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Repression of the Chromatin-Tethering Domain of Murine Leukemia Virus p12. J Virol 2016; 90:11197-11207. [PMID: 27707926 DOI: 10.1128/jvi.01084-16] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Accepted: 09/28/2016] [Indexed: 12/28/2022] Open
Abstract
Murine leukemia virus (MLV) p12, encoded within Gag, binds the viral preintegration complex (PIC) to the mitotic chromatin. This acts to anchor the viral PIC in the nucleus as the nuclear envelope re-forms postmitosis. Mutations within the p12 C terminus (p12 PM13 to PM15) block early stages in viral replication. Within the p12 PM13 region (p12 60PSPMA65), our studies indicated that chromatin tethering was not detected when the wild-type (WT) p12 protein (M63) was expressed as a green fluorescent protein (GFP) fusion; however, constructs bearing p12-I63 were tethered. N-terminal truncations of the activated p12-I63-GFP indicated that tethering increased further upon deletion of p12 25DLLTEDPPPY34, which includes the late domain required for viral assembly. The p12 PM15 sequence (p12 70RREPP74) is critical for wild-type viral viability; however, virions bearing the PM15 mutation (p12 70AAAAA74) with a second M63I mutant were viable, with a titer 18-fold lower than that of the WT. The p12 M63I mutation amplified chromatin tethering and compensated for the loss of chromatin binding of p12 PM15. Rescue of the p12-M63-PM15 nonviable mutant with prototype foamy virus (PFV) and Kaposi's sarcoma herpesvirus (KSHV) tethering sequences confirmed the function of p1270-74 in chromatin binding. Minimally, full-strength tethering was seen with only p12 61SPIASRLRGRR71 fused to GFP. These results indicate that the p12 C terminus alone is sufficient for chromatin binding and that the presence of the p12 25DLLTEDPPPY34 motif in the N terminus suppresses the ability to tether. IMPORTANCE This study defines a regulatory mechanism controlling the differential roles of the MLV p12 protein in early and late replication. During viral assembly and egress, the late domain within the p12 N terminus functions to bind host vesicle release factors. During viral entry, the C terminus of p12 is required for tethering to host mitotic chromosomes. Our studies indicate that the p12 domain including the PPPY late sequence temporally represses the p12 chromatin tethering motif. Maximal p12 tethering was identified with only an 11-amino-acid minimal chromatin tethering motif encoded at p1261-71 Within this region, the p12-M63I substitution switches p12 into a tethering-competent state, partially rescuing the p12-PM15 tethering mutant. A model for how this conformational change regulates early versus late functions is presented.
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Yousef H, Morgenthaler A, Schlesinger C, Bugaj L, Conboy IM, Schaffer DV. Age-Associated Increase in BMP Signaling Inhibits Hippocampal Neurogenesis. Stem Cells 2016; 33:1577-88. [PMID: 25538007 DOI: 10.1002/stem.1943] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2014] [Accepted: 11/30/2014] [Indexed: 12/28/2022]
Abstract
Hippocampal neurogenesis, the product of resident neural stem cell proliferation and differentiation, persists into adulthood but decreases with organismal aging, which may contribute to the age-related decline in cognitive function. The mechanisms that underlie this decrease in neurogenesis are not well understood, although evidence in general indicates that extrinsic changes in an aged stem cell niche can contribute to functional decline in old stem cells. Bone morphogenetic protein (BMP) family members are intercellular signaling proteins that regulate stem and progenitor cell quiescence, proliferation, and differentiation in various tissues and are likewise critical regulators of neurogenesis in young adults. Here, we establish that BMP signaling increases significantly in old murine hippocampi and inhibits neural progenitor cell proliferation. Furthermore, direct in vivo attenuation of BMP signaling via genetic and transgenic perturbations in aged mice led to elevated neural stem cell proliferation, and subsequent neurogenesis, in old hippocampi. Such advances in our understanding of mechanisms underlying decreased hippocampal neurogenesis with age may offer targets for the treatment of age-related cognitive decline.
