1
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Baldwin ET, van Eeuwen T, Hoyos D, Zalevsky A, Tchesnokov EP, Sánchez R, Miller BD, Di Stefano LH, Ruiz FX, Hancock M, Işik E, Mendez-Dorantes C, Walpole T, Nichols C, Wan P, Riento K, Halls-Kass R, Augustin M, Lammens A, Jestel A, Upla P, Xibinaku K, Congreve S, Hennink M, Rogala KB, Schneider AM, Fairman JE, Christensen SM, Desrosiers B, Bisacchi GS, Saunders OL, Hafeez N, Miao W, Kapeller R, Zaller DM, Sali A, Weichenrieder O, Burns KH, Götte M, Rout MP, Arnold E, Greenbaum BD, Romero DL, LaCava J, Taylor MS. Structures, functions and adaptations of the human LINE-1 ORF2 protein. Nature 2024; 626:194-206. [PMID: 38096902 PMCID: PMC10830420 DOI: 10.1038/s41586-023-06947-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Accepted: 12/07/2023] [Indexed: 01/05/2024]
Abstract
The LINE-1 (L1) retrotransposon is an ancient genetic parasite that has written around one-third of the human genome through a 'copy and paste' mechanism catalysed by its multifunctional enzyme, open reading frame 2 protein (ORF2p)1. ORF2p reverse transcriptase (RT) and endonuclease activities have been implicated in the pathophysiology of cancer2,3, autoimmunity4,5 and ageing6,7, making ORF2p a potential therapeutic target. However, a lack of structural and mechanistic knowledge has hampered efforts to rationally exploit it. We report structures of the human ORF2p 'core' (residues 238-1061, including the RT domain) by X-ray crystallography and cryo-electron microscopy in several conformational states. Our analyses identified two previously undescribed folded domains, extensive contacts to RNA templates and associated adaptations that contribute to unique aspects of the L1 replication cycle. Computed integrative structural models of full-length ORF2p show a dynamic closed-ring conformation that appears to open during retrotransposition. We characterize ORF2p RT inhibition and reveal its underlying structural basis. Imaging and biochemistry show that non-canonical cytosolic ORF2p RT activity can produce RNA:DNA hybrids, activating innate immune signalling through cGAS/STING and resulting in interferon production6-8. In contrast to retroviral RTs, L1 RT is efficiently primed by short RNAs and hairpins, which probably explains cytosolic priming. Other biochemical activities including processivity, DNA-directed polymerization, non-templated base addition and template switching together allow us to propose a revised L1 insertion model. Finally, our evolutionary analysis demonstrates structural conservation between ORF2p and other RNA- and DNA-dependent polymerases. We therefore provide key mechanistic insights into L1 polymerization and insertion, shed light on the evolutionary history of L1 and enable rational drug development targeting L1.
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Affiliation(s)
| | - Trevor van Eeuwen
- Laboratory of Cellular and Structural Biology, The Rockefeller University, New York, NY, USA
| | - David Hoyos
- Computational Oncology, Department of Epidemiology & Biostatistics, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Arthur Zalevsky
- Department of Bioengineering and Therapeutic Sciences University of California, San Francisco, San Francisco, CA, USA
- Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA, USA
- Quantitative Biology Institute, University of California, San Francisco, San Francisco, CA, USA
| | - Egor P Tchesnokov
- Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Alberta, Canada
| | | | - Bryant D Miller
- Department of Pathology, Dana Farber Cancer Institute and Harvard Medical School, Boston, MA, USA
| | - Luciano H Di Stefano
- European Research Institute for the Biology of Ageing, University Medical Center Groningen, Groningen, The Netherlands
| | - Francesc Xavier Ruiz
- Center for Advanced Biotechnology and Medicine and Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ, USA
| | - Matthew Hancock
- Department of Bioengineering and Therapeutic Sciences University of California, San Francisco, San Francisco, CA, USA
- Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA, USA
- Quantitative Biology Institute, University of California, San Francisco, San Francisco, CA, USA
| | - Esin Işik
- Department of Pathology, Dana Farber Cancer Institute and Harvard Medical School, Boston, MA, USA
| | - Carlos Mendez-Dorantes
- Department of Pathology, Dana Farber Cancer Institute and Harvard Medical School, Boston, MA, USA
| | - Thomas Walpole
- Charles River Laboratories, Chesterford Research Park, Saffron Walden, UK
| | - Charles Nichols
- Charles River Laboratories, Chesterford Research Park, Saffron Walden, UK
| | - Paul Wan
- Charles River Laboratories, Chesterford Research Park, Saffron Walden, UK
| | - Kirsi Riento
- Charles River Laboratories, Chesterford Research Park, Saffron Walden, UK
| | - Rowan Halls-Kass
- Charles River Laboratories, Chesterford Research Park, Saffron Walden, UK
| | | | - Alfred Lammens
- Proteros Biostructures GmbH, Martinsried, Planegg, Germany
| | - Anja Jestel
- Proteros Biostructures GmbH, Martinsried, Planegg, Germany
| | - Paula Upla
- Laboratory of Cellular and Structural Biology, The Rockefeller University, New York, NY, USA
| | - Kera Xibinaku
- Whitehead Institute for Biomedical Research, Cambridge, MA, USA
| | | | | | - Kacper B Rogala
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA, USA
- Stanford Cancer Institute, Stanford University School of Medicine, Stanford, CA, USA
| | - Anna M Schneider
- Structural Biology of Selfish RNA, Department of Protein Evolution, Max Planck Institute for Biology, Tübingen, Germany
| | | | | | | | | | | | | | | | | | | | - Andrej Sali
- Department of Bioengineering and Therapeutic Sciences University of California, San Francisco, San Francisco, CA, USA
- Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA, USA
- Quantitative Biology Institute, University of California, San Francisco, San Francisco, CA, USA
| | - Oliver Weichenrieder
- Structural Biology of Selfish RNA, Department of Protein Evolution, Max Planck Institute for Biology, Tübingen, Germany
| | - Kathleen H Burns
- Department of Pathology, Dana Farber Cancer Institute and Harvard Medical School, Boston, MA, USA.
