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Oscorbin IP, Filipenko ML. M-MuLV reverse transcriptase: Selected properties and improved mutants. Comput Struct Biotechnol J 2021; 19:6315-6327. [PMID: 34900141 PMCID: PMC8640165 DOI: 10.1016/j.csbj.2021.11.030] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Revised: 11/12/2021] [Accepted: 11/18/2021] [Indexed: 11/06/2022] Open
Abstract
Reverse transcriptases (RTs) are enzymes synthesizing DNA using RNA as the template and serving as the standard tools in modern biotechnology and molecular diagnostics. To date, the most commonly used reverse transcriptase is the enzyme from Moloney murine leukemia virus, M-MuLV RT. Since its discovery, M-MuLV RT has become indispensable for modern RNA studies; the range of M-MuLV RT applications is vast, from scientific tasks to clinical testing of human pathogens. This review will give a brief description of the structure, thermal stability, processivity, and fidelity, focusing on improving M-MuLV RT for practical usage.
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Affiliation(s)
- Igor P Oscorbin
- Institute of Chemical Biology and Fundamental Medicine SB RAS, 8 Lavrentiev Avenue, Novosibirsk 630090, Russia
| | - Maxim L Filipenko
- Institute of Chemical Biology and Fundamental Medicine SB RAS, 8 Lavrentiev Avenue, Novosibirsk 630090, Russia
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2
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Palikša S, Alzbutas G, Skirgaila R. Decreased Km to dNTPs is an essential M-MuLV reverse transcriptase adoption required to perform efficient cDNA synthesis in One-Step RT-PCR assay. Protein Eng Des Sel 2019; 31:79-89. [PMID: 29608777 DOI: 10.1093/protein/gzy003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Accepted: 02/05/2018] [Indexed: 01/27/2023] Open
Abstract
Personalized medicine and advanced diagnostic tools based on RNA analysis are focusing on fast and direct One-Step RT-PCR assays. First strand complementary DNA (cDNA) synthesized by the reverse transcriptase (RT) is exponentially amplified in the end-point or real-time PCR. Even a minor discrepancy in PCR conditions would result in big deviations during the data analysis. Thus, One-Step RT-PCR composition is typically based on the PCR buffer. In this study, we have used compartmentalized ribosome display technique for in vitro evolution of the Moloney Murine Leukemia Virus reverse transcriptase (M-MuLV RT) that would be able to perform efficient full-length cDNA synthesis in PCR buffer optimized for Thermus aquaticus DNA polymerase. The most frequent mutations found in a selected library were analyzed. Aside from the mutations, which switch off RNase H activity of RT and are beneficial for the full-length cDNA synthesis, we have identified several mutations in the active center of the enzyme (Q221R and V223A/M), which result in 4-5-fold decrease of Km for dNTPs (<0.2 mM). The selected mutations are in surprising agreement with the natural evolution process because they transformed the active center from the oncoretroviral M-MuLV RT-type to the lenitiviral enzyme-type. We believe that this was the major and essential phenotypic adjustment required to perform fast and efficient cDNA synthesis in PCR buffer at 0.2-mM concentration of each dNTP.
