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Matsuzaka Y, Yashiro R. Therapeutic Application and Structural Features of Adeno-Associated Virus Vector. Curr Issues Mol Biol 2024; 46:8464-8498. [PMID: 39194716 DOI: 10.3390/cimb46080499] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2024] [Revised: 07/02/2024] [Accepted: 07/12/2024] [Indexed: 08/29/2024] Open
Abstract
Adeno-associated virus (AAV) is characterized by non-pathogenicity, long-term infection, and broad tropism and is actively developed as a vector virus for gene therapy products. AAV is classified into more than 100 serotypes based on differences in the amino acid sequence of the capsid protein. Endocytosis involves the uptake of viral particles by AAV and accessory receptors during AAV infection. After entry into the cell, they are transported to the nucleus through the nuclear pore complex. AAVs mainly use proteoglycans as receptors to enter cells, but the types of sugar chains in proteoglycans that have binding ability are different. Therefore, it is necessary to properly evaluate the primary structure of receptor proteins, such as amino acid sequences and post-translational modifications, including glycosylation, and the higher-order structure of proteins, such as the folding of the entire capsid structure and the three-dimensional (3D) structure of functional domains, to ensure the efficacy and safety of biopharmaceuticals. To further enhance safety, it is necessary to further improve the efficiency of gene transfer into target cells, reduce the amount of vector administered, and prevent infection of non-target cells.
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Affiliation(s)
- Yasunari Matsuzaka
- Division of Molecular and Medical Genetics, Center for Gene and Cell Therapy, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo 108-8639, Japan
- Administrative Section of Radiation Protection, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira 187-8551, Japan
| | - Ryu Yashiro
- Administrative Section of Radiation Protection, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira 187-8551, Japan
- Department of Mycobacteriology, Leprosy Research Center, National Institute of Infectious Diseases, Tokyo 162-8640, Japan
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2
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Golm SK, Hübner W, Müller KM. Fluorescence Microscopy in Adeno-Associated Virus Research. Viruses 2023; 15:v15051174. [PMID: 37243260 DOI: 10.3390/v15051174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Revised: 05/02/2023] [Accepted: 05/07/2023] [Indexed: 05/28/2023] Open
Abstract
Research on adeno-associated virus (AAV) and its recombinant vectors as well as on fluorescence microscopy imaging is rapidly progressing driven by clinical applications and new technologies, respectively. The topics converge, since high and super-resolution microscopes facilitate the study of spatial and temporal aspects of cellular virus biology. Labeling methods also evolve and diversify. We review these interdisciplinary developments and provide information on the technologies used and the biological knowledge gained. The emphasis lies on the visualization of AAV proteins by chemical fluorophores, protein fusions and antibodies as well as on methods for the detection of adeno-associated viral DNA. We add a short overview of fluorescent microscope techniques and their advantages and challenges in detecting AAV.
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Affiliation(s)
- Susanne K Golm
- Cellular and Molecular Biotechnology, Faculty of Technology, Bielefeld University, 33615 Bielefeld, Germany
| | - Wolfgang Hübner
- Biomolecular Photonics, Faculty of Physics, Bielefeld University, 33615 Bielefeld, Germany
| | - Kristian M Müller
- Cellular and Molecular Biotechnology, Faculty of Technology, Bielefeld University, 33615 Bielefeld, Germany
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3
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Comment on Piña et al. Ten Approaches That Improve Immunostaining: A Review of the Latest Advances for the Optimization of Immunofluorescence. Int. J. Mol. Sci. 2022, 23, 1426. Int J Mol Sci 2022; 23:ijms23084372. [PMID: 35457190 PMCID: PMC9024666 DOI: 10.3390/ijms23084372] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2022] [Accepted: 04/12/2022] [Indexed: 11/17/2022] Open
Abstract
With great interest, I have read the article "Ten Approaches That Improve Immunostaining: A Review of the Latest Advances for the Optimization of Immunofluorescence" written by Piña et al. [...].
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Galibert L, Hyvönen A, Eriksson RAE, Mattola S, Aho V, Salminen S, Albers JD, Peltola SK, Weman S, Nieminen T, Ylä-Herttuala S, Lesch HP, Vihinen-Ranta M, Airenne KJ. Functional roles of the membrane-associated AAV protein MAAP. Sci Rep 2021; 11:21698. [PMID: 34737404 PMCID: PMC8568889 DOI: 10.1038/s41598-021-01220-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Accepted: 10/25/2021] [Indexed: 12/23/2022] Open
Abstract
With a limited coding capacity of 4.7 kb, adeno-associated virus (AAV) genome has evolved over-lapping genes to maximise the usage of its genome. An example is the recently found ORF in the cap gene, encoding membrane-associated accessory protein (MAAP), located in the same genomic region as the VP1/2 unique domain, but in a different reading frame. This 13 KDa protein, unique to the dependovirus genus, is not homologous to any known protein. Our studies confirm that MAAP translation initiates from the first CTG codon found in the VP1 ORF2. We have further observed MAAP localised in the plasma membrane, in the membranous structures in close proximity to the nucleus and to the nuclear envelope by co-transfecting with plasmids encoding the wild-type AAV (wt-AAV) genome and adenovirus (Ad) helper genes. While keeping VP1/2 protein sequence identical, both inactivation and truncation of MAAP translation affected the emergence and intracellular distribution of the AAV capsid proteins. We have demonstrated that MAAP facilitates AAV replication and has a role in controlling Ad infection. Additionally, we were able to improve virus production and capsid integrity through a C-terminal truncation of MAAP while other modifications led to increased packaging of contaminating, non-viral DNA. Our results show that MAAP plays a significant role in AAV infection, with profound implications for the production of therapeutic AAV vectors.
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Affiliation(s)
| | - Amira Hyvönen
- Kuopio Center for Gene and Cell Therapy, Kuopio, Finland ,grid.511728.8FinVector, Kuopio, Finland
| | - Reetta A. E. Eriksson
- Kuopio Center for Gene and Cell Therapy, Kuopio, Finland ,grid.9668.10000 0001 0726 2490A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - Salla Mattola
- grid.9681.60000 0001 1013 7965Department of Biological and Environmental Science and Nanoscience Center, University of Jyvaskyla, Jyväskylä, Finland
| | - Vesa Aho
- grid.9681.60000 0001 1013 7965Department of Biological and Environmental Science and Nanoscience Center, University of Jyvaskyla, Jyväskylä, Finland
| | - Sami Salminen
- grid.9681.60000 0001 1013 7965Department of Biological and Environmental Science and Nanoscience Center, University of Jyvaskyla, Jyväskylä, Finland
| | | | | | - Saija Weman
- Kuopio Center for Gene and Cell Therapy, Kuopio, Finland
| | - Tiina Nieminen
- Kuopio Center for Gene and Cell Therapy, Kuopio, Finland
| | - Seppo Ylä-Herttuala
- Kuopio Center for Gene and Cell Therapy, Kuopio, Finland ,grid.9668.10000 0001 0726 2490A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland ,grid.410705.70000 0004 0628 207XGene Therapy Unit and Research Center, Kuopio University Hospital, Kuopio, Finland
| | - Hanna P. Lesch
- Kuopio Center for Gene and Cell Therapy, Kuopio, Finland
| | - Maija Vihinen-Ranta
- grid.9681.60000 0001 1013 7965Department of Biological and Environmental Science and Nanoscience Center, University of Jyvaskyla, Jyväskylä, Finland
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The membrane associated accessory protein is an adeno-associated viral egress factor. Nat Commun 2021; 12:6239. [PMID: 34716331 PMCID: PMC8556243 DOI: 10.1038/s41467-021-26485-4] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Accepted: 09/28/2021] [Indexed: 12/19/2022] Open
Abstract
Adeno-associated viruses (AAV) rely on helper viruses to transition from latency to lytic infection. Some AAV serotypes are secreted in a pre-lytic manner as free or extracellular vesicle (EV)-associated particles, although mechanisms underlying such are unknown. Here, we discover that the membrane-associated accessory protein (MAAP), expressed from a frameshifted open reading frame in the AAV cap gene, is a novel viral egress factor. MAAP contains a highly conserved, cationic amphipathic domain critical for AAV secretion. Wild type or recombinant AAV with a mutated MAAP start site (MAAPΔ) show markedly attenuated secretion and correspondingly, increased intracellular retention. Trans-complementation with MAAP restored secretion of multiple AAV/MAAPΔ serotypes. Further, multiple processing and analytical methods corroborate that one plausible mechanism by which MAAP promotes viral egress is through AAV/EV association. In addition to characterizing a novel viral egress factor, we highlight a prospective engineering platform to modulate secretion of AAV vectors or other EV-associated cargo. Adeno-associated viruses can be secreted in a pre-lytic manner as free or extracellular vesicle (EV)-associated particles. Here, Elmore et al. show that the recently identified membrane-associated accessory protein (MAAP) functions as an AAV egress factor via association to EVs.
