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Akkawi C, Feuillard J, Diaz FL, Belkhir K, Godefroy N, Peloponese JM, Mougel M, Laine S. Murine leukemia virus (MLV) P50 protein induces cell transformation via transcriptional regulatory function. Retrovirology 2023; 20:16. [PMID: 37700325 PMCID: PMC10496198 DOI: 10.1186/s12977-023-00631-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2023] [Accepted: 08/18/2023] [Indexed: 09/14/2023] Open
Abstract
BACKGROUND The murine leukemia virus (MLV) has been a powerful model of pathogenesis for the discovery of genes involved in cancer. Its splice donor (SD')-associated retroelement (SDARE) is important for infectivity and tumorigenesis, but the mechanism remains poorly characterized. Here, we show for the first time that P50 protein, which is produced from SDARE, acts as an accessory protein that transregulates transcription and induces cell transformation. RESULTS By infecting cells with MLV particles containing SDARE transcript alone (lacking genomic RNA), we show that SDARE can spread to neighbouring cells as shown by the presence of P50 in infected cells. Furthermore, a role for P50 in cell transformation was demonstrated by CCK8, TUNEL and anchorage-independent growth assays. We identified the integrase domain of P50 as being responsible for transregulation of the MLV promoter using luciferase assay and RTqPCR with P50 deleted mutants. Transcriptomic analysis furthermore revealed that the expression of hundreds of cellular RNAs involved in cancerogenesis were deregulated in the presence of P50, suggesting that P50 induces carcinogenic processes via its transcriptional regulatory function. CONCLUSION We propose a novel SDARE-mediated mode of propagation of the P50 accessory protein in surrounding cells. Moreover, due to its transforming properties, P50 expression could lead to a cellular and tissue microenvironment that is conducive to cancer development.
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Affiliation(s)
- Charbel Akkawi
- Team R2D2: Retroviral RNA Dynamics and Delivery, IRIM, UMR9004, CNRS, University of Montpellier, Montpellier, France
| | - Jerome Feuillard
- Team R2D2: Retroviral RNA Dynamics and Delivery, IRIM, UMR9004, CNRS, University of Montpellier, Montpellier, France
| | - Felipe Leon Diaz
- Team R2D2: Retroviral RNA Dynamics and Delivery, IRIM, UMR9004, CNRS, University of Montpellier, Montpellier, France
| | - Khalid Belkhir
- ISEM, CNRS, EPHE, Université Montpellier, IRD, Montpellier, France
| | - Nelly Godefroy
- ISEM, CNRS, EPHE, Université Montpellier, IRD, Montpellier, France
| | | | - Marylene Mougel
- Team R2D2: Retroviral RNA Dynamics and Delivery, IRIM, UMR9004, CNRS, University of Montpellier, Montpellier, France.
| | - Sebastien Laine
- Team R2D2: Retroviral RNA Dynamics and Delivery, IRIM, UMR9004, CNRS, University of Montpellier, Montpellier, France.
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Schneider WM, Wu DT, Amin V, Aiyer S, Roth MJ. MuLV IN mutants responsive to HDAC inhibitors enhance transcription from unintegrated retroviral DNA. Virology 2012; 426:188-96. [PMID: 22365328 DOI: 10.1016/j.virol.2012.01.034] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2011] [Revised: 11/12/2011] [Accepted: 01/27/2012] [Indexed: 12/16/2022]
Abstract
For Moloney murine leukemia virus (M-MuLV), sustained viral infections require expression from an integrated provirus. For many applications, non-integrating retroviral vectors have been utilized to avoid the unwanted effects of integration, however, the level of expression from unintegrated DNA is significantly less than that of integrated provirus. We find that unintegrated DNA expression can be increased in the presence of HDAC inhibitors, such as TSA, when applied in combination with integrase (IN) mutations. These mutants include an active site mutation as well as catalytically active INs bearing mutations of K376 in the MuLV C-terminal domain of IN. MuLV IN K376 is homologous to K266 in HIV-1 IN, a known substrate for acetylation. The MuLV IN protein is acetylated by p300 in vitro, however, the effect of HDAC inhibitors on gene expression from unintegrated DNA is not dependent on the acetylation state of MuLV IN K376.
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Affiliation(s)
- William M Schneider
- University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA.