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Affiliation(s)
- S Palikša
- Thermo Fisher Scientific Baltics, UAB, LT-02241 Vilnius, Lithuania.,JSC Diagnolita, LT-10257 Vilnius, Lithuania
| | - G Alzbutas
- Thermo Fisher Scientific Baltics, UAB, LT-02241 Vilnius, Lithuania
| | - R Skirgaila
- Thermo Fisher Scientific Baltics, UAB, LT-02241 Vilnius, Lithuania
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3
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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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4
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Moser MJ, DiFrancesco RA, Gowda K, Klingele AJ, Sugar DR, Stocki S, Mead DA, Schoenfeld TW. Thermostable DNA polymerase from a viral metagenome is a potent RT-PCR enzyme. PLoS One 2012; 7:e38371. [PMID: 22675552 PMCID: PMC3366922 DOI: 10.1371/journal.pone.0038371] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2011] [Accepted: 05/04/2012] [Indexed: 02/03/2023] Open
Abstract
Viral metagenomic libraries are a promising but previously untapped source of new reagent enzymes. Deep sequencing and functional screening of viral metagenomic DNA from a near-boiling thermal pool identified clones expressing thermostable DNA polymerase (Pol) activity. Among these, 3173 Pol demonstrated both high thermostability and innate reverse transcriptase (RT) activity. We describe the biochemistry of 3173 Pol and report its use in single-enzyme reverse transcription PCR (RT-PCR). Wild-type 3173 Pol contains a proofreading 3′-5′ exonuclease domain that confers high fidelity in PCR. An easier-to-use exonuclease-deficient derivative was incorporated into a PyroScript RT-PCR master mix and compared to one-enzyme (Tth) and two-enzyme (MMLV RT/Taq) RT-PCR systems for quantitative detection of MS2 RNA, influenza A RNA, and mRNA targets. Specificity and sensitivity of 3173 Pol-based RT-PCR were higher than Tth Pol and comparable to three common two-enzyme systems. The performance and simplified set-up make this enzyme a potential alternative for research and molecular diagnostics.
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5
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Ndongwe TP, Adedeji AO, Michailidis E, Ong YT, Hachiya A, Marchand B, Ryan EM, Rai DK, Kirby KA, Whatley AS, Burke DH, Johnson M, Ding S, Zheng YM, Liu SL, Kodama EI, Delviks-Frankenberry KA, Pathak VK, Mitsuya H, Parniak MA, Singh K, Sarafianos SG. Biochemical, inhibition and inhibitor resistance studies of xenotropic murine leukemia virus-related virus reverse transcriptase. Nucleic Acids Res 2011; 40:345-59. [PMID: 21908397 PMCID: PMC3245923 DOI: 10.1093/nar/gkr694] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
We report key mechanistic differences between the reverse transcriptases (RT) of human immunodeficiency virus type-1 (HIV-1) and of xenotropic murine leukemia virus-related virus (XMRV), a gammaretrovirus that can infect human cells. Steady and pre-steady state kinetics demonstrated that XMRV RT is significantly less efficient in DNA synthesis and in unblocking chain-terminated primers. Surface plasmon resonance experiments showed that the gammaretroviral enzyme has a remarkably higher dissociation rate (koff) from DNA, which also results in lower processivity than HIV-1 RT. Transient kinetics of mismatch incorporation revealed that XMRV RT has higher fidelity than HIV-1 RT. We identified RNA aptamers that potently inhibit XMRV, but not HIV-1 RT. XMRV RT is highly susceptible to some nucleoside RT inhibitors, including Translocation Deficient RT inhibitors, but not to non-nucleoside RT inhibitors. We demonstrated that XMRV RT mutants K103R and Q190M, which are equivalent to HIV-1 mutants that are resistant to tenofovir (K65R) and AZT (Q151M), are also resistant to the respective drugs, suggesting that XMRV can acquire resistance to these compounds through the decreased incorporation mechanism reported in HIV-1.
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Affiliation(s)
- Tanyaradzwa P Ndongwe
- Christopher Bond Life Sciences Center, Department of Molecular Microbiology & Immunology, University of Missouri, School of Medicine, Columbia, MO 65211, USA
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6
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Xie J, Zhang P, Li C, Huang Q, Zhou R, Peng T. Mechanistic insights into the roles of three linked single-stranded template binding residues of MMLV reverse transcriptase in misincorporation and mispair extension fidelity of DNA synthesis. Gene 2011; 479:47-56. [DOI: 10.1016/j.gene.2011.02.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2011] [Revised: 02/07/2011] [Accepted: 02/13/2011] [Indexed: 11/25/2022]
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7
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Abstract
HIV-1 and other retroviruses exhibit mutation rates that are 1,000,000-fold greater than their host organisms. Error-prone viral replication may place retroviruses and other RNA viruses near the threshold of "error catastrophe" or extinction due to an intolerable load of deleterious mutations. Strategies designed to drive viruses to error catastrophe have been applied to HIV-1 and a number of RNA viruses. Here, we review the concept of extinguishing HIV infection by "lethal mutagenesis" and consider the utility of this new approach in combination with conventional antiretroviral strategies.