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Affiliation(s)
- Hanadie Yousef
- Department of Molecular and Cell Biology; Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305, USA; Center for Tissue Regeneration, Repair and Restoration, Veterans Administration Palo Alto Health Care System, Palo Alto, CA 94304, USA
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3
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Yousef H, Conboy MJ, Morgenthaler A, Schlesinger C, Bugaj L, Paliwal P, Greer C, Conboy IM, Schaffer D. Systemic attenuation of the TGF-β pathway by a single drug simultaneously rejuvenates hippocampal neurogenesis and myogenesis in the same old mammal. Oncotarget 2016; 6:11959-78. [PMID: 26003168 PMCID: PMC4494916 DOI: 10.18632/oncotarget.3851] [Citation(s) in RCA: 91] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Accepted: 04/24/2015] [Indexed: 12/18/2022] Open
Abstract
Stem cell function declines with age largely due to the biochemical imbalances in their tissue niches, and this work demonstrates that aging imposes an elevation in transforming growth factor β (TGF-β) signaling in the neurogenic niche of the hippocampus, analogous to the previously demonstrated changes in the myogenic niche of skeletal muscle with age. Exploring the hypothesis that youthful calibration of key signaling pathways may enhance regeneration of multiple old tissues, we found that systemically attenuating TGF-β signaling with a single drug simultaneously enhanced neurogenesis and muscle regeneration in the same old mice, findings further substantiated via genetic perturbations. At the levels of cellular mechanism, our results establish that the age-specific increase in TGF-β1 in the stem cell niches of aged hippocampus involves microglia and that such an increase is pro-inflammatory both in brain and muscle, as assayed by the elevated expression of β2 microglobulin (B2M), a component of MHC class I molecules. These findings suggest that at high levels typical of aged tissues, TGF-β1 promotes inflammation instead of its canonical role in attenuating immune responses. In agreement with this conclusion, inhibition of TGF-β1 signaling normalized B2M to young levels in both studied tissues.
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Affiliation(s)
- Hanadie Yousef
- Department of Molecular and Cellular Biology, UC Berkeley, Berkeley, CA, USA.,Current address: Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA
| | - Michael J Conboy
- Department of Bioengineering and California Institute for Quantitative Biosciences (QB3), UC Berkeley, Berkeley, CA, USA
| | - Adam Morgenthaler
- Department of Bioengineering and California Institute for Quantitative Biosciences (QB3), UC Berkeley, Berkeley, CA, USA
| | - Christina Schlesinger
- Department of Bioengineering and California Institute for Quantitative Biosciences (QB3), UC Berkeley, Berkeley, CA, USA
| | - Lukasz Bugaj
- Department of Bioengineering and California Institute for Quantitative Biosciences (QB3), UC Berkeley, Berkeley, CA, USA
| | - Preeti Paliwal
- Department of Bioengineering and California Institute for Quantitative Biosciences (QB3), UC Berkeley, Berkeley, CA, USA
| | - Christopher Greer
- Department of Bioengineering and California Institute for Quantitative Biosciences (QB3), UC Berkeley, Berkeley, CA, USA
| | - Irina M Conboy
- Department of Bioengineering and California Institute for Quantitative Biosciences (QB3), UC Berkeley, Berkeley, CA, USA
| | - David Schaffer
- Department of Bioengineering and California Institute for Quantitative Biosciences (QB3), UC Berkeley, Berkeley, CA, USA.,Department of Chemical and Biomolecular Engineering, UC Berkeley, Berkeley, CA, USA.,Helen Wills Neuroscience Institute, UC Berkeley, Berkeley, CA, USA
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4
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Viral DNA tethering domains complement replication-defective mutations in the p12 protein of MuLV Gag. Proc Natl Acad Sci U S A 2013; 110:9487-92. [PMID: 23661057 DOI: 10.1073/pnas.1221736110] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The p12 protein of murine leukemia virus (MuLV) group-specific antigen (Gag) is associated with the preintegration complex, and mutants of p12 (PM14) show defects in nuclear entry or retention. Here we show that p12 proteins engineered to encode peptide sequences derived from known viral tethering proteins can direct chromatin binding during the early phase of viral replication and rescue a lethal p12-PM14 mutant. Peptides studied included segments of Kaposi sarcoma herpesvirus latency-associated nuclear antigen (LANA)(1-23), human papillomavirus 8 E2, and prototype foamy virus chromatin-binding sequences. Amino acid substitutions in Kaposi sarcoma herpesvirus LANA and prototype foamy virus chromatin-binding sequences that blocked nucleosome association failed to rescue MuLV p12-PM14. Rescue by a larger LANA peptide, LANA(1-32), required second-site mutations that are predicted to reduce peptide binding affinity to chromosomes, suggesting that excessively high binding affinity interfered with Gag/p12 function. This is supported by confocal microscopy of chimeric p12-GFP fusion constructs showing the reverted proteins had weaker association to condensed mitotic chromosomes. Analysis of the integration-site selection of these chimeric viruses showed no significant change in integration profile compared with wild-type MuLV, suggesting release of the tethered p12 post mitosis, before viral integration.
