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Catalán-Tatjer D, Tzimou K, Nielsen LK, Lavado-García J. Unravelling the essential elements for recombinant adeno-associated virus (rAAV) production in animal cell-based platforms. Biotechnol Adv 2024; 73:108370. [PMID: 38692443 DOI: 10.1016/j.biotechadv.2024.108370] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2024] [Revised: 04/05/2024] [Accepted: 04/27/2024] [Indexed: 05/03/2024]
Abstract
Recombinant adeno-associated viruses (rAAVs) stand at the forefront of gene therapy applications, holding immense significance for their safe and efficient gene delivery capabilities. The constantly increasing and unmet demand for rAAVs underscores the need for a more comprehensive understanding of AAV biology and its impact on rAAV production. In this literature review, we delved into AAV biology and rAAV manufacturing bioprocesses, unravelling the functions and essentiality of proteins involved in rAAV production. We discuss the interconnections between these proteins and how they affect the choice of rAAV production platform. By addressing existing inconsistencies, literature gaps and limitations, this review aims to define a minimal set of genes that are essential for rAAV production, providing the potential to advance rAAV biomanufacturing, with a focus on minimizing the genetic load within rAAV-producing cells.
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Affiliation(s)
- David Catalán-Tatjer
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Denmark
| | - Konstantina Tzimou
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Denmark
| | - Lars K Nielsen
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Denmark; Australian Institute for Bioengineering and Nanotechnology, University of Queensland, Australia
| | - Jesús Lavado-García
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Denmark.
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2
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Zhang J, Frabutt DA, Chrzanowski M, Li N, Miller LM, Tian J, Mulcrone PL, Lam AK, Draper BE, Jarrold MF, Herzog RW, Xiao W. A novel class of self-complementary AAV vectors with multiple advantages based on cceAAV lacking mutant ITR. Mol Ther Methods Clin Dev 2024; 32:101206. [PMID: 38390555 PMCID: PMC10881427 DOI: 10.1016/j.omtm.2024.101206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2023] [Accepted: 01/30/2024] [Indexed: 02/24/2024]
Abstract
Self-complementary AAV vectors (scAAV) use a mutant inverted terminal repeat (mITR) for efficient packaging of complementary stranded DNA, enabling rapid transgene expression. However, inefficient resolution at the mITR leads to the packaging of monomeric or subgenomic AAV genomes. These noncanonical particles reduce transgene expression and may affect the safety of gene transfer. To address these issues, we have developed a novel class of scAAV vectors called covalently closed-end double-stranded AAV (cceAAV) that eliminate the mITR resolution step during production. Instead of using a mutant ITR, we used a 56-bp recognition sequence of protelomerase (TelN) to covalently join the top and bottom strands, allowing the vector to be generated with just a single ITR. To produce cceAAV vectors, the vector plasmid is initially digested with TelN, purified, and then subjected to a standard triple-plasmid transfection protocol followed by traditional AAV vector purification procedures. Such cceAAV vectors demonstrate yields comparable to scAAV vectors. Notably, we observed enhanced transgene expression as compared to traditional scAAV vectors. The treatment of mice with hemophilia B with cceAAV-FIX resulted in significantly enhanced long-term FIX expression. The cceAAV vectors hold several advantages over scAAV vectors, potentially leading to the development of improved human gene therapy drugs.
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Affiliation(s)
- Junping Zhang
- Herman B. Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Dylan A. Frabutt
- Herman B. Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | | | - Ning Li
- Herman B. Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | | | - Jiahe Tian
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Patrick L. Mulcrone
- Herman B. Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Anh K. Lam
- Herman B. Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | | | - Martin F. Jarrold
- Chemistry Department, Indiana University, Bloomington, IN 47405, USA
| | - Roland W. Herzog
- Herman B. Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Weidong Xiao
- Herman B. Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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3
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Wang Y, Fu Q, Park SY, Lee YS, Park SY, Lee DY, Yoon S. Decoding cellular mechanism of recombinant adeno-associated virus (rAAV) and engineering host-cell factories toward intensified viral vector manufacturing. Biotechnol Adv 2024; 71:108322. [PMID: 38336188 DOI: 10.1016/j.biotechadv.2024.108322] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2023] [Revised: 01/22/2024] [Accepted: 02/06/2024] [Indexed: 02/12/2024]
Abstract
Recombinant adeno-associated virus (rAAV) is one of the prominent gene delivery vehicles that has opened promising opportunities for novel gene therapeutic approaches. However, the current major viral vector production platform, triple transfection in mammalian cells, may not meet the increasing demand. Thus, it is highly required to understand production bottlenecks from the host cell perspective and engineer the cells to be more favorable and tolerant to viral vector production, thereby effectively enhancing rAAV manufacturing. In this review, we provided a comprehensive exploration of the intricate cellular process involved in rAAV production, encompassing various stages such as plasmid entry to the cytoplasm, plasmid trafficking and nuclear delivery, rAAV structural/non-structural protein expression, viral capsid assembly, genome replication, genome packaging, and rAAV release/secretion. The knowledge in the fundamental biology of host cells supporting viral replication as manufacturing factories or exhibiting defending behaviors against viral production is summarized for each stage. The control strategies from the perspectives of host cell and materials (e.g., AAV plasmids) are proposed as our insights based on the characterization of molecular features and our existing knowledge of the AAV viral life cycle, rAAV and other viral vector production in the Human embryonic kidney (HEK) cells.
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Affiliation(s)
- Yongdan Wang
- Department of Chemical Engineering, University of Massachusetts Lowell, Lowell, MA 01854, United States of America
| | - Qiang Fu
- Department of Biomedical Engineering and Biotechnology, University of Massachusetts Lowell, Lowell, MA 01854, United States of America
| | - So Young Park
- Department of Pharmaceutical Sciences, University of Massachusetts Lowell, Lowell, MA 01854, United States of America
| | - Yong Suk Lee
- Department of Pharmaceutical Sciences, University of Massachusetts Lowell, Lowell, MA 01854, United States of America
| | - Seo-Young Park
- School of Chemical Engineering, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 16419, Republic of Korea
| | - Dong-Yup Lee
- School of Chemical Engineering, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 16419, Republic of Korea
| | - Seongkyu Yoon
- Department of Chemical Engineering, University of Massachusetts Lowell, Lowell, MA 01854, United States of America.
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4
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Li X, Miller LM, Chrzanowski M, Tian J, Jarrold MF, Herzog RW, Xiao W, Draper B, Zhang J. Quantitative analysis of preferential utilization of AAV ITR as the packaging terminal signal. Front Bioeng Biotechnol 2023; 11:1327433. [PMID: 38173872 PMCID: PMC10761532 DOI: 10.3389/fbioe.2023.1327433] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Accepted: 12/05/2023] [Indexed: 01/05/2024] Open
Abstract
Genetic engineering advances have led to recombinant adeno-associated virus (rAAV) becoming an invaluable tool for the development of effective gene therapies. The production of rAAV is susceptible to off-target heterogeneous packaging, the effects of which are still being understood. Here, rAAV vectors with four-genome lengths were produced using both adherent and suspension HEK293 cells to understand the 5'ITR termination. AAV8 vectors were produced from the human FVIII plasmid for a full-length cargo of 4,707 nucleotides with specific truncations, creating smaller genomes. Conventionally, rAAV is characterized by differentiating empty capsids from full capsids, but for this work, that description is incomplete. The small genomes in this study were characterized by charge detection-mass spectrometry (CD-MS). Using CD-MS, packaged genomes in the range conventionally attributed to partials were resolved and quantified. In addition, alkaline gels and qPCR were used to assess the identity of the packaged genomes. Together, these results showed a propensity for unit-length genomes to be encapsidated. Packaged genomes occurred as replication intermediates emanating from the 5'ITR, indicating that HEK293 cells prefer unit-length genomes as opposed to the 5'ITR termination and heterogeneous DNA packaging observed previously from Sf9 cell systems. As both manufacturing processes are used and continually assessed to produce clinical material, such an understanding will benefit rAAV design for basic research and gene therapy.
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Affiliation(s)
- Xin Li
- Herman B Wells Center for Pediatric Research, Indiana University IUSM, Indianapolis, IN, United States
| | | | | | - Jiahe Tian
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, United States
| | - Martin F. Jarrold
- Chemistry Department, Indiana University, Bloomington, IN, United States
| | - Roland W. Herzog
- Herman B Wells Center for Pediatric Research, Indiana University IUSM, Indianapolis, IN, United States
| | - Weidong Xiao
- Herman B Wells Center for Pediatric Research, Indiana University IUSM, Indianapolis, IN, United States
| | | | - Junping Zhang
- Herman B Wells Center for Pediatric Research, Indiana University IUSM, Indianapolis, IN, United States
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5
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Madigan V, Zhang F, Dahlman JE. Drug delivery systems for CRISPR-based genome editors. Nat Rev Drug Discov 2023; 22:875-894. [PMID: 37723222 DOI: 10.1038/s41573-023-00762-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/06/2023] [Indexed: 09/20/2023]
Abstract
CRISPR-based drugs can theoretically manipulate any genetic target. In practice, however, these drugs must enter the desired cell without eliciting an unwanted immune response, so a delivery system is often required. Here, we review drug delivery systems for CRISPR-based genome editors, focusing on adeno-associated viruses and lipid nanoparticles. After describing how these systems are engineered and their subsequent characterization in preclinical animal models, we highlight data from recent clinical trials. Preclinical targeting mediated by polymers, proteins, including virus-like particles, and other vehicles that may deliver CRISPR systems in the future is also discussed.