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Affiliation(s)
- Robert A Smith
- Department of Pathology, University of Washington, Seattle, WA 18195, USA.
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8
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Mbisa JL, Nikolenko GN, Pathak VK. Mutations in the RNase H primer grip domain of murine leukemia virus reverse transcriptase decrease efficiency and accuracy of plus-strand DNA transfer. J Virol 2005; 79:419-27. [PMID: 15596835 PMCID: PMC538714 DOI: 10.1128/jvi.79.1.419-427.2005] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The RNase H primer grip of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) contacts the DNA primer strand and positions the template strand near the RNase H active site, influencing RNase H cleavage efficiency and specificity. Sequence alignments show that 6 of the 11 residues that constitute the RNase H primer grip have functional equivalents in murine leukemia virus (MLV) RT. We previously showed that a Y586F substitution in the MLV RNase H primer grip resulted in a 17-fold increase in substitutions within 18 nucleotides of adenine-thymine tracts, which are associated with a bent DNA conformation. To further determine the effects of the MLV RNase H primer grip on replication fidelity and viral replication, we performed additional mutational analysis. Using either beta-galactosidase (lacZ) or green fluorescent protein (GFP) reporter genes, we found that S557A, A558V, and Q559L substitutions resulted in statistically significant increases in viral mutation rates, ranging from 2.1- to 3.8-fold. DNA sequencing analysis of nonfluorescent GFP clones indicated that the mutations in RNase H primer grip significantly increased the frequency of deletions between the primer-binding site (PBS) and sequences downstream of the PBS. In addition, quantitative real-time PCR analysis of reverse transcription products revealed that the mutant RTs were substantially inefficient in plus-strand DNA transfer relative to the wild-type control. These results indicate that the MLV RNase H primer grip is an important determinant of in vivo fidelity of DNA synthesis and suggest that the mutant RT was unable to copy through the DNA-RNA junction of the minus-strand DNA and the tRNA because of its bent conformation resulting in error-prone plus-strand DNA transfer.
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Affiliation(s)
- Jean L Mbisa
- HIV Drug Resistance Program, National Cancer Institute at Frederick, Frederick, Maryland 21702-1201, USA
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9
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Nikolenko GN, Svarovskaia ES, Delviks KA, Pathak VK. Antiretroviral drug resistance mutations in human immunodeficiency virus type 1 reverse transcriptase increase template-switching frequency. J Virol 2004; 78:8761-70. [PMID: 15280484 PMCID: PMC479068 DOI: 10.1128/jvi.78.16.8761-8770.2004] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Template-switching events during reverse transcription are necessary for completion of retroviral replication and recombination. Structural determinants of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) that influence its template-switching frequency are not known. To identify determinants of HIV-1 RT that affect the frequency of template switching, we developed an in vivo assay in which RT template-switching events during viral replication resulted in functional reconstitution of the green fluorescent protein gene. A survey of single amino acid substitutions near the polymerase active site or deoxynucleoside triphosphate-binding site of HIV-1 RT indicated that several substitutions increased the rate of RT template switching. Several mutations associated with resistance to antiviral nucleoside analogs (K65R, L74V, E89G, Q151N, and M184I) dramatically increased RT template-switching frequencies by two- to sixfold in a single replication cycle. In contrast, substitutions in the RNase H domain (H539N, D549N) decreased the frequency of RT template switching by twofold. Depletion of intracellular nucleotide pools by hydroxyurea treatment of cells used as targets for infection resulted in a 1.8-fold increase in the frequency of RT template switching. These results indicate that the dynamic steady state between polymerase and RNase H activities is an important determinant of HIV-1 RT template switching and establish that HIV-1 recombination occurs by the previously described dynamic copy choice mechanism. These results also indicate that mutations conferring resistance to antiviral drugs can increase the frequency of RT template switching and may influence the rate of retroviral recombination and viral evolution.
