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Grandgenett DP, Engelman AN. Brief Histories of Retroviral Integration Research and Associated International Conferences. Viruses 2024; 16:604. [PMID: 38675945 PMCID: PMC11054761 DOI: 10.3390/v16040604] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2024] [Revised: 04/05/2024] [Accepted: 04/10/2024] [Indexed: 04/28/2024] Open
Abstract
The field of retroviral integration research has a long history that started with the provirus hypothesis and subsequent discoveries of the retroviral reverse transcriptase and integrase enzymes. Because both enzymes are essential for retroviral replication, they became valued targets in the effort to discover effective compounds to inhibit HIV-1 replication. In 2007, the first integrase strand transfer inhibitor was licensed for clinical use, and subsequently approved second-generation integrase inhibitors are now commonly co-formulated with reverse transcriptase inhibitors to treat people living with HIV. International meetings specifically focused on integrase and retroviral integration research first convened in 1995, and this paper is part of the Viruses Special Issue on the 7th International Conference on Retroviral Integration, which was held in Boulder Colorado in the summer of 2023. Herein, we overview key historical developments in the field, especially as they pertain to the development of the strand transfer inhibitor drug class. Starting from the mid-1990s, research advancements are presented through the lens of the international conferences. Our overview highlights the impact that regularly scheduled, subject-specific international meetings can have on community-building and, as a result, on field-specific collaborations and scientific advancements.
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Affiliation(s)
- Duane P. Grandgenett
- Department of Molecular Microbiology and Immunology, School of Medicine, Saint Louis University, St. Louis, MO 63104, USA
| | - Alan N. Engelman
- Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, MA 02215, USA
- Department of Medicine, Harvard Medical School, Boston, MA 02115, USA
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2
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Richetta C, Tu NQ, Delelis O. Different Pathways Conferring Integrase Strand-Transfer Inhibitors Resistance. Viruses 2022; 14:v14122591. [PMID: 36560595 PMCID: PMC9785060 DOI: 10.3390/v14122591] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Revised: 11/17/2022] [Accepted: 11/19/2022] [Indexed: 11/23/2022] Open
Abstract
Integrase Strand Transfer Inhibitors (INSTIs) are currently used as the most effective therapy in the treatment of human immunodeficiency virus (HIV) infections. Raltegravir (RAL) and Elvitegravir (EVG), the first generation of INSTIs used successfully in clinical treatment, are susceptible to the emergence of viral resistance and have a high rate of cross-resistance. To counteract these resistant mutants, second-generation INSTI drugs have been developed: Dolutegravir (DTG), Cabotegravir (CAB), and Bictegravir (BIC). However, HIV is also able to develop resistance mechanisms against the second-generation of INSTIs. This review describes the mode of action of INSTIs and then summarizes and evaluates some typical resistance mutations, such as substitution and insertion mutations. The role of unintegrated viral DNA is also discussed as a new pathway involved in conferring resistance to INSTIs. This allows us to have a more detailed understanding of HIV resistance to these inhibitors, which may contribute to the development of new INSTIs in the future.
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HIV-1 Preintegration Complex Preferentially Integrates the Viral DNA into Nucleosomes Containing Trimethylated Histone 3-Lysine 36 Modification and Flanking Linker DNA. J Virol 2022; 96:e0101122. [PMID: 36094316 PMCID: PMC9517705 DOI: 10.1128/jvi.01011-22] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
HIV-1 DNA is preferentially integrated into chromosomal hot spots by the preintegration complex (PIC). To understand the mechanism, we measured the DNA integration activity of PICs-extracted from infected cells-and intasomes, biochemically assembled PIC substructures using a number of relevant target substrates. We observed that PIC-mediated integration into human chromatin is preferred compared to genomic DNA. Surprisingly, nucleosomes lacking histone modifications were not preferred integration compared to the analogous naked DNA. Nucleosomes containing the trimethylated histone 3 lysine 36 (H3K36me3), an epigenetic mark linked to active transcription, significantly stimulated integration, but the levels remained lower than the naked DNA. Notably, H3K36me3-modified nucleosomes with linker DNA optimally supported integration mediated by the PIC but not by the intasome. Interestingly, optimal intasome-mediated integration required the cellular cofactor LEDGF. Unexpectedly, LEDGF minimally affected PIC-mediated integration into naked DNA but blocked integration into nucleosomes. The block for the PIC-mediated integration was significantly relieved by H3K36me3 modification. Mapping the integration sites in the preferred substrates revealed that specific features of the nucleosome-bound DNA are preferred for integration, whereas integration into naked DNA was random. Finally, biochemical and genetic studies demonstrate that DNA condensation by the H1 protein dramatically reduces integration, providing further evidence that features inherent to the open chromatin are preferred for HIV-1 integration. Collectively, these results identify the optimal target substrate for HIV-1 integration, report a mechanistic link between H3K36me3 and integration preference, and importantly, reveal distinct mechanisms utilized by the PIC for integration compared to the intasomes. IMPORTANCE HIV-1 infection is dependent on integration of the viral DNA into the host chromosomes. The preintegration complex (PIC) containing the viral DNA, the virally encoded integrase (IN) enzyme, and other viral/host factors carries out HIV-1 integration. HIV-1 integration is not dependent on the target DNA sequence, and yet the viral DNA is selectively inserted into specific "hot spots" of human chromosomes. A growing body of literature indicates that structural features of the human chromatin are important for integration targeting. However, the mechanisms that guide the PIC and enable insertion of the PIC-associated viral DNA into specific hot spots of the human chromosomes are not fully understood. In this study, we describe a biochemical mechanism for the preference of the HIV-1 DNA integration into open chromatin. Furthermore, our study defines a direct role for the histone epigenetic mark H3K36me3 in HIV-1 integration preference and identify an optimal substrate for HIV-1 PIC-mediated viral DNA integration.
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Jóźwik IK, Li W, Zhang DW, Wong D, Grawenhoff J, Ballandras-Colas A, Aiyer S, Cherepanov P, Engelman A, Lyumkis D. B-to-A transition in target DNA during retroviral integration. Nucleic Acids Res 2022; 50:8898-8918. [PMID: 35947647 PMCID: PMC9410886 DOI: 10.1093/nar/gkac644] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Revised: 07/06/2022] [Accepted: 07/19/2022] [Indexed: 01/21/2023] Open
Abstract
Integration into host target DNA (tDNA), a hallmark of retroviral replication, is mediated by the intasome, a multimer of integrase (IN) assembled on viral DNA (vDNA) ends. To ascertain aspects of tDNA recognition during integration, we have solved the 3.5 Å resolution cryo-EM structure of the mouse mammary tumor virus (MMTV) strand transfer complex (STC) intasome. The tDNA adopts an A-like conformation in the region encompassing the sites of vDNA joining, which exposes the sugar-phosphate backbone for IN-mediated strand transfer. Examination of existing retroviral STC structures revealed conservation of A-form tDNA in the analogous regions of these complexes. Furthermore, analyses of sequence preferences in genomic integration sites selectively targeted by six different retroviruses highlighted consistent propensity for A-philic sequences at the sites of vDNA joining. Our structure additionally revealed several novel MMTV IN-DNA interactions, as well as contacts seen in prior STC structures, including conserved Pro125 and Tyr149 residues interacting with tDNA. In infected cells, Pro125 substitutions impacted the global pattern of MMTV integration without significantly altering local base sequence preferences at vDNA insertion sites. Collectively, these data advance our understanding of retroviral intasome structure and function, as well as factors that influence patterns of vDNA integration in genomic DNA.
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Affiliation(s)
- Ilona K Jóźwik
- The Salk Institute for Biological Studies, La Jolla, CA 92037, USA
| | - Wen Li
- Department of Cancer Immunology and Virology, Dana-Farber Cancer Center, Boston, MA 02215, USA,Department of Medicine, Harvard Medical School, Boston, MA 02115, USA
| | - Da-Wei Zhang
- Department of Cancer Immunology and Virology, Dana-Farber Cancer Center, Boston, MA 02215, USA,Department of Medicine, Harvard Medical School, Boston, MA 02115, USA,Institute of Bioinformatics and Medical Engineering, School of Electrical and Information Engineering, Jiangsu University of Technology, Changzhou 213001, China
| | - Doris Wong
- Department of Cancer Immunology and Virology, Dana-Farber Cancer Center, Boston, MA 02215, USA
| | - Julia Grawenhoff
- Department of Cancer Immunology and Virology, Dana-Farber Cancer Center, Boston, MA 02215, USA
| | | | - Sriram Aiyer
- The Salk Institute for Biological Studies, La Jolla, CA 92037, USA
| | - Peter Cherepanov
- Chromatin Structure and Mobile DNA Laboratory, The Francis Crick Institute, London NW1 1AT, UK,Department of Infectious Disease, St-Mary's Campus, Imperial College London, London W2 1PG, UK
| | - Alan N Engelman
- Correspondence may also be addressed to Alan N. Engelman. Tel: +1 617 632 4361; Fax: +1 617 632 4338;
| | - Dmitry Lyumkis
- To whom correspondence should be addressed. Tel: +1 858 453 4100 (Ext 1155);
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5
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Abstract
Chromosome organisation is increasingly recognised as an essential component of genome regulation, cell fate and cell health. Within the realm of transposable elements (TEs) however, the spatial information of how genomes are folded is still only rarely integrated in experimental studies or accounted for in modelling. Whilst polymer physics is recognised as an important tool to understand the mechanisms of genome folding, in this commentary we discuss its potential applicability to aspects of TE biology. Based on recent works on the relationship between genome organisation and TE integration, we argue that existing polymer models may be extended to create a predictive framework for the study of TE integration patterns. We suggest that these models may offer orthogonal and generic insights into the integration profiles (or "topography") of TEs across organisms. In addition, we provide simple polymer physics arguments and preliminary molecular dynamics simulations of TEs inserting into heterogeneously flexible polymers. By considering this simple model, we show how polymer folding and local flexibility may generically affect TE integration patterns. The preliminary discussion reported in this commentary is aimed to lay the foundations for a large-scale analysis of TE integration dynamics and topography as a function of the three-dimensional host genome.