| | - Matthias Götte
- Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Alberta, Canada.
| | - Michael P Rout
- Laboratory of Cellular and Structural Biology, The Rockefeller University, New York, NY, USA.
| | - Eddy Arnold
- Center for Advanced Biotechnology and Medicine and Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ, USA.
| | - Benjamin D Greenbaum
- Computational Oncology, Department of Epidemiology & Biostatistics, Memorial Sloan Kettering Cancer Center, New York, NY, USA.
- Physiology, Biophysics & Systems Biology, Weill Cornell Medicine, Weill Cornell Medical College, New York, NY, USA.
| | | | - John LaCava
- Laboratory of Cellular and Structural Biology, The Rockefeller University, New York, NY, USA.
- European Research Institute for the Biology of Ageing, University Medical Center Groningen, Groningen, The Netherlands.
| | - Martin S Taylor
- Department of Pathology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA.
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2
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Ni P, Zhao Y, Zhou X, Liu Z, Huang Z, Ni Z, Sun Q, Zong Y. Efficient and versatile multiplex prime editing in hexaploid wheat. Genome Biol 2023; 24:156. [PMID: 37386475 PMCID: PMC10308706 DOI: 10.1186/s13059-023-02990-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2023] [Accepted: 06/15/2023] [Indexed: 07/01/2023] Open
Abstract
Prime editing is limited by low efficiency in plants. Here, we develop an upgraded engineered plant prime editor in hexaploid wheat, ePPEplus, by introducing a V223A substitution into reverse transcriptase in the ePPEmax* architecture. ePPEplus enhances the efficiency by an average 33.0-fold and 6.4-fold compared to the original PPE and ePPE, respectively. Importantly, a robust multiplex prime editing platform is established for simultaneous editing of four to ten genes in protoplasts and up to eight genes in regenerated wheat plants at frequencies up to 74.5%, thus expanding the applicability of prime editors for stacking of multiple agronomic traits.
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Affiliation(s)
- Pei Ni
- Frontiers Science Center for Molecular Design Breeding (MOE), Key Laboratory of Crop Heterosis and Utilization (MOE), and Beijing Key Laboratory of Crop Genetic Improvement, China Agricultural University, Beijing, 100193, China
| | - Yidi Zhao
- Frontiers Science Center for Molecular Design Breeding (MOE), Key Laboratory of Crop Heterosis and Utilization (MOE), and Beijing Key Laboratory of Crop Genetic Improvement, China Agricultural University, Beijing, 100193, China
| | - Ximeng Zhou
- Frontiers Science Center for Molecular Design Breeding (MOE), Key Laboratory of Crop Heterosis and Utilization (MOE), and Beijing Key Laboratory of Crop Genetic Improvement, China Agricultural University, Beijing, 100193, China
| | - Zehua Liu
- Frontiers Science Center for Molecular Design Breeding (MOE), Key Laboratory of Crop Heterosis and Utilization (MOE), and Beijing Key Laboratory of Crop Genetic Improvement, China Agricultural University, Beijing, 100193, China
| | - Zhengwei Huang
- Frontiers Science Center for Molecular Design Breeding (MOE), Key Laboratory of Crop Heterosis and Utilization (MOE), and Beijing Key Laboratory of Crop Genetic Improvement, China Agricultural University, Beijing, 100193, China
| | - Zhongfu Ni
- Frontiers Science Center for Molecular Design Breeding (MOE), Key Laboratory of Crop Heterosis and Utilization (MOE), and Beijing Key Laboratory of Crop Genetic Improvement, China Agricultural University, Beijing, 100193, China
| | - Qixin Sun
- Frontiers Science Center for Molecular Design Breeding (MOE), Key Laboratory of Crop Heterosis and Utilization (MOE), and Beijing Key Laboratory of Crop Genetic Improvement, China Agricultural University, Beijing, 100193, China
| | - Yuan Zong
- Frontiers Science Center for Molecular Design Breeding (MOE), Key Laboratory of Crop Heterosis and Utilization (MOE), and Beijing Key Laboratory of Crop Genetic Improvement, China Agricultural University, Beijing, 100193, China.
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3
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Masuda T, Kotani O, Yokoyama M, Abe Y, Kawai G, Sato H. Cis-Allosteric Regulation of HIV-1 Reverse Transcriptase by Integrase. Viruses 2022; 15:31. [PMID: 36680070 PMCID: PMC9864105 DOI: 10.3390/v15010031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Revised: 12/19/2022] [Accepted: 12/19/2022] [Indexed: 12/24/2022] Open
Abstract
Reverse transcriptase (RT) and integrase (IN) are encoded tandemly in the pol genes of retroviruses. We reported recently that HIV-1 RT and IN need to be supplied as the pol precursor intermediates, in which RT and IN are in fusion form (RTIN) to exert efficient reverse transcription in the context of HIV-1 replication. The mechanism underlying RTIN's effect, however, remains to be elucidated. In this study, we examined the effect of IN fusion on RT during reverse transcription by an in vitro cell-free assay, using recombinant HIV-1 RTIN (rRTIN). We found that, compared to recombinant RT (rRT), rRTIN generated significantly higher cDNAs under physiological concentrations of dNTPs (less than 10 μM), suggesting increased affinity of RTIN to dNTPs. Importantly, the cleavage of RTIN with HIV-1 protease reduced cDNA levels at a low dose of dNTPs. Similarly, sensitivities against RT inhibitors were significantly altered in RTIN form. Finally, analysis of molecular dynamics simulations of RT and RTIN suggested that IN can influence the structural dynamics of the RT active center and the inhibitor binding pockets in cis. Thus, we demonstrated, for the first time, the cis-allosteric regulatory roles of IN in RT structure and enzymatic activity.