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Affiliation(s)
- Galina N Nikolenko
- HIV Drug Resistance Program, NCI-Frederick, Bldg. 535, Rm. 334, Frederick, MD 21702, USA
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10
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Menéndez-Arias L. Molecular basis of fidelity of DNA synthesis and nucleotide specificity of retroviral reverse transcriptases. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 2003; 71:91-147. [PMID: 12102562 DOI: 10.1016/s0079-6603(02)71042-8] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Reverse transcription involves the conversion of viral genomic RNAinto proviral double-stranded DNA that integrates into the host cell genome. Cellular DNA polymerases replicate the integrated viral DNA and RNA polymerase II transcribes the proviral DNA into RNA genomes that are packaged into virions. Although mutations can be introduced at any of these replication steps, reverse transcriptase (RT) errors play a major role in retroviral mutation. This review summarizes our current knowledge on fidelity of reverse transcriptases. Estimates of retroviral mutation rates or fidelity of retroviral RTs are discussed in the context of the different techniques used for this purpose (i.e., retroviral vectors replicated in culture, misinsertion and mispair extension fidelity assay, etc.). In vitro fidelity assays provide information on the RT's accuracy during the elongation reaction of DNA synthesis. In addition, other steps such as initiation of reverse transcription, or strand transfer, and factors including viral proteins such as Vpr [in the case of the human immunodeficiency virus type 1 (HIV-1)] have been shown to influence fidelity. A comprehensive description of the effect of amino acid substitutions on the fidelity of HIV-1 RT is presented. Published data point to certain dNTP-binding residues, as well as to various amino acids involved in interactions with the template or the primer strand, and to residues in the minor groove-binding track as major components of the fidelity center of retroviral RTs. Implications of these studies include the design of novel therapeutic strategies leading to virus extinction, by increasing the viral mutation rate beyond a tolerable threshold.
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Affiliation(s)
- Luis Menéndez-Arias
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Cantoblanco, Spain
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11
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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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12
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Zhang WH, Svarovskaia ES, Barr R, Pathak VK. Y586F mutation in murine leukemia virus reverse transcriptase decreases fidelity of DNA synthesis in regions associated with adenine-thymine tracts. Proc Natl Acad Sci U S A 2002; 99:10090-5. [PMID: 12119402 PMCID: PMC126629 DOI: 10.1073/pnas.152186199] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Using in vivo fidelity assays in which bacterial beta-galactosidase or green fluorescent protein genes served as reporters of mutations, we have identified a murine leukemia virus (MLV) RNase H mutant (Y586F) that exhibited an increase in the retroviral mutation rate approximately 5-fold in a single replication cycle. DNA-sequencing analysis indicated that the Y586F mutation increased the frequency of substitution mutations 17-fold within 18 nt of adenine-thymine tracts (AAAA, TTTT, or AATT), which are known to induce DNA bending. Sequence alignments indicate that MLV Y586 is equivalent to HIV-1 Y501, a component of the recently described RNase H primer grip domain, which contacts and positions the DNA primer strand near the RNase H active site. The results suggest that wild-type reverse transcriptase (RT) facilitates a specific conformation of the template-primer duplex at the polymerase active site that is important for accuracy of DNA synthesis; when an adenine-thymine tract is within 18 nt of the polymerase active site, the Y586F mutant RT cannot facilitate this specific template-primer conformation, leading to an increase in the frequency of substitution mutations. These findings indicate that the RNase H primer grip can affect the template-primer conformation at the polymerase active site and that the MLV Y586 residue and template-primer conformation are important determinants of RT fidelity.