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Michieletto D, Lusic M, Marenduzzo D, Orlandini E. Physical principles of retroviral integration in the human genome. Nat Commun 2019; 10:575. [PMID: 30718508 PMCID: PMC6362086 DOI: 10.1038/s41467-019-08333-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Accepted: 12/13/2018] [Indexed: 12/26/2022] Open
Abstract
Certain retroviruses, including HIV, insert their DNA in a non-random fraction of the host genome via poorly understood selection mechanisms. Here, we develop a biophysical model for retroviral integration as stochastic and quasi-equilibrium topological reconnections between polymers. We discover that physical effects, such as DNA accessibility and elasticity, play important and universal roles in this process. Our simulations predict that integration is favoured within nucleosomal and flexible DNA, in line with experiments, and that these biases arise due to competing energy barriers associated with DNA deformations. By considering a long chromosomal region in human T-cells during interphase, we discover that at these larger scales integration sites are predominantly determined by chromatin accessibility. Finally, we propose and solve a reaction-diffusion problem that recapitulates the distribution of HIV hot-spots within T-cells. With few generic assumptions, our model can rationalise experimental observations and identifies previously unappreciated physical contributions to retroviral integration site selection.
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Affiliation(s)
- D. Michieletto
- SUPA, School of Physics and Astronomy, University of Edinburgh, Peter Guthrie Tait Road, Edinburgh, EH9 3FD UK
| | - M. Lusic
- Department of Infectious Diseases, Integrative Virology, Heidelberg University Hospital and German Center for Infection Research, Im Neuenheimer Feld 344, 69120 Heidelberg, Germany
| | - D. Marenduzzo
- SUPA, School of Physics and Astronomy, University of Edinburgh, Peter Guthrie Tait Road, Edinburgh, EH9 3FD UK
| | - E. Orlandini
- Dipartimento di Fisica e Astronomia and Sezione INFN, Universitá di Padova, Via Marzolo 8, 35131 Padova, Italy
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Prototype foamy virus intasome aggregation is mediated by outer protein domains and prevented by protocatechuic acid. Sci Rep 2019; 9:132. [PMID: 30644416 PMCID: PMC6333793 DOI: 10.1038/s41598-018-36725-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Accepted: 11/23/2018] [Indexed: 12/01/2022] Open
Abstract
The integrase (IN) enzyme of retrovirus prototype foamy virus (PFV) consists of four domains: amino terminal extension (NED), amino terminus (NTD), catalytic core (CCD), and carboxyl terminus domains (CTD). A tetramer of PFV IN with two viral DNA ends forms the functional intasome. Two inner monomers are catalytically active while the CCDs of the two outer monomers appear to play only structural roles. The NED, NTD, and CTD of the outer monomers are disordered in intasome structures. Truncation mutants reveal that integration to a supercoiled plasmid increases without the outer monomer CTDs present. Deletion of the outer CTDs enhances the lifetime of the intasome compared to full length (FL) IN or deletion of the outer monomer NTDs. High ionic strength buffer or several additives, particularly protocatechuic acid (PCA), enhance the integration of FL intasomes by preventing aggregation. These data confirm previous studies suggesting the disordered outer domains of PFV intasomes are not required for intasome assembly or integration. Instead, the outer CTDs contribute to aggregation of PFV intasomes which may be inhibited by high ionic strength buffer or the small molecule PCA.
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Abstract
Replication-defective retroviral vectors have been used for more than 25 years as a tool for efficient and stable insertion of therapeutic transgenes in human cells. Patients suffering from severe genetic diseases have been successfully treated by transplantation of autologous hematopoietic stem-progenitor cells (HSPCs) transduced with retroviral vectors, and the first of this class of therapies, Strimvelis, has recently received market authorization in Europe. Some clinical trials, however, resulted in severe adverse events caused by vector-induced proto-oncogene activation, which showed that retroviral vectors may retain a genotoxic potential associated to proviral integration in the human genome. The adverse events sparked a renewed interest in the biology of retroviruses, which led in a few years to a remarkable understanding of the molecular mechanisms underlying retroviral integration site selection within mammalian genomes. This review summarizes the current knowledge on retrovirus-host interactions at the genomic level, and the peculiar mechanisms by which different retroviruses, and their related gene transfer vectors, integrate in, and interact with, the human genome. This knowledge provides the basis for the development of safer and more efficacious retroviral vectors for human gene therapy.
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Affiliation(s)
| | - Fulvio Mavilio
- Department of Life Sciences, University of Modena and Reggio Emilia, 41125 Modena, Italy
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9
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Integration site selection by retroviruses and transposable elements in eukaryotes. Nat Rev Genet 2017; 18:292-308. [PMID: 28286338 DOI: 10.1038/nrg.2017.7] [Citation(s) in RCA: 145] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Transposable elements and retroviruses are found in most genomes, can be pathogenic and are widely used as gene-delivery and functional genomics tools. Exploring whether these genetic elements target specific genomic sites for integration and how this preference is achieved is crucial to our understanding of genome evolution, somatic genome plasticity in cancer and ageing, host-parasite interactions and genome engineering applications. High-throughput profiling of integration sites by next-generation sequencing, combined with large-scale genomic data mining and cellular or biochemical approaches, has revealed that the insertions are usually non-random. The DNA sequence, chromatin and nuclear context, and cellular proteins cooperate in guiding integration in eukaryotic genomes, leading to a remarkable diversity of insertion site distribution and evolutionary strategies.
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10
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Grawenhoff J, Engelman AN. Retroviral integrase protein and intasome nucleoprotein complex structures. World J Biol Chem 2017; 8:32-44. [PMID: 28289517 PMCID: PMC5329712 DOI: 10.4331/wjbc.v8.i1.32] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Revised: 12/24/2016] [Accepted: 01/14/2017] [Indexed: 02/05/2023] Open
Abstract
Retroviral replication proceeds through the integration of a DNA copy of the viral RNA genome into the host cellular genome, a process that is mediated by the viral integrase (IN) protein. IN catalyzes two distinct chemical reactions: 3’-processing, whereby the viral DNA is recessed by a di- or trinucleotide at its 3’-ends, and strand transfer, in which the processed viral DNA ends are inserted into host chromosomal DNA. Although IN has been studied as a recombinant protein since the 1980s, detailed structural understanding of its catalytic functions awaited high resolution structures of functional IN-DNA complexes or intasomes, initially obtained in 2010 for the spumavirus prototype foamy virus (PFV). Since then, two additional retroviral intasome structures, from the α-retrovirus Rous sarcoma virus (RSV) and β-retrovirus mouse mammary tumor virus (MMTV), have emerged. Here, we briefly review the history of IN structural biology prior to the intasome era, and then compare the intasome structures of PFV, MMTV and RSV in detail. Whereas the PFV intasome is characterized by a tetrameric assembly of IN around the viral DNA ends, the newer structures harbor octameric IN assemblies. Although the higher order architectures of MMTV and RSV intasomes differ from that of the PFV intasome, they possess remarkably similar intasomal core structures. Thus, retroviral integration machineries have adapted evolutionarily to utilize disparate IN elements to construct convergent intasome core structures for catalytic function.
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The Multifaceted Contributions of Chromatin to HIV-1 Integration, Transcription, and Latency. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2016; 328:197-252. [PMID: 28069134 DOI: 10.1016/bs.ircmb.2016.08.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The capacity of the human immunodeficiency virus (HIV-1) to establish latent infections constitutes a major barrier to the development of a cure for HIV-1. In latent infection, replication competent HIV-1 provirus is integrated within the host genome but remains silent, masking the infected cells from the activity of the host immune response. Despite the progress in elucidating the molecular players that regulate HIV-1 gene expression, the mechanisms driving the establishment and maintenance of latency are still not fully understood. Transcription from the HIV-1 genome occurs in the context of chromatin and is subjected to the same regulatory mechanisms that drive cellular gene expression. Much like in eukaryotic genes, the nucleosomal landscape of the HIV-1 promoter and its position within genomic chromatin are determinants of its transcriptional activity. Understanding the multilayered chromatin-mediated mechanisms that underpin HIV-1 integration and expression is of utmost importance for the development of therapeutic strategies aimed at reducing the pool of latently infected cells. In this review, we discuss the impact of chromatin structure on viral integration, transcriptional regulation and latency, and the host factors that influence HIV-1 replication by regulating chromatin organization. Finally, we describe therapeutic strategies under development to target the chromatin-HIV-1 interplay.
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Pasi M, Mornico D, Volant S, Juchet A, Batisse J, Bouchier C, Parissi V, Ruff M, Lavery R, Lavigne M. DNA minicircles clarify the specific role of DNA structure on retroviral integration. Nucleic Acids Res 2016; 44:7830-47. [PMID: 27439712 PMCID: PMC5027509 DOI: 10.1093/nar/gkw651] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Accepted: 07/11/2016] [Indexed: 01/26/2023] Open
Abstract
Chromatin regulates the selectivity of retroviral integration into the genome of infected cells. At the nucleosome level, both histones and DNA structure are involved in this regulation. We propose a strategy that allows to specifically study a single factor: the DNA distortion induced by the nucleosome. This strategy relies on mimicking this distortion using DNA minicircles (MCs) having a fixed rotational orientation of DNA curvature, coupled with atomic-resolution modeling. Contrasting MCs with linear DNA fragments having identical sequences enabled us to analyze the impact of DNA distortion on the efficiency and selectivity of integration. We observed a global enhancement of HIV-1 integration in MCs and an enrichment of integration sites in the outward-facing DNA major grooves. Both of these changes are favored by LEDGF/p75, revealing a new, histone-independent role of this integration cofactor. PFV integration is also enhanced in MCs, but is not associated with a periodic redistribution of integration sites, thus highlighting its distinct catalytic properties. MCs help to separate the roles of target DNA structure, histone modifications and integrase (IN) cofactors during retroviral integration and to reveal IN-specific regulation mechanisms.