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Steinrigl A, Nosek D, Ertl R, Günzburg WH, Salmons B, Klein D. Mutations in the catalytic core or the C-terminus of murine leukemia virus (MLV) integrase disrupt virion infectivity and exert diverse effects on reverse transcription. Virology 2007; 362:50-9. [PMID: 17258786 DOI: 10.1016/j.virol.2006.11.037] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2006] [Revised: 09/19/2006] [Accepted: 11/22/2006] [Indexed: 11/30/2022]
Abstract
Understanding of the structures and functions of the retroviral integrase (IN), a key enzyme in the viral replication cycle, is essential for developing antiretroviral treatments and facilitating the development of safer gene therapy vehicles. Thus, four MLV IN-mutants were constructed in the context of a retroviral vector system, harbouring either a substitution in the catalytic centre, deletions in the C-terminus, or combinations of both modifications. IN-mutants were tested for their performance in different stages of the viral replication cycle: RNA-packaging; RT-activity; transient and stable infection efficiency; dynamics of reverse transcription and nuclear entry. All mutant vectors packaged viral RNA with wild-type efficiencies and displayed only slight reductions in RT-activity. Deletion of either the IN C-terminus alone, or in addition to part of the catalytic domain exerted contrasting effects on intracellular viral DNA levels, implying that IN influences reverse transcription in more than one direction.
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Affiliation(s)
- Adolf Steinrigl
- Research Institute for Virology and Biomedicine, University of Veterinary Medicine, A-1210 Vienna, Austria
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Puglia J, Wang T, Smith-Snyder C, Cote M, Scher M, Pelletier JN, John S, Jonsson CB, Roth MJ. Revealing domain structure through linker-scanning analysis of the murine leukemia virus (MuLV) RNase H and MuLV and human immunodeficiency virus type 1 integrase proteins. J Virol 2006; 80:9497-510. [PMID: 16973554 PMCID: PMC1617218 DOI: 10.1128/jvi.00856-06] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2006] [Accepted: 07/07/2006] [Indexed: 11/20/2022] Open
Abstract
Linker-scanning libraries were generated within the 3' terminus of the Moloney murine leukemia virus (M-MuLV) pol gene encoding the connection-RNase H domains of reverse transcriptase (RT) as well as the structurally related M-MuLV and human immunodeficiency virus type 1 (HIV-1) integrase (IN) proteins. Mutations within the M-MuLV proviral vectors were Tn7 based and resulted in 15-bp insertions. Mutations within an HIV-1 IN bacterial expression vector were based on Tn5 and resulted in 57-bp insertions. The effects of the insertions were examined in vivo (M-MuLV) and in vitro (HIV-1). A total of 178 individual M-MuLV constructs were analyzed; 40 in-frame insertions within RT connection-RNase H, 108 in-frame insertions within IN, 13 insertions encoding stop codons within RNase H, and 17 insertions encoding stop codons within IN. For HIV-1 IN, 56 mutants were analyzed. In both M-MuLV and HIV-1 IN, regions are identified which functionally tolerate multiple-linker insertions. For MuLV, these correspond to the RT-IN proteolytic junction, the junction between the IN core and C terminus, and the C terminus of IN. For HIV-1 IN, in addition to the junction between the IN core and C terminus and the C terminus of IN, insertions between the N terminus and core domains maintained integration and disintegration activity. Of the 40 in-frame insertions within the M-MuLV RT connection-RNase H domains, only the three C-terminal insertions mapping to the RT-IN proteolytic junction were viable. These results correlate with deletion studies mapping the domain and subdomain boundaries of RT and IN. Importantly, these genetic footprints provide a means to identify nonessential regions within RT and IN for targeted gene therapy applications.