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Affiliation(s)
- Wen-Hui Zhang
- HIV Drug Resistance Program, National Cancer Institute, National Institutes of Health, Frederick, MD 21702, USA
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13
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Brincat JL, Pfeiffer JK, Telesnitsky A. RNase H activity is required for high-frequency repeat deletion during Moloney murine leukemia virus replication. J Virol 2002; 76:88-95. [PMID: 11739674 PMCID: PMC135712 DOI: 10.1128/jvi.76.1.88-95.2002] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
It has been postulated that retroviral recombination, like strong stop template switching, requires the RNase H activity of reverse transcriptase. To address this hypothesis, Moloney murine leukemia virus-based vectors, which were designed to test the recombination-related property of direct repeat deletion, were encapsidated in virions engineered to contain phenotypic mixtures of wild-type and RNase H catalytic site point mutant reverse transcriptase. Integrated provirus titers per milliliter were determined for these phenotypically mixed virions, and vector proviruses were screened to determine what percentage contained repeat deletions. The results revealed a steady decline in direct repeat deletion frequency that correlated with decreases in functional RNase H, with greater than fourfold decreases in repeat deletion frequency observed when 95% of virion reverse transcriptase was RNase H defective. Parallel experiments were performed to address effects of molar excesses of RNase H relative to functional DNA polymerase. These experiments demonstrated that increasing the stoichiometry of RNase H relative to the amount of functional DNA polymerase had minimal effects on direct repeat deletion frequency. DNA synthesis was error prone when directed principally by RNase H mutant reverse transcriptase, suggesting a role for RNase H catalytic integrity in the fidelity of intracellular reverse transcription.
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Affiliation(s)
- Jennifer L Brincat
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan 48109-0620, USA
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14
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Dang Q, Hu WS. Effects of homology length in the repeat region on minus-strand DNA transfer and retroviral replication. J Virol 2001; 75:809-20. [PMID: 11134294 PMCID: PMC113977 DOI: 10.1128/jvi.75.2.809-820.2001] [Citation(s) in RCA: 33] [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
Homology between the two repeat (R) regions in the retroviral genome mediates minus-strand DNA transfer during reverse transcription. We sought to define the effects of R homology lengths on minus-strand DNA transfer. We generated five murine leukemia virus (MLV)-based vectors that contained identical sequences but different lengths of the 3' R (3, 6, 12, 24 and 69 nucleotides [nt]); 69 nt is the full-length MLV R. After one round of replication, viral titers from the vector with a full-length downstream R were compared with viral titers generated from the other four vectors with reduced R lengths. Viral titers generated from vectors with R lengths reduced to one-third (24 nt) or one-sixth (12 nt) that of the wild type were not significantly affected; however, viral titers generated from vectors with only 3- or 6-nt homology in the R region were significantly lower. Because expression and packaging of the RNA were similar among all the vectors, the differences in the viral titers most likely reflected the impact of the homology lengths on the efficiency of minus-strand DNA transfer. The molecular nature of minus-strand DNA transfer was characterized in 63 proviruses. Precise R-to-R transfer was observed in most proviruses generated from vectors with 12-, 24-, or 69-nt homology in R, whereas aberrant transfers were predominantly used to generate proviruses from vectors with 3- or 6-nt homology. Reverse transcription using RNA transcribed from an upstream promoter, termed read-in RNA transcripts, resulted in most of the aberrant transfers. These data demonstrate that minus-strand DNA transfer is homology driven and a minimum homology length is required for accurate and efficient minus-strand DNA transfer.