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6
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Zhao X, Tikoo SK. Nuclear and Nucleolar Localization of Bovine Adenovirus-3 Protein V. Front Microbiol 2021; 11:579593. [PMID: 33488533 PMCID: PMC7815533 DOI: 10.3389/fmicb.2020.579593] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Accepted: 12/03/2020] [Indexed: 02/01/2023] Open
Abstract
The L2 region of bovine adenovirus-3 (BAdV-3) encodes a Mastadenovirus genus-specific protein, designated as pV, which is important for the production of progeny viruses. Here, we demonstrate that BAdV-3 pV, expressed as 55 kDa protein, localizes to the nucleus and specifically targets nucleolus of the infected cells. Analysis of deletion mutants of pV suggested that amino acids 81–120, 190–210, and 380–389 act as multiple nuclear localization signals (NLS), which also appear to serve as the binding sites for importin α-3 protein, a member of the importin α/β nuclear import receptor pathway. Moreover, pV amino acids 21–50 and 380–389 appear to act as nucleolar localization signals (NoLs). Interestingly, amino acids 380–389 appear to act both as NLS and as NoLS. The presence of NoLS is essential for the production of infectious progeny virions, as deletion of both NoLs are lethal for the production of infectious BAdV-3. Analysis of mutant BAV.pVd1d3 (isolated in pV completing CRL cells) containing deletion/mutation of both NoLS in non-complementing CRL cells not only revealed the altered intracellular localization of mutant pV but also reduced the expression of some late proteins. However, it does not appear to affect the incorporation of viral proteins, including mutant pV, in BAV.pVd1d3 virions. Further analysis of CsCl purified BAV.pVd1d3 suggested the presence of thermo-labile virions with disrupted capsids, which appear to affect the infectivity of the progeny virions. Our results suggest that pV contains overlapping and non-overlapping NoLS/NLS. Moreover, the presence of both NoLS appear essential for the production of stable and infectious progeny BAV.pVd1d3 virions.
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Affiliation(s)
- Xin Zhao
- VIDO-InterVac, University of Saskatchewan, Saskatoon, SK, Canada.,Department of Veterinary Microbiology, University of Saskatchewan, Saskatoon, SK, Canada
| | - Suresh K Tikoo
- VIDO-InterVac, University of Saskatchewan, Saskatoon, SK, Canada.,Department of Veterinary Microbiology, University of Saskatchewan, Saskatoon, SK, Canada.,Vaccinology and Imuunothepapeutics Program, School of Public Health, University of Saskatchewan, Saskatoon, SK, Canada
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7
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Iwakawa H, Takahashi H, Machida Y, Machida C. Roles of ASYMMETRIC LEAVES2 (AS2) and Nucleolar Proteins in the Adaxial-Abaxial Polarity Specification at the Perinucleolar Region in Arabidopsis. Int J Mol Sci 2020; 21:E7314. [PMID: 33022996 PMCID: PMC7582388 DOI: 10.3390/ijms21197314] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Revised: 09/27/2020] [Accepted: 09/29/2020] [Indexed: 12/14/2022] Open
Abstract
Leaves of Arabidopsis develop from a shoot apical meristem grow along three (proximal-distal, adaxial-abaxial, and medial-lateral) axes and form a flat symmetric architecture. ASYMMETRIC LEAVES2 (AS2), a key regulator for leaf adaxial-abaxial partitioning, encodes a plant-specific nuclear protein and directly represses the abaxial-determining gene ETTIN/AUXIN RESPONSE FACTOR3 (ETT/ARF3). How AS2 could act as a critical regulator, however, has yet to be demonstrated, although it might play an epigenetic role. Here, we summarize the current understandings of the genetic, molecular, and cellular functions of AS2. A characteristic genetic feature of AS2 is the presence of a number of (about 60) modifier genes, mutations of which enhance the leaf abnormalities of as2. Although genes for proteins that are involved in diverse cellular processes are known as modifiers, it has recently become clear that many modifier proteins, such as NUCLEOLIN1 (NUC1) and RNA HELICASE10 (RH10), are localized in the nucleolus. Some modifiers including ribosomal proteins are also members of the small subunit processome (SSUP). In addition, AS2 forms perinucleolar bodies partially colocalizing with chromocenters that include the condensed inactive 45S ribosomal RNA genes. AS2 participates in maintaining CpG methylation in specific exons of ETT/ARF3. NUC1 and RH10 genes are also involved in maintaining the CpG methylation levels and repressing ETT/ARF3 transcript levels. AS2 and nucleolus-localizing modifiers might cooperatively repress ETT/ARF3 to develop symmetric flat leaves. These results raise the possibility of a nucleolus-related epigenetic repression system operating for developmental genes unique to plants and predict that AS2 could be a molecule with novel functions that cannot be explained by the conventional concept of transcription factors.
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Affiliation(s)
- Hidekazu Iwakawa
- Graduate School of Bioscience and Biotechnology, Chubu University, 1200, Matsumoto-cho, Kasugai, Aichi 487-8501, Japan;
| | - Hiro Takahashi
- Graduate School of Medical Sciences, Kanazawa University, Kakuma-machi, Kanazawa, Ishikawa 920-1192, Japan;
| | - Yasunori Machida
- Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan
| | - Chiyoko Machida
- Graduate School of Bioscience and Biotechnology, Chubu University, 1200, Matsumoto-cho, Kasugai, Aichi 487-8501, Japan;
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8
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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: 33] [Impact Index Per Article: 8.3] [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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9
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Establishment of a Recombinant AAV2/HBoV1 Vector Production System in Insect Cells. Genes (Basel) 2020; 11:genes11040439. [PMID: 32316599 PMCID: PMC7231168 DOI: 10.3390/genes11040439] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Revised: 04/10/2020] [Accepted: 04/15/2020] [Indexed: 12/13/2022] Open
Abstract
We have previously developed an rAAV2/HBoV1 vector in which a recombinant adeno-associated virus 2 (rAAV2) genome is pseudopackaged into a human bocavirus 1 (HBoV1) capsid. Recently, the production of rAAV2/HBoV1 in human embryonic kidney (HEK) 293 cells has been greatly improved in the absence of any HBoV1 nonstructural proteins (NS). This NS-free production system yields over 16-fold more vectors than the original production system that necessitates NS expression. The production of rAAV with infection of baculovirus expression vector (BEV) in the suspension culture of Sf9 insect cells is highly efficient and scalable. Since the replication of the rAAV2 genome in the BEV system is well established, we aimed to develop a BEV system to produce the rAAV2/HBoV1 vector in Sf9 cells. We optimized the usage of translation initiation signals of the HBoV1 capsid proteins (Cap), and constructed a BEV Bac-AAV2Rep-HBoV1Cap, which expresses the AAV2 Rep78 and Rep52 as well as the HBoV1 VP1, VP2, and VP3 at the appropriate ratios. We found that it is sufficient as a trans helper to the production of rAAV2/HBoV1 in Sf9 cells that were co-infected with the transfer Bac-AAV2ITR-GFP-luc that carried a 5.4-kb oversized rAAV2 genome with dual reporters. Further study found that incorporation of an HBoV1 small NS, NP1, in the system maximized the viral DNA replication and thus the rAAV2/HBoV1 vector production at a level similar to that of the rAAV2 vector in Sf9 cells. However, the transduction potency of the rAAV2/HBoV1 vector produced from BEV-infected Sf9 cells was 5-7-fold lower in polarized human airway epithelia than that packaged in HEK293 cells. Transmission electron microscopy analysis found that the vector produced in Sf9 cells had a high percentage of empty capsids, suggesting the pseudopackage of the rAAV2 genome in HBoV1 capsid is not as efficient as in the capsids of AAV2. Nevertheless, our study demonstrated that the rAAV2/HBoV1 can be produced in insect cells with BEVs at a comparable yield to rAAV, and that the highly efficient expression of the HBoV1 capsid proteins warrants further optimization.