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Affiliation(s)
- Jennifer Puglia
- Department of Biochemistry, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, 675 Hoes Lane, Piscataway, NJ 08854, USA
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Stagliano KW, Emadi A, Lu Z, Malinakova HC, Twenter B, Yu M, Holland LE, Rom AM, Harwood JS, Amin R, Johnson AA, Pommier Y. Regiocontrolled synthesis and HIV inhibitory activity of unsymmetrical binaphthoquinone and trimeric naphthoquinone derivatives of conocurvone. Bioorg Med Chem 2006; 14:5651-65. [PMID: 16737818 DOI: 10.1016/j.bmc.2006.04.034] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2006] [Revised: 04/10/2006] [Accepted: 04/13/2006] [Indexed: 11/27/2022]
Abstract
Unsymmetrical biquinone and trimeric quinone derivatives were synthesized using halotriflate-biselectrophilic naphthoquinones through stepwise regioselective quinone substitution chemistry and evaluated for their ability to inhibit the cytopathogenic effects of HIV-1 using an MTT colorimetric assay. Compounds were also screened for their ability to inhibit the activity of HIV-1 integrase in vitro. Pyranylated trimeric quinones and biquinones exhibited both antiviral activity and integrase inhibitory activity. Conocurvone 1 and trimeric quinone 21 were the most potent HIV integrase inhibitors in the series. All of the biquinones showed HIV inhibitory activity. Simple methoxy substituted biquinones did not inhibit HIV-1 integrase.
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Affiliation(s)
- Kenneth W Stagliano
- Department of Biological, Chemical and Physical Sciences, Illinois Institute of Technology, Chicago, 60616, USA
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Miles LR, Agresta BE, Khan MB, Tang S, Levin JG, Powell MD. Effect of polypurine tract (PPT) mutations on human immunodeficiency virus type 1 replication: a virus with a completely randomized PPT retains low infectivity. J Virol 2005; 79:6859-67. [PMID: 15890925 PMCID: PMC1112125 DOI: 10.1128/jvi.79.11.6859-6867.2005] [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: 10/14/2004] [Accepted: 01/20/2005] [Indexed: 12/22/2022] Open
Abstract
We introduced polypurine tract (PPT) mutations, which we had previously tested in an in vitro assay, into the viral clone NL4-3KFSdelta nef. Each mutant was tested for single-round infectivity and virion production. All of the PPT mutations had an effect on replication; however, mutation of the 5' end appeared to have less of an effect on infectivity than mutation of the 3' end of the PPT sequence. Curiously, a mutation in which the entire PPT sequence was randomized (PPTSUB) retained 12% of the infectivity of the wild type (WT) in a multinuclear activation of galactosidase indicator assay. Supernatants from these infections contained viral particles, as evidenced by the presence of p24 antigen. Two-long terminal repeat (2-LTR) circle junction analysis following PPTSUB infection revealed that the mutant could form a high percentage of normal junctions. Quantification of the 2-LTR circles using real-time PCR revealed that number of 2-LTR circles from cells infected with the PPTSUB mutant was 3.5 logs greater than 2-LTR circles from cells infected with WT virus. To determine whether the progeny virions from a PPTSUB infection could undergo further rounds of replication, we introduced the PPTSUB mutation into a replication-competent virus. Our results show that the mutant virus is able to replicate and that the infectivity of the progeny virions increases with each passage, quickly reverting to a WT PPT sequence. Together, these experiments confirm that the 3' end of the PPT is important for plus-strand priming and that a virus that completely lacks a PPT can replicate at a low level.
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Affiliation(s)
- Lesa R Miles
- Department of Microbiology, Biochemistry and Immunology, Morehouse School of Medicine, 720 Westview Dr. S. W., Atlanta, GA 30310, USA
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Delelis O, Petit C, Leh H, Mbemba G, Mouscadet JF, Sonigo P. A novel function for spumaretrovirus integrase: an early requirement for integrase-mediated cleavage of 2 LTR circles. Retrovirology 2005; 2:31. [PMID: 15904533 PMCID: PMC1180852 DOI: 10.1186/1742-4690-2-31] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2005] [Accepted: 05/18/2005] [Indexed: 01/01/2023] Open
Abstract
Retroviral integration is central to viral persistence and pathogenesis, cancer as well as host genome evolution. However, it is unclear why integration appears essential for retrovirus production, especially given the abundance and transcriptional potential of non-integrated viral genomes. The involvement of retroviral endonuclease, also called integrase (IN), in replication steps apart from integration has been proposed, but is usually considered to be accessory. We observe here that integration of a retrovirus from the spumavirus family depends mainly on the quantity of viral DNA produced. Moreover, we found that IN directly participates to linear DNA production from 2-LTR circles by specifically cleaving the conserved palindromic sequence found at LTR-LTR junctions. These results challenge the prevailing view that integrase essential function is to catalyze retroviral DNA integration. Integrase activity upstream of this step, by controlling linear DNA production, is sufficient to explain the absolute requirement for this enzyme. The novel role of IN over 2-LTR circle junctions accounts for the pleiotropic effects observed in cells infected with IN mutants. It may explain why 1) 2-LTR circles accumulate in vivo in mutants carrying a defective IN while their linear and integrated DNA pools decrease; 2) why both LTRs are processed in a concerted manner. It also resolves the original puzzle concerning the integration of spumaretroviruses. More generally, it suggests to reassess 2-LTR circles as functional intermediates in the retrovirus cycle and to reconsider the idea that formation of the integrated provirus is an essential step of retrovirus production.