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Affiliation(s)
- Marco Pasi
- MMSB UMR5086 University of Lyon I/CNRS, Institut de Biologie et Chimie des Protéines, 7 passage du Vercors, Lyon 69367, France
| | - Damien Mornico
- Institut Pasteur-Bioinformatics and Biostatistics Hub-C3BI, USR 3756 IP-CNRS, Paris 75015, France
| | - Stevenn Volant
- Institut Pasteur-Bioinformatics and Biostatistics Hub-C3BI, USR 3756 IP-CNRS, Paris 75015, France
| | - Anna Juchet
- Institut Pasteur, Unité de Virologie Moléculaire et Vaccinologie, UMR 3569 IP-CNRS, Paris 75015, France
| | - Julien Batisse
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Dpt de Biologie Structurale Intégrative, UDS, U596 INSERM, UMR7104 CNRS, Illkirch 67400, France
| | - Christiane Bouchier
- Institut Pasteur, PF1, Plate-forme Génomique-Pôle Biomics, Citech, Paris 75015, France
| | - Vincent Parissi
- Laboratoire de Microbiologie Fondamentale et Pathogénicité, UMR 5234 CNRS-Université de Bordeaux, Bordeaux 33000, France
| | - Marc Ruff
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Dpt de Biologie Structurale Intégrative, UDS, U596 INSERM, UMR7104 CNRS, Illkirch 67400, France
| | - Richard Lavery
- MMSB UMR5086 University of Lyon I/CNRS, Institut de Biologie et Chimie des Protéines, 7 passage du Vercors, Lyon 69367, France
| | - Marc Lavigne
- Institut Pasteur, Unité de Virologie Moléculaire et Vaccinologie, UMR 3569 IP-CNRS, Paris 75015, France
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13
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Lopez MA, Mackler RM, Yoder KE. Removal of nuclease contamination during purification of recombinant prototype foamy virus integrase. J Virol Methods 2016; 235:134-138. [PMID: 27269588 DOI: 10.1016/j.jviromet.2016.06.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Revised: 05/31/2016] [Accepted: 06/04/2016] [Indexed: 10/21/2022]
Abstract
Retroviral infection requires integration of the viral genome into the host genome. Recombinant integrase proteins may be purified following bacterial expression. A bulk biochemical assay of integrase function relies on the conversion of supercoiled plasmids to linear or relaxed circles. Single molecule molecular tweezer assays of integrase also evaluate the conversion of supercoiled DNA to nicked and broken species. A bacterial nuclease that co-purifies with retroviral integrase may affect the quantitation of integration activity in bulk or single molecule assays. During purification of retroviral integrase from bacteria, fractions may be screened for contaminating nuclease activity. In order to efficiently separate the nuclease from integrase, the binding affinities of each protein must differ. We find that a co-purifying nuclease may be efficiently separated from integrase based on heparin affinity, but not ionic affinity.
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Affiliation(s)
- Miguel A Lopez
- Molecular Virology, Immunology, and Medical Genetics, The Ohio State University College of Medicine, Columbus, OH 43210, United States
| | - Randi M Mackler
- Molecular Virology, Immunology, and Medical Genetics, The Ohio State University College of Medicine, Columbus, OH 43210, United States
| | - Kristine E Yoder
- Molecular Virology, Immunology, and Medical Genetics, The Ohio State University College of Medicine, Columbus, OH 43210, United States.
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14
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Abstract
The retroviral integrases are virally encoded, specialized recombinases that catalyze the insertion of viral DNA into the host cell's DNA, a process that is essential for virus propagation. We have learned a great deal since the existence of an integrated form of retroviral DNA (the provirus) was first proposed by Howard Temin in 1964. Initial studies focused on the genetics and biochemistry of avian and murine virus DNA integration, but the pace of discovery increased substantially with advances in technology, and an influx of investigators focused on the human immunodeficiency virus. We begin with a brief account of the scientific landscape in which some of the earliest discoveries were made, and summarize research that led to our current understanding of the biochemistry of integration. A more detailed account of recent analyses of integrase structure follows, as they have provided valuable insights into enzyme function and raised important new questions.
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Affiliation(s)
- Mark D Andrake
- Institute for Cancer Research, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111; ,
| | - Anna Marie Skalka
- Institute for Cancer Research, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111; ,
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15
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Serrao E, Engelman AN. Sites of retroviral DNA integration: From basic research to clinical applications. Crit Rev Biochem Mol Biol 2015; 51:26-42. [PMID: 26508664 DOI: 10.3109/10409238.2015.1102859] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
One of the most crucial steps in the life cycle of a retrovirus is the integration of the viral DNA (vDNA) copy of the RNA genome into the genome of an infected host cell. Integration provides for efficient viral gene expression as well as for the segregation of viral genomes to daughter cells upon cell division. Some integrated viruses are not well expressed, and cells latently infected with human immunodeficiency virus type 1 (HIV-1) can resist the action of potent antiretroviral drugs and remain dormant for decades. Intensive research has been dedicated to understanding the catalytic mechanism of integration, as well as the viral and cellular determinants that influence integration site distribution throughout the host genome. In this review, we summarize the evolution of techniques that have been used to recover and map retroviral integration sites, from the early days that first indicated that integration could occur in multiple cellular DNA locations, to current technologies that map upwards of millions of unique integration sites from single in vitro integration reactions or cell culture infections. We further review important insights gained from the use of such mapping techniques, including the monitoring of cell clonal expansion in patients treated with retrovirus-based gene therapy vectors, or patients with acquired immune deficiency syndrome (AIDS) on suppressive antiretroviral therapy (ART). These insights span from integrase (IN) enzyme sequence preferences within target DNA (tDNA) at the sites of integration, to the roles of host cellular proteins in mediating global integration distribution, to the potential relationship between genomic location of vDNA integration site and retroviral latency.
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Affiliation(s)
- Erik Serrao
- a Department of Cancer Immunology and Virology , Dana-Farber Cancer Institute , Boston , MA , USA
| | - Alan N Engelman
- a Department of Cancer Immunology and Virology , Dana-Farber Cancer Institute , Boston , MA , USA
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16
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DNA Physical Properties and Nucleosome Positions Are Major Determinants of HIV-1 Integrase Selectivity. PLoS One 2015; 10:e0129427. [PMID: 26075397 PMCID: PMC4468133 DOI: 10.1371/journal.pone.0129427] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Accepted: 05/09/2015] [Indexed: 02/06/2023] Open
Abstract
Retroviral integrases (INs) catalyse the integration of the reverse transcribed viral DNA into the host cell genome. This process is selective, and chromatin has been proposed to be a major factor regulating this step in the viral life cycle. However, the precise underlying mechanisms are still under investigation. We have developed a new in vitro integration assay using physiologically-relevant, reconstituted genomic acceptor chromatin and high-throughput determination of nucleosome positions and integration sites, in parallel. A quantitative analysis of the resulting data reveals a chromatin-dependent redistribution of the integration sites and establishes a link between integration sites and nucleosome positions. The co-activator LEDGF/p75 enhanced integration but did not modify the integration sites under these conditions. We also conducted an in cellulo genome-wide comparative study of nucleosome positions and human immunodeficiency virus type-1 (HIV-1) integration sites identified experimentally in vivo. These studies confirm a preferential integration in nucleosome-covered regions. Using a DNA mechanical energy model, we show that the physical properties of DNA probed by IN binding are important in determining IN selectivity. These novel in vitro and in vivo approaches confirm that IN has a preference for integration into a nucleosome, and suggest the existence of two levels of IN selectivity. The first depends on the physical properties of the target DNA and notably, the energy required to fit DNA into the IN catalytic pocket. The second depends on the DNA deformation associated with DNA wrapping around a nucleosome. Taken together, these results indicate that HIV-1 IN is a shape-readout DNA binding protein.
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Key determinants of target DNA recognition by retroviral intasomes. Retrovirology 2015; 12:39. [PMID: 25924943 PMCID: PMC4422553 DOI: 10.1186/s12977-015-0167-3] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2015] [Accepted: 04/20/2015] [Indexed: 12/11/2022] Open
Abstract
Background Retroviral integration favors weakly conserved palindrome sequences at the sites of viral DNA joining and generates a short (4–6 bp) duplication of host DNA flanking the provirus. We previously determined two key parameters that underlie the target DNA preference for prototype foamy virus (PFV) and human immunodeficiency virus type 1 (HIV-1) integration: flexible pyrimidine (Y)/purine (R) dinucleotide steps at the centers of the integration sites, and base contacts with specific integrase residues, such as Ala188 in PFV integrase and Ser119 in HIV-1 integrase. Here we examined the dinucleotide preference profiles of a range of retroviruses and correlated these findings with respect to length of target site duplication (TSD). Results Integration datasets covering six viral genera and the three lengths of TSD were accessed from the literature or generated in this work. All viruses exhibited significant enrichments of flexible YR and/or selection against rigid RY dinucleotide steps at the centers of integration sites, and the magnitude of this enrichment inversely correlated with TSD length. The DNA sequence environments of in vivo-generated HIV-1 and PFV sites were consistent with integration into nucleosomes, however, the local sequence preferences were largely independent of target DNA chromatinization. Integration sites derived from cells infected with the gammaretrovirus reticuloendotheliosis virus strain A (Rev-A), which yields a 5 bp TSD, revealed the targeting of global chromatin features most similar to those of Moloney murine leukemia virus, which yields a 4 bp duplication. In vitro assays revealed that Rev-A integrase interacts with and is catalytically stimulated by cellular bromodomain containing 4 protein. Conclusions Retroviral integrases have likely evolved to bend target DNA to fit scissile phosphodiester bonds into two active sites for integration, and viruses that cut target DNA with a 6 bp stagger may not need to bend DNA as sharply as viruses that cleave with 4 bp or 5 bp staggers. For PFV and HIV-1, the selection of signature bases and central flexibility at sites of integration is largely independent of chromatin structure. Furthermore, global Rev-A integration is likely directed to chromatin features by bromodomain and extraterminal domain proteins. Electronic supplementary material The online version of this article (doi:10.1186/s12977-015-0167-3) contains supplementary material, which is available to authorized users.