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Affiliation(s)
- Victoria Madigan
- Broad Institute of MIT and Harvard, Cambridge, MA, USA
- McGovern Institute for Brain Research at MIT, Cambridge, MA, USA
- Department of Brain and Cognitive Science, Massachusetts Institute of Technology, Cambridge, MA, USA
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
- Howard Hughes Medical Institute, Cambridge, MA, USA
| | - Feng Zhang
- Broad Institute of MIT and Harvard, Cambridge, MA, USA
- McGovern Institute for Brain Research at MIT, Cambridge, MA, USA
- Department of Brain and Cognitive Science, Massachusetts Institute of Technology, Cambridge, MA, USA
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
- Howard Hughes Medical Institute, Cambridge, MA, USA
| | - James E Dahlman
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University School of Medicine, Atlanta, GA, USA.
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6
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Jalšić L, Lytvyn V, Elahi SM, Hrapovic S, Nassoury N, Chahal PS, Gaillet B, Gilbert R. Inducible HEK293 AAV packaging cell lines expressing Rep proteins. Mol Ther Methods Clin Dev 2023; 30:259-275. [PMID: 37560197 PMCID: PMC10407821 DOI: 10.1016/j.omtm.2023.07.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Accepted: 07/11/2023] [Indexed: 08/11/2023]
Abstract
Packaging or producer cell lines for scalable recombinant adeno-associated virus (rAAV) production have been notoriously difficult to create due in part to the cytostatic nature of the Rep proteins required for AAV production. The most difficult challenge being creating AAV packaging cell lines using HEK293 parental cells, currently the best mammalian platform for rAAV production due to the constitutive expression of E1A in HEK293 cells, a key REP transcription activator. Using suspension and serum-free media adapted HEK293SF carrying a gene expression regulation system induced by addition of cumate and coumermycin, we were able to create REP-expressing AAV packaging cells. This was achieved by carefully choosing two of the AAV Rep proteins (Rep 40 and 68), using two inducible promoters with different expression levels and integrating into the cells through lentiviral vector transduction. Three of our best clones produced rAAV titers comparable to titers obtained by standard triple plasmid transfection of their parental cells. These clones were stable for up to 7 weeks under continuous cultures condition. rAAV production from one clone was also validated at scale of 1 L in a wave bioreactor using serum-free suspension culture.
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Affiliation(s)
- Lovro Jalšić
- Département de Génie Chimique, Université Laval, Québec, QC G1V0A6, Canada
- Department of Production Platforms and Analytics, Human Health Therapeutics Research Center, National Research Council Canada, Montréal, QC H4P 2R2, Canada
| | - Viktoria Lytvyn
- Department of Production Platforms and Analytics, Human Health Therapeutics Research Center, National Research Council Canada, Montréal, QC H4P 2R2, Canada
| | - Seyyed Mehdy Elahi
- Department of Production Platforms and Analytics, Human Health Therapeutics Research Center, National Research Council Canada, Montréal, QC H4P 2R2, Canada
| | - Sabahudin Hrapovic
- Advanced Biomaterials and Chemical Synthesis Team, Aquatic and Crop Resource Development Research Centre, National Research Council Canada, Montréal, QC H4P 2R2, Canada
| | - Nasha Nassoury
- Department of Production Platforms and Analytics, Human Health Therapeutics Research Center, National Research Council Canada, Montréal, QC H4P 2R2, Canada
| | - Parminder Singh Chahal
- Department of Production Platforms and Analytics, Human Health Therapeutics Research Center, National Research Council Canada, Montréal, QC H4P 2R2, Canada
| | - Bruno Gaillet
- Département de Génie Chimique, Université Laval, Québec, QC G1V0A6, Canada
| | - Rénald Gilbert
- Département de Génie Chimique, Université Laval, Québec, QC G1V0A6, Canada
- Department of Production Platforms and Analytics, Human Health Therapeutics Research Center, National Research Council Canada, Montréal, QC H4P 2R2, Canada
- Department of Bioengineering, McGill University, Montréal, QC H3A 0E9 Canada
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Chen P, Wojdyla JA, Colasanti O, Li Z, Qin B, Wang M, Lohmann V, Cui S. Biochemical and structural characterization of hepatitis A virus 2C reveals an unusual ribonuclease activity on single-stranded RNA. Nucleic Acids Res 2022; 50:9470-9489. [PMID: 35947700 PMCID: PMC9458454 DOI: 10.1093/nar/gkac671] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Accepted: 07/22/2022] [Indexed: 12/24/2022] Open
Abstract
The HAV nonstructural protein 2C is essential for virus replication; however, its precise function remains elusive. Although HAV 2C shares 24-27% sequence identity with other 2Cs, key motifs are conserved. Here, we demonstrate that HAV 2C is an ATPase but lacking helicase activity. We identified an ATPase-independent nuclease activity of HAV 2C with a preference for polyuridylic single-stranded RNAs. We determined the crystal structure of an HAV 2C fragment to 2.2 Å resolution, containing an ATPase domain, a region equivalent to enterovirus 2C zinc-finger (ZFER) and a C-terminal amphipathic helix (PBD). The PBD of HAV 2C occupies a hydrophobic pocket (Pocket) in the adjacent 2C, and we show the PBD-Pocket interaction is vital for 2C functions. We identified acidic residues that are essential for the ribonuclease activity and demonstrated mutations at these sites abrogate virus replication. We built a hexameric-ring model of HAV 2C, revealing the ribonuclease-essential residues clustering around the central pore of the ring, whereas the ATPase active sites line up at the gaps between adjacent 2Cs. Finally, we show the ribonuclease activity is shared by other picornavirus 2Cs. Our findings identified a previously unfound activity of picornavirus 2C, providing novel insights into the mechanisms of virus replication.
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Affiliation(s)
| | | | | | | | - Bo Qin
- NHC Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, PR China
| | - Meitian Wang
- Swiss Light Source at the Paul Scherrer Institute, CH-5232 Villigen, Switzerland
| | - Volker Lohmann
- Correspondence may also be addressed to Volker Lohmann. Tel: +49 6221 56 6449; Fax: +49 6221 56 4570;
| | - Sheng Cui
- To whom correspondence should be addressed. Tel: +86 10 67828669; Fax: +86 10 67855012;
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8
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Mietzsch M, Eddington C, Jose A, Hsi J, Chipman P, Henley T, Choudhry M, McKenna R, Agbandje-McKenna M. Improved Genome Packaging Efficiency of Adeno-associated Virus Vectors Using Rep Hybrids. J Virol 2021; 95:e0077321. [PMID: 34287038 PMCID: PMC8428402 DOI: 10.1128/jvi.00773-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Accepted: 07/03/2021] [Indexed: 01/11/2023] Open
Abstract
Recombinant adeno-associated viruses (rAAVs) are one of the most commonly used vectors for a variety of gene therapy applications. In the last 2 decades, research focused primarily on the characterization and isolation of new cap, genes resulting in hundreds of natural and engineered AAV capsid variants, while the rep gene, the other major AAV open reading frame, has been less studied. This is due to the fact that the rep gene from AAV serotype 2 (AAV2) enables the single-stranded DNA packaging of recombinant genomes into most AAV serotype and engineered capsids. However, a major by-product of all vector productions is empty AAV capsids, lacking the encapsidated vector genome, especially for non-AAV2 vectors. Despite the packaging process being considered the rate-limiting step for rAAV production, none of the rep genes from the other AAV serotypes have been characterized for their packaging efficiency. Thus, in this study AAV2 rep was replaced with the rep gene of a select number of AAV serotypes. However, this led to a lowering of capsid protein expression, relative to the standard AAV2-rep system. In further experiments the 3' end of the AAV2 rep gene was reintroduced to promote increased capsid expression and a series of chimeras between the different AAV Rep proteins were generated and characterized for their vector genome packaging ability. The utilization of these novel Rep hybrids increased the percentage of genome containing (full) capsids approximately 2- to -4-fold for all of the non-AAV2 serotypes tested. Thus, these Rep chimeras could revolutionize rAAV production. IMPORTANCE A major by-product of all adeno-associated virus (AAV) vector production systems are "empty" capsids, void of the desired therapeutic gene, and thus do not provide any curative benefit for the treatment of the targeted disease. In fact, empty capsids can potentially elicit additional immune responses in vivo gene therapies if not removed by additional purification steps. Thus, there is a need to increase the genome packaging efficiency and reduce the number of empty capsids from AAV biologics. The novel Rep hybrids from different AAV serotypes described in this study are capable of reducing the percentage of empty capsids in all tested AAV serotypes and improve overall yields of genome-containing AAV capsids at the same time. They can likely be integrated easily into existing AAV manufacturing protocols to optimize the production of the generated AAV gene therapy products.