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Knyazhanskaya ES, Kondrashina OV, Gottikh MB. Approaches to site-directed DNA integration based on transposases and retroviral integrases. Mol Biol 2011. [DOI: 10.1134/s0026893311060069] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Cohen S, Au S, Panté N. How viruses access the nucleus. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2010; 1813:1634-45. [PMID: 21167871 DOI: 10.1016/j.bbamcr.2010.12.009] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2010] [Revised: 11/24/2010] [Accepted: 12/08/2010] [Indexed: 10/25/2022]
Abstract
Many viruses depend on nuclear proteins for replication. Therefore, their viral genome must enter the nucleus of the host cell. In this review we briefly summarize the principles of nucleocytoplasmic transport, and then describe the diverse strategies used by viruses to deliver their genomes into the host nucleus. Some of the emerging mechanisms include: (1) nuclear entry during mitosis, when the nuclear envelope is disassembled, (2) viral genome release in the cytoplasm followed by entry of the genome through the nuclear pore complex (NPC), (3) capsid docking at the cytoplasmic side of the NPC, followed by genome release, (4) nuclear entry of intact capsids through the NPC, followed by genome release, and (5) nuclear entry via virus-induced disruption of the nuclear envelope. Which mechanism a particular virus uses depends on the size and structure of the virus, as well as the cellular cues used by the virus to trigger capsid disassembly and genome release. This article is part of a Special Issue entitled: Regulation of Signaling and Cellular Fate through Modulation of Nuclear Protein Import.
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Affiliation(s)
- Sarah Cohen
- Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, British Columbia, Canada
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The Gag cleavage product, p12, is a functional constituent of the murine leukemia virus pre-integration complex. PLoS Pathog 2010; 6:e1001183. [PMID: 21085616 PMCID: PMC2978732 DOI: 10.1371/journal.ppat.1001183] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2010] [Accepted: 10/07/2010] [Indexed: 02/08/2023] Open
Abstract
The p12 protein is a cleavage product of the Gag precursor of the murine leukemia virus (MLV). Specific mutations in p12 have been described that affect early stages of infection, rendering the virus replication-defective. Such mutants showed normal generation of genomic DNA but no formation of circular forms, which are markers of nuclear entry by the viral DNA. This suggested that p12 may function in early stages of infection but the precise mechanism of p12 action is not known. To address the function and follow the intracellular localization of the wt p12 protein, we generated tagged p12 proteins in the context of a replication-competent virus, which allowed for the detection of p12 at early stages of infection by immunofluorescence. p12 was found to be distributed to discrete puncta, indicative of macromolecular complexes. These complexes were localized to the cytoplasm early after infection, and thereafter accumulated adjacent to mitotic chromosomes. This chromosomal accumulation was impaired for p12 proteins with a mutation that rendered the virus integration-defective. Immunofluorescence demonstrated that intracellular p12 complexes co-localized with capsid, a known constituent of the MLV pre-integration complex (PIC), and immunofluorescence combined with fluorescent in situ hybridization (FISH) revealed co-localization of the p12 proteins with the incoming reverse transcribed viral DNA. Interactions of p12 with the capsid and with the viral DNA were also demonstrated by co-immunoprecipitation. These results imply that p12 proteins are components of the MLV PIC. Furthermore, a large excess of wt PICs did not rescue the defect in integration of PICs derived from mutant p12 particles, demonstrating that p12 exerts its function as part of this complex. Altogether, these results imply that p12 proteins are constituent of the MLV PIC and function in directing the PIC from the cytoplasm towards integration. All retroviruses reverse transcribe their RNA genome to a DNA copy in the cytoplasm of the infected cell. To be expressed, the viral genomic DNA has to travel to the cell nucleus and to integrate into the cellular chromosomes. This trafficking is governed by cellular and viral proteins that associate with the viral genome to form a ‘pre-integration complex’ (PIC), yet the full composition of this complex is unknown. Former studies showed that for the murine leukemia virus (MLV), mutations in a viral protein named p12 abrogate MLV infection, after reverse transcription and prior to the integration step, suggesting a role for this protein in early stages of infection. However, the precise mechanism of p12 action is not known. We combined microscopic, genetic and biochemical techniques to provide evidence that the p12 protein is part of the MLV PIC and that it exerts its function from within this complex. These analyses also suggest a role for p12 in the trafficking of the PIC from the cytoplasm to the chromosomes of the infected cell. Altogether, these findings highlight an important ‘building block’ of a complex that is essential for MLV infection.