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Benleulmi MS, Matysiak J, Henriquez DR, Vaillant C, Lesbats P, Calmels C, Naughtin M, Leon O, Skalka AM, Ruff M, Lavigne M, Andreola ML, Parissi V. Intasome architecture and chromatin density modulate retroviral integration into nucleosome. Retrovirology 2015; 12:13. [PMID: 25807893 PMCID: PMC4358916 DOI: 10.1186/s12977-015-0145-9] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2014] [Accepted: 01/19/2015] [Indexed: 01/19/2023] Open
Abstract
Background Retroviral integration depends on the interaction between intasomes, host chromatin and cellular targeting cofactors as LEDGF/p75 or BET proteins. Previous studies indicated that the retroviral integrase, by itself, may play a role in the local integration site selection within nucleosomal target DNA. We focused our study on this local association by analyzing the intrinsic properties of various retroviral intasomes to functionally accommodate different chromatin structures in the lack of other cofactors. Results Using in vitro conditions allowing the efficient catalysis of full site integration without these cofactors, we show that distinct retroviral integrases are not equally affected by chromatin compactness. Indeed, while PFV and MLV integration reactions are favored into dense and stable nucleosomes, HIV-1 and ASV concerted integration reactions are preferred into poorly dense chromatin regions of our nucleosomal acceptor templates. Predicted nucleosome occupancy around integration sites identified in infected cells suggests the presence of a nucleosome at the MLV and HIV-1 integration sites surrounded by differently dense chromatin. Further analyses of the relationships between the in vitro integration site selectivity and the structure of the inserted DNA indicate that structural constraints within intasomes could account for their ability to accommodate nucleosomal DNA and could dictate their capability to bind nucleosomes functionally in these specific chromatin contexts. Conclusions Thus, both intasome architecture and compactness of the chromatin surrounding the targeted nucleosome appear important determinants of the retroviral integration site selectivity. This supports a mechanism involving a global targeting of the intasomes toward suitable chromatin regions followed by a local integration site selection modulated by the intrinsic structural constraints of the intasomes governing the target DNA bending and dictating their sensitivity toward suitable specific nucleosomal structures and density. Electronic supplementary material The online version of this article (doi:10.1186/s12977-015-0145-9) contains supplementary material, which is available to authorized users.
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Abstract
Retroviruses and LTR retrotransposons are transposable elements that encapsidate the RNAs that are intermediates in the transposition of DNA copies of their genomes (proviruses), from one cell (or one locus) to another. Mechanistic similarities in DNA transposase enzymes and retroviral/retrotransposon integrases underscore the close evolutionary relationship among these elements. The retroviruses are very ancient infectious agents, presumed to have evolved from Ty3/Gypsy LTR retrotransposons (1), and DNA copies of their sequences can be found embedded in the genomes of most, if not all, members of the tree of life. All retroviruses share a specific gene arrangement and similar replication strategies. However, given their ancestries and occupation of diverse evolutionary niches, it should not be surprising that unique sequences have been acquired in some retroviral genomes and that the details of the mechanism by which their transposition is accomplished can vary. While every step in the retrovirus lifecycle is, in some sense, relevant to transposition, this Chapter focuses mainly on the early phase of retroviral replication, during which viral DNA is synthesized and integrated into its host genome. Some of the initial studies that set the stage for current understanding are highlighted, as well as more recent findings obtained through use of an ever-expanding technological toolbox including genomics, proteomics, and siRNA screening. Persistence in the area of structural biology has provided new insight into conserved mechanisms as well as variations in detail among retroviruses, which can also be instructive.
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Affiliation(s)
- Anna Marie Skalka
- Fox Chase Cancer Center 333 Cottman Avenue Philadelphia, PA 19111 United States 2157282192 2157282778 (fax)
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Preclinical profile of BI 224436, a novel HIV-1 non-catalytic-site integrase inhibitor. Antimicrob Agents Chemother 2014; 58:3233-44. [PMID: 24663024 DOI: 10.1128/aac.02719-13] [Citation(s) in RCA: 76] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
BI 224436 is an HIV-1 integrase inhibitor with effective antiviral activity that acts through a mechanism that is distinct from that of integrase strand transfer inhibitors (INSTIs). This 3-quinolineacetic acid derivative series was identified using an enzymatic integrase long terminal repeat (LTR) DNA 3'-processing assay. A combination of medicinal chemistry, parallel synthesis, and structure-guided drug design led to the identification of BI 224436 as a candidate for preclinical profiling. It has antiviral 50% effective concentrations (EC50s) of <15 nM against different HIV-1 laboratory strains and cellular cytotoxicity of >90 μM. BI 224436 also has a low, ∼2.1-fold decrease in antiviral potency in the presence of 50% human serum and, by virtue of a steep dose-response curve slope, exhibits serum-shifted EC95 values ranging between 22 and 75 nM. Passage of virus in the presence of inhibitor selected for either A128T, A128N, or L102F primary resistance substitutions, all mapping to a conserved allosteric pocket on the catalytic core of integrase. BI 224436 also retains full antiviral activity against recombinant viruses encoding INSTI resistance substitutions N155S, Q148H, and E92Q. In drug combination studies performed in cellular antiviral assays, BI 224436 displays an additive effect in combination with most approved antiretrovirals, including INSTIs. BI 224436 has drug-like in vitro absorption, distribution, metabolism, and excretion (ADME) properties, including Caco-2 cell permeability, solubility, and low cytochrome P450 inhibition. It exhibited excellent pharmacokinetic profiles in rat (clearance as a percentage of hepatic flow [CL], 0.7%; bioavailability [F], 54%), monkey (CL, 23%; F, 82%), and dog (CL, 8%; F, 81%). Based on the excellent biological and pharmacokinetic profile, BI 224436 was advanced into phase 1 clinical trials.
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Understanding lentiviral vector chromatin targeting: working to reduce insertional mutagenic potential for gene therapy. Gene Ther 2012; 20:581-8. [PMID: 23171920 DOI: 10.1038/gt.2012.88] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Replication-deficient retroviruses have been successfully utilized as vectors, offering an efficient, stable method of therapeutic gene delivery. Many examples exist proving this mode of integrative gene transfer is both effective and safe in cultured systems and clinical trials. Along with their success, severe side effects have occurred with early retroviral vectors causing a shift in the approach to vector design before further clinical testing. Several alternative delivery methods are available but lentiviral vectors (LV) are among the most favorable as they are already well understood. LV offer safer integration site selection profiles and a lower degree of genotoxicity, compared with γ-retroviral vectors. Following their introduction, development of the self-inactivating vector configuration was a huge step to this mode of therapy but did not confer full protection against insertional mutagenesis. As a result integration, modeling must be improved to eventually avoid this possibility. The cellular factor LEDGF/p75 seems to play an essential role in the process of LV site selection and its interactions with chromatin are being quickly resolved. LEDGF/p75 is at the center of one example directed integration effort where recombinant products bias the integration event, a step toward fully directed integration into pre-determined benign loci. A more accurate picture of the details of LEDGF/p75 in the natural integration process is emerging, including new binding specificities, chromatin interaction kinetics and additional cellular factors. Together with next-generation sequencing technology and bio-informatics to analyze integration patterns, these advancements will lead to highly focused directed integration, accelerating wide-spread acceptance of LV for gene therapy.
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Pichavant C, Tremblay JP. Generation of lentiviral vectors for use in skeletal muscle research. Methods Mol Biol 2012; 798:285-295. [PMID: 22130843 DOI: 10.1007/978-1-61779-343-1_16] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Gene therapy is a promising approach for the treatment of a variety of disorders including genetic diseases and cancer. Among the viral vectors used in gene therapy, the lentiviral vector, based on HIV-1, is the only integrative vector able to transduce nondividing cells. The first generation of lentiviral vector was -established in 1996. Since then, other generations of lentiviral vector packaging systems were developed to improve this first vector. In this chapter, we describe these different packaging systems, the generation of lentiviral vector from productive cells, the 293T cell line, and the transduction of myogenic cells with a lentiviral vector as well.
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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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Lesbats P, Lavigne M, Parissi V. HIV-1 integration into chromatin: new insights and future perspectives. Future Virol 2011. [DOI: 10.2217/fvl.11.84] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Human AIDS, owing to HIV-1, remains a major health issue despite the numerous antiviral compounds that are now available. One of the main obstacles for these antiviral strategies is the appearance of highly resistant viral strains, making the search for new antiviral targets a crucial issue. The insertion of the viral genome into the cell chromosomal DNA, catalyzed by the retroviral integrase enzyme, is required for stable infection and thus constitutes a suitable target for the antiretroviral molecules currently used in therapy. The precise mechanism of interaction between the integration complex (intasome) and the target chromatin remains poorly understood, thus restricting the development of new therapeutic strategies and original methods to control gene transfer in gene therapy. In this article, we summarize the data obtained in this field and underline recent results highlighting this process and paving the way for new and more detailed understanding of this mechanism.