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Affiliation(s)
- Mario Mietzsch
- Department of Biochemistry and Molecular Biology, Center for Structural Biology, McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, Florida, USA
| | - Courtnee Eddington
- Department of Biochemistry and Molecular Biology, Center for Structural Biology, McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, Florida, USA
| | - Ariana Jose
- Department of Biochemistry and Molecular Biology, Center for Structural Biology, McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, Florida, USA
| | - Jane Hsi
- Department of Biochemistry and Molecular Biology, Center for Structural Biology, McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, Florida, USA
| | - Paul Chipman
- Department of Biochemistry and Molecular Biology, Center for Structural Biology, McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, Florida, USA
| | - Tom Henley
- Intima Bioscience, New York, New York, USA
| | | | - Robert McKenna
- Department of Biochemistry and Molecular Biology, Center for Structural Biology, McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, Florida, USA
| | - Mavis Agbandje-McKenna
- Department of Biochemistry and Molecular Biology, Center for Structural Biology, McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, Florida, USA
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Ruhel R, Mazumder M, Gnanasekaran P, Kumar M, Gourinath S, Chakraborty S. Functional implications of residues of the B' motif of geminivirus replication initiator protein in its helicase activity. FEBS J 2021; 288:6492-6509. [PMID: 34092039 DOI: 10.1111/febs.16053] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Revised: 04/15/2021] [Accepted: 06/04/2021] [Indexed: 01/03/2023]
Abstract
Geminivirus replication initiator protein (Rep) is a multifunctional viral protein required for replication. During the process of viral replication, Rep acts as a site- and strand-specific endonuclease, ligase, ATPase, and helicase. B' motif and β-hairpin loop of the geminivirus Rep are conserved and important for Rep-mediated helicase activity required for viral replication. To dissect the roles of various amino acid residues of the B' motif and β-hairpin loop of the geminivirus Rep helicase in its process of unwinding DNA, we investigated eight conserved residues near the ATP active site or the ssDNA contact channel. Our strategy was to mutate these residues to alanines and investigate the effects of these mutations on various biochemical activities associated with DNA unwinding. We looked into the ATP binding, ATP hydrolysis, DNA binding, and DNA unwinding activities of the wild-type and mutant Rep proteins. These investigations showed four residues (Arg279, Asp280, Tyr287, and Pro290) affecting the DNA unwinding activity. A structural model analysis confirmed the B' loop and ssDNA binding loop to be connected through a β-hairpin structure, suggesting that changes on one loop might affect the other and that these residues function by acting in concert. Viral genomes containing Rep proteins having these mutations in the B' motif did not replicate in planta. Taken together, these results indicated all four residues to be implicated in helicase activity mediated by Rep and demonstrated the significance, for viral replication, of the B' motif and β-hairpin loop of the C-terminal region of the Rep protein.
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Affiliation(s)
- Rajrani Ruhel
- Molecular Virology Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
| | - Mohit Mazumder
- Structural Biology Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
| | - Prabu Gnanasekaran
- Molecular Virology Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
| | - Manish Kumar
- Molecular Virology Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
| | - Samudrala Gourinath
- Structural Biology Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
| | - Supriya Chakraborty
- Molecular Virology Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
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10
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Characterization of Viral Genome Encapsidated in Adeno-associated Recombinant Vectors Produced in Yeast Saccharomyces cerevisiae. Mol Biotechnol 2021; 63:156-165. [PMID: 33392920 DOI: 10.1007/s12033-020-00294-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/18/2020] [Indexed: 12/29/2022]
Abstract
Adeno-associated virus (AAV) is a small, non-enveloped virus used as vector in gene therapy, mainly produced in human cells and in baculovirus systems. Intense studies on these platforms led to the production of vectors with titers between 103 and 105 viral genomes (vg) per cells. In spite of this, vector yields need to be improved to satisfy the high product demands of clinical trials and future commercialization. Our studies and those of other groups have explored the possibility to exploit the yeast Saccharomyces cerevisiae to produce rAAV. We previously demonstrated that yeast supports AAV genome replication and capsid assembly. The purpose of this study was to evaluate the quality of the encapsidated AAV DNA. Here, we report the construction of a yeast strain expressing Rep68/40 from an integrated copy of the Rep gene under the control of the yeast constitutive ADH promoter and Capsid proteins from the Cap gene under the control of an inducible GAL promoter. Our results indicate that a portion of AAV particles generated by this system contains encapsidated AAV DNA. However, the majority of encapsidated DNA consists of fragmented regions of the transgene cassette, with ITRs being the most represented sequences. Altogether, these data indicate that, in yeast, encapsidation occurs with low efficiency and that rAAVs resemble pseudo-vectors that are present in clinical-grade rAAV preparations.
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Santosh V, Musayev FN, Jaiswal R, Zárate-Pérez F, Vandewinkel B, Dierckx C, Endicott M, Sharifi K, Dryden K, Henckaerts E, Escalante CR. The Cryo-EM structure of AAV2 Rep68 in complex with ssDNA reveals a malleable AAA+ machine that can switch between oligomeric states. Nucleic Acids Res 2020; 48:12983-12999. [PMID: 33270897 PMCID: PMC7736791 DOI: 10.1093/nar/gkaa1133] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Revised: 11/01/2020] [Accepted: 11/27/2020] [Indexed: 11/13/2022] Open
Abstract
The adeno-associated virus (AAV) non-structural Rep proteins catalyze all the DNA transactions required for virus viability including, DNA replication, transcription regulation, genome packaging, and during the latent phase, site-specific integration. Rep proteins contain two multifunctional domains: an Origin Binding Domain (OBD) and a SF3 helicase domain (HD). Studies have shown that Rep proteins have a dynamic oligomeric behavior where the nature of the DNA substrate molecule modulates its oligomeric state. In the presence of ssDNA, Rep68 forms a large double-octameric ring complex. To understand the mechanisms underlying AAV Rep function, we investigated the cryo-EM and X-ray structures of Rep68-ssDNA complexes. Surprisingly, Rep68 generates hybrid ring structures where the OBD forms octameric rings while the HD forms heptamers. Moreover, the binding to ATPγS promotes a large conformational change in the entire AAA+ domain that leads the HD to form both heptamer and hexamers. The HD oligomerization is driven by an interdomain linker region that acts as a latch to 'catch' the neighboring HD subunit and is flexible enough to permit the formation of different stoichiometric ring structures. Overall, our studies show the structural basis of AAV Rep's structural flexibility required to fulfill its multifunctional role during the AAV life cycle.
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Affiliation(s)
- Vishaka Santosh
- Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, VA, USA
| | - Faik N Musayev
- Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University School of Medicine, Richmond, VA, USA
| | - Rahul Jaiswal
- Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, VA, USA
| | - Francisco Zárate-Pérez
- Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, VA, USA
- The Massey Cancer Center,Virginia Commonwealth University School of Medicine, Richmond, VA, USA
| | - Bram Vandewinkel
- Department of Cellular and Molecular Medicine and Department of Microbiology, Immunology and Transplantation, KU Leuven, Leuven, Belgium
| | - Caroline Dierckx
- Department of Cellular and Molecular Medicine and Department of Microbiology, Immunology and Transplantation, KU Leuven, Leuven, Belgium
| | - Molly Endicott
- Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, VA, USA
| | - Kamyar Sharifi
- Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, VA, USA
| | - Kelly Dryden
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA, USA
| | - Els Henckaerts
- Department of Cellular and Molecular Medicine and Department of Microbiology, Immunology and Transplantation, KU Leuven, Leuven, Belgium
| | - Carlos R Escalante
- Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, VA, USA
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12
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Maurer AC, Weitzman MD. Adeno-Associated Virus Genome Interactions Important for Vector Production and Transduction. Hum Gene Ther 2020; 31:499-511. [PMID: 32303138 PMCID: PMC7232694 DOI: 10.1089/hum.2020.069] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2020] [Accepted: 04/16/2020] [Indexed: 12/12/2022] Open
Abstract
Recombinant adeno-associated virus has emerged as one of the most promising gene therapy delivery vectors. Development of these vectors took advantage of key features of the wild-type adeno-associated virus (AAV), enabled by basic studies of the underlying biology and requirements for transcription, replication, and packaging of the viral genome. Each step in generating and utilizing viral vectors involves numerous molecular interactions that together determine the efficiency of vector production and gene delivery. Once delivered into the cell, interactions with host proteins will determine the fate of the viral genome, and these will impact the intended goal of gene delivery. Here, we provide an overview of known interactions of the AAV genome with viral and cellular proteins involved in its amplification, packaging, and expression. Further appreciation of how the AAV genome interacts with host factors will enhance how this simple virus can be harnessed for an array of vector purposes that benefit human health.