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Lim KI, Klimczak R, Yu JH, Schaffer DV. Specific insertions of zinc finger domains into Gag-Pol yield engineered retroviral vectors with selective integration properties. Proc Natl Acad Sci U S A 2010; 107:12475-80. [PMID: 20616052 PMCID: PMC2906550 DOI: 10.1073/pnas.1001402107] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Retroviral vectors offer benefits of efficient delivery and stable gene expression; however, their clinical use raises the concerns of insertional mutagenesis and potential oncogenesis due to genomic integration preferences in transcriptional start sites (TSS). We have shifted the integration preferences of retroviral vectors by generating a library of viral variants with a DNA-binding domain inserted at random positions throughout murine leukemia virus Gag-Pol, then selecting for variants that are viable and exhibit altered integration properties. We found seven permissive zinc finger domain (ZFD) insertion sites throughout Gag-Pol, including within p12, reverse transcriptase, and integrase. Comprehensive genome integration analysis showed that several ZFD insertions yielded retroviral vector variants with shifted integration patterns that did not favor TSS. Furthermore, integration site analysis revealed selective integration for numerous mutants. For example, two retroviral variants with a given ZFD at appropriate positions in Gag-Pol strikingly integrated primarily into four common sites out of 3.1 x 10(9) possible human genome locations (P = 4.6 x 10(-29)). Our findings demonstrate that insertion of DNA-binding motifs into multiple locations in Gag-Pol can make considerable progress toward engineering safer retroviral vectors that integrate into a significantly narrowed pool of sites on human genome and overcome the preference for TSS.
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Affiliation(s)
- Kwang-il Lim
- Departments of Chemical Engineering and Bioengineering and The Helen Wills Neuroscience Institute, University of California, 278 Stanley Hall, Berkeley, CA 94720-3220
| | - Ryan Klimczak
- Departments of Chemical Engineering and Bioengineering and The Helen Wills Neuroscience Institute, University of California, 278 Stanley Hall, Berkeley, CA 94720-3220
| | - Julie H. Yu
- Departments of Chemical Engineering and Bioengineering and The Helen Wills Neuroscience Institute, University of California, 278 Stanley Hall, Berkeley, CA 94720-3220
| | - David V. Schaffer
- Departments of Chemical Engineering and Bioengineering and The Helen Wills Neuroscience Institute, University of California, 278 Stanley Hall, Berkeley, CA 94720-3220
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9
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Carlson ME, Conboy MJ, Hsu M, Barchas L, Jeong J, Agrawal A, Mikels AJ, Agrawal S, Schaffer DV, Conboy IM. Relative roles of TGF-beta1 and Wnt in the systemic regulation and aging of satellite cell responses. Aging Cell 2009; 8:676-89. [PMID: 19732043 PMCID: PMC2783265 DOI: 10.1111/j.1474-9726.2009.00517.x] [Citation(s) in RCA: 190] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Muscle stem (satellite) cells are relatively resistant to cell-autonomous aging. Instead, their endogenous signaling profile and regenerative capacity is strongly influenced by the aged P-Smad3, differentiated niche, and by the aged circulation. With respect to muscle fibers, we previously established that a shift from active Notch to excessive transforming growth factor-beta (TGF-β) induces CDK inhibitors in satellite cells, thereby interfering with productive myogenic responses. In contrast, the systemic inhibitor of muscle repair, elevated in old sera, was suggested to be Wnt. Here, we examined the age-dependent myogenic activity of sera TGF-β1, and its potential cross-talk with systemic Wnt. We found that sera TGF-β1 becomes elevated within aged humans and mice, while systemic Wnt remained undetectable in these species. Wnt also failed to inhibit satellite cell myogenicity, while TGF-β1 suppressed regenerative potential in a biphasic fashion. Intriguingly, young levels of TGF-β1 were inhibitory and young sera suppressed myogenesis if TGF-β1 was activated. Our data suggest that platelet-derived sera TGF-β1 levels, or endocrine TGF-β1 levels, do not explain the age-dependent inhibition of muscle regeneration by this cytokine. In vivo, TGF-β neutralizing antibody, or a soluble decoy, failed to reduce systemic TGF-β1 and rescue myogenesis in old mice. However, muscle regeneration was improved by the systemic delivery of a TGF-β receptor kinase inhibitor, which attenuated TGF-β signaling in skeletal muscle. Summarily, these findings argue against the endocrine path of a TGF-β1-dependent block on muscle regeneration, identify physiological modalities of age-imposed changes in TGF-β1, and introduce new therapeutic strategies for the broad restoration of aged organ repair.