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Affiliation(s)
- Paul Lesbats
- Laboratoire MCMP, UMR 5234 CNRS-Université de Bordeaux Victor Segalen, 146 rue Léo Saignat, 33076 Bordeaux cedex, France
| | - Marc Lavigne
- Institut Pasteur, UMR 3015 CNRS, 25 rue du Dr Roux, 75724 Paris cedex 15, France
- Laboratoire Joliot-Curie, USR3010, ENS de Lyon, 46, allée d’Italie 69364, Lyon, France
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Katz RA, Merkel G, Andrake MD, Roder H, Skalka AM. Retroviral integrases promote fraying of viral DNA ends. J Biol Chem 2011; 286:25710-8. [PMID: 21622554 DOI: 10.1074/jbc.m111.229179] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
In the initial step of integration, retroviral integrase (IN) introduces precise nicks in the degenerate, short inverted repeats at the ends of linear viral DNA. The scissile phosphodiester bond is located immediately 3' of a highly conserved CA/GT dinucleotide, usually 2 bp from the ends. These nicks create new recessed 3'-OH viral DNA ends that are required for joining to host cell DNA. Previous studies have indicated that unpairing, "fraying," of the viral DNA ends by IN contributes to end recognition or catalysis. Here, we report that end fraying can be detected independently of catalysis with both avian sarcoma virus (ASV) and human immunodeficiency virus type 1 (HIV-1) IN proteins by use of fluorescence resonance energy transfer (FRET). The results were indicative of an IN-induced intramolecular conformational change in the viral DNA ends (cis FRET). Fraying activity is tightly coupled to the DNA binding capabilities of these enzymes, as follows: an inhibitor effective against both IN proteins was shown to block ASV IN DNA binding and end fraying, with similar dose responses; ASV IN substitutions that reduced DNA binding also reduced end fraying activity; and HIV-1 IN DNA binding and end fraying were both undetectable in the absence of a metal cofactor. Consistent with our previous results, end fraying is sequence-independent, suggesting that the DNA terminus per se is a major structural determinant for recognition. We conclude that frayed ends represent a functional intermediate in which DNA termini can be sampled for suitability for endonucleolytic processing.
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Affiliation(s)
- Richard A Katz
- Institute for Cancer Research, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA
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26
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Soto MJ, Peña Á, Vallejo FG. A genomic and bioinformatics analysis of the integration of HIV in peripheral blood mononuclear cells. AIDS Res Hum Retroviruses 2011; 27:547-55. [PMID: 20919923 DOI: 10.1089/aid.2010.0182] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The mechanistic basis of the target-site preference of lentivirus DNA integration is not well understood. In the present in silico study, we describe the integrational profile of simultaneous HIV-1 and HIV-2 infection. A total of 352 genomic DNA sequences from human peripheral blood mononuclear cells (PBMCs) obtained from GenBank and possessing the 5' LTR of HIV were used to characterize the structure and composition of local chromatin associated with high frequency integration sites. These sequences were aligned with the draft human genome (hg18) using BLAST (NCBI) and BLAT (UCSC) in order to derive information about chromosome localization, functional aspects of coding protein genes, CpG island number, and repetitive elements flanking integration sites. No significant differences in the integrational profile between HIV-1 and HIV-2 were found. However, we observed a tendency in both lentiviruses to integrate in the vicinity of protein coding genes. Multiple regression analysis showed a strong correlation between the number of genes and the number of CpG islands in regions with high integration frequency, mainly in chromosome 17 (R = 0.95, p < 0.05). Our results provide strong evidence that HIV-1 and HIV-2 have common genomic environments in the local chromatin regions with high gene density and CpG islands. The understanding of local genomic environments with a high frequency of integration would be the starting point to develop novel antiviral strategies for lentiviral infection.
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Affiliation(s)
- María Juliana Soto
- Molecular Biology and Pathogenesis Laboratory, Department of Physiological Sciences, School of Basic Sciences, Faculty of Health, Universidad del Valle, Cali, Colombia
| | - Ángela Peña
- Molecular Biology and Pathogenesis Laboratory, Department of Physiological Sciences, School of Basic Sciences, Faculty of Health, Universidad del Valle, Cali, Colombia
| | - Felipe García Vallejo
- Molecular Biology and Pathogenesis Laboratory, Department of Physiological Sciences, School of Basic Sciences, Faculty of Health, Universidad del Valle, Cali, Colombia
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27
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Nowrouzi A, Glimm H, von Kalle C, Schmidt M. Retroviral vectors: post entry events and genomic alterations. Viruses 2011; 3:429-55. [PMID: 21994741 PMCID: PMC3185758 DOI: 10.3390/v3050429] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2011] [Revised: 03/24/2011] [Accepted: 04/05/2011] [Indexed: 12/16/2022] Open
Abstract
The curative potential of retroviral vectors for somatic gene therapy has been demonstrated impressively in several clinical trials leading to sustained long-term correction of the underlying genetic defect. Preclinical studies and clinical monitoring of gene modified hematopoietic stem and progenitor cells in patients have shown that biologically relevant vector induced side effects, ranging from in vitro immortalization to clonal dominance and oncogenesis in vivo, accompany therapeutic efficiency of integrating retroviral gene transfer systems. Most importantly, it has been demonstrated that the genotoxic potential is not identical among all retroviral vector systems designed for clinical application. Large scale viral integration site determination has uncovered significant differences in the target site selection of retrovirus subfamilies influencing the propensity for inducing genetic alterations in the host genome. In this review we will summarize recent insights gained on the mechanisms of insertional mutagenesis based on intrinsic target site selection of different retrovirus families. We will also discuss examples of side effects occurring in ongoing human gene therapy trials and future prospectives in the field.
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Affiliation(s)
- Ali Nowrouzi
- Department of Translational Oncology, German Cancer Research Center, Im Neuenheimer Feld 581, 69120 Heidelberg, Germany; E-Mail: (A.N.)
- National Center for Tumor Diseases, Im Neuenheimer Feld 581, 69120 Heidelberg, Germany
| | - Hanno Glimm
- Department of Translational Oncology, German Cancer Research Center, Im Neuenheimer Feld 581, 69120 Heidelberg, Germany; E-Mail: (A.N.)
- National Center for Tumor Diseases, Im Neuenheimer Feld 581, 69120 Heidelberg, Germany
| | - Christof von Kalle
- Department of Translational Oncology, German Cancer Research Center, Im Neuenheimer Feld 581, 69120 Heidelberg, Germany; E-Mail: (A.N.)
- National Center for Tumor Diseases, Im Neuenheimer Feld 581, 69120 Heidelberg, Germany
- Authors to whom correspondence should be addressed; E-Mails: (C.v.K.); (M.S.); Tel.: +49-6221-56-6991; +49-6221-42-1600; Fax: +49-6221-56-6930; +49-6221-42-1611
| | - Manfred Schmidt
- Department of Translational Oncology, German Cancer Research Center, Im Neuenheimer Feld 581, 69120 Heidelberg, Germany; E-Mail: (A.N.)
- National Center for Tumor Diseases, Im Neuenheimer Feld 581, 69120 Heidelberg, Germany
- Authors to whom correspondence should be addressed; E-Mails: (C.v.K.); (M.S.); Tel.: +49-6221-56-6991; +49-6221-42-1600; Fax: +49-6221-56-6930; +49-6221-42-1611
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28
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Lesbats P, Botbol Y, Chevereau G, Vaillant C, Calmels C, Arneodo A, Andreola ML, Lavigne M, Parissi V. Functional coupling between HIV-1 integrase and the SWI/SNF chromatin remodeling complex for efficient in vitro integration into stable nucleosomes. PLoS Pathog 2011; 7:e1001280. [PMID: 21347347 PMCID: PMC3037357 DOI: 10.1371/journal.ppat.1001280] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2010] [Accepted: 01/08/2011] [Indexed: 11/18/2022] Open
Abstract
Establishment of stable HIV-1 infection requires the efficient integration of the retroviral genome into the host DNA. The molecular mechanism underlying the control of this process by the chromatin structure has not yet been elucidated. We show here that stably associated nucleosomes strongly inhibit in vitro two viral-end integration by decreasing the accessibility of DNA to integrase. Remodeling of the chromatinized template by the SWI/SNF complex, whose INI1 major component interacts with IN, restores and redirects the full-site integration into the stable nucleosome region. These effects are not observed after remodeling by other human remodeling factors such as SNF2H or BRG1 lacking the integrase binding protein INI1. This suggests that the restoration process depends on the direct interaction between IN and the whole SWI/SNF complex, supporting a functional coupling between the remodeling and integration complexes. Furthermore, in silico comparison between more than 40,000 non-redundant cellular integration sites selected from literature and nucleosome occupancy predictions also supports that HIV-1 integration is promoted in the genomic region of weaker intrinsic nucleosome density in the infected cell. Our data indicate that some chromatin structures can be refractory for integration and that coupling between nucleosome remodeling and HIV-1 integration is required to overcome this natural barrier.
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Affiliation(s)
- Paul Lesbats
- Laboratoire MCMP, UMR 5234 CNRS-Université Victor Segalen Bordeaux 2, Bordeaux, France
| | - Yair Botbol
- Institut Pasteur, UMR 3015 CNRS, Paris, France
| | | | - Cédric Vaillant
- Laboratoire Joliot-Curie, USR3010, ENS de Lyon, Lyon, France
| | - Christina Calmels
- Laboratoire MCMP, UMR 5234 CNRS-Université Victor Segalen Bordeaux 2, Bordeaux, France
| | - Alain Arneodo
- Laboratoire Joliot-Curie, USR3010, ENS de Lyon, Lyon, France
| | - Marie-Line Andreola
- Laboratoire MCMP, UMR 5234 CNRS-Université Victor Segalen Bordeaux 2, Bordeaux, France
| | | | - Vincent Parissi
- Laboratoire MCMP, UMR 5234 CNRS-Université Victor Segalen Bordeaux 2, Bordeaux, France
- * E-mail:
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Cherepanov P, Maertens GN, Hare S. Structural insights into the retroviral DNA integration apparatus. Curr Opin Struct Biol 2011; 21:249-56. [PMID: 21277766 DOI: 10.1016/j.sbi.2010.12.005] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2010] [Revised: 12/22/2010] [Accepted: 12/31/2010] [Indexed: 02/07/2023]
Abstract
Retroviral replication depends on successful integration of the viral genetic material into a host cell chromosome. Virally encoded integrase, an enzyme from the DDE(D) nucleotidyltransferase superfamily, is responsible for the key DNA cutting and joining steps associated with this process. Insights into the structural and mechanistic aspects of integration are directly relevant for the development of antiretroviral drugs. Recent breakthroughs have led to biochemical and structural characterization of the principal integration intermediates revealing the tetramer of integrase that catalyzes insertion of both 3' viral DNA ends into a sharply bent target DNA. This review discusses the mechanism of retroviral DNA integration and the mode of action of HIV-1 integrase strand transfer inhibitors in light of the recent visualization of the prototype foamy virus intasome, target DNA capture and strand transfer complexes.