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Affiliation(s)
- Olivier Delelis
- Génétique des virus, Département des Maladies Infectieuses, Institut Cochin, INSERM U567, CNRS UMR8104, Université René Descartes, 22 rue Méchain, 75014 Paris, France
| | - Caroline Petit
- Génétique des virus, Département des Maladies Infectieuses, Institut Cochin, INSERM U567, CNRS UMR8104, Université René Descartes, 22 rue Méchain, 75014 Paris, France
| | - Herve Leh
- Bioalliancepharma, 59 boulevard Martial Valin, 75015 Paris, France
| | - Gladys Mbemba
- LBPA, CNRS UMR8113, Ecole Normale Supérieure de Cachan, 61 avenue du Président Wilson, 94235, Cachan, France
| | - Jean-François Mouscadet
- LBPA, CNRS UMR8113, Ecole Normale Supérieure de Cachan, 61 avenue du Président Wilson, 94235, Cachan, France
| | - Pierre Sonigo
- Génétique des virus, Département des Maladies Infectieuses, Institut Cochin, INSERM U567, CNRS UMR8104, Université René Descartes, 22 rue Méchain, 75014 Paris, France
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Reinke RA, Lee DJ, McDougall BR, King PJ, Victoria J, Mao Y, Lei X, Reinecke MG, Robinson WE. L-chicoric acid inhibits human immunodeficiency virus type 1 integration in vivo and is a noncompetitive but reversible inhibitor of HIV-1 integrase in vitro. Virology 2004; 326:203-19. [PMID: 15302207 DOI: 10.1016/j.virol.2004.06.005] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2004] [Revised: 02/17/2004] [Accepted: 06/01/2004] [Indexed: 11/22/2022]
Abstract
The human immunodeficiency virus (HIV) integrase (IN) must covalently join the viral cDNA into a host chromosome for productive HIV infection. l-Chicoric acid (l-CA) enters cells poorly but is a potent inhibitor of IN in vitro. Using quantitative real-time polymerase chain reaction (PCR), l-CA inhibits integration at concentrations from 500 nM to 10 microM but also inhibits entry at concentrations above 1 microM. Using recombinant HIV IN, steady-state kinetic analyses with l-CA were consistent with a noncompetitive or irreversible mechanism of inhibition. IN, in the presence or absence of l-CA, was successively washed. Inhibition of IN diminished, demonstrating that l-CA was reversibly bound to the protein. These data demonstrate that l-CA is a noncompetitive but reversible inhibitor of IN in vitro and of HIV integration in vivo. Thus, l-CA likely interacts with amino acids other than those which bind substrate.