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Luo L, Ando S, Sakamoto Y, Suzuki T, Takahashi H, Ishibashi N, Kojima S, Kurihara D, Higashiyama T, Yamamoto KT, Matsunaga S, Machida C, Sasabe M, Machida Y. The formation of perinucleolar bodies is important for normal leaf development and requires the zinc-finger DNA-binding motif in Arabidopsis ASYMMETRIC LEAVES2. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2020; 101:1118-1134. [PMID: 31639235 PMCID: PMC7155070 DOI: 10.1111/tpj.14579] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Revised: 09/30/2019] [Accepted: 10/08/2019] [Indexed: 05/27/2023]
Abstract
In Arabidopsis, the ASYMMETRIC LEAVES2 (AS2) protein plays a key role in the formation of flat symmetric leaves via direct repression of the abaxial gene ETT/ARF3. AS2 encodes a plant-specific nuclear protein that contains the AS2/LOB domain, which includes a zinc-finger (ZF) motif that is conserved in the AS2/LOB family. We have shown that AS2 binds to the coding DNA of ETT/ARF3, which requires the ZF motif. AS2 is co-localized with AS1 in perinucleolar bodies (AS2 bodies). To identify the amino acid signals in AS2 required for formation of AS2 bodies and function(s) in leaf formation, we constructed recombinant DNAs that encoded mutant AS2 proteins fused to yellow fluorescent protein. We examined the subcellular localization of these proteins in cells of cotyledons and leaf primordia of transgenic plants and cultured cells. The amino acid signals essential for formation of AS2 bodies were located within and adjacent to the ZF motif. Mutant AS2 that failed to form AS2 bodies also failed to rescue the as2-1 mutation. Our results suggest the importance of the formation of AS2 bodies and the nature of interactions of AS2 with its target DNA and nucleolar factors including NUCLEOLIN1. The partial overlap of AS2 bodies with perinucleolar chromocenters with condensed ribosomal RNA genes implies a correlation between AS2 bodies and the chromatin state. Patterns of AS2 bodies in cells during interphase and mitosis in leaf primordia were distinct from those in cultured cells, suggesting that the formation and distribution of AS2 bodies are developmentally modulated in plants.
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Affiliation(s)
- Lilan Luo
- Division of Biological ScienceGraduate School of ScienceNagoya UniversityNagoyaAichi464‐8602Japan
- Present address:
Institute of Genetics and Developmental BiologyChinese Academy of SciencesBeijing100101China
| | - Sayuri Ando
- Graduate School of Bioscience and BiotechnologyChubu UniversityKasugaiAichi487‐8501Japan
| | - Yuki Sakamoto
- Department of Applied Biological ScienceFaculty of Science and TechnologyTokyo University of ScienceNodaChiba278‐8510Japan
- Department of Biological SciencesGraduate School of ScienceOsaka University1‐1 Machikaneyama‐choToyonakaOsaka560‐0043Japan
| | - Takanori Suzuki
- Division of Biological ScienceGraduate School of ScienceNagoya UniversityNagoyaAichi464‐8602Japan
- Central Research InstituteIshihara Sangyo Kaisha, Ltd.2‐3‐1 Nishi‐ShibukawaKusatsuShiga525‐0025Japan
| | - Hiro Takahashi
- Graduate School of Medical SciencesKanazawa UniversityKakuma‐machiKanazawaIshikawa920‐1192Japan
| | - Nanako Ishibashi
- Division of Biological ScienceGraduate School of ScienceNagoya UniversityNagoyaAichi464‐8602Japan
| | - Shoko Kojima
- Graduate School of Bioscience and BiotechnologyChubu UniversityKasugaiAichi487‐8501Japan
| | - Daisuke Kurihara
- JST, PRESTOFuro‐cho, Chikusa‐kuNagoyaAichi464‐8601Japan
- Institute of Transformative Bio‐Molecules (ITbM)Nagoya UniversityFuro‐cho, Chiku00sa‐kuNagoyaAichi464‐8601Japan
| | - Tetsuya Higashiyama
- Division of Biological ScienceGraduate School of ScienceNagoya UniversityNagoyaAichi464‐8602Japan
- Institute of Transformative Bio‐Molecules (ITbM)Nagoya UniversityFuro‐cho, Chiku00sa‐kuNagoyaAichi464‐8601Japan
- Department of Biological SciencesGraduate School of ScienceUniversity of Tokyo7‐3‐1 Hongo, Bukyo‐kuTokyo113‐0033Japan
| | - Kotaro T. Yamamoto
- Division of Biological SciencesFaculty of ScienceHokkaido UniversitySapporo060‐0810Japan
| | - Sachihiro Matsunaga
- Department of Applied Biological ScienceFaculty of Science and TechnologyTokyo University of ScienceNodaChiba278‐8510Japan
| | - Chiyoko Machida
- Graduate School of Bioscience and BiotechnologyChubu UniversityKasugaiAichi487‐8501Japan
| | - Michiko Sasabe
- Department of BiologyFaculty of Agriculture and Life ScienceHirosaki University3 Bunkyo‐choHirosaki036‐8561Japan
| | - Yasunori Machida
- Division of Biological ScienceGraduate School of ScienceNagoya UniversityNagoyaAichi464‐8602Japan
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Identification and Characterization of the Nucleolar Localization Signal of Autographa californica Multiple Nucleopolyhedrovirus LEF5. J Virol 2020; 94:JVI.01891-19. [PMID: 31776271 DOI: 10.1128/jvi.01891-19] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2019] [Accepted: 11/19/2019] [Indexed: 11/20/2022] Open
Abstract
Autographa californica multiple nucleopolyhedrovirus (AcMNPV) late expression factor 5 (LEF5) is highly conserved in all sequenced baculovirus genomes and plays an important role in production of infectious viral progeny. In this study, nucleolar localization of AcMNPV LEF5 was characterized. Through transcriptome analysis, we identified two putative nucleolar proteins, Spodoptera frugiperda nucleostemin (SfNS) and fibrillarin (SfFBL), from Sf9 cells. Immunofluorescence analysis demonstrated that SfNS and SfFBL were localized to the nucleolus. AcMNPV infection resulted in reorganization of the nucleoli of infected cells. Colocalization of LEF5 and SfNS showed that AcMNPV LEF5 was localized to the nucleolus in Sf9 cells. Bioinformatic analysis revealed that basic amino acids of LEF5 are enriched at residues 184 to 213 and may contain a nucleolar localization signal (NoLS). Green fluorescent protein (GFP) fused to NoLS of AcMNPV LEF5 localized to the nucleoli of transfected cells. Multiple-point mutation analysis demonstrated that amino acid residues 197 to 204 are important for nucleolar localization of LEF5. To identify whether the NoLS in AcMNPV LEF5 is important for production of viral progeny, a lef5-null AcMNPV bacmid was constructed; several NoLS-mutated LEF5 proteins were reinserted into the lef5-null AcMNPV bacmid with a GFP reporter. The constructs containing point mutations at residues 185 to 189 or 197 to 204 in AcMNPV LEF5 resulted in reduction in production of infectious viral progeny and occlusion body yield in bacmid-transfected cells. Together, these data suggested that AcMNPV LEF5 contains an NoLS, which is important for nucleolar localization of LEF5, progeny production, and occlusion body production.IMPORTANCE Many viruses, including human and plant viruses, target nucleolar functions as part of their infection strategy. However, nucleolar localization for baculovirus proteins has not yet been characterized. In this study, two nucleolar proteins, SfNS and SfFBL, were identified in Sf9 cells. Our results showed that Autographa californica multiple nucleopolyhedrovirus (AcMNPV) infection resulted in redistribution of the nucleoli of infected cells. We demonstrated that AcMNPV late expression factor 5 (LEF5) could localize to the nucleolus and contains a nucleolar localization signal (NoLS), which is important for nucleolar localization of AcMNPV LEF5 and for production of viral progeny and yield of occlusion bodies.
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12
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Le DT, Radukic MT, Müller KM. Adeno-associated virus capsid protein expression in Escherichia coli and chemically defined capsid assembly. Sci Rep 2019; 9:18631. [PMID: 31819093 PMCID: PMC6901487 DOI: 10.1038/s41598-019-54928-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Accepted: 11/20/2019] [Indexed: 01/17/2023] Open
Abstract
Research and clinical applications of recombinant adeno-associated virus (rAAV) significantly increased in recent years alongside regulatory approvals of rAAV gene therapy products. To date, all rAAV vectors as well as AAV empty capsids are produced in eukaryotic cells. We explored a new route to generate AAV capsids with the aim to analyze capsid assembly in a chemically defined setting and pave the way for new production methods and applications based on AAV virus-like particles (VLPs). We generated these empty capsids by bacterial expression and subsequent concomitant protein refolding and VLP formation. AAV serotype 2 structural protein VP3 was expressed in Escherichia coli. VLPs formed as demonstrated by dynamic light scattering, atomic force microscopy, and ELISA. Furthermore, VLPs internalized into human HeLa cells. To extend the application range of the VLPs, we tested peptide insertions, at the genetic level, in a surface loop (amino acid position 587) or at the C-terminus of VP3 and these variants also formed VLPs. VLPs developed without assembly-activating protein (AAP), but adding purified recombinant AAP to the refolding process increased capsid yield. Our findings offer a new route to understand AAV assembly biology and open a toolbox for AAV production strategies that might enable capsid display for vaccination and matching of capsids with cargoes at large scale and low cost.