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Affiliation(s)
- Peter Cherepanov
- Division of Infectious Diseases, Imperial College London, St. Mary's Campus, Norfolk Place, London W2 1PG, UK.
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The host genomic environment of the provirus determines the abundance of HTLV-1-infected T-cell clones. Blood 2011; 117:3113-22. [PMID: 21228324 DOI: 10.1182/blood-2010-10-312926] [Citation(s) in RCA: 235] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Human T-lymphotropic virus type 1 (HTLV-1) persists by driving clonal proliferation of infected T lymphocytes. A high proviral load predisposes to HTLV-1-associated diseases. Yet the reasons for the variation within and between persons in the abundance of HTLV-1-infected clones remain unknown. We devised a high-throughput protocol to map the genomic location and quantify the abundance of > 91,000 unique insertion sites of the provirus from 61 HTLV-1(+) persons and > 2100 sites from in vitro infection. We show that a typical HTLV-1-infected host carries between 500 and 5000 unique insertion sites. We demonstrate that negative selection dominates during chronic infection, favoring establishment of proviruses integrated in transcriptionally silenced DNA: this selection is significantly stronger in asymptomatic carriers. We define a parameter, the oligoclonality index, to quantify clonality. The high proviral load characteristic of HTLV-1-associated inflammatory disease results from a larger number of unique insertion sites than in asymptomatic carriers and not, as previously thought, from a difference in clonality. The abundance of established HTLV-1 clones is determined by genomic features of the host DNA flanking the provirus. HTLV-1 clonal expansion in vivo is favored by orientation of the provirus in the same sense as the nearest host gene.
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Pandhare J, Dash C. A prospective on drug abuse-associated epigenetics and HIV-1 replication. Life Sci 2010; 88:995-9. [PMID: 20951145 DOI: 10.1016/j.lfs.2010.10.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2010] [Revised: 09/22/2010] [Accepted: 10/02/2010] [Indexed: 01/18/2023]
Abstract
Drugs of abuse serve as cofactors to susceptibility to HIV infection and disease progression. Although clinical reports indicate association between HIV/AIDS and drug use, the molecular mechanism of infection susceptibility and disease progression remains unclear. Drugs such as cocaine exert their addictive effects in part by epigenetic mechanisms. Given that epigenetic modifications play an important role in HIV-1 life cycle, it is essential to unravel whether drug abuse-associated epigenetic changes may contribute to HIV/AIDS. In this article we will provide a prospective on the impact of epigenetic mechanisms on HIV-1 life cycle.
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Affiliation(s)
- Jui Pandhare
- Center for AIDS Health Disparities Research and Department of Biochemistry and Cancer Biology, Meharry Medical College School of Medicine, Nashville,TN, USA
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Kim S, Rusmevichientong A, Dong B, Remenyi R, Silverman RH, Chow SA. Fidelity of target site duplication and sequence preference during integration of xenotropic murine leukemia virus-related virus. PLoS One 2010; 5:e10255. [PMID: 20421928 PMCID: PMC2857682 DOI: 10.1371/journal.pone.0010255] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2010] [Accepted: 03/28/2010] [Indexed: 11/18/2022] Open
Abstract
Xenotropic murine leukemia virus (MLV)-related virus (XMRV) is a new human retrovirus associated with prostate cancer and chronic fatigue syndrome. The causal relationship of XMRV infection to human disease and the mechanism of pathogenicity have not been established. During retrovirus replication, integration of the cDNA copy of the viral RNA genome into the host cell chromosome is an essential step and involves coordinated joining of the two ends of the linear viral DNA into staggered sites on target DNA. Correct integration produces proviruses that are flanked by a short direct repeat, which varies from 4 to 6 bp among the retroviruses but is invariant for each particular retrovirus. Uncoordinated joining of the two viral DNA ends into target DNA can cause insertions, deletions, or other genomic alterations at the integration site. To determine the fidelity of XMRV integration, cells infected with XMRV were clonally expanded and DNA sequences at the viral-host DNA junctions were determined and analyzed. We found that a majority of the provirus ends were correctly processed and flanked by a 4-bp direct repeat of host DNA. A weak consensus sequence was also detected at the XMRV integration sites. We conclude that integration of XMRV DNA involves a coordinated joining of two viral DNA ends that are spaced 4 bp apart on the target DNA and proceeds with high fidelity.
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Affiliation(s)
- Sanggu Kim
- Biomedical Engineering Interdepartmental Program, University of California Los Angeles, Los Angeles, California, United States of America
| | - Alice Rusmevichientong
- Department of Molecular and Medical Pharmacology, Molecular Biology Institute, and University of California Los Angeles AIDS Institute, University of California Los Angeles School of Medicine, Los Angeles, California, United States of America
| | - Beihua Dong
- Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Roland Remenyi
- Department of Molecular and Medical Pharmacology, Molecular Biology Institute, and University of California Los Angeles AIDS Institute, University of California Los Angeles School of Medicine, Los Angeles, California, United States of America
| | - Robert H. Silverman
- Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Samson A. Chow
- Biomedical Engineering Interdepartmental Program, University of California Los Angeles, Los Angeles, California, United States of America
- Department of Molecular and Medical Pharmacology, Molecular Biology Institute, and University of California Los Angeles AIDS Institute, University of California Los Angeles School of Medicine, Los Angeles, California, United States of America
- * E-mail:
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Integrase and integration: biochemical activities of HIV-1 integrase. Retrovirology 2008; 5:114. [PMID: 19091057 PMCID: PMC2615046 DOI: 10.1186/1742-4690-5-114] [Citation(s) in RCA: 153] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2008] [Accepted: 12/17/2008] [Indexed: 01/12/2023] Open
Abstract
Integration of retroviral DNA is an obligatory step of retrovirus replication because proviral DNA is the template for productive infection. Integrase, a retroviral enzyme, catalyses integration. The process of integration can be divided into two sequential reactions. The first one, named 3'-processing, corresponds to a specific endonucleolytic reaction which prepares the viral DNA extremities to be competent for the subsequent covalent insertion, named strand transfer, into the host cell genome by a trans-esterification reaction. Recently, a novel specific activity of the full length integrase was reported, in vitro, by our group for two retroviral integrases (HIV-1 and PFV-1). This activity of internal cleavage occurs at a specific palindromic sequence mimicking the LTR-LTR junction described into the 2-LTR circles which are peculiar viral DNA forms found during viral infection. Moreover, recent studies demonstrated the existence of a weak palindromic consensus found at the integration sites. Taken together, these data underline the propensity of retroviral integrases for binding symmetrical sequences and give perspectives for targeting specific sequences used for gene therapy.
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Merkel G, Andrake MD, Ramcharan J, Skalka AM. Oligonucleotide-based assays for integrase activity. Methods 2008; 47:243-8. [PMID: 19010419 DOI: 10.1016/j.ymeth.2008.10.024] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2008] [Revised: 10/20/2008] [Accepted: 10/22/2008] [Indexed: 12/01/2022] Open
Abstract
Oligonucleotide assays have been invaluable for elucidation of the molecular mechanisms of retroviral integrases. A suite of rapid and sensitive fluorescence assays to measure the DNA binding, processing, and joining activities of integrase (IN) is described here. The assays are especially useful for characterizing the major activities of the enzyme, and for handling large numbers of samples efficiently. They can greatly facilitate further biochemical and structural analyses for HIV-1 and other IN proteins. The assays can also be adapted for moderate-high throughput testing of various inhibitory compounds.
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Affiliation(s)
- George Merkel
- Institute for Cancer Research, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111, USA
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Faye B, Arnaud F, Peyretaillade E, Brasset E, Dastugue B, Vaury C. Functional characteristics of a highly specific integrase encoded by an LTR-retrotransposon. PLoS One 2008; 3:e3185. [PMID: 18784842 PMCID: PMC2527525 DOI: 10.1371/journal.pone.0003185] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2008] [Accepted: 08/03/2008] [Indexed: 12/18/2022] Open
Abstract
Background The retroviral Integrase protein catalyzes the insertion of linear viral DNA into host cell DNA. Although different retroviruses have been shown to target distinctive chromosomal regions, few of them display a site-specific integration. ZAM, a retroelement from Drosophila melanogaster very similar in structure and replication cycle to mammalian retroviruses is highly site-specific. Indeed, ZAM copies target the genomic 5′-CGCGCg-3′ consensus-sequences. To enlighten the determinants of this high integration specificity, we investigated the functional properties of its integrase protein denoted ZAM-IN. Principal Findings Here we show that ZAM-IN displays the property to nick DNA molecules in vitro. This endonuclease activity targets specific sequences that are present in a 388 bp fragment taken from the white locus and known to be a genomic ZAM integration site in vivo. Furthermore, ZAM-IN displays the unusual property to directly bind specific genomic DNA sequences. Two specific and independent sites are recognized within the 388 bp fragment of the white locus: the CGCGCg sequence and a closely apposed site different in sequence. Conclusion This study strongly argues that the intrinsic properties of ZAM-IN, ie its binding properties and its endonuclease activity, play an important part in ZAM integration specificity. Its ability to select two binding sites and to nick the DNA molecule reminds the strategy used by some site-specific recombination enzymes and forms the basis for site-specific integration strategies potentially useful in a broad range of genetic engineering applications.