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Affiliation(s)
- Q Dang
- Department of Microbiology and Immunology, School of Medicine, West Virginia University, Morgantown, West Virginia 26506, USA
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15
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Halvas EK, Svarovskaia ES, Pathak VK. Role of murine leukemia virus reverse transcriptase deoxyribonucleoside triphosphate-binding site in retroviral replication and in vivo fidelity. J Virol 2000; 74:10349-58. [PMID: 11044079 PMCID: PMC110909 DOI: 10.1128/jvi.74.22.10349-10358.2000] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Retroviral populations exhibit a high evolutionary potential, giving rise to extensive genetic variation. Error-prone DNA synthesis catalyzed by reverse transcriptase (RT) generates variation in retroviral populations. Structural features within RTs are likely to contribute to the high rate of errors that occur during reverse transcription. We sought to determine whether amino acids within murine leukemia virus (MLV) RT that contact the deoxyribonucleoside triphosphate (dNTP) substrate are important for in vivo fidelity of reverse transcription. We utilized the previously described ANGIE P encapsidating cell line, which expresses the amphotropic MLV envelope and a retroviral vector (pGA-1). pGA-1 expresses the bacterial beta-galactosidase gene (lacZ), which serves as a reporter of mutations. Extensive mutagenesis was performed on residues likely to interact with the dNTP substrate, and the effects of these mutations on the fidelity of reverse transcription were determined. As expected, most substitution mutations of amino acids that directly interact with the dNTP substrate significantly reduced viral titers (>10,000-fold), indicating that these residues played a critical role in catalysis and viral replication. However, the D153A and A154S substitutions, which are predicted to affect the interactions with the triphosphate, resulted in statistically significant increases in the mutation rate. In addition, the conservative substitution F155W, which may affect interactions with the base and the ribose, increased the mutation rate 2.8-fold. Substitutions of residues in the vicinity of the dNTP-binding site also resulted in statistically significant decreases in fidelity (1. 3- to 2.4-fold). These results suggest that mutations of residues that contact the substrate dNTP can affect viral replication as well as alter the fidelity of reverse transcription.
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Affiliation(s)
- E K Halvas
- Mary Babb Randolph Cancer Center and Department of Biochemistry, West Virginia University, Morgantown, West Virginia 26506, USA
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16
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Cheslock SR, Anderson JA, Hwang CK, Pathak VK, Hu WS. Utilization of nonviral sequences for minus-strand DNA transfer and gene reconstitution during retroviral replication. J Virol 2000; 74:9571-9. [PMID: 11000228 PMCID: PMC112388 DOI: 10.1128/jvi.74.20.9571-9579.2000] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Minus-strand DNA transfer, an essential step in retroviral reverse transcription, is mediated by the two repeat (R) regions in the viral genome. It is unclear whether R simply serves as a homologous sequence to mediate the strand transfer or contains specific sequences to promote strand transfer. To test the hypothesis that the molecular mechanism by which R mediates strand transfer is based on homology rather than specific sequences, we examined whether nonviral sequences can be used to facilitate minus-strand DNA transfer. The green fluorescent protein (GFP) gene was divided into GF and FP fragments, containing the 5' and 3' portions of GFP, respectively, with an overlapping F fragment (85 bp). FP and GF were inserted into the 5' and 3' long terminal repeats, respectively, of a murine leukemia virus-based vector. Utilization of the F fragment to mediate minus-strand DNA transfer should reconstitute GFP during reverse transcription. Flow cytometry analyses demonstrated that GFP was expressed in 73 to 92% of the infected cells, depending on the structure of the viral construct. This indicated that GFP was reconstituted at a high frequency; molecular characterization further confirmed the accurate reconstitution of GFP. These data indicated that nonviral sequences could be used to efficiently mediate minus-strand DNA transfer. Therefore, placement and homology, not specific sequence context, are the important elements in R for minus-strand DNA transfer. In addition, these experiments demonstrate that minus-strand DNA transfer can be used to efficiently reconstitute genes for gene therapy applications.