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Affiliation(s)
- Dinh To Le
- Cellular and Molecular Biotechnology, Faculty of Technology, Bielefeld University, Bielefeld, Germany
| | - Marco T Radukic
- Cellular and Molecular Biotechnology, Faculty of Technology, Bielefeld University, Bielefeld, Germany
| | - Kristian M Müller
- Cellular and Molecular Biotechnology, Faculty of Technology, Bielefeld University, Bielefeld, Germany.
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13
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Maurer AC, Pacouret S, Cepeda Diaz AK, Blake J, Andres-Mateos E, Vandenberghe LH. The Assembly-Activating Protein Promotes Stability and Interactions between AAV's Viral Proteins to Nucleate Capsid Assembly. Cell Rep 2019; 23:1817-1830. [PMID: 29742436 DOI: 10.1016/j.celrep.2018.04.026] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Revised: 07/31/2017] [Accepted: 04/04/2018] [Indexed: 11/30/2022] Open
Abstract
The adeno-associated virus (AAV) vector is a preferred delivery platform for in vivo gene therapy. Natural and engineered variations of the AAV capsid affect a plurality of phenotypes relevant to gene therapy, including vector production and host tropism. Fundamental to these aspects is the mechanism of AAV capsid assembly. Here, the role of the viral co-factor assembly-activating protein (AAP) was evaluated in 12 naturally occurring AAVs and 9 putative ancestral capsid intermediates. The results demonstrate increased capsid protein stability and VP-VP interactions in the presence of AAP. The capsid's dependence on AAP can be partly overcome by strengthening interactions between monomers within the assembly, as illustrated by the transfer of a minimal motif defined by a phenotype-to-phylogeny mapping method. These findings suggest that the emergence of AAP within the Dependovirus genus relaxes structural constraints on AAV assembly in favor of increasing the degrees of freedom for the capsid to evolve.
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Affiliation(s)
- Anna C Maurer
- Grousbeck Gene Therapy Center, Schepens Eye Research Institute, Massachusetts Eye and Ear, Boston, MA 02114, USA; Ocular Genomics Institute, Department of Ophthalmology, Harvard Medical School, Boston, MA 02114, USA
| | - Simon Pacouret
- Grousbeck Gene Therapy Center, Schepens Eye Research Institute, Massachusetts Eye and Ear, Boston, MA 02114, USA; Ocular Genomics Institute, Department of Ophthalmology, Harvard Medical School, Boston, MA 02114, USA; INSERM UMR 1089, University of Nantes, Nantes University Hospital, 22 Boulevard Benoni Goullin, 44200 Nantes, France
| | - Ana Karla Cepeda Diaz
- Grousbeck Gene Therapy Center, Schepens Eye Research Institute, Massachusetts Eye and Ear, Boston, MA 02114, USA; Ocular Genomics Institute, Department of Ophthalmology, Harvard Medical School, Boston, MA 02114, USA
| | - Jessica Blake
- Grousbeck Gene Therapy Center, Schepens Eye Research Institute, Massachusetts Eye and Ear, Boston, MA 02114, USA; Ocular Genomics Institute, Department of Ophthalmology, Harvard Medical School, Boston, MA 02114, USA
| | - Eva Andres-Mateos
- Grousbeck Gene Therapy Center, Schepens Eye Research Institute, Massachusetts Eye and Ear, Boston, MA 02114, USA; Ocular Genomics Institute, Department of Ophthalmology, Harvard Medical School, Boston, MA 02114, USA
| | - Luk H Vandenberghe
- Grousbeck Gene Therapy Center, Schepens Eye Research Institute, Massachusetts Eye and Ear, Boston, MA 02114, USA; Ocular Genomics Institute, Department of Ophthalmology, Harvard Medical School, Boston, MA 02114, USA; Harvard Stem Cell Institute, Harvard University, Cambridge, MA 02138, USA; The Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA.
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14
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Maurer AC, Cepeda Diaz AK, Vandenberghe LH. Residues on Adeno-associated Virus Capsid Lumen Dictate Interactions and Compatibility with the Assembly-Activating Protein. J Virol 2019; 93:e02013-18. [PMID: 30651367 PMCID: PMC6430561 DOI: 10.1128/jvi.02013-18] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Accepted: 01/04/2019] [Indexed: 01/09/2023] Open
Abstract
The adeno-associated virus (AAV) serves as a broadly used vector system for in vivo gene delivery. The process of AAV capsid assembly remains poorly understood. The viral cofactor assembly-activating protein (AAP) is required for maximum AAV production and has multiple roles in capsid assembly, namely, trafficking of the structural proteins (VP) to the nuclear site of assembly, promoting the stability of VP against multiple degradation pathways, and facilitating stable interactions between VP monomers. The N-terminal 60 amino acids of AAP (AAPN) are essential for these functions. Presumably, AAP must physically interact with VP to execute its multiple functions, but the molecular nature of the AAP-VP interaction is not well understood. Here, we query how structurally related AAVs functionally engage AAP from AAV serotype 2 (AAP2) toward virion assembly. These studies led to the identification of key residues on the lumenal capsid surface that are important for AAP-VP and for VP-VP interactions. Replacing a cluster of glutamic acid residues with a glutamine-rich motif on the conserved VP beta-barrel structure of variants incompatible with AAP2 creates a gain-of-function mutant compatible with AAP2. Conversely, mutating positively charged residues within the hydrophobic region of AAP2 and conserved core domains within AAPN creates a gain-of-function AAP2 mutant that rescues assembly of the incompatible variant. Our results suggest a model for capsid assembly where surface charge/neutrality dictates an interaction between AAPN and the lumenal VP surface to nucleate capsid assembly.IMPORTANCE Efforts to engineer the AAV capsid to gain desirable properties for gene therapy (e.g., tropism, reduced immunogenicity, and higher potency) require that capsid modifications do not affect particle assembly. The relationship between VP and the cofactor that facilitates its assembly, AAP, is central to both assembly preservation and vector production. Understanding the requirements for this compatibility can inform manufacturing strategies to maximize production and reduce costs. Additionally, library-based approaches that simultaneously examine a large number of capsid variants would benefit from a universally functional AAP, which could hedge against overlooking variants with potentially valuable phenotypes that were lost during vector library production due to incompatibility with the cognate AAP. Studying interactions between the structural and nonstructural components of AAV enhances our fundamental knowledge of capsid assembly mechanisms and the protein-protein interactions required for productive assembly of the icosahedral capsid.
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Affiliation(s)
- Anna C Maurer
- Grousbeck Gene Therapy Center, Schepens Eye Research Institute, Mass Eye and Ear, Boston, Massachusetts, USA
- Ocular Genomics Institute, Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, USA
| | - Ana Karla Cepeda Diaz
- Grousbeck Gene Therapy Center, Schepens Eye Research Institute, Mass Eye and Ear, Boston, Massachusetts, USA
- Ocular Genomics Institute, Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, USA
| | - Luk H Vandenberghe
- Grousbeck Gene Therapy Center, Schepens Eye Research Institute, Mass Eye and Ear, Boston, Massachusetts, USA
- Ocular Genomics Institute, Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, USA
- The Broad Institute of Harvard and MIT, Cambridge, Massachusetts, USA
- Harvard Stem Cell Institute, Harvard University, Cambridge, Massachusetts, USA
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15
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Herrmann AK, Bender C, Kienle E, Grosse S, El Andari J, Botta J, Schürmann N, Wiedtke E, Niopek D, Grimm D. A Robust and All-Inclusive Pipeline for Shuffling of Adeno-Associated Viruses. ACS Synth Biol 2019; 8:194-206. [PMID: 30513195 DOI: 10.1021/acssynbio.8b00373] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Adeno-associated viruses (AAV) are attractive templates for engineering of synthetic gene delivery vectors. A particularly powerful technology for breeding of novel vectors with improved properties is DNA family shuffling, i.e., generation of chimeric capsids by homology-driven DNA recombination. Here, to make AAV DNA shuffling available to a wider community, we present a robust experimental and bioinformatical pipeline comprising: (i) standardized and partially codon-optimized plasmids carrying 12 different AAV capsid genes; (ii) a scalable protocol including troubleshooting guide for viral library production; and (iii) the freely available software SALANTO for comprehensive analysis of chimeric AAV DNA and protein sequences. Moreover, we describe a set of 12 premade and ready-to-use AAV libraries. Finally, we demonstrate the usefulness of DNA barcoding technology to trace AAV capsid libraries within a complex mixture. Our protocols and resources facilitate the implementation and tailoring of AAV evolution technology in any laboratory interested in customized viral gene transfer.