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Affiliation(s)
- Anna C. Maurer
- Department of Molecular and Cell Biology, University of California, Berkeley, California, USA
| | - Matthew D. Weitzman
- Division of Protective Immunity, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
- Division of Cancer Pathobiology, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
- Department of Pathology and Laboratory Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, USA
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13
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Subramanian S, Maurer AC, Bator CM, Makhov AM, Conway JF, Turner KB, Marden JH, Vandenberghe LH, Hafenstein SL. Filling Adeno-Associated Virus Capsids: Estimating Success by Cryo-Electron Microscopy. Hum Gene Ther 2019; 30:1449-1460. [PMID: 31530236 DOI: 10.1089/hum.2019.041] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Adeno-associated viruses (AAVs) have been employed successfully as gene therapy vectors in treating various genetic diseases for almost two decades. However, transgene packaging is usually imperfect, and developing a rapid and accurate method for measuring the proportion of DNA encapsidation is an important step for improving the downstream process of large scale vector production. In this study, we used two-dimensional class averages and three-dimensional classes, intermediate outputs in the single particle cryo-electron microscopy (cryo-EM) image reconstruction pipeline, to determine the proportion of DNA-packaged and empty capsid populations. Two different preparations of AAV3 were analyzed to estimate the minimum number of particles required to be sampled by cryo-EM in order for robust calculation of the proportion of the full versus empty capsids in any given sample. Cost analysis applied to the minimum amount of data required for a valid ratio suggests that cryo-EM is an effective approach to analyze vector preparations.
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Affiliation(s)
- Suriyasri Subramanian
- Department of Medicine, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania
| | - Anna C Maurer
- Grousbeck Gene Therapy Center, Schepens Eye Research Institute, Massachusetts Eye and Ear, Boston, Massachusetts.,Department of Ophthalmology, Harvard Medical School, Ocular Genomics Institute, Boston, Massachusetts.,The Broad Institute of Harvard and MIT, Cambridge, Massachusetts
| | - Carol M Bator
- Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, Pennsylvania
| | - Alexander M Makhov
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - James F Conway
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Kevin B Turner
- Gene Therapy Program, Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - James H Marden
- Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, Pennsylvania.,Department of Biology, Pennsylvania State University, University Park, Pennsylvania
| | - Luk H Vandenberghe
- Grousbeck Gene Therapy Center, Schepens Eye Research Institute, Massachusetts Eye and Ear, Boston, Massachusetts.,Department of Ophthalmology, Harvard Medical School, Ocular Genomics Institute, Boston, Massachusetts.,The Broad Institute of Harvard and MIT, Cambridge, Massachusetts
| | - Susan L Hafenstein
- Department of Medicine, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania.,Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, Pennsylvania.,Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, Pennsylvania
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14
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Agúndez L, Zárate-Pérez F, Meier AF, Bardelli M, Llosa M, Escalante CR, Linden RM, Henckaerts E. Exchange of functional domains between a bacterial conjugative relaxase and the integrase of the human adeno-associated virus. PLoS One 2018; 13:e0200841. [PMID: 30016371 PMCID: PMC6049929 DOI: 10.1371/journal.pone.0200841] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Accepted: 07/02/2018] [Indexed: 12/21/2022] Open
Abstract
Endonucleases of the HUH family are specialized in processing single-stranded DNA in a variety of evolutionarily highly conserved biological processes related to mobile genetic elements. They share a structurally defined catalytic domain for site-specific nicking and strand-transfer reactions, which is often linked to the activities of additional functional domains, contributing to their overall versatility. To assess if these HUH domains could be interchanged, we created a chimeric protein from two distantly related HUH endonucleases, containing the N-terminal HUH domain of the bacterial conjugative relaxase TrwC and the C-terminal DNA helicase domain of the human adeno-associated virus (AAV) replicase and site-specific integrase. The purified chimeric protein retained oligomerization properties and DNA helicase activities similar to Rep68, while its DNA binding specificity and cleaving-joining activity at oriT was similar to TrwC. Interestingly, the chimeric protein could catalyse site-specific integration in bacteria with an efficiency comparable to that of TrwC, while the HUH domain of TrwC alone was unable to catalyze this reaction, implying that the Rep68 C-terminal helicase domain is complementing the TrwC HUH domain to achieve site-specific integration into TrwC targets in bacteria. Our results illustrate how HUH domains could have acquired through evolution other domains in order to attain new roles, contributing to the functional flexibility observed in this protein superfamily.
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Affiliation(s)
- Leticia Agúndez
- Department of Infectious Diseases, School of Immunology and Microbial Sciences, King's College London, London, United Kingdom
| | - Francisco Zárate-Pérez
- Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia, United States of America
| | - Anita F. Meier
- Department of Infectious Diseases, School of Immunology and Microbial Sciences, King's College London, London, United Kingdom
| | - Martino Bardelli
- Department of Infectious Diseases, School of Immunology and Microbial Sciences, King's College London, London, United Kingdom
| | - Matxalen Llosa
- Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC), Universidad de Cantabria-CSIC-SODERCAN, Santander, Spain
- * E-mail: (EH); (ML)
| | - Carlos R. Escalante
- Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia, United States of America
| | - R. Michael Linden
- Department of Infectious Diseases, School of Immunology and Microbial Sciences, King's College London, London, United Kingdom
| | - Els Henckaerts
- Department of Infectious Diseases, School of Immunology and Microbial Sciences, King's College London, London, United Kingdom
- * E-mail: (EH); (ML)
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15
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Bennett A, Mietzsch M, Agbandje-McKenna M. Understanding capsid assembly and genome packaging for adeno-associated viruses. Future Virol 2017; 12:283-297. [PMID: 36776482 PMCID: PMC9910337 DOI: 10.2217/fvl-2017-0011] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Adeno-associated viruses (AAVs) are promising therapeutic viral vectors. Their capsid is assembled from viral proteins VP1, VP2 and VP3, aided by an assembly-activating protein, followed by replication protein mediated packaging of their 4.7-kb genome with inverted terminal repeats as packaging signals. To aid improvement of AAV vectors, knowledge of viral determinants of successful capsid assembly and genome packaging is important. We review the current knowledge of these two processes and efforts to overcome limited DNA packaging capacity and limit the packaging of unwanted foreign DNA in vector development. Residues involved in essential capsid assembly and genome packaging interactions cannot be manipulated in vector engineering. This information thus aids strategies to improve vector production and to increase AAV packaging capacity toward improved efficacy of this vector system.
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Affiliation(s)
- Antonette Bennett
- Department of Biochemistry & Molecular Biology, Center for Structure Biology, McKnight Brain Institute, University of Florida, Gainesville, FL 32610-0245, USA
| | - Mario Mietzsch
- Department of Biochemistry & Molecular Biology, Center for Structure Biology, McKnight Brain Institute, University of Florida, Gainesville, FL 32610-0245, USA
| | - Mavis Agbandje-McKenna
- Department of Biochemistry & Molecular Biology, Center for Structure Biology, McKnight Brain Institute, University of Florida, Gainesville, FL 32610-0245, USA,Author for correspondence: Tel.: +1 352 294 8393;
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16
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Minute Virus of Canines NP1 Protein Governs the Expression of a Subset of Essential Nonstructural Proteins via Its Role in RNA Processing. J Virol 2017; 91:JVI.00260-17. [PMID: 28356522 DOI: 10.1128/jvi.00260-17] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Accepted: 03/24/2017] [Indexed: 12/24/2022] Open
Abstract
Parvoviruses use a variety of means to control the expression of their compact genomes. The bocaparvovirus minute virus of canines (MVC) encodes a small, genus-specific protein, NP1, which governs access to the viral capsid gene via its role in alternative polyadenylation and alternative splicing of the single MVC pre-mRNA. In addition to NP1, MVC encodes five additional nonstructural proteins (NS) that share an initiation codon at the left end of the genome and which are individually encoded by alternative multiply spliced mRNAs. We found that three of these proteins were encoded by mRNAs that excise the NP1-regulated MVC intron immediately upstream of the internal polyadenylation site, (pA)p, and that generation of these proteins was thus regulated by NP1. Splicing of their progenitor mRNAs joined the amino termini of these proteins to the NP1 open reading frame, and splice site mutations that prevented their expression inhibited virus replication in a host cell-dependent manner. Thus, in addition to controlling capsid gene access, NP1 also controls the expression of three of the five identified NS proteins via its role in governing MVC pre-mRNA splicing.IMPORTANCE The Parvovirinae are small nonenveloped icosahedral viruses that are important pathogens in many animal species, including humans. Minute virus of canine (MVC) is an autonomous parvovirus in the genus Bocaparvovirus It has a single promoter that generates a single pre-mRNA. NP1, a small genus-specific MVC protein, participates in the processing of this pre-mRNA and so controls capsid gene access via its role in alternative internal polyadenylation and splicing. We show that NP1 also controls the expression of three of the five identified NS proteins via its role in governing MVC pre-mRNA splicing. These NS proteins together are required for virus replication in a host cell-dependent manner.