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Affiliation(s)
- Takao Masuda
- Department of Immunotherapeutics, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Yushima, 1-5-45 Bunkyo-ku, Tokyo 113-8519, Japan
| | - Osamu Kotani
- Laboratory of Viral Genomics, Pathogen Genomics Center, National Institute of Infectious Diseases, Gakuen, 4-7-1, Musashimurayama-shi, Tokyo 208-0011, Japan
| | - Masaru Yokoyama
- Laboratory of Viral Genomics, Pathogen Genomics Center, National Institute of Infectious Diseases, Gakuen, 4-7-1, Musashimurayama-shi, Tokyo 208-0011, Japan
| | - Yuya Abe
- Department of Immunotherapeutics, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Yushima, 1-5-45 Bunkyo-ku, Tokyo 113-8519, Japan
| | - Gota Kawai
- Department of Life Science, Faculty of Advanced Engineering, Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino-shi, Chiba 275-0016, Japan
| | - Hironori Sato
- Laboratory of Viral Genomics, Pathogen Genomics Center, National Institute of Infectious Diseases, Gakuen, 4-7-1, Musashimurayama-shi, Tokyo 208-0011, Japan
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4
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Stevens LJ, Pruijssers AJ, Lee HW, Gordon CJ, Tchesnokov EP, Gribble J, George AS, Hughes TM, Lu X, Li J, Perry JK, Porter DP, Cihlar T, Sheahan TP, Baric RS, Götte M, Denison MR. Mutations in the SARS-CoV-2 RNA-dependent RNA polymerase confer resistance to remdesivir by distinct mechanisms. Sci Transl Med 2022; 14:eabo0718. [PMID: 35482820 PMCID: PMC9097878 DOI: 10.1126/scitranslmed.abo0718] [Citation(s) in RCA: 104] [Impact Index Per Article: 52.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Accepted: 04/14/2022] [Indexed: 12/19/2022]
Abstract
The nucleoside analog remdesivir (RDV) is a Food and Drug Administration-approved antiviral for treatment of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections. Thus, it is critical to understand factors that promote or prevent RDV resistance. We passaged SARS-CoV-2 in the presence of increasing concentrations of GS-441524, the parent nucleoside of RDV. After 13 passages, we isolated three viral lineages with phenotypic resistance as defined by increases in half-maximal effective concentration from 2.7- to 10.4-fold. Sequence analysis identified nonsynonymous mutations in nonstructural protein 12 RNA-dependent RNA polymerase (nsp12-RdRp): V166A, N198S, S759A, V792I, and C799F/R. Two lineages encoded the S759A substitution at the RdRp Ser759-Asp-Asp active motif. In one lineage, the V792I substitution emerged first and then combined with S759A. Introduction of S759A and V792I substitutions at homologous nsp12 positions in murine hepatitis virus demonstrated transferability across betacoronaviruses; introduction of these substitutions resulted in up to 38-fold RDV resistance and a replication defect. Biochemical analysis of SARS-CoV-2 RdRp encoding S759A demonstrated a roughly 10-fold decreased preference for RDV-triphosphate (RDV-TP) as a substrate, whereas nsp12-V792I diminished the uridine triphosphate concentration needed to overcome template-dependent inhibition associated with RDV. The in vitro-selected substitutions identified in this study were rare or not detected in the greater than 6 million publicly available nsp12-RdRp consensus sequences in the absence of RDV selection. The results define genetic and biochemical pathways to RDV resistance and emphasize the need for additional studies to define the potential for emergence of these or other RDV resistance mutations in clinical settings.