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Affiliation(s)
- Anne-Kathrin Herrmann
- Cluster of Excellence CellNetworks, Department of Infectious Diseases, Virology and Center for Quantitative Analysis of Molecular and Cellular Biosystems (BioQuant), Heidelberg University Hospital, Heidelberg, 69120, Germany
| | - Christian Bender
- Translational Oncology at the University Medical Center of the Johannes Gutenberg University, Mainz, 55131, Germany
| | - Eike Kienle
- Cluster of Excellence CellNetworks, Department of Infectious Diseases, Virology and Center for Quantitative Analysis of Molecular and Cellular Biosystems (BioQuant), Heidelberg University Hospital, Heidelberg, 69120, Germany
| | - Stefanie Grosse
- Cluster of Excellence CellNetworks, Department of Infectious Diseases, Virology and Center for Quantitative Analysis of Molecular and Cellular Biosystems (BioQuant), Heidelberg University Hospital, Heidelberg, 69120, Germany
| | - Jihad El Andari
- Cluster of Excellence CellNetworks, Department of Infectious Diseases, Virology and Center for Quantitative Analysis of Molecular and Cellular Biosystems (BioQuant), Heidelberg University Hospital, Heidelberg, 69120, Germany
| | - Julia Botta
- Cluster of Excellence CellNetworks, Department of Infectious Diseases, Virology and Center for Quantitative Analysis of Molecular and Cellular Biosystems (BioQuant), Heidelberg University Hospital, Heidelberg, 69120, Germany
- Synthetic Biology Group, Institute for Pharmacy and Biotechnology (IPMB) and Center for Quantitative Analysis of Molecular and Cellular Biosystems (BioQuant), University of Heidelberg, Heidelberg, 69120, Germany
| | - Nina Schürmann
- Cluster of Excellence CellNetworks, Department of Infectious Diseases, Virology and Center for Quantitative Analysis of Molecular and Cellular Biosystems (BioQuant), Heidelberg University Hospital, Heidelberg, 69120, Germany
| | - Ellen Wiedtke
- Cluster of Excellence CellNetworks, Department of Infectious Diseases, Virology and Center for Quantitative Analysis of Molecular and Cellular Biosystems (BioQuant), Heidelberg University Hospital, Heidelberg, 69120, Germany
| | - Dominik Niopek
- Synthetic Biology Group, Institute for Pharmacy and Biotechnology (IPMB) and Center for Quantitative Analysis of Molecular and Cellular Biosystems (BioQuant), University of Heidelberg, Heidelberg, 69120, Germany
| | - Dirk Grimm
- Cluster of Excellence CellNetworks, Department of Infectious Diseases, Virology and Center for Quantitative Analysis of Molecular and Cellular Biosystems (BioQuant), Heidelberg University Hospital, Heidelberg, 69120, Germany
- German Center for Infection Research (DZIF) and German Center for Cardiovascular Research (DZHK), Heidelberg, 69120, Germany
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16
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Herrmann AK, Große S, Börner K, Krämer C, Wiedtke E, Gunkel M, Grimm D. Impact of the Assembly-Activating Protein on Molecular Evolution of Synthetic Adeno-Associated Virus Capsids. Hum Gene Ther 2018; 30:21-35. [PMID: 29978729 DOI: 10.1089/hum.2018.085] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Over the last decade, the role of the assembly-activating protein (AAP) has begun to be dissected for the formation of adeno-associated virus (AAV) capsids based on different viral serotypes. Recently, the authors' group has specifically studied AAP's relevance during production of AAV gene therapy vectors in mammalian or insect cells, and AAP was found to be essential for capsid protein stabilization and generation of functional vector particles. Here, the lingering question is additionally addressed of whether molecular AAV evolution via DNA family shuffling of viral capsid genes would perturb AAP functionality due to concurrent and inadvertent recombination of the AAP open reading frame. To this end, a battery of complementary experiments was conducted in which: (1) the ability of chimeric AAP from AAVDJ, a hybrid of serotypes 2, 8, and 9, was tested to rescue AAP knockouts in the three parental serotypes; (2) the functionality of 60 chimeric AAPs extracted from five shuffled, unselected capsid libraries was measured; (3) whether production of different shuffled libraries, 10 wild-type serotypes or 25 individual chimeric capsids, can be enhanced by overexpression of AAP cocktails was assessed; and (4) the activity of 12 chimeric AAPs isolated from a shuffled library that was iteratively selected in vivo in mouse livers was studied. Collectively, the data demonstrate a remarkable tolerance of AAP for recombination via DNA family shuffling, evidenced by the findings that (1) all chimeric AAPs studied here retained at least partial activity, even in cases where the cognate hybrid capsid may be non-functional, and that (2) ectopic AAP overexpression did not enhance production of shuffled AAV chimeras or libraries, implying that the inherently encoded hybrid AAP variants are sufficiently active. Together, this work provides compelling evidence that AAP is not rate limiting during AAV capsid shuffling and thereby relieves a major concern in the field of AAV vector evolution.
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Affiliation(s)
- Anne-Kathrin Herrmann
- 1 Department of Infectious Diseases/Virology, Heidelberg University Hospital, Cluster of Excellence CellNetworks, Heidelberg, Germany.,2 BioQuant Center, University of Heidelberg, Heidelberg, Germany
| | - Stefanie Große
- 1 Department of Infectious Diseases/Virology, Heidelberg University Hospital, Cluster of Excellence CellNetworks, Heidelberg, Germany.,2 BioQuant Center, University of Heidelberg, Heidelberg, Germany
| | - Kathleen Börner
- 1 Department of Infectious Diseases/Virology, Heidelberg University Hospital, Cluster of Excellence CellNetworks, Heidelberg, Germany.,2 BioQuant Center, University of Heidelberg, Heidelberg, Germany.,3 German Center for Infection Research (DZIF), partner site Heidelberg, Germany
| | - Chiara Krämer
- 1 Department of Infectious Diseases/Virology, Heidelberg University Hospital, Cluster of Excellence CellNetworks, Heidelberg, Germany.,2 BioQuant Center, University of Heidelberg, Heidelberg, Germany
| | - Ellen Wiedtke
- 1 Department of Infectious Diseases/Virology, Heidelberg University Hospital, Cluster of Excellence CellNetworks, Heidelberg, Germany.,2 BioQuant Center, University of Heidelberg, Heidelberg, Germany
| | - Manuel Gunkel
- 2 BioQuant Center, University of Heidelberg, Heidelberg, Germany.,4 CellNetworks Advanced Biological Screening Facility, University of Heidelberg, Heidelberg, Germany
| | - Dirk Grimm
- 1 Department of Infectious Diseases/Virology, Heidelberg University Hospital, Cluster of Excellence CellNetworks, Heidelberg, Germany.,2 BioQuant Center, University of Heidelberg, Heidelberg, Germany.,3 German Center for Infection Research (DZIF), partner site Heidelberg, Germany
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17
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APOBEC3H Subcellular Localization Determinants Define Zipcode for Targeting HIV-1 for Restriction. Mol Cell Biol 2018; 38:MCB.00356-18. [PMID: 30224517 DOI: 10.1128/mcb.00356-18] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2018] [Accepted: 09/11/2018] [Indexed: 12/22/2022] Open
Abstract
APOBEC enzymes are DNA cytosine deaminases that normally serve as virus restriction factors, but several members, including APOBEC3H, also contribute to cancer mutagenesis. Despite their importance in multiple fields, little is known about cellular processes that regulate these DNA mutating enzymes. We show that APOBEC3H exists in two distinct subcellular compartments, cytoplasm and nucleolus, and that the structural determinants for each mechanism are genetically separable. First, native and fluorescently tagged APOBEC3Hs localize to these two compartments in multiple cell types. Second, a series of genetic, pharmacologic, and cell biological studies demonstrate active cytoplasmic and nucleolar retention mechanisms, whereas nuclear import and export occur through passive diffusion. Third, APOBEC3H cytoplasmic retention determinants relocalize APOBEC3A from a passive cell-wide state to the cytosol and, additionally, endow potent HIV-1 restriction activity. These results indicate that APOBEC3H has a structural zipcode for subcellular localization and selecting viral substrates for restriction.