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17
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Seyffert M, Glauser DL, Schraner EM, de Oliveira AP, Mansilla-Soto J, Vogt B, Büning H, Linden RM, Ackermann M, Fraefel C. Novel Mutant AAV2 Rep Proteins Support AAV2 Replication without Blocking HSV-1 Helpervirus Replication. PLoS One 2017; 12:e0170908. [PMID: 28125695 PMCID: PMC5268427 DOI: 10.1371/journal.pone.0170908] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Accepted: 01/12/2017] [Indexed: 11/19/2022] Open
Abstract
As their names imply, parvoviruses of the genus Dependovirus rely for their efficient replication on the concurrent presence of a helpervirus, such as herpesvirus, adenovirus, or papilloma virus. Adeno-associated virus 2 (AAV2) is such an example, which in turn can efficiently inhibit the replication of each helpervirus by distinct mechanisms. In a previous study we have shown that expression of the AAV2 rep gene is not compatible with efficient replication of herpes simplex virus 1 (HSV-1). In particular, the combined DNA-binding and ATPase/helicase activities of the Rep68/78 proteins have been shown to exert opposite effects on the replication of AAV2 and HSV-1. While essential for AAV2 DNA replication these protein activities account for the Rep-mediated inhibition of HSV-1 replication. Here, we describe a novel Rep mutant (Rep-D371Y), which displayed an unexpected phenotype. Rep-D371Y did not block HSV-1 replication, but still supported efficient AAV2 replication, at least when a double-stranded AAV2 genome template was used. We also found that the capacity of Rep-D371Y to induce apoptosis and a Rep-specific DNA damage response was significantly reduced compared to wild-type Rep. These findings suggest that AAV2 Rep-helicase subdomains exert diverging activities, which contribute to distinct steps of the AAV2 life cycle. More important, the novel AAV2 mutant Rep-D371Y may allow deciphering yet unsolved activities of the AAV2 Rep proteins such as DNA second-strand synthesis, genomic integration or packaging, which all involve the Rep-helicase activity.
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Affiliation(s)
- Michael Seyffert
- Institute of Virology, University of Zurich, Zurich, Switzerland
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, United States of America
| | | | - Elisabeth M. Schraner
- Institute of Virology, University of Zurich, Zurich, Switzerland
- Institute of Veterinary Anatomy, University of Zurich, Zurich, Switzerland
| | | | - Jorge Mansilla-Soto
- Center for Cell Engineering, Memorial Sloan Kettering Cancer Center, New York, New York, United States of America
| | - Bernd Vogt
- Institute of Virology, University of Zurich, Zurich, Switzerland
| | - Hildegard Büning
- Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
- Institute for Experimental Hematology, Hannover Medical School, Hannover, Germany
| | - R. Michael Linden
- Department of Infectious Diseases, King’s College London, London, United Kingdom
| | | | - Cornel Fraefel
- Institute of Virology, University of Zurich, Zurich, Switzerland
- * E-mail:
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18
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Zarate-Perez F, Santosh V, Bardelli M, Agundez L, Linden RM, Henckaerts E, Escalante CR. Determination of Adeno-associated Virus Rep DNA Binding Using Fluorescence Anisotropy. Bio Protoc 2017; 7:e2194. [PMID: 28612042 DOI: 10.21769/bioprotoc.2194] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022] Open
Abstract
Quantitative measurement of proteins binding to DNA is a requisite to fully characterize the structural determinants of complex formation necessary to understand the DNA transactions that regulate cellular processes. Here we describe a detailed protocol to measure binding affinity of the adeno-associated virus (AAV) Rep68 protein for the integration site AAVS1 using fluorescent anisotropy. This protocol can be used to measure the binding constants of any DNA binding protein provided the substrate DNA is fluorescently labeled.
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Affiliation(s)
- Francisco Zarate-Perez
- Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond VA, USA
| | - Vishaka Santosh
- Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond VA, USA
| | - Martino Bardelli
- Department of Infectious Diseases, King's College London, London, United Kingdom
| | - Leticia Agundez
- Department of Infectious Diseases, King's College London, London, United Kingdom
| | - R Michael Linden
- Department of Infectious Diseases, King's College London, London, United Kingdom
| | - Els Henckaerts
- Department of Infectious Diseases, King's College London, London, United Kingdom
| | - Carlos R Escalante
- Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond VA, USA
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19
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Musayev FN, Zarate-Perez F, Bardelli M, Bishop C, Saniev EF, Linden RM, Henckaerts E, Escalante CR. Structural Studies of AAV2 Rep68 Reveal a Partially Structured Linker and Compact Domain Conformation. Biochemistry 2015; 54:5907-19. [PMID: 26314310 PMCID: PMC4636433 DOI: 10.1021/acs.biochem.5b00610] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Adeno-associated virus (AAV) nonstructural proteins Rep78 and Rep68 carry out all DNA transactions that regulate the AAV life cycle. They share two multifunctional domains: an N-terminal origin binding/nicking domain (OBD) from the HUH superfamily and a SF3 helicase domain. A short linker of ∼20 amino acids that is critical for oligomerization and function connects the two domains. Although X-ray structures of the AAV5 OBD and AAV2 helicase domains have been determined, information about the full-length protein and linker conformation is not known. This article presents the solution structure of AAV2 Rep68 using small-angle X-ray scattering (SAXS). We first determined the X-ray structures of the minimal AAV2 Rep68 OBD and of the OBD with the linker region. These X-ray structures reveal novel features that include a long C-terminal α-helix that protrudes from the core of the protein at a 45° angle and a partially structured linker. SAXS studies corroborate that the linker is not extended, and we show that a proline residue in the linker is critical for Rep68 oligomerization and function. SAXS-based rigid-body modeling of Rep68 confirms these observations, showing a compact arrangement of the two domains in which they acquire a conformation that positions key residues in all domains on one face of the protein, poised to interact with DNA.
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Affiliation(s)
- Faik N. Musayev
- Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, Richmond, Virginia 23298, United States
| | - Francisco Zarate-Perez
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, Virginia 23298, United States
| | - Martino Bardelli
- Department of Infectious Diseases, King’s College London, London SE1 9RT, United Kingdom
| | - Clayton Bishop
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, Virginia 23298, United States
| | - Emil F. Saniev
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, Virginia 23298, United States
| | - R. Michael Linden
- Department of Infectious Diseases, King’s College London, London SE1 9RT, United Kingdom
- UCL Gene Therapy Consortium, UCL Cancer Institute, University College London, London WC1E 6DD, United Kingdom
| | - Els Henckaerts
- Department of Infectious Diseases, King’s College London, London SE1 9RT, United Kingdom
| | - Carlos R. Escalante
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, Virginia 23298, United States
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20
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Adeno-Associated Virus Type 2 Rep68 Can Bind to Consensus Rep-Binding Sites on the Herpes Simplex Virus 1 Genome. J Virol 2015; 89:11150-8. [PMID: 26292324 DOI: 10.1128/jvi.01370-15] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Accepted: 08/11/2015] [Indexed: 01/10/2023] Open
Abstract
Adeno-associated virus type 2 is known to inhibit replication of herpes simplex virus 1 (HSV-1). This activity has been linked to the helicase- and DNA-binding domains of the Rep68/Rep78 proteins. Here, we show that Rep68 can bind to consensus Rep-binding sites on the HSV-1 genome and that the Rep helicase activity can inhibit replication of any DNA if binding is facilitated. Therefore, we hypothesize that inhibition of HSV-1 replication involves direct binding of Rep68/Rep78 to the HSV-1 genome.
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21
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George B, Ruhel R, Mazumder M, Sharma VK, Jain SK, Gourinath S, Chakraborty S. Mutational analysis of the helicase domain of a replication initiator protein reveals critical roles of Lys 272 of the B' motif and Lys 289 of the β-hairpin loop in geminivirus replication. J Gen Virol 2014; 95:1591-1602. [PMID: 24728710 DOI: 10.1099/vir.0.064923-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2023] Open
Abstract
Replication initiator protein (Rep) is indispensable for rolling-circle replication of geminiviruses, a group of plant-infecting circular ssDNA viruses. However, the mechanism of DNA unwinding by circular ssDNA virus-encoded helicases is unknown. To understand geminivirus Rep function, we compared the sequence and secondary structure of Rep with those of bovine papillomavirus E1 and employed charged residue-to-alanine scanning mutagenesis to generate a set of single-substitution mutants in Walker A (K227), in Walker B (D261, 262), and within or adjacent to the B' motif (K272, K286 and K289). All mutants were asymptomatic and viral accumulation could not be detected by Southern blotting in both tomato and N. benthamiana plants. Furthermore, the K272 and K289 mutants were deficient in DNA binding and unwinding. Biochemical studies and modelling data based on comparisons with the known structures of SF3 helicases suggest that the conserved lysine (K289) located in a predicted β-hairpin loop may interact with ssDNA, while lysine 272 in the B' motif (K272) located on the outer surface of the protein is presumably involved in coupling ATP-induced conformational changes to DNA binding. To the best of our knowledge, this is the first time that the roles of the B' motif and the adjacent β-hairpin loop in geminivirus replication have been elucidated.
