, Im DS, Ni T, Xiao X, Samulski RJ, Muzyczka N. Features of the adeno-associated virus origin involved in substrate recognition by the viral Rep protein. J Virol 1993; 67:6096-104. [PMID: 8396670 PMCID: PMC238031 DOI: 10.1128/jvi.67.10.6096-6104.1993] [Citation(s) in RCA: 102] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
We previously demonstrated that the adeno-associated virus (AAV) Rep68 and Rep78 proteins are able to nick the AAV origin of DNA replication at the terminal resolution site (trs) in an ATP-dependent manner. Using four types of modified or mutant substrates, we now have investigated the substrate requirements of Rep68 in the trs endonuclease reaction. In the first kind of substrate, portions of the hairpinned AAV terminal repeat were deleted. Only deletions that retained virtually all of the small internal palindromes of the AAV terminal repeat were active in the endonuclease reaction. This result confirmed previous genetic and biochemical evidence that the secondary structure of the terminal repeat was an important feature for substrate recognition. In the second type of substrate, the trs was moved eight bases further away from the end of the genome. The mutant was nicked at a 50-fold-lower frequency relative to a wild-type origin, and the nick occurred at the correct trs sequence despite its new position. This finding indicated that the endonuclease reaction required a specific sequence at the trs in addition to the correct secondary structure. It also suggested that the minimum trs recognition sequence extended three bases from the cut site in the 3' direction. The third type of substrate harbored mismatched base pairs at the trs. The mismatch substrates contained a wild-type sequence on the strand normally cut but an incorrect sequence on the complementary strand. All of the mismatch mutants were capable of being nicked in the presence of ATP. However, there was substantial variation in the level of activity, suggesting that the sequence on the opposite strand may also be recognized during nicking. Analysis of the mismatch mutants also suggested that a single-stranded trs was a viable substrate for the enzyme. This interpretation was confirmed by analysis of the fourth type of substrate tested, which contained a single-stranded trs. This substrate was also cleaved efficiently by the enzyme provided that the correct strand was present in the substrate. In addition, the single-stranded substrate no longer required ATP as a cofactor for nicking. Finally, all of the substrates with mutant trss bound the Rep protein as efficiently as the wild-type did. This finding indicated that the sequence at the cut site was not involved in recognition of the terminal repeat for specific binding by the enzyme. We concluded that substrate recognition by the AAV Rep protein involves at least two and possibly as many as four features of the AAV terminal repeat.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- R O Snyder
- Department of Microbiology, State University of New York at Stony Brook Medical School 11794-8621
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48
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Abstract
Cell extracts from murine A9 or human HeLa cells containing wild-type copies the NS1 polypeptide of minute virus of mice (MVM), produced from a recombinant vaccinia virus, can support the resolution of viral 3' termini from palindromic junction fragments of dimeric, replicative-form MVM DNA. Resolution resulted in the generation of two new viral termini, one associated with each arm of the junction palindrome. Telomeres were created in two configurations, "extended" forms, which were covalently associated with NS1 molecules, and smaller "turn-around" forms in which a single arm of the palindrome terminated at the axis of dyad symmetry in a covalent bond which cross-linked the two strands. The in vitro resolution reaction was asymmetric, generating predominantly extended-form termini from one arm of the palindrome but predominantly turn-around forms from the other. This asymmetry was independent of the type of cell used to prepare the in vitro extract or the orientation of the palindrome in the plasmid and was obtained for all cloned junction sequences of 156 bp or more. Two modified forms of the duplex junction fragment, which appeared to be intermediates in the resolution process since they were nicked, covalently linked to NS1, and associated with newly synthesized DNA, were identified. The structures of these intermediates suggest that resolution is initiated by preferential nicking at one of the two candidate resolution sites. The asymmetric nature of this resolution reaction is discussed in terms of current models of MVM DNA replication.
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Affiliation(s)
- S F Cotmore
- Departments of Laboratory Medicine, Yale University School of Medicine, New Haven, Connecticut 06510
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49
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Abstract
Recent characterization of integration of the human parvovirus, adeno-associated virus, has uncovered the exciting occurrence of targeted integration. Thus far, such specific integration has been found to be unique among the eukaryotic viruses. The molecular details of the steps involved in virus integration are actively being pursued and should yield significant information for our understanding of the mechanisms of DNA transposition.
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Affiliation(s)
- R J Samulski
- Department of Biological Sciences, University of Pittsburgh, Pennsylvania 15260
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50
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Dumas B, Jourdan M, Pascaud AM, Bergoin M. Complete nucleotide sequence of the cloned infectious genome of Junonia coenia densovirus reveals an organization unique among parvoviruses. Virology 1992; 191:202-22. [PMID: 1413502 DOI: 10.1016/0042-6822(92)90182-o] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
We previously constructed a recombinant plasmid, pBRJ, encompassing an infectious Junonia coenia densovirus (JcDNV) genome (M. Jourdan et al. (1990). Virology 179, 403-409). We report here the complete viral sequence of pBRJ. The genome, 5908 nucleotides (nt) long, consists of an internal unique sequence flanked by long (517 nt) inverted terminal repeats. The first 96 bases of one extremity can fold into a typical Y-shaped hairpin structure. The opposite extremity is incomplete, lacking 88 nt. These terminal structures, similar to those of dependoviruses, human parvovirus B19 and Bombyx mori densovirus (BmDNV), strongly suggest a common mechanism of DNA replication for these parvoviruses. JcDNV genomic organization is unique among parvoviruses in that coding sequences are evenly distributed in the 5' half of both strands. On one strand, the major open reading frame (ORF1) encodes the four structural proteins. On the complementary strand, ORF2, ORF3 (included in ORF2), and ORF4 probably encode nonstructural proteins. JcDNV genome has little DNA homology with vertebrate parvoviruses and surprisingly even less with the two densoviruses presently sequenced. ORF1 contains the highly conserved PGY and G-rich regions and ORF2 the NTP-binding domain common to most structural and to all nonstructural vertebrate parvoviral ORFs, respectively. The single homology between JcDNV and BmDNV is unexpectedly located in JcDNV NTP-binding domain and BmDNV ORF2 assumed to encode structural polypeptides. Only a weak homology exists between JcDNV and Aedes DNV in their NTP-binding domain.
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Affiliation(s)
- B Dumas
- Centre de Recherches Roussel Uclaf, Romainville, France
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