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Affiliation(s)
- Morgan E Carlson
- Department of Bioengineering, University of California-Berkeley, Berkeley, CA 94720, USA.
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10
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Capsid modification of adeno-associated virus and tumor targeting gene therapy. Sci Bull (Beijing) 2008. [DOI: 10.1007/s11434-008-0487-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Abstract
Viruses can be engineered to efficiently deliver exogenous genes, but their natural gene delivery properties often fail to meet human therapeutic needs. Therefore, engineering viral vectors with new properties, including enhanced targeting abilities and resistance to immune responses, is a growing area of research. This review discusses protein engineering approaches to generate viral vectors with novel gene delivery capabilities. Rational design of viral vectors has yielded successful advances in vitro, and to an extent in vivo. However, there is often insufficient knowledge of viral structure-function relationships to reengineer existing functions or create new capabilities, such as virus-cell interactions, whose molecular basis is distributed throughout the primary sequence of the viral proteins. Therefore, high-throughput library and directed evolution methods offer alternative approaches to engineer viral vectors with desired properties. Parallel and integrated efforts in rational and library-based design promise to aid the translation of engineered viral vectors toward the clinic.
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Affiliation(s)
- David V Schaffer
- The Department of Chemical Engineering, the Department of Bioengineering, and The Helen Wills Neuroscience Institute, University of California, Berkeley, CA 94720-3220, USA.
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12
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Koerber JT, Jang JH, Schaffer DV. DNA shuffling of adeno-associated virus yields functionally diverse viral progeny. Mol Ther 2008; 16:1703-9. [PMID: 18728640 PMCID: PMC2683895 DOI: 10.1038/mt.2008.167] [Citation(s) in RCA: 130] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Adeno-associated virus (AAV) vectors are extremely effective gene-delivery vehicles for a broad range of applications. However, the therapeutic efficacy of these and other vectors is currently limited by barriers to safe, efficient gene delivery, including pre-existing antiviral immunity, and infection of off-target cells. Recently, we have implemented directed evolution of AAV, involving the generation of randomly mutagenized viral libraries based on serotype 2 and high-throughput selection, to engineer enhanced viral vectors. Here, we significantly extend this capability by performing high-efficiency in vitro recombination to create a large (10(7)), diverse library of random chimeras of numerous parent AAV serotypes (AAV1, 2, 4-6, 8, and 9). In order to analyze the extent to which such highly chimeric viruses can be viable, we selected the library for efficient viral packaging and infection, and successfully recovered numerous novel chimeras. These new viruses exhibited a broad range of cell tropism both in vitro and in vivo and enhanced resistance to human intravenous immunoglobulin (IVIG), highlighting numerous functional differences between these chimeras and their parent serotypes. Thus, directed evolution can potentially yield unlimited numbers of new AAV variants with novel gene-delivery properties, and subsequent analysis of these variants can further extend basic knowledge of AAV biology.