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Affiliation(s)
- Laura J. Stevens
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN, 37232, USA
| | - Andrea J. Pruijssers
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN, 37232, USA
- Vanderbilt Institute for Infection, Immunology, and Inflammation, Nashville, TN, 37232, USA
| | - Hery W. Lee
- Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, AB, T6G 2T9, CA
| | - Calvin J. Gordon
- Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, AB, T6G 2T9, CA
| | - Egor P. Tchesnokov
- Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, AB, T6G 2T9, CA
| | - Jennifer Gribble
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, TN, 37232, USA
| | - Amelia S. George
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN, 37232, USA
| | - Tia M. Hughes
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN, 37232, USA
| | - Xiaotao Lu
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN, 37232, USA
| | - Jiani Li
- Gilead Sciences, Inc, Foster City, CA, 94404, USA
| | | | | | - Tomas Cihlar
- Gilead Sciences, Inc, Foster City, CA, 94404, USA
| | - Timothy P. Sheahan
- Department of Epidemiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Ralph S. Baric
- Department of Epidemiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Matthias Götte
- Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, AB, T6G 2T9, CA
| | - Mark R. Denison
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN, 37232, USA
- Vanderbilt Institute for Infection, Immunology, and Inflammation, Nashville, TN, 37232, USA
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, TN, 37232, USA
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5
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Huber C, von Watzdorf J, Marx A. 5-methylcytosine-sensitive variants of Thermococcus kodakaraensis DNA polymerase. Nucleic Acids Res 2016; 44:9881-9890. [PMID: 27651460 PMCID: PMC5175357 DOI: 10.1093/nar/gkw812] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Revised: 09/03/2016] [Accepted: 09/05/2016] [Indexed: 12/28/2022] Open
Abstract
DNA methylation of cytosine in eukaryotic cells is a common epigenetic modification, which plays an important role in gene expression and thus affects various cellular processes like development and carcinogenesis. The occurrence of 5-methyl-2'-deoxycytosine (5mC) as well as the distribution pattern of this epigenetic marker were shown to be crucial for gene regulation and can serve as important biomarkers for diagnostics. DNA polymerases distinguish little, if any, between incorporation opposite C and 5mC, which is not surprising since the site of methylation is not involved in Watson-Crick recognition. Here, we describe the development of a DNA polymerase variant that incorporates the canonical 2'-deoxyguanosine 5'-monophosphate (dGMP) opposite C with higher efficiency compared to 5mC. The variant of Thermococcus kodakaraensis (KOD) exo- DNA polymerase was discovered by screening mutant libraries that were built by rational design. We discovered that an amino acid substitution at a single site that does not directly interact with the templating nucleobase, may alter the ability of the DNA polymerase in processing C in comparison to 5mC. Employing these findings in combination with a nucleotide, which is fluorescently labeled at the terminal phosphate, indicates the potential use of the mutant DNA polymerase in the detection of 5mC.
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Affiliation(s)
- Claudia Huber
- Department of Chemistry, Konstanz Research School Chemical Biology, University of Konstanz, Universitätsstraße 10, D-78457 Konstanz, Germany
| | - Janina von Watzdorf
- Department of Chemistry, Konstanz Research School Chemical Biology, University of Konstanz, Universitätsstraße 10, D-78457 Konstanz, Germany
| | - Andreas Marx
- Department of Chemistry, Konstanz Research School Chemical Biology, University of Konstanz, Universitätsstraße 10, D-78457 Konstanz, Germany
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6
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Sharma PL, Nurpeisov V, Schinazi RF. Retrovirus Reverse Transcriptases Containing a Modified YXDD Motif. ACTA ACUST UNITED AC 2016; 16:169-82. [PMID: 16004080 DOI: 10.1177/095632020501600303] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The YXDD motif, where X is a variable amino acid, is highly conserved among various viral RNA-dependent DNA polymerases. Mutations in the YXDD motif can abolish enzymatic activity, alter the processivity and fidelity of enzymes and decrease virus infectivity. This review provides a summary of the significant documented studies on the YXDD motif of HIV-1, simian immunodeficiency virus, feline immunodeficiency virus and murine leukaemia virus and the impact of mutation that this motif has had on viral pathogenesis and drug treatment.
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Affiliation(s)
- Prem L Sharma
- Laboratory of Biochemical Pharmacology and Department of Pediatrics, Emory University School of Medicine, Atlanta, GA, USA
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7
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Activity of a novel combined antiretroviral therapy of gemcitabine and decitabine in a mouse model for HIV-1. Antimicrob Agents Chemother 2012; 56:1942-8. [PMID: 22271861 DOI: 10.1128/aac.06161-11] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The emergence of drug resistance threatens to limit the use of current anti-HIV-1 drugs and highlights the need to expand the number of treatment options available for HIV-1-infected individuals. Our previous studies demonstrated that two clinically approved drugs, decitabine and gemcitabine, potently inhibited HIV-1 replication in cell culture through a mechanism that is distinct from the mechanisms for the drugs currently used to treat HIV-1 infection. We further demonstrated that gemcitabine inhibited replication of a related retrovirus, murine leukemia virus (MuLV), in vivo using the MuLV-based LP-BM5/murine AIDS (MAIDS) mouse model at doses that were not toxic. Since decitabine and gemcitabine inhibited MuLV and HIV-1 replication with similar potency in cell culture, the current study examined the efficacy and toxicity of the drug combination using the MAIDS model. The data demonstrate that the drug combination inhibited disease progression, as detected by histopathology, viral loads, and spleen weights, at doses lower than those that would be required if the drugs were used individually. The combination of decitabine and gemcitabine exerted antiviral activity at doses that were not toxic. These findings indicate that the combination of decitabine and gemcitabine shows potent antiretroviral activity at nontoxic doses and should be further investigated for clinical relevance.
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8
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Greggs WM, Clouser CL, Patterson SE, Mansky LM. Discovery of drugs that possess activity against feline leukemia virus. J Gen Virol 2012; 93:900-905. [PMID: 22258856 DOI: 10.1099/vir.0.039909-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Feline leukemia virus (FeLV) is a gammaretrovirus that is a significant cause of neoplastic-related disorders affecting cats worldwide. Treatment options for FeLV are limited, associated with serious side effects, and can be cost-prohibitive. The development of drugs used to treat a related retrovirus, human immunodeficiency virus type 1 (HIV-1), has been rapid, leading to the approval of five drug classes. Although structural differences affect the susceptibility of gammaretroviruses to anti-HIV drugs, the similarities in mechanism of replication suggest that some anti-HIV-1 drugs may also inhibit FeLV. This study demonstrates the anti-FeLV activity of four drugs approved by the US FDA (Food and Drug Administration) at non-toxic concentrations. Of these, tenofovir and raltegravir are anti-HIV-1 drugs, while decitabine and gemcitabine are approved to treat myelodysplastic syndromes and pancreatic cancer, respectively, but also have anti-HIV-1 activity in cell culture. Our results indicate that these drugs may be useful for FeLV treatment and should be investigated for mechanism of action and suitability for veterinary use.