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Affiliation(s)
- Ryan A Reinke
- Department of Microbiology and Molecular Genetics, University of California, Irvine 92697-4800, USA
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Saenz DT, Loewen N, Peretz M, Whitwam T, Barraza R, Howell KG, Holmes JM, Good M, Poeschla EM. Unintegrated lentivirus DNA persistence and accessibility to expression in nondividing cells: analysis with class I integrase mutants. J Virol 2004; 78:2906-20. [PMID: 14990709 PMCID: PMC353756 DOI: 10.1128/jvi.78.6.2906-2920.2004] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2003] [Accepted: 11/08/2003] [Indexed: 11/20/2022] Open
Abstract
The circumstances under which unintegrated lentivirus DNA can persist and be a functional template for transcription and protein expression are not clear. We constructed and validated the first class I (nonpleiotropic) integrase (IN) mutants for a non-human lentivirus (feline immunodeficiency virus [FIV]) and analyzed both these and known class I human immunodeficiency virus type 1 IN mutants. The FIV IN mutants (D66V and D66V/D118A) had class I properties: Gag/Pol precursor expression, proteolytic processing, particle formation, and reverse transcriptase (RT) production were normal, while the transduction of dividing fibroblasts was prevented and integration was blocked. When injected into rat retinas, the wild-type (WT) vector produced extensive, persistent transgene expression, compared with only rare positive neuronal cells for the IN mutant vector. In contrast, both WT and mutant vectors produced entirely equivalent, effective transduction levels of primary rat neurons (retinal ganglion cells). By testing the hypothesis that the unexpected retinal neuron transduction was related to cell cycle status, we found that when fibroblasts were growth arrested, transduction and internally promoted transgene expression were not inhibited at all by the class I FIV or HIV-1 IN mutations. Cells were then transduced under aphidicolin arrest and were released from the block 48 h later. Vector expression was stable and durable during repeated passaging in WT vector-transduced cells, while the release of cells transduced with equivalent RT units of class I IN mutant FIV or HIV vector resulted in a steady decline of expression, from 97 to 0% of cells by day 10. Southern blot and PCR analyses showed a lack of integration, irrespective of cell cycle, for the class I mutants and an increase in one- and two-long terminal repeat circular and linear unintegrated DNAs in growth-arrested cells. We conclude that if cell division is prevented, unintegrated FIV and HIV-1 vector DNAs can produce high-level internally promoted transgene expression equivalent to WT vectors. The expression correlates with the unintegrated DNA levels. These observations may facilitate the study of the roles of IN and other preintegration complex components in preintegration phases of infection by (i) providing an alternative way to monitor unintegrated nuclear cDNA forms, (ii) restricting ascertainment to the transcriptionally functional subset of unintegrated DNA, (iii) enabling analysis in individual, nondividing cells, and (iv) uncoupling other potential functions of IN from integration.
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Affiliation(s)
- Dyana T Saenz
- Molecular Medicine Program, Departments of Immunology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA
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Villanueva RA, Jonsson CB, Jones J, Georgiadis MM, Roth MJ. Differential multimerization of Moloney murine leukemia virus integrase purified under nondenaturing conditions. Virology 2003; 316:146-60. [PMID: 14599799 PMCID: PMC5653259 DOI: 10.1016/s0042-6822(03)00559-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Retroviral integrases (IN) catalyze the integration of the reverse-transcribed viral DNA into the host genome, an essential process leading to virus replication. For Moloney murine leukemia virus (M-MuLV) IN, the limited solubility of the recombinant protein has restricted the development of biophysical and structural analyses. Herein, recombinant M-MuLV IN proteins, either full length or two nonoverlapping domain constructs, were purified under non-denaturing conditions from solubilized bacterial extracts by Ni(2+)-NTA resins. Additionally, WT IN was further purified by heparin chromatography. All of the purified proteins were shown to be active and stable. WT M-MuLV IN chromatographed with a peak corresponding with a dimer by gel filtration chromatography. In contrast, the single point mutant C209A IN migrated predominantly as a tetramer. For both proteins, fractions in equilibrium between dimers and tetramers were competent to assemble concerted two-end integrations and yielded a unique strand-transfer profile in the presence of a 28-mer U5 oligonucleotide substrate, indicative of a distinct conformation within the synaptic complex. This specific target-site selection was not observed with a shorter 20-mer U5 substrate. These studies provide the foundation for biophysical and structural analysis on M-MuLV IN and the mechanism of retroviral integration.