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Affiliation(s)
- Biju George
- Department of Biotechnology, Jamia Hamdard University, New Delhi, India
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
| | - Rajrani Ruhel
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
| | - Mohit Mazumder
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
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22
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Cotmore SF, Tattersall P. Parvovirus diversity and DNA damage responses. Cold Spring Harb Perspect Biol 2013; 5:cshperspect.a012989. [PMID: 23293137 DOI: 10.1101/cshperspect.a012989] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Parvoviruses have a linear single-stranded DNA genome, around 5 kb in length, with short imperfect terminal palindromes that fold back on themselves to form duplex hairpin telomeres. These contain most of the cis-acting information required for viral "rolling hairpin" DNA replication, an evolutionary adaptation of rolling-circle synthesis in which the hairpins create duplex replication origins, prime complementary strand synthesis, and act as hinges to reverse the direction of the unidirectional cellular fork. Genomes are packaged vectorially into small, rugged protein capsids ~260 Å in diameter, which mediate their delivery directly into the cell nucleus, where they await their host cell's entry into S phase under its own cell cycle control. Here we focus on genus-specific variations in genome structure and replication, and review host cell responses that modulate the nuclear environment.
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Affiliation(s)
- Susan F Cotmore
- Department of Laboratory Medicine, Yale University School of Medicine, New Haven, CT 06510, USA
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23
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Oligomeric properties of adeno-associated virus Rep68 reflect its multifunctionality. J Virol 2012; 87:1232-41. [PMID: 23152528 DOI: 10.1128/jvi.02441-12] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The adeno-associated virus (AAV) encodes four regulatory proteins called Rep. The large AAV Rep proteins Rep68 and Rep78 are essential factors required in almost every step of the viral life cycle. Structurally, they share two domains: a modified version of the AAA(+) domain that characterizes the SF3 family of helicases and an N-terminal domain that binds DNA specifically. The combination of these two domains imparts extraordinary multifunctionality to work as initiators of DNA replication and regulators of transcription, in addition to their essential role during site-specific integration. Although most members of the SF3 family form hexameric rings in vitro, the oligomeric nature of Rep68 is unclear due to its propensity to aggregate in solution. We report here a comprehensive study to determine the oligomeric character of Rep68 using a combination of methods that includes sedimentation velocity ultracentrifugation, electron microscopy, and hydrodynamic modeling. We have determined that residue Cys151 induces Rep68 to aggregate in vitro. We show that Rep68 displays a concentration-dependent dynamic oligomeric behavior characterized by the presence of two populations: one with monomers and dimers in slow equilibrium and a second one consisting of a mixture of multiple-ring structures of seven and eight members. The presence of either ATP or ADP induces formation of larger complexes formed by the stacking of multiple rings. Taken together, our results support the idea of a Rep68 molecule that exhibits the flexible oligomeric behavior needed to perform the wide range of functions occurring during the AAV life cycle.
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24
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The adeno-associated virus type 5 small rep proteins expressed via internal translation initiation are functional. J Virol 2012; 87:296-303. [PMID: 23077303 DOI: 10.1128/jvi.02547-12] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Although precluded from using splicing to produce multiple small Rep proteins, adeno-associated virus type 5 (AAV5) generates a Rep40-like protein by alternative translation initiation at an internal AUG. A defined region upstream of the internal AUG was both required and sufficient to program internal initiation within AAV5 and may act similarly in heterologous contexts. The internally initiated AAV5 Rep40-like protein was functional and had helicase activity similar to that of AAV2 Rep40. Surprisingly, both the AAV5 Rep40-like protein and Rep52 were able to be translated from the AAV5 upstream P7-generated RNAs; however, the relative level of small to large Rep proteins was reduced compared to that of the wild type. A P19 mutant AAV5 infectious clone generated near-wild-type levels of the double-stranded monomer replicative form (mRF) replicative intermediate but reduced levels of virus, consistent with the previously defined role of Rep40-like proteins in genome encapsidation. Levels of mutant virus were dramatically reduced upon amplification.
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25
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Abstract
The Adeno-associated viruses (AAVs) are not associated with any diseases, and their ability to package non-genomic DNA and to transduce different cell/tissue populations has generated significant interest in understanding their basic biology in efforts to improve their utilization for corrective gene delivery. This includes their capsid structure, cellular tropism and interactions for entry, uncoating, replication, DNA packaging, capsid assembly, and antibody neutralization. The human and nonhuman primate AAVs are clustered into serologically distinct genetic clade and serotype groups, which have distinct cellular/tissue tropisms and transduction efficiencies. These properties are highly dependent upon the AAV capsid amino acid sequence, their capsid structure, and their interactions with host cell factors, including cell surface receptors, co-receptors, signaling molecules, proteins involved in host DNA replication, and host-derived antibodies. This chapter reviews the current structural information on AAV capsids and the capsid viral protein regions playing a role in the cellular interactions conferring an infective phenotype, which are then used to annotate the functional regions of the capsid. Based on the current data, the indication is that the AAVs, like other members of the Parvoviridae and other ssDNA viruses that form a T = 1 capsid, have evolved a multifunctional capsid with conserved core regions as is required for efficient capsid trafficking, capsid assembly, and genome packaging. Disparate surface loop structures confer differential receptor recognition and are involved in antibody recognition. The role of structural regions in capsid uncoating remains to be elucidated.
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Affiliation(s)
- Mavis Agbandje-McKenna
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL, USA.
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26
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DNA-binding activity of adeno-associated virus Rep is required for inverted terminal repeat-dependent complex formation with herpes simplex virus ICP8. J Virol 2011; 86:2859-63. [PMID: 22205745 DOI: 10.1128/jvi.06364-11] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Herpes simplex virus (HSV) helper functions for (AAV) replication comprise HSV ICP8 and helicase-primase UL5/UL52/UL8. Here we show that N-terminal amino acids of AAV Rep78 that contact the Rep-binding site within the AAV inverted terminal repeat (ITR) are required for ternary-complex formation with infected-cell protein 8 (ICP8) on AAV single-strand DNA (ssDNA) in vitro and for colocalization in nuclear replication domains in vivo. Our data suggest that HSV-dependent AAV replication is initiated by Rep contacting the AAV ITR and by cooperative binding of ICP8 on AAV ssDNA.
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The amino acid linker between the endonuclease and helicase domains of adeno-associated virus type 5 Rep plays a critical role in DNA-dependent oligomerization. J Virol 2011; 86:3337-46. [PMID: 22205752 DOI: 10.1128/jvi.06775-11] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The adeno-associated virus (AAV) genome encodes four Rep proteins, all of which contain an SF3 helicase domain. The larger Rep proteins, Rep78 and Rep68, are required for viral replication, whereas Rep40 and Rep52 are needed to package AAV genomes into preformed capsids; these smaller proteins are missing the site-specific DNA-binding and endonuclease domain found in Rep68/78. Other viral SF3 helicases, such as the simian virus 40 large T antigen and the papillomavirus E1 protein, are active as hexameric assemblies. However, Rep40 and Rep52 have not been observed to form stable oligomers on their own or with DNA, suggesting that important determinants of helicase multimerization lie outside the helicase domain. Here, we report that when the 23-residue linker that connects the endonuclease and helicase domains is appended to the adeno-associated virus type 5 (AAV5) helicase domain, the resulting protein forms discrete complexes on DNA consistent with single or double hexamers. The formation of these complexes does not require the Rep binding site sequence, nor is it nucleotide dependent. These complexes have stimulated ATPase and helicase activities relative to the helicase domain alone, indicating that they are catalytically relevant, a result supported by negative-stain electron microscopy images of hexameric rings. Similarly, the addition of the linker region to the AAV5 Rep endonuclease domain also confers on it the ability to bind and multimerize on nonspecific double-stranded DNA. We conclude that the linker is likely a key contributor to Rep68/78 DNA-dependent oligomerization and may play an important role in mediating Rep68/78's conversion from site-specific DNA binding to nonspecific DNA unwinding.
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Structure of a packaging-defective mutant of minute virus of mice indicates that the genome is packaged via a pore at a 5-fold axis. J Virol 2011; 85:4822-7. [PMID: 21367911 DOI: 10.1128/jvi.02598-10] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The parvovirus minute virus of mice (MVM) packages a single copy of its linear single-stranded DNA genome into preformed capsids, in a process that is probably driven by a virus-encoded helicase. Parvoviruses have a roughly cylindrically shaped pore that surrounds each of the 12 5-fold vertices. The pore, which penetrates the virion shell, is created by the juxtaposition of 10 antiparallel β-strands, two from each of the 5-fold-related capsid proteins. There is a bottleneck in the channel formed by the symmetry-related side chains of the leucines at position 172. We report here the X-ray crystal structure of the particles produced by a leucine-to-tryptophan mutation at position 172 and the analysis of its biochemical properties. The mutant capsid had its 5-fold channel blocked, and the particles were unable to package DNA, strongly suggesting that the 5-fold pore is the packaging portal for genome entry.