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Affiliation(s)
- Willie M Greggs
- Comparative Molecular Biosciences Graduate Program, College of Veterinary Medicine, University of Minnesota, MN 55455, USA.,Institute for Molecular Virology, Academic Health Center, University of Minnesota, MN 55455 USA
| | - Christine L Clouser
- Department of Diagnostic and Biological Sciences, School of Dentistry, University of Minnesota, MN 55455, USA.,Institute for Molecular Virology, Academic Health Center, University of Minnesota, MN 55455 USA
| | - Steven E Patterson
- Center for Drug Design, Academic Health Center, University of Minnesota, MN 55455, USA.,Institute for Molecular Virology, Academic Health Center, University of Minnesota, MN 55455 USA
| | - Louis M Mansky
- Department of Microbiology, Medical School, University of Minnesota, MN 55455, USA.,Comparative Molecular Biosciences Graduate Program, College of Veterinary Medicine, University of Minnesota, MN 55455, USA.,Center for Drug Design, Academic Health Center, University of Minnesota, MN 55455, USA.,Institute for Molecular Virology, Academic Health Center, University of Minnesota, MN 55455 USA.,Department of Diagnostic and Biological Sciences, School of Dentistry, University of Minnesota, MN 55455, USA
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9
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Smith RA, Gottlieb GS, Miller AD. Susceptibility of the human retrovirus XMRV to antiretroviral inhibitors. Retrovirology 2010; 7:70. [PMID: 20807431 PMCID: PMC2939604 DOI: 10.1186/1742-4690-7-70] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2010] [Accepted: 08/31/2010] [Indexed: 11/10/2022] Open
Abstract
Background XMRV (xenotropic murine leukemia virus-related virus) is the first known example of an exogenous gammaretrovirus that can infect humans. A limited number of reports suggest that XMRV is intrinsically resistant to many of the antiretroviral drugs used to treat HIV-1 infection, but is sensitive to a small subset of these inhibitors. In the present study, we used a novel marker transfer assay to directly compare the antiviral drug sensitivities of XMRV and HIV-1 under identical conditions in the same host cell type. Results We extend the findings of previous studies by showing that, in addition to AZT and tenofovir, XMRV and HIV-1 are equally sensitive to AZddA (3'-azido-2',3'-dideoxyadenosine), AZddG (3'-azido-2',3'-dideoxyguanosine) and adefovir. These results indicate that specific 3'-azido or acyclic nucleoside analog inhibitors of HIV-1 reverse transcriptase (RT) also block XMRV infection with comparable efficacy in vitro. Our data confirm that XMRV is highly resistant to the non-nucleoside RT inhibitors nevirapine and efavirenz and to inhibitors of HIV-1 protease. In addition, we show that the integrase inhibitors raltegravir and elvitegravir are active against XMRV, with EC50 values in the nanomolar range. Conclusions Our analysis demonstrates that XMRV exhibits a distinct pattern of nucleoside analog susceptibility that correlates with the structure of the pseudosugar moiety and that XMRV is sensitive to a broader range of antiretroviral drugs than has previously been reported. We suggest that the divergent drug sensitivity profiles of XMRV and HIV-1 are partially explained by specific amino acid differences in their respective protease, RT and integrase sequences. Our data provide a basis for choosing specific antiretroviral drugs for clinical studies in XMRV-infected patients.
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Affiliation(s)
- Robert A Smith
- Department of Pathology, University of Washington, Seattle, USA.
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10
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Götte M, Rausch JW, Marchand B, Sarafianos S, Le Grice SF. Reverse transcriptase in motion: conformational dynamics of enzyme-substrate interactions. BIOCHIMICA ET BIOPHYSICA ACTA 2010; 1804:1202-12. [PMID: 19665597 PMCID: PMC2930377 DOI: 10.1016/j.bbapap.2009.07.020] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2009] [Accepted: 07/28/2009] [Indexed: 11/26/2022]
Abstract
Human immunodeficiency virus type 1 reverse transcriptase (HIV-1 RT) catalyzes synthesis of integration-competent, double-stranded DNA from the single-stranded viral RNA genome, combining both polymerizing and hydrolytic functions to synthesize approximately 20,000 phosphodiester bonds. Despite a wealth of biochemical studies, the manner whereby the enzyme adopts different orientations to coordinate its DNA polymerase and ribonuclease (RNase) H activities has remained elusive. Likewise, the lower processivity of HIV-1 RT raises the issue of polymerization site targeting, should the enzyme re-engage its nucleic acid substrate several hundred nucleotides from the primer terminus. Although X-ray crystallography has clearly contributed to our understanding of RT-containing nucleoprotein complexes, it provides a static picture, revealing few details regarding motion of the enzyme on the substrate. Recent development of site-specific footprinting and the application of single molecule spectroscopy have allowed us to follow individual steps in the reverse transcription process with significantly greater precision. Progress in these areas and the implications for investigational and established inhibitors that interfere with RT motion on nucleic acid is reviewed here.