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Affiliation(s)
- Rodrigo A. Villanueva
- Department of Biochemistry, University of Medicine and Dentistry of New Jersey–Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, NJ 08854, USA
| | - Colleen B. Jonsson
- Department of Chemistry and Biochemistry, New Mexico State University, Las Cruces, NM 88003, USA
| | - Jennifer Jones
- Department of Biochemistry, University of Medicine and Dentistry of New Jersey–Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, NJ 08854, USA
| | - Millie M. Georgiadis
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Monica J. Roth
- Department of Biochemistry, University of Medicine and Dentistry of New Jersey–Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, NJ 08854, USA
- Corresponding author. Fax +1-732-235-4783. (M.J. Roth)
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Padow M, Lai L, Deivanayagam C, DeLucas LJ, Weiss RB, Dunn DM, Wu X, Kappes JC. Replication of chimeric human immunodeficiency virus type 1 (HIV-1) containing HIV-2 integrase (IN): naturally selected mutations in IN augment DNA synthesis. J Virol 2003; 77:11050-9. [PMID: 14512553 PMCID: PMC224969 DOI: 10.1128/jvi.77.20.11050-11059.2003] [Citation(s) in RCA: 18] [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
The human immunodeficiency virus type 1 (HIV-1) integrase (IN) protein augments the initiation of reverse transcription. Chimeric HIV-1 containing HIV-2 IN (SG3(IN2)) is severely impaired in virus infectivity and DNA synthesis. To analyze the nature of this defect, we infected T cells with the chimeric SG3(IN2) virus and by continuous passage in cell culture selected for virus with improved replication properties. Viruses from two different time points were chosen for further analysis, an early culture-adapted virus (CF-65) that exhibited an intermediate level of infectivity, and a later-passaged virus (CF-131) that was significantly more infectious. Sequence analysis of multiple clones derived from the CF-65 virus culture demonstrated a diversity of mutations in the reverse transcriptase (RT) and a common V204I IN mutation. Analysis of clones derived from the CF-131 virus indicated the selection of two additional IN mutations, Q96H and K127E, and a fixed V179I RT mutation. By cloning RT and/or IN sequences back into the original SG3(IN2) chimeric virus, we demonstrated that mutations in both RT and IN contributed to the improvement in viral fitness. The effect of the HIV-2IN(IN(2)) mutations on virus DNA synthesis was analyzed by packaging IN(2) mutants into HIV-1 as Vpr-IN(2) fusion proteins. This analysis revealed that the Q96H, K127E and V204I mutations increased the infectivity of the chimeric virus by augmenting the initiation of viral cDNA synthesis in infected cells. The Q96H and K127E mutations are present in adjacent helical structures on the surface of the IN protein and together account for most of the increase observed in DNA synthesis. Our findings provide evidence that the IN protein augments the initiation of reverse transcription through specific interactions with other viral components comprising the initiation complex. Moreover, they implicate specific regions on the surface of IN that may help to elucidate mechanisms by which the HIV-1 IN protein augments the initiation of HIV-1 reverse transcription in vivo.
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Affiliation(s)
- Marcus Padow
- Departments of Microbiology. Medicine. Center for Biophysical Sciences and Engineering, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA
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Abstract
Spumaviruses are complex retroviruses whose replication cycle resembles that of hepadnaviruses, especially by a late-occurring reverse transcription step. The possible existence of an early reverse transcription as observed in other retroviruses was not documented. Using real-time quantitative PCR, we addressed directly the kinetics of DNA synthesis during spumavirus infection. An early phase of viral DNA synthesis developed until 3 h postinfection, followed by a second phase, culminating 10 h postinfection. Both phases were abolished by the reverse transcriptase inhibitor 3'-azido-3'-deoxythymidine. Similar to other retroviruses, circular forms of viral DNA harboring two long terminal repeats were mainly found in the nucleus of infected cells. Interestingly, a fraction of these circular forms were detected in the cytoplasm and in extracellular virions, a feature shared with hepadnaviruses. Combined with packaging of both viral DNA and RNA genomes in virions, early and late reverse transcription might allow spumavirus to maximize its genome replication.