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18
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Lee EJ, Guenther CM, Suh J. Adeno-Associated Virus (AAV) Vectors: Rational Design Strategies for Capsid Engineering. CURRENT OPINION IN BIOMEDICAL ENGINEERING 2018; 7:58-63. [PMID: 31106283 DOI: 10.1016/j.cobme.2018.09.004] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Adeno-associated virus (AAV) consists of a simple genome, infects mammalian cells, displays nonpathogenicity in humans, and spans an array of serotypes and variants bearing distinct tissue tropisms. These attributes lend AAV tremendous promise as a gene delivery vector, further substantiated by its extensive testing in human clinical trials. Rational design approaches to capsid engineering leverage current scientific knowledge of AAV to further modulate, enhance and optimize the performance of the vectors. Capsid modification strategies include amino acid point mutations, peptide domain insertions, and chemical biology approaches. Through such efforts, insights regarding AAV capsid sequence-structure-function relationships can be learned. Developments over the last 5 years in rational design-based capsid engineering approaches will be presented and discussed.
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Affiliation(s)
- Esther J Lee
- Department of Bioengineering, Rice University, 6500 Main St., MS-142, Houston, TX 77030, USA
| | - Caitlin M Guenther
- Department of Bioengineering, Rice University, 6500 Main St., MS-142, Houston, TX 77030, USA
| | - Junghae Suh
- Department of Bioengineering, Rice University, 6500 Main St., MS-142, Houston, TX 77030, USA
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19
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Mapping and Engineering Functional Domains of the Assembly-Activating Protein of Adeno-associated Viruses. J Virol 2018; 92:JVI.00393-18. [PMID: 29695425 DOI: 10.1128/jvi.00393-18] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Accepted: 04/19/2018] [Indexed: 12/28/2022] Open
Abstract
Adeno-associated viruses (AAVs) encode a unique assembly-activating protein (AAP) within their genomes that is essential for capsid assembly. Studies to date have focused on establishing the role of AAP as a chaperone that mediates the stability, nucleolar transport, and assembly of AAV capsid proteins. Here, we map structure-function correlates of AAP using secondary structure analysis, followed by deletion and substitutional mutagenesis of specific domains, namely, the N-terminal hydrophobic region (HR), conserved core (CC), proline-rich region (PRR), threonine/serine-rich region (T/S), and basic region (BR). First, we establish that the centrally located PRR and T/S are flexible linker domains that can either be deleted completely or replaced by heterologous functional domains that enable ancillary functions such as fluorescent imaging or increased AAP stability. We also demonstrate that the C-terminal BR domains can be substituted with heterologous nuclear or nucleolar localization sequences that display various abilities to support AAV capsid assembly. Further, by replacing the BR domain with immunoglobulin (IgG) Fc domains, we assessed AAP complexation with AAV capsid subunits and demonstrate that the hydrophobic region (HR) and the conserved core (CC) in the AAP N terminus are the sole determinants for viral protein (VP) recognition. However, VP recognition alone is not sufficient for capsid assembly. Our study sheds light on the modular structure-function correlates of AAP and provides multiple approaches to engineer AAP that might prove useful toward understanding and controlling AAV capsid assembly.IMPORTANCE Adeno-associated viruses (AAVs) encode a unique assembly-activating protein (AAP) within their genomes that is essential for capsid assembly. Understanding how AAP acts as a chaperone for viral assembly could help improve efficiency and potentially control this process. Our studies reveal that AAP has a modular architecture, with each module playing a distinct role and can be engineered for carrying out new functions.
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20
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Powers JM, Chang XL, Song Z, Nakai H. A Quantitative Dot Blot Assay for AAV Titration and Its Use for Functional Assessment of the Adeno-associated Virus Assembly-activating Proteins. J Vis Exp 2018. [PMID: 29985340 DOI: 10.3791/56766] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
While adeno-associated virus (AAV) is widely accepted as an attractive vector for gene therapy, it also serves as a model virus for understanding virus biology. In the latter respect, the recent discovery of a non-structural AAV protein, termed assembly-activating protein (AAP), has shed new light on the processes involved in assembly of the viral capsid VP proteins into a capsid. Although many AAV serotypes require AAP for assembly, we have recently reported that AAV4, 5, and 11 are exceptions to this rule. Furthermore, we demonstrated that AAPs and assembled capsids of different serotypes localize to different subcellular compartments. This unexpected heterogeneity in the biological properties and functional roles of AAPs among different AAV serotypes underscores the importance of studies on AAPs derived from diverse serotypes. This manuscript details a straightforward dot blot assay for AAV quantitation and its application to assess AAP dependency and serotype specificity in capsid assembly. To demonstrate the utility of this dot blot assay, we set out to characterize capsid assembly and AAP dependency of Snake AAV, a previously uncharacterized reptile AAV, as well as AAV5 and AAV9, which have previously been shown to be AAP-independent and AAP-dependent serotypes, respectively. The assay revealed that Snake AAV capsid assembly requires Snake AAP and cannot be promoted by AAPs from AAV5 and AAV9. The assay also showed that, unlike many of the common serotype AAPs that promote heterologous capsid assembly by cross-complementation, Snake AAP does not promote assembly of AAV9 capsids. In addition, we show that the choice of nuclease significantly affects the readout of the dot blot assay, and thus, choosing an optimal enzyme is critical for successful assessment of AAV titers.
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Affiliation(s)
- John M Powers
- Department of Molecular and Medical Genetics, Oregon Health & Science University
| | - Xiao Lan Chang
- Department of Molecular and Medical Genetics, Oregon Health & Science University
| | - Zhen Song
- Department of Molecular and Medical Genetics, Oregon Health & Science University
| | - Hiroyuki Nakai
- Department of Molecular and Medical Genetics, Oregon Health & Science University; Department of Molecular Microbiology and Immunology, Oregon Health & Science University;
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21
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Herrmann AK, Grimm D. High-Throughput Dissection of AAV-Host Interactions: The Fast and the Curious. J Mol Biol 2018; 430:2626-2640. [PMID: 29782834 DOI: 10.1016/j.jmb.2018.05.022] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Revised: 05/10/2018] [Accepted: 05/11/2018] [Indexed: 12/24/2022]
Abstract
Over 50 years after its initial description, adeno-associated virus (AAV) remains the most exciting but also most elusive study object in basic or applied virology. On the one hand, its simple structure not only facilitates investigations into virus biology but, combined with the availability of numerous natural AAV variants with distinct infection efficiency and specificity, also makes AAV a preferred substrate for engineering of gene delivery vectors. On the other hand, it is striking to witness a recent flurry of reports that highlight and partially close persistent gaps in our understanding of AAV virus and vector biology. This is all the more perplexing considering that recombinant AAVs have already been used in >160 clinical trials and recently been commercialized as gene therapeutics. Here, we discuss a reason for these advances in AAV research, namely, the advent and application of powerful high-throughput technology for dissection of AAV-host interactions and optimization of AAV gene therapy vectors. As relevant examples, we focus on the discovery of (i) a "new" cellular AAV receptor, AAVR, (ii) host restriction factors for AAV entry, and (iii) AAV capsid determinants that mediate trafficking through the blood-brain barrier. While items i/ii are prototypes of extra- or intracellular AAV host factors that were identified via high-throughput screenings, item iii exemplifies the power of molecular evolution to investigate the virus itself. In the future, we anticipate that these and other key technologies will continue to accelerate the dissection of AAV biology and will yield a wealth of new designer viruses for clinical use.
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Affiliation(s)
- Anne-Kathrin Herrmann
- Cluster of Excellence CellNetworks,Virus-Host Interaction Group, Department of Infectious Diseases/Virology, Heidelberg University Hospital, Im Neuenheimer Feld 267, 69120 Heidelberg, Germany; BioQuant Center, University of Heidelberg, Im Neuenheimer Feld 267, 69120 Heidelberg, Germany
| | - Dirk Grimm
- Cluster of Excellence CellNetworks,Virus-Host Interaction Group, Department of Infectious Diseases/Virology, Heidelberg University Hospital, Im Neuenheimer Feld 267, 69120 Heidelberg, Germany; BioQuant Center, University of Heidelberg, Im Neuenheimer Feld 267, 69120 Heidelberg, Germany; German Center for Infection Research (DZIF), Partner site Heidelberg, 69120 Heidelberg, Germany.