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Affiliation(s)
- Matthias Götte
- Department of Microbiology & Immunology, McGill University, Montreal, QC, Canada, H3A 2B4
| | - Jason W. Rausch
- RT Biochemistry Section, HIV Drug Resistance Program, National Cancer Institute, Frederick, MD, USA
| | - Bruno Marchand
- Christopher Bond Life Sciences Center, Department of Molecular Microbiology & Immunology, University of Missouri School of Medicine, Columbia, MO 65211, USA
| | - Stefan Sarafianos
- Christopher Bond Life Sciences Center, Department of Molecular Microbiology & Immunology, University of Missouri School of Medicine, Columbia, MO 65211, USA
| | - Stuart F.J. Le Grice
- RT Biochemistry Section, HIV Drug Resistance Program, National Cancer Institute, Frederick, MD, USA
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11
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Sakuma R, Sakuma T, Ohmine S, Silverman RH, Ikeda Y. Xenotropic murine leukemia virus-related virus is susceptible to AZT. Virology 2009; 397:1-6. [PMID: 19959199 DOI: 10.1016/j.virol.2009.11.013] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2009] [Revised: 10/20/2009] [Accepted: 11/06/2009] [Indexed: 10/20/2022]
Abstract
The xenotropic murine leukemia virus-related virus (XMRV) is a human retrovirus, recently isolated from tissues of prostate cancer patients with impaired RNase L activity. In this study, we evaluated 10 licensed anti-HIV-1 compounds for their activity against XMRV, including protease inhibitors (PI), nucleoside reverse transcriptase (RT) inhibitors (NRTI), non-nucleoside RT inhibitors (NNRTI) and an integrase inhibitor. No PI affected XMRV production; even high concentrations of Ritonavir failed to inhibit the maturation of XMRV Gag polyproteins. Among the NRTI, NNRTI and integrase inhibitors used in this study, only AZT blocked XMRV infection and replication through inhibition of viral reverse transcription. This sensitivity of XMRV to AZT may be explained by the modest homology in the motif D sequences of HIV-1 and XMRV reverse transcriptases. If XMRV becomes established as an etiological agent for prostate cancer or other diseases, AZT may be useful for preventing or treating XMRV infections in humans.
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Affiliation(s)
- Ryuta Sakuma
- Department of Molecular Medicine, Mayo Clinic, Rochester, MN 55906, USA
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12
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Gao L, Hanson MN, Balakrishnan M, Boyer PL, Roques BP, Hughes SH, Kim B, Bambara RA. Apparent defects in processive DNA synthesis, strand transfer, and primer elongation of Met-184 mutants of HIV-1 reverse transcriptase derive solely from a dNTP utilization defect. J Biol Chem 2008; 283:9196-205. [PMID: 18218634 DOI: 10.1074/jbc.m710148200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The 2',3'-dideoxy-3'-thiacytidine drug-resistant M184I HIV-1 reverse transcriptase (RT) has been shown to synthesize DNA with decreased processivity compared with the wild-type RT. M184A displays an even more severe processivity defect. However, the basis of this decreased processivity has been unclear, and both primer-template binding and dNTP interaction defects have been proposed to account for it. In this study, we show that the altered properties of the M184I and M184A RT mutants that we have measured, including decreased processivity, a slower rate of primer extension, and increased strand transfer activity, can all be explained by a defect in dNTP utilization. These alterations are observed only at low dNTP concentration and vanish as the dNTP concentration is raised. The mutant RTs exhibit a normal dissociation rate from a DNA primer-RNA template while paused during synthesis. Slower than normal synthesis at physiological dNTP concentration, coupled with normal dissociation from the primer-template, results in the lowered processivity. The mutant RTs exhibit normal DNA 3'-end-directed and RNA 5'-end-directed ribonuclease H activity. The reduced rate of DNA synthesis causes an increase in the ratio of ribonuclease H to polymerase activity thereby promoting increased strand transfer. These latter results are consistent with an observed higher rate of recombination by HIV-1 strains with Met-184 mutations.
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Affiliation(s)
- Lu Gao
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, NY 14642, USA
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13
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Diallo K, Götte M, Wainberg MA. Molecular impact of the M184V mutation in human immunodeficiency virus type 1 reverse transcriptase. Antimicrob Agents Chemother 2004; 47:3377-83. [PMID: 14576091 PMCID: PMC253767 DOI: 10.1128/aac.47.11.3377-3383.2003] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- Karidia Diallo
- McGill AIDS Centre, Lady Davis Institute-Jewish General Hospital and Department of Microbiology and Immunology, McGill University, Montreal, Québec H3T 1E2, Canada
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14
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Boyer PL, Stenbak CR, Clark PK, Linial ML, Hughes SH. Characterization of the polymerase and RNase H activities of human foamy virus reverse transcriptase. J Virol 2004; 78:6112-21. [PMID: 15163704 PMCID: PMC416499 DOI: 10.1128/jvi.78.12.6112-6121.2004] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Foamy virus (FV) replication, while related to that of orthoretroviruses, differs at a number of steps. Several of these differences involve the reverse transcriptase (RT). There appear to be fewer RTs present in FV than in orthoretroviruses; we previously proposed that the polymerase of FV RT was more active than orthoretroviral RTs to compensate for the numerical difference. Here we present further characterization of the RT of FV. The polymerase activity of FV RT was greater than that of human immunodeficiency virus type 1 RT in a variety of assays. We also examined the RNase H activity of FV RT, and we propose that FV RT has a basic loop in the RNase H domain. Although the sequence of the basic loop of FV RT is different from the basic loop of either Moloney leukemia virus RNase H or Escherichia coli RNase H, the FV RT basic loop appears to have a similar function.