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Affiliation(s)
- Olivier Delelis
- Département des Maladies Infectieuses, Institut Cochin, INSERM U 567 et CNRS UMR 8104, 22 rue Méchain, 75014 Paris, France
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Seamon JA, Jones KS, Miller C, Roth MJ. Inserting a nuclear targeting signal into a replication-competent Moloney murine leukemia virus affects viral export and is not sufficient for cell cycle-independent infection. J Virol 2002; 76:8475-84. [PMID: 12134052 PMCID: PMC155121 DOI: 10.1128/jvi.76.16.8475-8484.2002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The effects of inserting reported nuclear localization signals (NLSs) into the Moloney murine leukemia virus (Mo-MuLV) integrase (IN) protein, within a replication-competent viral construct, were studied. In contrast to the virus harboring IN fused to the simian virus 40 (SV40) large T antigen NLS (SV40 NLS) (J. A. Seamon, M. Adams, S. Sengupta, and M. J. Roth, Virology 274:412-419, 2000), a codon-modified SV40 NLS was stably expressed during viral propagation. Incorporation of the codon-modified SV40 NLS into IN, however, altered the packaging of the Gag-Pol precursor in the virus; viral particles contained decreased levels of reverse transcriptase (RT) and IN. In addition, the virus showed delayed kinetics of viral DNA synthesis upon infection. A panel of infectious MuLVs containing alternative IN-NLS fusions was generated and assayed for cell cycle-independent infection. Viral infection with the NLS-tagged proteins, however, remained dependent on passage of the cells through mitosis. This finding has direct implications for engineering murine-based retroviral vectors for gene therapy.
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Affiliation(s)
- Jennifer A Seamon
- Department of Biochemistry, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway 08854, USA
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Abd-Elazem IS, Chen HS, Bates RB, Huang RCC. Isolation of two highly potent and non-toxic inhibitors of human immunodeficiency virus type 1 (HIV-1) integrase from Salvia miltiorrhiza. Antiviral Res 2002; 55:91-106. [PMID: 12076754 DOI: 10.1016/s0166-3542(02)00011-6] [Citation(s) in RCA: 126] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Water soluble extracts of the herbal plant, Salvia miltiorrhiza (Danshen) exhibited potent effect against HIV-1 integrase activity in vitro and viral replication in vivo. We have developed an extensive purification scheme to isolate effective, non-toxic inhibitors against human immunodeficiency virus type 1 (HIV-1) using the 3'-processing activity of integrase as a purification guide and assay. Two water soluble compounds, M(5)22 and M(5)32, have been discovered by isolating them from S. miltiorrhiza roots in purities of >99.5% as shown by NMR spectral analysis with yields of 0.018 and 0.038%, respectively. Structural determination revealed that M(5)22 is lithospermic acid and M(5)32 is lithospermic acid B. These two structurally related compounds are potent anti-HIV inhibitors and showed no cytotoxicity to H9 cells at high concentrations (CC(100)>297 microM for M(5)22 and >223 microM for M(5)32). The IC50 for inhibition of 3'-processing by HIV-1 integrase was found to be 0.83 microM for M(5)22 and 0.48 microM for M(5)32. In addition, M(5)22 and M(5)32 inhibited HIV-1 integrase catalytic activities of 3'-joining to the target DNA with IC50 of 0.48 microM for M(5)22 and 0.37 microM for M(5)32. Furthermore, kinetic and mechanistic studies suggested that drug binding to HIV-1 integrase and inhibition of enzymatic activity occur at a fast rate. Both M(5)22 and M(5)32 do not prevent HIV entry in H9 cells. They also show no inhibition of reverse transcriptase activity in infected cells. The levels of intracellular strong stop and full-length viral DNA remained unchanged following drug treatment. However, both inhibitors strongly suppressed the acute HIV-1 infection of H9 cells with IC50 values of 2 and 6.9 microM for M(5)22 and M(5)32, respectively. Thus these two selective integrase inhibitors hold promise as a novel class of therapeutic drugs for AIDS based on their high potencies and absence of cytotoxicity.