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22
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Brooks WH. Viral Impact in Autoimmune Diseases: Expanding the "X Chromosome-Nucleolus Nexus" Hypothesis. Front Immunol 2017; 8:1657. [PMID: 29234321 PMCID: PMC5712313 DOI: 10.3389/fimmu.2017.01657] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2017] [Accepted: 11/13/2017] [Indexed: 12/19/2022] Open
Abstract
Viruses are suspected of significant roles in autoimmune diseases but the mechanisms are unclear. We get some insight by considering demands a virus places on host cells. Viruses not only require production of their own proteins, RNA and/or DNA, but also production of additional cellular machinery, such as ribosomes, to handle the increased demands. Since the nucleolus is a major site of RNA processing and ribonucleoprotein assembly, nucleoli are targeted by viruses, directly when viral RNA and proteins enter the nucleolus and indirectly when viruses induce increased expression of cellular polyamine genes. Polyamines are at high levels in nucleoli to assist in RNA folding. The size and activity of nucleoli increase directly with increases in polyamines. Nucleolar expansion due to abnormal increases in polyamines could disrupt nearby chromatin, such as the inactive X chromosome, leading to expression of previously sequestered DNA. Sudden expression of a large concentration of Alu elements from the disrupted inactive X can compete with RNA transcripts containing intronic Alu sequences that normally maintain nucleolar structural integrity. Such disruption of nucleolar activity can lead to misfolded RNAs, misassembled ribonucleoprotein complexes, and fragmentation of the nucleolus. Many autoantigens in lupus are, at least transiently, components of the nucleolus. Considering these effects of viruses, the “X chromosome–nucleolus nexus” hypothesis, which proposed disruption of the inactive X by the nucleolus during stress, is now expanded here to propose subsequent disruption of the nucleolus by previously sequestered Alu elements, which can fragment the nucleolus, leading to generation of autoantigens.
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Affiliation(s)
- Wesley H Brooks
- Department of Chemistry, University of South Florida, Tampa, FL, United States
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23
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Wang Q, Wu Z, Zhang J, Firrman J, Wei H, Zhuang Z, Liu L, Miao L, Hu Y, Li D, Diao Y, Xiao W. A Robust System for Production of Superabundant VP1 Recombinant AAV Vectors. MOLECULAR THERAPY-METHODS & CLINICAL DEVELOPMENT 2017; 7:146-156. [PMID: 29255740 PMCID: PMC5721209 DOI: 10.1016/j.omtm.2017.11.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Accepted: 11/01/2017] [Indexed: 01/31/2023]
Abstract
Recombinant adeno-associated viral (rAAV) vectors have been widely used in human gene therapy. One major impediment to its broad application is the inability to produce high-quality vectors in mass quantity. Here, an efficient and scalable suspension cell culture system for the production of rAAV vectors is described. In this system, the AAV trans factors, Rep78, Rep52, VP1, VP2, and VP3, were stably integrated into a single vaccinia virus carrier by maximizing the use of alternative codons between genes with identical amino acids, and the cis rAAV genome was carried by an E1/E3 gene-deleted adenovirus. Infection of improved, E1 integrated, suspension-cultured cells with these two viral vectors resulted in the robust production of rAAV vectors. The newly enhanced system can consistently produce ∼1 × 1015 genome containing rAAV vectors per liter of suspension cells. Moreover, the capsid composition of rAAV vectors produced by this system is markedly different from those produced using the traditional system in that the VP1 protein is more abundant than the VP2 protein (19:1 versus 1:1). The unique VP1 superabundant rAAV vectors produced in this new system exhibited improved transduction in vivo after intravitreal injection.
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Affiliation(s)
- Qizhao Wang
- School of Biomedical Sciences, Huaqiao University, Quanzhou, Fujian, China.,Sol Sherry Thrombosis Research Center, Temple University, Philadelphia, PA, USA.,Byers Eye Institute, Stanford University School of Medicine, Stanford, CA, USA
| | - Zhongren Wu
- Sol Sherry Thrombosis Research Center, Temple University, Philadelphia, PA, USA
| | - Junping Zhang
- Sol Sherry Thrombosis Research Center, Temple University, Philadelphia, PA, USA
| | - Jenni Firrman
- Department of Microbiology and Immunology, Temple University, Philadelphia, PA, USA.,United States Department of Agriculture, ARS, ERRC, Wyndmoor, PA, USA
| | - Hongying Wei
- Sol Sherry Thrombosis Research Center, Temple University, Philadelphia, PA, USA
| | - Zhengjing Zhuang
- School of Biomedical Sciences, Huaqiao University, Quanzhou, Fujian, China
| | - LinShu Liu
- United States Department of Agriculture, ARS, ERRC, Wyndmoor, PA, USA
| | - Linqing Miao
- Shriners Hospital Pediatric Research Center, Temple University, Philadelphia, PA, USA
| | - Yang Hu
- Byers Eye Institute, Stanford University School of Medicine, Stanford, CA, USA
| | - Dong Li
- Department of Clinical Laboratory, Tongji Hospital of Tongji University, Shanghai, China
| | - Yong Diao
- School of Biomedical Sciences, Huaqiao University, Quanzhou, Fujian, China
| | - Weidong Xiao
- School of Biomedical Sciences, Huaqiao University, Quanzhou, Fujian, China.,Sol Sherry Thrombosis Research Center, Temple University, Philadelphia, PA, USA.,Department of Microbiology and Immunology, Temple University, Philadelphia, PA, USA.,Cardiovascular Research Center, Temple University, Philadelphia, PA, USA.,Department of Clinical Laboratory, Tongji Hospital of Tongji University, Shanghai, China
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Grimm D, Büning H. Small But Increasingly Mighty: Latest Advances in AAV Vector Research, Design, and Evolution. Hum Gene Ther 2017; 28:1075-1086. [DOI: 10.1089/hum.2017.172] [Citation(s) in RCA: 86] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Affiliation(s)
- Dirk Grimm
- Heidelberg University Hospital, Cluster of Excellence CellNetworks, Department of Infectious Diseases, Virology, Heidelberg, Germany
- BioQuant Center, University of Heidelberg, Heidelberg, Germany
- German Center for Infection Research (DZIF), partner site Heidelberg, Germany
| | - Hildegard Büning
- Institute of Experimental Hematology, Hannover Medical School, Hannover, Germany
- Cluster of Excellence REBIRTH, Hannover Medical School, Hannover, Germany
- German Center for Infection Research (DZIF), partner site Hannover-Braunschweig, Germany
- Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
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25
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Grosse S, Penaud-Budloo M, Herrmann AK, Börner K, Fakhiri J, Laketa V, Krämer C, Wiedtke E, Gunkel M, Ménard L, Ayuso E, Grimm D. Relevance of Assembly-Activating Protein for Adeno-associated Virus Vector Production and Capsid Protein Stability in Mammalian and Insect Cells. J Virol 2017; 91:e01198-17. [PMID: 28768875 PMCID: PMC5625497 DOI: 10.1128/jvi.01198-17] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Accepted: 07/28/2017] [Indexed: 12/16/2022] Open
Abstract
The discovery that adeno-associated virus 2 (AAV2) encodes an eighth protein, called assembly-activating protein (AAP), transformed our understanding of wild-type AAV biology. Concurrently, it raised questions about the role of AAP during production of recombinant vectors based on natural or molecularly engineered AAV capsids. Here, we show that AAP is indeed essential for generation of functional recombinant AAV2 vectors in both mammalian and insect cell-based vector production systems. Surprisingly, we observed that AAV2 capsid proteins VP1 to -3 are unstable in the absence of AAP2, likely due to rapid proteasomal degradation. Inhibition of the proteasome led to an increase of intracellular VP1 to -3 but neither triggered assembly of functional capsids nor promoted nuclear localization of the capsid proteins. Together, this underscores the crucial and unique role of AAP in the AAV life cycle, where it rapidly chaperones capsid assembly, thus preventing degradation of free capsid proteins. An expanded analysis comprising nine alternative AAV serotypes (1, 3 to 9, and rh10) showed that vector production always depends on the presence of AAP, with the exceptions of AAV4 and AAV5, which exhibited AAP-independent, albeit low-level, particle assembly. Interestingly, AAPs from all 10 serotypes could cross-complement AAP-depleted helper plasmids during vector production, despite there being distinct intracellular AAP localization patterns. These were most pronounced for AAP4 and AAP5, congruent with their inability to rescue an AAV2/AAP2 knockout. We conclude that AAP is key for assembly of genuine capsids from at least 10 different AAV serotypes, which has implications for vectors derived from wild-type or synthetic AAV capsids.IMPORTANCE Assembly of adeno-associated virus 2 (AAV2) is regulated by the assembly-activating protein (AAP), whose open reading frame overlaps with that of the viral capsid proteins. As the majority of evidence was obtained using virus-like particles composed solely of the major capsid protein VP3, AAP's role in and relevance for assembly of genuine AAV capsids have remained largely unclear. Thus, we established a trans-complementation assay permitting assessment of AAP functionality during production of recombinant vectors based on complete AAV capsids and derived from any serotype. We find that AAP is indeed a critical factor not only for AAV2, but also for generation of vectors derived from nine other AAV serotypes. Moreover, we identify a new role of AAP in maintaining capsid protein stability in mammalian and insect cells. Thereby, our study expands our current understanding of AAV/AAP biology, and it concomitantly provides insights into the importance of AAP for AAV vector production.