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Affiliation(s)
- S R Cheslock
- Department of Microbiology and Immunology, West Virginia University, Morgantown, West Virginia, 26506, USA
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17
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Pfeiffer JK, Georgiadis MM, Telesnitsky A. Structure-based moloney murine leukemia virus reverse transcriptase mutants with altered intracellular direct-repeat deletion frequencies. J Virol 2000; 74:9629-36. [PMID: 11000235 PMCID: PMC112395 DOI: 10.1128/jvi.74.20.9629-9636.2000] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Template switching rates of Moloney murine leukemia virus reverse transcriptase mutants were tested using a retroviral vector-based direct-repeat deletion assay. The reverse transcriptase mutants contained alterations in residues that modeling of substrates into the catalytic core had suggested might affect interactions with primer and/or template strands. As assessed by the frequency of functional lacZ gene generation from vectors in which lacZ was disrupted by insertion of a sequence duplication, the frequency of template switching varied more than threefold among fully replication-competent mutants. Some mutants displayed deletion rates that were lower and others displayed rates that were higher than that of wild-type virus. Replication for the mutants with the most significant alterations in template switching frequencies was similar to that of the wild type. These data suggest that reverse transcriptase template switching rates can be altered significantly without destroying normal replication functions.
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Affiliation(s)
- J K Pfeiffer
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan 48109-0620, USA
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Svarovskaia ES, Delviks KA, Hwang CK, Pathak VK. Structural determinants of murine leukemia virus reverse transcriptase that affect the frequency of template switching. J Virol 2000; 74:7171-8. [PMID: 10888659 PMCID: PMC112237 DOI: 10.1128/jvi.74.15.7171-7178.2000] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Retroviral reverse transcriptases (RTs) frequently switch templates within the same RNA or between copackaged viral RNAs to generate mutations and recombination. To identify structural elements of murine leukemia virus RT important for template switching, we developed an in vivo assay in which RT template switching within direct repeats functionally reconstituted the green fluorescent protein gene. We quantified the effect of mutations in the YXDD motif, the deoxynucleoside triphosphate binding site, the thumb domain, and the RNase H domain of RT and hydroxyurea treatment on the frequencies of template switching. Hydroxyurea treatment and some mutations in RT increased the frequency of RT template switching up to fivefold, while all of the mutations tested in the RNase H domain decreased the frequency of template switching by twofold. Based on these results, we propose a dynamic copy choice model in which both the rate of DNA polymerization and the rate of RNA degradation influence the frequency of RT template switching.
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Affiliation(s)
- E S Svarovskaia
- Department of Biochemistry, West Virginia University, Morgantown, West Virginia 26506, USA
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Halvas EK, Svarovskaia ES, Freed EO, Pathak VK. Wild-type and YMDD mutant murine leukemia virus reverse transcriptases are resistant to 2',3'-dideoxy-3'-thiacytidine. J Virol 2000; 74:6669-74. [PMID: 10864683 PMCID: PMC112179 DOI: 10.1128/jvi.74.14.6669-6674.2000] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The antiretroviral nucleoside analog 2',3'-dideoxy-3'-thiacytidine (3TC) is a potent inhibitor of wild-type human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT). A methionine-to-valine or methionine-to-isoleucine substitution at residue 184 in the HIV-1 YMDD motif, which is located at the RT active site, leads to a high level of resistance to 3TC. We sought to determine whether 3TC can inhibit the replication of wild-type murine leukemia virus (MLV), which contains V223 at the YVDD active site motif of the MLV RT, and of the V223M, V223I, V223A, and V223S mutant RTs. Surprisingly, the wild type and all four of the V223 mutants of MLV RT were highly resistant to 3TC. These results indicate that determinants outside the YVDD motif of MLV RT confer a high level of resistance to 3TC. Therefore, structural differences among similar RTs might result in widely divergent sensitivities to antiretroviral nucleoside analogs.
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Affiliation(s)
- E K Halvas
- Mary Babb Randolph Cancer Center and Department of Biochemistry, West Virginia University, Morgantown, West Virginia 26506, USA
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