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Abstract
Adeno-associated viruses (AAV) are widely spread throughout the human population, yet no pathology has been associated with infection. This fact, together with the availability of simple molecular techniques to alter the packaged viral genome, has made AAV a serious contender in the search for an ideal gene therapy delivery vehicle. However, our understanding of the intriguing features of this virus is far from exhausted and it is likely that the mechanisms underlying the viral lifestyle will reveal possible novel strategies that can be employed in future clinical approaches. One such aspect is the unique approach AAV has evolved in order to establish latency. In the absence of a cellular milieu that will support productive viral replication, wild-type AAV can integrate its genome site specifically into a locus on human chromosome 19 (termed AAVS1), where it resides without apparent effects on the host cell until cellular conditions are changed by outside influences, such as adenovirus super-infection, which will lead to the rescue of the viral genome and productive replication. This article will introduce the biology of AAV, the unique viral strategy of targeted genome integration and address relevant questions within the context of attempts to establish therapeutic approaches that will utilize targeted gene addition to the human genome.
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Affiliation(s)
- Els Henckaerts
- Department of Infectious Diseases, King's College London School of Medicine, Guy's Hospital, London, SE1 9RT, UK
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Parrish CR. Structures and functions of parvovirus capsids and the process of cell infection. Curr Top Microbiol Immunol 2010; 343:149-76. [PMID: 20397069 DOI: 10.1007/82_2010_33] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
To infect a cell, the parvovirus or adeno-associated virus (AAV) genome must be delivered from outside the plasma membrane to the nucleus, and in the process, the capsid must follow a series of binding and trafficking steps and also undergo necessary changes that result in exposure or release the ssDNA genome at the appropriate time and place within the cell. The 25 nm parvovirus capsid is comprised of two or three forms of a single protein, and although it is robust and stable, it is still sufficiently flexible to allow the exposure of several internal components at appropriate times during cell infection. The capsid can also accommodate insertion of peptides into surface loops, and capsid proteins from different viral serotypes can be shuffled to create novel functional variants. The capsids of the different viruses bind to one or more cell receptors, and for at least some viruses, the insertion of additional or alternative receptor binding sequences or structures into the capsid can expand or redirect its tropism. The infection process after cell binding involves receptor-mediated endocytosis followed by viral trafficking through the endosomal systems. That endosomal trafficking may be complex and prolonged for hours or be relatively brief. Generally only a small proportion of the particles taken up enter the cytoplasm after altering the endosomal membrane through the activity of a VP1-encoded phospholipase A2 domain that becomes released to the outside of the viral particle. Modifications to the capsid that can occur within the endosome or cytoplasm include structural changes to expose internal components, ubiquination and proteosomal processing, and possible trafficking of particles on molecular motors. It is still not clear how the genomes enter the nucleus, but nuclear pore-dependent entry of particles or permeabilization of nuclear membranes have been proposed. Those processes control the infection, pathogenesis, and host ranges of the autonomous viruses and determine the effectiveness of gene therapy using AAV capsids.
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Affiliation(s)
- Colin R Parrish
- Baker Institute for Animal Health, Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY, 14853, USA.
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DNA structure modulates the oligomerization properties of the AAV initiator protein Rep68. PLoS Pathog 2009; 5:e1000513. [PMID: 19593381 PMCID: PMC2702170 DOI: 10.1371/journal.ppat.1000513] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2009] [Accepted: 06/16/2009] [Indexed: 11/27/2022] Open
Abstract
Rep68 is a multifunctional protein of the adeno-associated virus (AAV), a parvovirus that is mostly known for its promise as a gene therapy vector. In addition to its role as initiator in viral DNA replication, Rep68 is essential for site-specific integration of the AAV genome into human chromosome 19. Rep68 is a member of the superfamily 3 (SF3) helicases, along with the well-studied initiator proteins simian virus 40 large T antigen (SV40-LTag) and bovine papillomavirus (BPV) E1. Structurally, SF3 helicases share two domains, a DNA origin interaction domain (OID) and an AAA+ motor domain. The AAA+ motor domain is also a structural feature of cellular initiators and it functions as a platform for initiator oligomerization. Here, we studied Rep68 oligomerization in vitro in the presence of different DNA substrates using a variety of biophysical techniques and cryo-EM. We found that a dsDNA region of the AAV origin promotes the formation of a complex containing five Rep68 subunits. Interestingly, non-specific ssDNA promotes the formation of a double-ring Rep68, a known structure formed by the LTag and E1 initiator proteins. The Rep68 ring symmetry is 8-fold, thus differing from the hexameric rings formed by the other SF3 helicases. However, similiar to LTag and E1, Rep68 rings are oriented head-to-head, suggesting that DNA unwinding by the complex proceeds bidirectionally. This novel Rep68 quaternary structure requires both the DNA binding and AAA+ domains, indicating cooperativity between these regions during oligomerization in vitro. Our study clearly demonstrates that Rep68 can oligomerize through two distinct oligomerization pathways, which depend on both the DNA structure and cooperativity of Rep68 domains. These findings provide insight into the dynamics and oligomeric adaptability of Rep68 and serve as a step towards understanding the role of this multifunctional protein during AAV DNA replication and site-specific integration. Adeno-associated virus (AAV) is a parvovirus with a linear single-stranded DNA genome. Thus far, it is the only eukaryotic virus known to integrate its genome in human cells in a specific region of chromosome 19. Because no pathologies have been associated with AAV, there is great interest in using AAV as a vector for gene therapy. The genetic information of AAV encodes for both the structural Capsid proteins and the Rep proteins. We have studied a protein called Rep68, which is essential for both AAV genome replication and site-specific integration in chromosome 19, and found that it forms distinct structures in the presence of different DNA structures. Of particular interest is the formation of a Rep68 structure composed of two opposite rings, which resemble the structures formed by the large T antigen and E1 viral proteins of the tumor-inducing Simian virus 40 (SV40) and papilloma viruses, respectively. The double-ring structure of these viral proteins is essential for viral DNA replication, which suggests that AAV has evolved a similar mechanism of DNA replication that relies on a double-ring Rep68. Moreover, Rep68 encounters different DNA structures during viral genome replication, and our results show how Rep68 can adapt to these changes.
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Rajagopal V, Patel SS. Viral Helicases. VIRAL GENOME REPLICATION 2009. [PMCID: PMC7121818 DOI: 10.1007/b135974_20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Helicases are motor proteins that use the free energy of NTP hydrolysis to catalyze the unwinding of duplex nucleic acids. Helicases participate in almost all processes involving nucleic acids. Their action is critical for replication, recombination, repair, transcription, translation, splicing, mRNA editing, chromatin remodeling, transport, and degradation (Matson and Kaiser-Rogers 1990; Matson et al. 1994; Mendonca et al. 1995; Luking et al. 1998).
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Dignam SS, Collaco RF, Bieszczad J, Needham P, Trempe JP, Dignam JD. Coupled ATP and DNA binding of adeno-associated virus Rep40 helicase. Biochemistry 2007; 46:568-76. [PMID: 17209567 DOI: 10.1021/bi061762v] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Adeno-associated virus 2 Rep40 helicase is involved in packaging single-stranded genomic DNA into virions. ATPase activity was stimulated 5-10-fold by DNA, depending upon assay conditions. The concentration dependence of Rep40 ATPase activity in the absence and presence of DNA indicates that the monomer is inactive and that the active enzyme is at least a dimer. Binding to oligonucleotides, examined by fluorescence anisotropy, was positively cooperative and required ATP or ATPgammaS; ADP and AMPPCP did not promote binding. The cooperativity and the nucleotide requirement were also demonstrated by surface plasmon resonance. Although the Rep40 behaves as a monomer in solution, it binds to DNA as an oligomer. The requirement of a nucleotide for DNA binding and the stimulation of ATPase activity by DNA indicate that the two processes are linked. Glutaraldehyde cross-linking generated a species that migrates as a trimer on sodium dodecyl sulfate (SDS) gel electrophoresis; ATPS promoted the formation of this species and higher order oligomers. The predominant cross-linked species was a trimer in the absence of ATPgammaS, regardless of whether duplex or single-stranded DNA was present. In the presence of duplex or single-stranded DNA and ATPgammaS, glutaraldehyde cross-linking generated a species that behaved as a dimer on SDS gel elctrophoresis. Sucrose-gradient velocity sedimentation of Rep40 gave an S20,w of 3 in the absence of ligands or in the presence of a 26 bp duplex DNA. The S20,w was 3.5 in the presence of ATPgammaS and 7 and 7.6 in the presence of DNA and ATPgammaS.