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Affiliation(s)
- Paul L Boyer
- HIV Drug Resistance Program, National Cancer Institute-FCRDC, P.O. Box B, Building 539, Room 130A, Frederick, MD 21702-1201, USA
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15
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Julias JG, Boyer PL, McWilliams MJ, Alvord WG, Hughes SH. Mutations at position 184 of human immunodeficiency virus type-1 reverse transcriptase affect virus titer and viral DNA synthesis. Virology 2004; 322:13-21. [PMID: 15063112 DOI: 10.1016/j.virol.2004.01.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2003] [Revised: 12/29/2003] [Accepted: 01/08/2004] [Indexed: 11/24/2022]
Abstract
Methionine at position 184 of human immunodeficiency virus type-1 (HIV-1) reverse transcriptase (RT) was changed to valine, isoleucine, threonine, or alanine in an HIV-1-based vector. The vectors were analyzed for replication capacity and for resistance to the nucleoside analog 2',3'-dideoxy-3'thiacytidine (3TC) using a single-cycle assay. Viruses containing the valine or isoleucine mutations were highly resistant to 3TC and replicated almost as well as the wild-type virus. The virus containing the threonine mutation was resistant to 3TC, but replicated about 30% as well as the wild-type. The alanine mutation conferred partial resistance to 3TC, but replicated poorly. The amounts of viral DNA synthesized decreased in 3TC-treated cells when the cells were infected with wild-type virus and the M184A mutant. The effect of these mutations on the generation of the ends of the linear viral DNA was determined using the sequence of the 2-LTR circle junctions. The M184T mutation increased the proportion of 2-LTR circle junctions containing a tRNA insertion, suggesting that the mutation affected the RNase H activity of RT.
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Affiliation(s)
- John G Julias
- Basic Research Program, SAIC-Frederick, Inc., NCI-Frederick, Frederick, MD 21702-1201, USA
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16
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Tuske S, Sarafianos SG, Clark AD, Ding J, Naeger LK, White KL, Miller MD, Gibbs CS, Boyer PL, Clark P, Wang G, Gaffney BL, Jones RA, Jerina DM, Hughes SH, Arnold E. Structures of HIV-1 RT-DNA complexes before and after incorporation of the anti-AIDS drug tenofovir. Nat Struct Mol Biol 2004; 11:469-74. [PMID: 15107837 DOI: 10.1038/nsmb760] [Citation(s) in RCA: 132] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2004] [Accepted: 03/18/2004] [Indexed: 12/12/2022]
Abstract
Tenofovir, also known as PMPA, R-9-(2-(phosphonomethoxypropyl)adenine, is a nucleotide reverse transcriptase (RT) inhibitor. We have determined the crystal structures of two related complexes of HIV-1 RT with template primer and tenofovir: (i) a ternary complex at a resolution of 3.0 A of RT crosslinked to a dideoxy-terminated DNA with tenofovir-diphosphate bound as the incoming substrate; and (ii) a RT-DNA complex at a resolution of 3.1 A with tenofovir at the 3' primer terminus. The tenofovir nucleotide in the tenofovir-terminated structure seems to adopt multiple conformations. Some nucleoside reverse transcriptase inhibitors, including 3TC and AZT, have elements ('handles') that project beyond the corresponding elements on normal dNTPs (the 'substrate envelope'). HIV-1 RT resistance mechanisms to AZT and 3TC take advantage of these handles; tenofovir's structure lacks handles that could protrude through the substrate envelope to cause resistance.
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Affiliation(s)
- Steve Tuske
- Center for Advanced Biotechnology and Medicine and Rutgers University Department of Chemistry and Chemical Biology, 679 Hoes Lane, Piscataway, New Jersey 08854-5638, USA
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17
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Balestrieri E, Forte G, Matteucci C, Mastino A, Macchi B. Effect of lamivudine on transmission of human T-cell lymphotropic virus type 1 to adult peripheral blood mononuclear cells in vitro. Antimicrob Agents Chemother 2002; 46:3080-3. [PMID: 12183277 PMCID: PMC127437 DOI: 10.1128/aac.46.9.3080-3083.2002] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The effects of lamivudine (3TC) on in vitro infection of peripheral blood mononuclear cells (PBMC) from healthy donors with human T-cell lymphotropic virus type 1 (HTLV-1) were investigated. Direct measures of viral replication (viral DNA, RNA, and protein) all gave similar, very high 50% inhibitory concentrations in comparison with those previously reported for zidovudine. Nevertheless, 3TC inhibited HTLV-1-driven long-term growth of infected PBMC in vitro at concentrations (6.25 micro M) which had poor or no direct antiviral effects, suggesting that another mechanism may be playing a role.