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Affiliation(s)
- James T Koerber
- Department of Chemical Engineering, University of California at Berkeley, Berkeley, California 94720-1462, USA
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Jang JH, Lim KI, Schaffer DV. Library selection and directed evolution approaches to engineering targeted viral vectors. Biotechnol Bioeng 2007; 98:515-24. [PMID: 17614321 DOI: 10.1002/bit.21541] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Gene therapy, to delivery of genetic material to a patient for therapeutic benefit, has significant promise for translating basic knowledge of disease mechanism into biomedical treatments. The clinical development of the field has been slowed, however, by the need for improvements in the properties and capabilities of gene delivery vehicles. Vehicles based on viruses offer the potential for efficient gene delivery, but because viruses did not evolve to serve human therapeutic needs, many of their properties require significant improvement, including their safety, efficiency, and capacity for targeted gene delivery. Since viruses are highly complex biological entities, engineering such properties at the molecular level can be challenging. However, there has been significant progress in developing approaches that mimic the mechanisms by which viruses arose in the first place. In particular, library-based selection, the generation of one diverse genetic library and selection for new properties, and directed evolution, based on the multiple rounds of library generation and selection for iterative improvement of function, have strong potential in engineering novel properties into these complex biomolecular assemblies. This review will discuss progress in the application of peptide display, library selection, and directed evolution technologies toward engineering vectors based on retrovirus, adeno-associated virus, and adenovirus that are capable of targeted delivery to specific cell types. In addition to creating biomedically useful products, these approaches have future potential to yield novel insights into viral structure-function relationships.
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Affiliation(s)
- Jae-Hyung Jang
- Department of Chemical Engineering and Helen Wills Neuroscience Institute, University of California, 201 Gilman Hall, Berkeley, California 94720, USA
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Kwon I, Schaffer DV. Designer gene delivery vectors: molecular engineering and evolution of adeno-associated viral vectors for enhanced gene transfer. Pharm Res 2007; 25:489-99. [PMID: 17763830 PMCID: PMC2265771 DOI: 10.1007/s11095-007-9431-0] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2007] [Accepted: 08/03/2007] [Indexed: 12/23/2022]
Abstract
Gene delivery vectors based on adeno-associated virus (AAV) are highly promising due to several desirable features of this parent virus, including a lack of pathogenicity, efficient infection of dividing and non-dividing cells, and sustained maintenance of the viral genome. However, several problems should be addressed to enhance the utility of AAV vectors, particularly those based on AAV2, the best characterized AAV serotype. First, altering viral tropism would be advantageous for broadening its utility in various tissue or cell types. In response to this need, vector pseudotyping, mosaic capsids, and targeting ligand insertion into the capsid have shown promise for altering AAV specificity. In addition, library selection and directed evolution have recently emerged as promising approaches to modulate AAV tropism despite limited knowledge of viral structure-function relationships. Second, pre-existing immunity to AAV must be addressed for successful clinical application of AAV vectors. "Shielding" polymers, site-directed mutagenesis, and alternative AAV serotypes have shown success in avoiding immune neutralization. Furthermore, directed evolution of the AAV capsid is a high throughput approach that has yielded vectors with substantial resistance to neutralizing antibodies. Molecular engineering and directed evolution of AAV vectors therefore offer promise for generating 'designer' gene delivery vectors with enhanced properties.
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Affiliation(s)
- Inchan Kwon
- Department of Chemical Engineering and Helen Wills Neuroscience Institute, University of California, 201 Gilman Hall, Berkeley, California 94720-1462 USA
| | - David V. Schaffer
- Department of Chemical Engineering and Helen Wills Neuroscience Institute, University of California, 201 Gilman Hall, Berkeley, California 94720-1462 USA
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Fassati A. HIV infection of non-dividing cells: a divisive problem. Retrovirology 2006; 3:74. [PMID: 17067381 PMCID: PMC1635064 DOI: 10.1186/1742-4690-3-74] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2006] [Accepted: 10/26/2006] [Indexed: 02/07/2023] Open
Abstract
Understanding how lentiviruses can infect terminally differentiated, non-dividing cells has proven a very complex and controversial problem. It is, however, a problem worth investigating, for it is central to HIV-1 transmission and AIDS pathogenesis. Here I shall attempt to summarise what is our current understanding for HIV-1 infection of non-dividing cells. In some cases I shall also attempt to make sense of controversies in the field and advance one or two modest proposals.
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Affiliation(s)
- Ariberto Fassati
- Wohl Virion Centre and MRC-UCL Centre for Medical Molecular Virology, Division of Infection and Immunity, University College London, 46 Cleveland Street, London W1T 4JF, UK.
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