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Affiliation(s)
- Babacar Faye
- UMR/CNRS 6247, Clermont Université, INSERM, U931, Faculté de Médecine, Clermont-Ferrand, France
| | - Frederick Arnaud
- UMR/CNRS 6247, Clermont Université, INSERM, U931, Faculté de Médecine, Clermont-Ferrand, France
| | - Eric Peyretaillade
- UMR/CNRS 6247, Clermont Université, INSERM, U931, Faculté de Médecine, Clermont-Ferrand, France
| | - Emilie Brasset
- UMR/CNRS 6247, Clermont Université, INSERM, U931, Faculté de Médecine, Clermont-Ferrand, France
| | - Bernard Dastugue
- UMR/CNRS 6247, Clermont Université, INSERM, U931, Faculté de Médecine, Clermont-Ferrand, France
| | - Chantal Vaury
- UMR/CNRS 6247, Clermont Université, INSERM, U931, Faculté de Médecine, Clermont-Ferrand, France
- * E-mail:
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Daniel R, Smith JA. Integration site selection by retroviral vectors: molecular mechanism and clinical consequences. Hum Gene Ther 2008; 19:557-68. [PMID: 18533894 DOI: 10.1089/hum.2007.148] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Retroviral DNA integration into the host cell genome is an essential feature of the retroviral life cycle. The ability to integrate their DNA into the DNA of infected cells also makes retroviruses attractive vectors for delivery of therapeutic genes into the genome of cells carrying adverse mutations in their cellular DNA. Sequencing of the entire human genome has enabled identification of integration site preferences of both replication-competent retroviruses and retroviral vectors. These results, together with the unfortunate outcome of a gene therapy trial, in which integration of a retroviral vector in the vicinity of a protooncogene was associated with the development of leukemia, have stimulated efforts to elucidate the molecular mechanism underlying integration site selection by retroviral vectors, as well as the development of methods to direct integration to specific DNA sequences and chromosomal regions. This review outlines our current knowledge of the mechanism of integration site selection by retroviruses in vitro, in cultured cells, and in vivo; the outcome of several of the more recent gene therapy trials, which employed these vectors; and the efforts of several laboratories to develop vectors that integrate at predetermined sites in the human genome.
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Affiliation(s)
- René Daniel
- Division of Infectious Diseases, Center for Human Virology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA 19107, USA.
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Albanese A, Arosio D, Terreni M, Cereseto A. HIV-1 pre-integration complexes selectively target decondensed chromatin in the nuclear periphery. PLoS One 2008; 3:e2413. [PMID: 18545681 PMCID: PMC2398779 DOI: 10.1371/journal.pone.0002413] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2008] [Accepted: 04/15/2008] [Indexed: 12/18/2022] Open
Abstract
Integration of the double-stranded DNA copy of the HIV-1 genome into host chromosomal DNA is a requirement for efficient viral replication. Integration preferentially occurs within active transcription units, however chromosomal site specificity does not correlate with any strong primary sequence. To investigate whether the nuclear architecture may affect viral integration we have developed an experimental system where HIV-1 viral particles can be visualized within the nuclear compartment. Fluorescently labeled HIV-1 virions were engineered by fusing integrase, the viral protein that catalyzes the integration reaction, to fluorescent proteins. Viral tests demonstrate that the infectivity of fluorescent virions, including the integration step, is not altered as compared to wild-type virus. 3-D confocal microscopy allowed a detailed analysis of the spatial and temporal distribution of the pre-integration complexes (PICs) within the nucleus at different moments following infection; the fluorescently labeled PICs preferentially distribute in decondensed areas of the chromatin with a striking positioning in the nuclear periphery, while heterochromatin regions are largely disfavored. These observations provide a first indication of how the nuclear architecture may initially orient the selection of retroviral integration sites.
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Affiliation(s)
- Alberto Albanese
- Laboratory of Molecular Biology Scuola Normale Superiore, Pisa, Italy
- NEST, CNR-INFM and Scuola Normale Superiore, Pisa, Italy
| | - Daniele Arosio
- NEST, CNR-INFM and Scuola Normale Superiore, Pisa, Italy
- * E-mail: (AC); (DA)
| | - Mariaelena Terreni
- Laboratory of Molecular Biology Scuola Normale Superiore, Pisa, Italy
- NEST, CNR-INFM and Scuola Normale Superiore, Pisa, Italy
| | - Anna Cereseto
- Laboratory of Molecular Biology Scuola Normale Superiore, Pisa, Italy
- NEST, CNR-INFM and Scuola Normale Superiore, Pisa, Italy
- * E-mail: (AC); (DA)
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HTLV-1 integration into transcriptionally active genomic regions is associated with proviral expression and with HAM/TSP. PLoS Pathog 2008; 4:e1000027. [PMID: 18369476 PMCID: PMC2265437 DOI: 10.1371/journal.ppat.1000027] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2007] [Accepted: 02/19/2008] [Indexed: 01/20/2023] Open
Abstract
Human T-lymphotropic virus type 1 (HTLV-1) causes leukaemia or chronic inflammatory disease in ∼5% of infected hosts. The level of proviral expression of HTLV-1 differs significantly among infected people, even at the same proviral load (proportion of infected mononuclear cells in the circulation). A high level of expression of the HTLV-1 provirus is associated with a high proviral load and a high risk of the inflammatory disease of the central nervous system known as HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). But the factors that control the rate of HTLV-1 proviral expression remain unknown. Here we show that proviral integration sites of HTLV-1 in vivo are not randomly distributed within the human genome but are associated with transcriptionally active regions. Comparison of proviral integration sites between individuals with high and low levels of proviral expression, and between provirus-expressing and provirus non-expressing cells from within an individual, demonstrated that frequent integration into transcription units was associated with an increased rate of proviral expression. An increased frequency of integration sites in transcription units in individuals with high proviral expression was also associated with the inflammatory disease HAM/TSP. By comparing the distribution of integration sites in human lymphocytes infected in short-term cell culture with those from persistent infection in vivo, we infer the action of two selective forces that shape the distribution of integration sites in vivo: positive selection for cells containing proviral integration sites in transcriptionally active regions of the genome, and negative selection against cells with proviral integration sites within transcription units. The human leukaemia virus HTLV-1 causes a lifelong infection that cannot be cleared by the immune system. By integrating into the host's DNA, the virus can lie dormant within the cell. The virus can then be reactivated, by processes that are only partly understood, causing the infected cell to multiply and leading to an increase in the quantity of virus in the infected person. In some infected people, the virus is reactivated much faster than in others, and such people are more likely to develop HTLV-1-associated inflammatory diseases such as HAM/TSP, which results in paralysis of the legs. It is not understood what determines this rate of viral reactivation in each person. In this study, we found that integration of HTLV-1 in the host's DNA close to other genes was associated with faster viral reactivation and a higher probability of HAM/TSP. By comparing the viral integration site positions in samples from patients and in cells infected with HTLV-1 in the laboratory, we can identify some of the major forces that allow the virus to persist lifelong whilst avoiding eradication by the immune response.
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Nord AS, Vranizan K, Tingley W, Zambon AC, Hanspers K, Fong LG, Hu Y, Bacchetti P, Ferrin TE, Babbitt PC, Doniger SW, Skarnes WC, Young SG, Conklin BR. Modeling insertional mutagenesis using gene length and expression in murine embryonic stem cells. PLoS One 2007; 2:e617. [PMID: 17637833 PMCID: PMC1910612 DOI: 10.1371/journal.pone.0000617] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2007] [Accepted: 05/31/2007] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND High-throughput mutagenesis of the mammalian genome is a powerful means to facilitate analysis of gene function. Gene trapping in embryonic stem cells (ESCs) is the most widely used form of insertional mutagenesis in mammals. However, the rules governing its efficiency are not fully understood, and the effects of vector design on the likelihood of gene-trapping events have not been tested on a genome-wide scale. METHODOLOGY/PRINCIPAL FINDINGS In this study, we used public gene-trap data to model gene-trap likelihood. Using the association of gene length and gene expression with gene-trap likelihood, we constructed spline-based regression models that characterize which genes are susceptible and which genes are resistant to gene-trapping techniques. We report results for three classes of gene-trap vectors, showing that both length and expression are significant determinants of trap likelihood for all vectors. Using our models, we also quantitatively identified hotspots of gene-trap activity, which represent loci where the high likelihood of vector insertion is controlled by factors other than length and expression. These formalized statistical models describe a high proportion of the variance in the likelihood of a gene being trapped by expression-dependent vectors and a lower, but still significant, proportion of the variance for vectors that are predicted to be independent of endogenous gene expression. CONCLUSIONS/SIGNIFICANCE The findings of significant expression and length effects reported here further the understanding of the determinants of vector insertion. Results from this analysis can be applied to help identify other important determinants of this important biological phenomenon and could assist planning of large-scale mutagenesis efforts.