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Affiliation(s)
- Emanuela Balestrieri
- Department of Microbiological, Genetic and Molecular Science, University of Messina, Messina, Italy
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18
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Boyer PL, Sarafianos SG, Arnold E, Hughes SH. Nucleoside analog resistance caused by insertions in the fingers of human immunodeficiency virus type 1 reverse transcriptase involves ATP-mediated excision. J Virol 2002; 76:9143-51. [PMID: 12186898 PMCID: PMC136461 DOI: 10.1128/jvi.76.18.9143-9151.2002] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Although anti-human immunodeficiency virus type 1 (HIV-1) therapy has prolonged the lives of patients, drug resistance is a significant problem. Of particular concern are mutations that cause cross-resistance to a particular class of drugs. Among the mutations that cause resistance to several nucleoside analogs are the insertion of amino acids in the fingers subdomain of HIV-1 reverse transcriptase (RT) at positions 69 and 70. These insertions are usually associated with changes in the flanking amino acids and with a change to F or Y at position 215. We have proposed that the T215F/Y mutation makes the binding of ATP to HIV-1 RT more effective, which increases the excision of 3-azido-3'-deoxythymidine-5'-monophosphate (AZTMP) in vitro and increases zidovudine (AZT) resistance in vivo. Although the mechanism of AZT resistance involves enhanced excision, resistance to 3TC involves a block to incorporation of the analog. We measured the effects of fingers insertion mutations on the misincorporation and excision of several nucleoside analogs. RT variants with the amino acid insertions in the fingers and T215Y have a decreased level of misincorporation of ddATP and 3TCTP. These mutants also have the ability to excise AZTMP by ATP-dependent pyrophosphorylysis. However, unlike the classic AZT resistance mutations (M41L/D67N/K70R/T215Y or F/K219E or Q), the combination of the amino acid insertions in the fingers and the T215Y mutation allows efficient excision of ddTMP and d4TMP, even when relatively high levels of deoxynucleoside triphosphates are present in the reaction. Although the dideoxynucleoside analogs of other nucleosides were excised more slowly than AZTMP, ddTMP, and d4TMP, the mutants with the fingers insertion and T215Y excised all of the nucleoside analogs that were tested more efficiently than wild-type RT or a mutant RT carrying the classical AZT resistance mutations. In the ternary complex (RT/template-primer/dNTP), the presence of the bound dNTP prevents the end of the primer from gaining access to the nucleotide binding site (N site) where excision occurs. Gel shift analysis showed that the amino acid insertions in the fingers destabilized the ternary complex compared to wild-type HIV-1 RT. If the ternary complex is unstable, the end of the primer can gain access to the N site and excision can occur. This could explain the enhanced excision of the nucleoside analogs.
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Affiliation(s)
- Paul L Boyer
- HIV Drug Resistance Program, National Cancer Institute, National Institutes of Health, Frederick, Maryland 21702-1201, USA
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19
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Rinke CS, Boyer PL, Sullivan MD, Hughes SH, Linial ML. Mutation of the catalytic domain of the foamy virus reverse transcriptase leads to loss of processivity and infectivity. J Virol 2002; 76:7560-70. [PMID: 12097569 PMCID: PMC136390 DOI: 10.1128/jvi.76.15.7560-7570.2002] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Foamy virus (FV) replication is resistant to most nucleoside analog reverse transcriptase (RT) inhibitors. In an attempt to create a 2',3'-dideoxy-3'-thiacytidine (3TC)-sensitive virus, the second residue in the highly conserved YXDD motif of simian foamy virus-chimpanzee (human isolate) [SFVcpz(hu)] RT was changed from Val (V) to Met (M). Unexpectedly, the resultant virus, SFVcpz(hu) RT-V313M, replicated poorly, and Met rapidly reverted to Val. Despite the presence of approximately 50% of wild-type RT activity in RT-V313M virions, full-length DNA products were not detected in transfected cells. Using purified recombinant enzymes, we found that the wild-type FV RT is significantly more processive than human immunodeficiency virus type 1 RT. However, the V313M mutant has about 40% of the wild-type level of FV RT activity and has a lower processivity than the wild-type FV enzyme. The V313M mutant RT is also relatively resistant to 3TC. These results suggest that the decrease in RT activity and processivity of FV RT-V313M prevents completion of reverse transcription and greatly diminishes viral replication.
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Affiliation(s)
- Carolyn S Rinke
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA
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20
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Boyer PL, Sarafianos SG, Arnold E, Hughes SH. The M184V mutation reduces the selective excision of zidovudine 5'-monophosphate (AZTMP) by the reverse transcriptase of human immunodeficiency virus type 1. J Virol 2002; 76:3248-56. [PMID: 11884549 PMCID: PMC136050 DOI: 10.1128/jvi.76.7.3248-3256.2002] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The M184V mutation in human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) causes resistance to lamivudine, but it also increases the sensitivity of the virus to zidovudine (3'-azido-3'-deoxythymidine; AZT). This sensitization to AZT is seen both in the presence and the absence of the mutations that confer resistance to AZT. AZT resistance is due to enhanced excision of AZT 5'-monophosphate (AZTMP) from the end of the primer by the RT of the resistant virus. Published data suggest that the excision reaction involves pyrophosphorolysis but that the likely in vivo pyrophosphate donor is not pyrophosphate but ATP. The mutations that lead to AZT resistance enhance ATP binding and, in so doing, enhance pyrophosphorolysis. The excision reaction is specific for AZT because HIV-1 RT, which can form a closed complex with a dideoxy-terminated primer and an incoming deoxynucleoside triphosphate (dNTP), does not form the closed complex with an AZTMP-terminated primer and an incoming dNTP. This means that an AZTMP-terminated primer has better access to the site where it can be excised. The M184V mutation alters the polymerase active site in a fashion that specifically interferes with ATP-mediated excision of AZTMP from the end of the primer strand. The M184V mutation does not affect the incorporation of AZT 5'-triphosphate (AZTTP), either in the presence or the absence of mutations that enhance AZTMP excision. However, in the presence of ATP, the M184V mutation does decrease the ability of HIV-1 RT to carry out AZTMP excision. Based on these results, and on the results of other excision experiments, we present a model to explain how the M184V mutation affects AZTMP excision.
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Affiliation(s)
- Paul L Boyer
- HIV Drug Resistance Program, National Cancer Institute, Frederick, Maryland 21702-1201, USA
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