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Affiliation(s)
- Stefanie Grosse
- Department of Infectious Diseases/Virology, Heidelberg University Hospital, Cluster of Excellence CellNetworks, Heidelberg, Germany
- BioQuant Center, University of Heidelberg, Heidelberg, Germany
| | - Magalie Penaud-Budloo
- INSERM UMR1089, University of Nantes, Centre Hospitalier Universitaire, Nantes, France
| | - Anne-Kathrin Herrmann
- Department of Infectious Diseases/Virology, Heidelberg University Hospital, Cluster of Excellence CellNetworks, Heidelberg, Germany
- BioQuant Center, University of Heidelberg, Heidelberg, Germany
| | - Kathleen Börner
- Department of Infectious Diseases/Virology, Heidelberg University Hospital, Cluster of Excellence CellNetworks, Heidelberg, Germany
- BioQuant Center, University of Heidelberg, Heidelberg, Germany
- German Center for Infection Research, Partner Site Heidelberg, Heidelberg, Germany
| | - Julia Fakhiri
- Department of Infectious Diseases/Virology, Heidelberg University Hospital, Cluster of Excellence CellNetworks, Heidelberg, Germany
- BioQuant Center, University of Heidelberg, Heidelberg, Germany
| | - Vibor Laketa
- Department of Infectious Diseases/Virology, Heidelberg University Hospital, Cluster of Excellence CellNetworks, Heidelberg, Germany
- German Center for Infection Research, Partner Site Heidelberg, Heidelberg, Germany
| | - Chiara Krämer
- Department of Infectious Diseases/Virology, Heidelberg University Hospital, Cluster of Excellence CellNetworks, Heidelberg, Germany
- BioQuant Center, University of Heidelberg, Heidelberg, Germany
| | - Ellen Wiedtke
- Department of Infectious Diseases/Virology, Heidelberg University Hospital, Cluster of Excellence CellNetworks, Heidelberg, Germany
- BioQuant Center, University of Heidelberg, Heidelberg, Germany
| | - Manuel Gunkel
- BioQuant Center, University of Heidelberg, Heidelberg, Germany
- CellNetworks Advanced Biological Screening Facility, University of Heidelberg, Heidelberg, Germany
| | - Lucie Ménard
- INSERM UMR1089, University of Nantes, Centre Hospitalier Universitaire, Nantes, France
| | - Eduard Ayuso
- INSERM UMR1089, University of Nantes, Centre Hospitalier Universitaire, Nantes, France
| | - Dirk Grimm
- Department of Infectious Diseases/Virology, Heidelberg University Hospital, Cluster of Excellence CellNetworks, Heidelberg, Germany
- BioQuant Center, University of Heidelberg, Heidelberg, Germany
- German Center for Infection Research, Partner Site Heidelberg, Heidelberg, Germany
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26
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Adeno-associated Virus (AAV) Assembly-Activating Protein Is Not an Essential Requirement for Capsid Assembly of AAV Serotypes 4, 5, and 11. J Virol 2017; 91:JVI.01980-16. [PMID: 27852862 PMCID: PMC5244341 DOI: 10.1128/jvi.01980-16] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Accepted: 10/24/2016] [Indexed: 01/02/2023] Open
Abstract
Adeno-associated virus (AAV) vectors have made great progress in their use for gene therapy; however, fundamental aspects of AAV's capsid assembly remain poorly characterized. In this regard, the discovery of assembly-activating protein (AAP) sheds new light on this crucial part of AAV biology and vector production. Previous studies have shown that AAP is essential for assembly; however, how its mechanistic roles in assembly might differ among AAV serotypes remains uncharacterized. Here, we show that biological properties of AAPs and capsid assembly processes are surprisingly distinct among AAV serotypes 1 to 12. In the study, we investigated subcellular localizations and assembly-promoting functions of AAP1 to -12 (i.e., AAPs derived from AAV1 to -12, respectively) and examined the AAP dependence of capsid assembly processes of these 12 serotypes using combinatorial approaches that involved immunofluorescence and transmission electron microscopy, barcode-Seq (i. e., a high-throughput quantitative method using DNA barcodes and a next-generation sequencing technology), and quantitative dot blot assays. This study revealed that AAP1 to -12 are all localized in the nucleus with serotype-specific differential patterns of nucleolar association; AAPs and assembled capsids do not necessarily colocalize; AAPs are promiscuous in promoting capsid assembly of other serotypes, with the exception of AAP4, -5, -11, and -12; assembled AAV5, -8, and -9 capsids are excluded from the nucleolus, in contrast to the nucleolar enrichment of assembled AAV2 capsids; and, surprisingly, AAV4, -5, and -11 capsids are not dependent on AAP for assembly. These observations highlight the serotype-dependent heterogeneity of the capsid assembly process and challenge current notions about the role of AAP and the nucleolus in capsid assembly. IMPORTANCE Assembly-activating protein (AAP) is a recently discovered adeno-associated virus (AAV) protein that promotes capsid assembly and provides new opportunities for research in assembly. Previous studies on AAV serotype 2 (AAV2) showed that assembly takes place in the nucleolus and is dependent on AAP and that capsids colocalize with AAP in the nucleolus during the assembly process. However, through the investigation of 12 different AAV serotypes (AAV1 to -12), we find that AAP is not an essential requirement for capsid assembly of AAV4, -5, and -11, and AAP, assembled capsids, and the nucleolus do not colocalize for all the serotypes. In addition, we find that there are both serotype-restricted and serotype-promiscuous AAPs in their assembly roles. These findings challenge widely held beliefs about the importance of the nucleolus and AAP in AAV assembly and show the heterogeneous nature of the assembly process within the AAV family.
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Gil-Farina I, Schmidt M. Interaction of vectors and parental viruses with the host genome. Curr Opin Virol 2016; 21:35-40. [PMID: 27474966 DOI: 10.1016/j.coviro.2016.07.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2016] [Revised: 07/05/2016] [Accepted: 07/06/2016] [Indexed: 01/31/2023]
Abstract
Viral replication by acquisition of the host cell biology represents a central part of a virus life cycle. Thereby, integration into the host genome constitutes a successful strategy to ensure viral persistence and viruses have developed different mechanisms to integrate and benefit from cell's transcriptional and translational machinery. While lentiviral (e.g. HIV) integration is influenced by the chromatin landscape encountered upon nuclear entry, certain parvoviruses (e.g. AAV) integrate specifically within genomic regions bearing increasingly known sequence motifs. Gene therapy exploits these viral persistence strategies to achieve efficient and safe long-term transgene expression. Here we focus on two widely used vectors and their parental viruses, HIV and AAV, to discuss recent insights into lentiviral vector oncogenicity by alteration of endogenous transcripts as well as the unresolved AAV vectors genotoxic potential.
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Affiliation(s)
- Irene Gil-Farina
- Department of Translational Oncology, National Center for Tumor Diseases and German Cancer Research Center, 69120 Heidelberg, Germany
| | - Manfred Schmidt
- Department of Translational Oncology, National Center for Tumor Diseases and German Cancer Research Center, 69120 Heidelberg, Germany.
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28
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Both the Exact Target Site Sequence and a Long Poly(A) Tail Are Required for Precise Insertion of the 18S Ribosomal DNA-Specific Non-Long Terminal Repeat Retrotransposon R7Ag. Mol Cell Biol 2016; 36:1494-508. [PMID: 26976636 DOI: 10.1128/mcb.00970-15] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2015] [Accepted: 03/02/2016] [Indexed: 11/20/2022] Open
Abstract
Ribosomal elements (R elements) are site-specific non-long terminal repeat (LTR) retrotransposons that target ribosomal DNA (rDNA). To elucidate how R elements specifically access their target sites, we isolated and characterized the 18S rDNA-specific R element R7Ag from Anopheles gambiae Using an in vivo and ex vivo recombinant baculovirus retrotransposition system, we found that the exact host 18S rDNA sequence at the target site is essential for the precise insertion of R7Ag. In addition, a long poly(A) tail is necessary for the accurate initiation of R7Ag reverse transcription, a novel mechanism found in non-LTR elements. We further compared the subcellular localizations of proteins in R7Ag as well as R1Bm, another R element that targets 28S rDNA. Although the open reading frame 1 proteins (ORF1ps) of both R7Ag and R1Bm localized predominantly in the cytoplasm, ORF2 proteins (ORF2ps) colocalized in the nucleus with the nucleolar marker fibrillarin. The ORF1ps and ORF2ps of both R elements colocalized largely in the nuclear periphery and to a lesser extent within the nucleus. These results suggest that R7Ag and R1Bm proteins may access nucleolar rDNA targets in an ORF2p-dependent manner.
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