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Affiliation(s)
- Alex S. Nord
- Department of Medicine, MacDonald Medical Research Laboratories, University of California at Los Angeles, California, United States of America
- Gladstone Institute of Cardiovascular Disease, San Francisco, California, United States of America
- Departments of Biopharmaceutical Sciences and Pharmaceutical Chemistry, University of California at San Francisco, California, United States of America
- * To whom correspondence should be addressed. E-mail: (AN); (BC)
| | - Karen Vranizan
- Gladstone Institute of Cardiovascular Disease, San Francisco, California, United States of America
- Functional Genomics Laboratory, University of California at Berkeley, California, United States of America
| | - Whittemore Tingley
- Gladstone Institute of Cardiovascular Disease, San Francisco, California, United States of America
- Department of Medicine, University of California at San Francisco, California, United States of America
| | - Alexander C. Zambon
- Gladstone Institute of Cardiovascular Disease, San Francisco, California, United States of America
- Department of Medicine, University of California at San Francisco, California, United States of America
| | - Kristina Hanspers
- Gladstone Institute of Cardiovascular Disease, San Francisco, California, United States of America
- Department of Medicine, University of California at San Francisco, California, United States of America
| | - Loren G. Fong
- Department of Medicine, MacDonald Medical Research Laboratories, University of California at Los Angeles, California, United States of America
| | - Yan Hu
- Department of Medicine, MacDonald Medical Research Laboratories, University of California at Los Angeles, California, United States of America
| | - Peter Bacchetti
- Department of Epidemiology and Biostatistics, University of California at San Francisco, California, United States of America
| | - Thomas E. Ferrin
- Departments of Biopharmaceutical Sciences and Pharmaceutical Chemistry, University of California at San Francisco, California, United States of America
| | - Patricia C. Babbitt
- Departments of Biopharmaceutical Sciences and Pharmaceutical Chemistry, University of California at San Francisco, California, United States of America
| | - Scott W. Doniger
- Gladstone Institute of Cardiovascular Disease, San Francisco, California, United States of America
- Washington University School of Medicine, St. Louis, Missouri, United States of America
| | | | - Stephen G. Young
- Department of Medicine, MacDonald Medical Research Laboratories, University of California at Los Angeles, California, United States of America
| | - Bruce R. Conklin
- Gladstone Institute of Cardiovascular Disease, San Francisco, California, United States of America
- Department of Medicine, University of California at San Francisco, California, United States of America
- Department of Molecular and Cellular Pharmacology, University of California at San Francisco, California, United States of America
- * To whom correspondence should be addressed. E-mail: (AN); (BC)
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40
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Wang GP, Ciuffi A, Leipzig J, Berry CC, Bushman FD. HIV integration site selection: analysis by massively parallel pyrosequencing reveals association with epigenetic modifications. Genome Res 2007; 17:1186-94. [PMID: 17545577 PMCID: PMC1933515 DOI: 10.1101/gr.6286907] [Citation(s) in RCA: 347] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Integration of retroviral DNA into host cell DNA is a defining feature of retroviral replication. HIV integration is known to be favored in active transcription units, which promotes efficient transcription of the viral genes, but the molecular mechanisms responsible for targeting are not fully clarified. Here we used pyrosequencing to map 40,569 unique sites of HIV integration. Computational prediction of nucleosome positions in target DNA indicated that integration sites are periodically distributed on the nucleosome surface, consistent with favored integration into outward-facing DNA major grooves in chromatin. Analysis of integration site positions in the densely annotated ENCODE regions revealed a wealth of new associations between integration frequency and genomic features. Integration was particularly favored near transcription-associated histone modifications, including H3 acetylation, H4 acetylation, and H3 K4 methylation, but was disfavored in regions rich in transcription-inhibiting modifications, which include H3 K27 trimethylation and DNA CpG methylation. Statistical modeling indicated that effects of histone modification on HIV integration were partially independent of other genomic features influencing integration. The pyrosequencing and bioinformatic methods described here should be useful for investigating many aspects of retroviral DNA integration.
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Affiliation(s)
- Gary P. Wang
- University of Pennsylvania, School of Medicine, Department of Microbiology, Philadelphia, Pennsylvania 19104-6076, USA
| | - Angela Ciuffi
- University of Pennsylvania, School of Medicine, Department of Microbiology, Philadelphia, Pennsylvania 19104-6076, USA
| | - Jeremy Leipzig
- University of Pennsylvania, School of Medicine, Department of Microbiology, Philadelphia, Pennsylvania 19104-6076, USA
| | - Charles C. Berry
- Department of Family/Preventive Medicine, University of California, San Diego School of Medicine, San Diego, California 92093, USA
| | - Frederic D. Bushman
- University of Pennsylvania, School of Medicine, Department of Microbiology, Philadelphia, Pennsylvania 19104-6076, USA
- Corresponding author.E-mail ; fax (215) 573-4856
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41
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Lieberman PM. Chromatin regulation of virus infection. Trends Microbiol 2006; 14:132-40. [PMID: 16458005 DOI: 10.1016/j.tim.2006.01.001] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2005] [Revised: 12/14/2005] [Accepted: 01/16/2006] [Indexed: 02/02/2023]
Abstract
Cellular chromatin forms a dynamic structure that maintains the stability and accessibility of the host DNA genome. Viruses that enter and persist in the nucleus must, therefore, contend with the forces that drive chromatin formation and regulate chromatin structure. In some cases, cellular chromatin inhibits viral gene expression and replication by suppressing DNA accessibility. In other cases, cellular chromatin provides essential structure and organization to the viral genome and is necessary for successful completion of the viral life cycle. Consequently, viruses have acquired numerous mechanisms to manipulate cellular chromatin to ensure viral genome survival and propagation.
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Wu X, Li Y, Crise B, Burgess SM, Munroe DJ. Weak palindromic consensus sequences are a common feature found at the integration target sites of many retroviruses. J Virol 2005; 79:5211-4. [PMID: 15795304 PMCID: PMC1069554 DOI: 10.1128/jvi.79.8.5211-5214.2005] [Citation(s) in RCA: 127] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Integration into the host genome is one of the hallmarks of the retroviral life cycle and is catalyzed by virus-encoded integrases. While integrase has strict sequence requirements for the viral DNA ends, target site sequences have been shown to be very diverse. We carefully examined a large number of integration target site sequences from several retroviruses, including human immunodeficiency virus type 1, simian immunodeficiency virus, murine leukemia virus, and avian sarcoma-leukosis virus, and found that a statistical palindromic consensus, centered on the virus-specific duplicated target site sequence, was a common feature at integration target sites for these retroviruses.
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Affiliation(s)
- Xiaolin Wu
- Laboratory of Molecular Technology, Scientific Application International Corporation, National Cancer Institute at Frederick, 915 Toll House Ave., Frederick, MD 21701, USA
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Ason B, Knauss DJ, Balke AM, Merkel G, Skalka AM, Reznikoff WS. Targeting Tn5 transposase identifies human immunodeficiency virus type 1 inhibitors. Antimicrob Agents Chemother 2005; 49:2035-43. [PMID: 15855529 PMCID: PMC1087639 DOI: 10.1128/aac.49.5.2035-2043.2005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2004] [Revised: 10/12/2004] [Accepted: 12/29/2004] [Indexed: 11/20/2022] Open
Abstract
Human immunodeficiency virus (HIV) type 1 (HIV-1) integrase is an underutilized drug target for the treatment of HIV infection. One limiting factor is the lack of costructural data for use in the rational design or modification of integrase inhibitors. Tn5 transposase is a structurally well characterized, related protein that may serve as a useful surrogate. However, little data exist on inhibitor cross-reactivity. Here we screened 16,000 compounds using Tn5 transposase as the target and identified 20 compounds that appear to specifically inhibit complex assembly. Six were found to also inhibit HIV-1 integrase. These compounds likely interact with a highly conserved region presumably within the catalytic core. Most promising, several cinnamoyl derivatives were found to inhibit HIV transduction in cells. The identification of integrase inhibitors from a screen using Tn5 transposase as the target illustrates the utility of Tn5 as a surrogate for HIV-1 integration even though the relationship between the two systems is limited to the active site architecture and catalytic mechanism.
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Affiliation(s)
- Brandon Ason
- Department of Biochemistry, University of Wisconsin-Madison, 433 Babcock Drive, Madison, WI 53706-1544, USA
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Narezkina A, Taganov KD, Litwin S, Stoyanova R, Hayashi J, Seeger C, Skalka AM, Katz RA. Genome-wide analyses of avian sarcoma virus integration sites. J Virol 2004; 78:11656-63. [PMID: 15479807 PMCID: PMC523270 DOI: 10.1128/jvi.78.21.11656-11663.2004] [Citation(s) in RCA: 133] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The chromosomal features that influence retroviral integration site selection are not well understood. Here, we report the mapping of 226 avian sarcoma virus (ASV) integration sites in the human genome. The results show that the sites are distributed over all chromosomes, and no global bias for integration site selection was detected. However, RNA polymerase II transcription units (protein-encoding genes) appear to be favored targets of ASV integration. The integration frequency within genes is similar to that previously described for murine leukemia virus but distinct from the higher frequency observed with human immunodeficiency virus type 1. We found no evidence for preferred ASV integration sites over the length of genes and immediate flanking regions. Microarray analysis of uninfected HeLa cells revealed that the expression levels of ASV target genes were similar to the median level for all genes represented in the array. Although expressed genes were targets for integration, we found no preference for integration into highly expressed genes. Our results provide a more detailed description of the chromosomal features that may influence ASV integration and support the idea that distinct, virus-specific mechanisms mediate integration site selection. Such differences may be relevant to viral pathogenesis and provide utility in retroviral vector design.
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Affiliation(s)
- Anna Narezkina
- Fox Chase Cancer Center, Institute for Cancer Research, 333 Cottman Ave., Philadelphia, PA 19111-2497, USA
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Kulkarni A, Pavithra L, Rampalli S, Mogare D, Babu K, Shiekh G, Ghosh S, Chattopadhyay S. HIV-1 integration sites are flanked by potential MARs that alone can act as promoters. Biochem Biophys Res Commun 2004; 322:672-7. [PMID: 15325282 DOI: 10.1016/j.bbrc.2004.07.170] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2004] [Indexed: 10/26/2022]
Abstract
Matrix attachment regions (MARs) are cis regulatory elements that modulate gene expression in a tissue and cell stage specific manner. Recent reports show that viral integration within the genome takes place at nonrandom active genes. We have checked for the presence of MARs in the vicinity of the reported 524 HIV-1 integration sites. Our studies show that in 92.5% cases, MARs flank the integration sites. Similarly, for adeno-associated virus, two potential MARs were present next to the integration site on the human chromosome. Earlier we have shown that short MAR sequences present upstream of HIV-1 LTR promote processive transcription at a distance. Here, using a well-studied IgH-MAR and another potential MAR from p53 promoter, we demonstrate that MARs alone can act as promoters. Thus, we propose that MAR elements near the HIV-1 integration sites can act as potential promoters, which may facilitate proviral integration and transcription.
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Affiliation(s)
- Asavari Kulkarni
- National Center for Cell Science, Pune University Campus, Ganeshkhind, Pune-411 007, India
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