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Affiliation(s)
- Susan S Dignam
- Department of Biochemistry and Cancer Biology, University of Toledo College of Medicine, 3035 Arlington Avenue, Toledo, Ohio 43614-5804, USA
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Kumar A, Meinke G, Reese DK, Moine S, Phelan PJ, Fradet-Turcotte A, Archambault J, Bohm A, Bullock PA. Model for T-antigen-dependent melting of the simian virus 40 core origin based on studies of the interaction of the beta-hairpin with DNA. J Virol 2007; 81:4808-18. [PMID: 17287270 PMCID: PMC1900137 DOI: 10.1128/jvi.02451-06] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The interaction of simian virus 40 (SV40) T antigen (T-ag) with the viral origin has served as a model for studies of site-specific recognition of a eukaryotic replication origin and the mechanism of DNA unwinding. These studies have revealed that a motif termed the "beta-hairpin" is necessary for assembly of T-ag on the SV40 origin. Herein it is demonstrated that residues at the tip of the "beta-hairpin" are needed to melt the origin-flanking regions and that the T-ag helicase domain selectively assembles around one of the newly generated single strands in a manner that accounts for its 3'-to-5' helicase activity. Furthermore, T-ags mutated at the tip of the "beta-hairpin" are defective for oligomerization on duplex DNA; however, they can assemble on hybrid duplex DNA or single-stranded DNA (ssDNA) substrates provided the strand containing the 3' extension is present. Collectively, these experiments indicate that residues at the tip of the beta-hairpin generate ssDNA in the core origin and that the ssDNA is essential for subsequent oligomerization events.
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Affiliation(s)
- Anuradha Kumar
- Department of Biochemistry A703, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA
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Clérot D, Bernardi F. DNA helicase activity is associated with the replication initiator protein rep of tomato yellow leaf curl geminivirus. J Virol 2006; 80:11322-30. [PMID: 16943286 PMCID: PMC1642161 DOI: 10.1128/jvi.00924-06] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Rep protein of tomato yellow leaf curl Sardinia virus (TYLCSV), a single-stranded DNA virus of plants, is the replication initiator essential for virus replication. TYLCSV Rep has been classified among ATPases associated with various cellular activities (AAA+ ATPases), in superfamily 3 of small DNA and RNA virus replication initiators whose paradigmatic member is simian virus 40 large T antigen. Members of this family are DNA- or RNA-dependent ATPases with helicase activity necessary for viral replication. Another distinctive feature of AAA+ ATPases is their quaternary structure, often composed of hexameric rings. TYLCSV Rep has ATPase activity, but the helicase activity, which is instrumental in further characterization of the mechanism of rolling-circle replication used by geminiviruses, has been a longstanding question. We present results showing that TYLCSV Rep lacking the 121 N-terminal amino acids has helicase activity comparable to that of the other helicases: requirements for a 3' overhang and 3'-to-5' polarity of unwinding, with some distinct features and with a minimal AAA+ ATPase domain. We also show that the helicase activity is dependent on the oligomeric state of the protein.
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Affiliation(s)
- Danielle Clérot
- Institut des Sciences du Végétal, CNRS, Avenue de la Terrasse, 91198 Gif-sur-Yvette Cedex, France
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36
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Hunnicutt LE, Hunter WB, Cave RD, Powell CA, Mozoruk JJ. Genome sequence and molecular characterization of Homalodisca coagulata virus-1, a novel virus discovered in the glassy-winged sharpshooter (Hemiptera: Cicadellidae). Virology 2006; 350:67-78. [PMID: 16574186 DOI: 10.1016/j.virol.2006.02.034] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2005] [Revised: 12/14/2005] [Accepted: 02/15/2006] [Indexed: 01/24/2023]
Abstract
The complete nucleotide sequence of a novel single-stranded RNA virus infecting the glassy-winged sharpshooter, Homalodisca coagulata, has been determined. In silico analysis of H. coagulata virus-1 (HoCV-1) revealed a 9321-nt polyadenylated genome encoding two large open reading frames (ORF1 and ORF2) separated by a 182-nt intergenic region (IGR). The deduced amino acid sequence of the 5'-proximal ORF (ORF1, nt 420-5807) exhibited conserved core motifs characteristic of the helicases, cysteine proteases, and RNA-dependent RNA polymerases of other insect-infecting picorna-like viruses. A structural model created using Mfold exposed a series of stem loop (SL) structures immediately preceding the second ORF which are analogous to an internal ribosome entry site (IRES), suggesting that ORF2 begins with a noncognate GCA triplet rather than the canonical AUG. This 3' ORF2 (5990-8740) showed significant similarity to the structural proteins of members of the family Dicistroviridae, particularly those belonging to the genus Cripavirus. Evidence demonstrating relatedness of these viruses regarding genome organization, amino acid sequence similarity, and putative replication strategy substantiate inclusion of HoCV-1 into this taxonomic position.
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Affiliation(s)
- Laura E Hunnicutt
- USDA ARS U.S. Horticultural Research Laboratory, 2001 S. Rock Rd., Ft. Pierce, FL 34945, USA
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Bleker S, Pawlita M, Kleinschmidt JA. Impact of capsid conformation and Rep-capsid interactions on adeno-associated virus type 2 genome packaging. J Virol 2006; 80:810-20. [PMID: 16378983 PMCID: PMC1346863 DOI: 10.1128/jvi.80.2.810-820.2006] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Single-stranded genomes of adeno-associated virus (AAV) are packaged into preformed capsids. It has been proposed that packaging is initiated by interaction of genome-bound Rep proteins to the capsid, thereby targeting the genome to the portal of encapsidation. Here we describe a panel of mutants with amino acid exchanges in the pores at the fivefold axes of symmetry on AAV2 capsids with reduced packaging and reduced Rep-capsid interaction. Mutation of two threonines at the rim of the fivefold pore nearly completely abolished Rep-capsid interaction and packaging. This suggests a Rep-binding site at the highly conserved amino acids at or close to the pores formed by the capsid protein pentamers. A different mutant (P. Wu, W. Xiao, T. Conlon, J. Hughes, M. Agbandje-McKenna, T. Ferkol, T. Flotte, and N. Muzyczka, J. Virol. 74:8635-8647, 2000) with an amino acid exchange at the interface of capsid protein pentamers led to a complete block of DNA encapsidation. Analysis of the capsid conformation of this mutant revealed that the pores at the fivefold axes were occupied by VP1/VP2 N termini, thereby preventing DNA introduction into the capsid. Nevertheless, the corresponding capsids had more Rep proteins bound than wild-type AAV, showing that correct Rep interaction with the capsid depends on a defined capsid conformation. Both mutant types together support the conclusion that the pores at the fivefold symmetry axes are involved in genome packaging and that capsid conformation-dependent Rep-capsid interactions play an essential role in the packaging process.
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Affiliation(s)
- Svenja Bleker
- German Cancer Research Centre, Infection and Cancer Research Program, Division of Tumor Virology, Im Neuenheimer Feld 242, 69120 Heidelberg, Germany
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Cotmore SF, Tattersall P. Encapsidation of minute virus of mice DNA: aspects of the translocation mechanism revealed by the structure of partially packaged genomes. Virology 2005; 336:100-12. [PMID: 15866075 DOI: 10.1016/j.virol.2005.03.007] [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] [Received: 01/02/2005] [Revised: 02/22/2005] [Accepted: 03/08/2005] [Indexed: 11/29/2022]
Abstract
Minute virus of mice (MVM) packages a single, negative-sense copy of its linear single-stranded DNA genome, but a chimeric virus, MML, in which >95% MVM sequence was fused to the right-hand terminus of LuIII, packages >40% positive-sense DNA. While encapsidation of both MML strands begins efficiently, genome translocation frequently stalls at specific sites in positive-sense DNA. Internalized sequences, derived from the 3' end of the strand, ranged from 1 to 5 kb in length, with species of around 2 kb predominating. When nuclease activity during isolation was minimized, these truncated species were found to be part of pre-excised 5 kb single-strands. Similarly, some partially encapsidated negative-sense DNAs were observed, forming a continuum of protected 3' sequences between 1 and 3 kb in length, but these were less abundant and more uniformly distributed than their positive-sense counterparts, indicating that the negative strand has evolved for efficient internalization. The paucity of protected DNAs shorter than 1-2 kb suggests that translocation is biphasic, proceeding efficiently through the first (3') third of the genome, but prone to stall thereafter. Sequences with conspicuous secondary structure, including stem-loop and guanidine rich regions, were found to interrupt packaging, especially when positioned near the 5' end of the strand. Since VP2 amino-terminal peptides were exposed at the particle surface in all packaging intermediates, extrusion of this peptide precedes translocation of the full-length strand.
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Affiliation(s)
- Susan F Cotmore
- Department of Laboratory Medicine, Yale University Medical School, 333 Cedar Street, New Haven, CT 067510, USA
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