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Affiliation(s)
- Ibrahim S Abd-Elazem
- Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, The Johns Hopkins University, Baltimore, MD 21205, USA
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16
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Lai L, Liu H, Wu X, Kappes JC. Moloney murine leukemia virus integrase protein augments viral DNA synthesis in infected cells. J Virol 2001; 75:11365-72. [PMID: 11689617 PMCID: PMC114722 DOI: 10.1128/jvi.75.23.11365-11372.2001] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mutations in the IN domain of retroviral DNA may affect multiple steps of the virus life cycle, suggesting that the IN protein may have other functions in addition to its integration function. We previously reported that the human immunodeficiency virus type 1 IN protein is required for efficient viral DNA synthesis and that this function requires specific interaction with other viral components but not enzyme (integration) activity. In this report, we characterized the structure and function of the Moloney murine leukemia virus (MLV) IN protein in viral DNA synthesis. Using an MLV vector containing green fluorescent protein as a sensitive reporter for virus infection, we found that mutations in either the catalytic triad (D184A) or the HHCC motif (H61A) reduced infectivity by approximately 1,000-fold. Mutations that deleted the entire IN (DeltaIN) or 34 C-terminal amino acid residues (Delta34) were more severely defective, with infectivity levels consistently reduced by 10,000-fold. Immunoblot analysis indicated that these mutants were similar to wild-type MLV with respect to virion production and proteolytic processing of the Gag and Pol precursor proteins. Using semiquantitative PCR to analyze viral cDNA synthesis in infected cells, we found the Delta34 and DeltaIN mutants to be markedly impaired while the D184A and H61A mutants synthesized cDNA at levels similar to the wild type. The DNA synthesis defect was rescued by complementing the Delta34 and DeltaIN mutants in trans with either wild-type IN or the D184A mutant IN, provided as a Gag-IN fusion protein. However, the DNA synthesis defect of DeltaIN mutant virions could not be complemented with the Delta34 IN mutant. Taken together, these analyses strongly suggested that the MLV IN protein itself is required for efficient viral DNA synthesis and that this function may be conserved among other retroviruses.
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Affiliation(s)
- L Lai
- Department of Medicine, University of Alabama at Birmingham, 35294, USA
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17
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Abstract
Integration of retrovirus DNA is a specific process catalyzed by the integrase protein acting to join the viral substrate DNA (att) sequences of about 10 bases at the ends of the long terminal repeat (LTR) to various sites in the host target cell DNA. Although the interaction is sequence specific, the att sequences of different retroviruses are largely unrelated to one another and usually differ between the two ends of the viral DNA. To define substrate sequence specificity, we designed an "in vitro evolution" scheme to select an optimal substrate sequence by competitive integration in vitro from a large pool of partially randomized substrates. Integrated substrates are enriched by PCR amplification and then regenerated and subjected to subsequent cycles of selection and enrichment. Using this approach, we obtained the optimal substrate sequence of 5'-ACGACAACA-3' for avian sarcoma-leukosis virus (ASLV) and 5'-AACA(A/C)AGCA-3' for human immunodeficiency virus type 1, which differed from those found at both ends of the viral DNA. Clonal analysis of the integration products showed that ASLV integrase can use a wide variety of substrate sequences in vitro, although the consensus sequence was identical to the selected sequence. By a competition assay, the selected nucleotide at position 4 improved the in vitro integration efficiency over that of the wild-type sequence. Viral mutants bearing the optimal sequence replicated at wild-type levels, with the exception of some mutations disrupting the U5 RNA secondary structure important for reverse transcription, which were significantly impaired. Thus, maximizing the efficiency of integration may not be of major importance for efficient retrovirus replication.
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Affiliation(s)
- H Zhou
- Departments of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA
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18
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Abstract
There are two retroviral integration loci. One encodes the transacting IN protein, which is cleaved from the carboxyl terminus of the Gag-Pol polyprotein precursor during virus assembly. The second locus is the cis-acting attachment (att) site, comprising the terminal sequences at the U3 and U5 ends of linear viral cDNA. Integrase and att site mutant viruses can be blocked at different steps of the viral replication cycle. Class I IN mutants are blocked specifically at the integration step. Class II IN mutants, on the other hand, display pleiotropic defects, most notably in virion morphogenesis and/or reverse transcription. Mutations in the U5 end att site can also disrupt reverse transcription in addition to integration. It is prudent to use caution when interpreting results of in vivo mutagenesis experiments that target retroviral IN and the att site.
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Affiliation(s)
- A Engelman
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA
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19
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Yang F, Leon O, Greenfield NJ, Roth MJ. Functional interactions of the HHCC domain of moloney murine leukemia virus integrase revealed by nonoverlapping complementation and zinc-dependent dimerization. J Virol 1999; 73:1809-17. [PMID: 9971758 PMCID: PMC104420 DOI: 10.1128/jvi.73.3.1809-1817.1999] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/1998] [Accepted: 12/09/1998] [Indexed: 11/20/2022] Open
Abstract
The retroviral integrase (IN) is required for the integration of viral DNA into the host genome. The N terminus of IN contains an HHCC zinc finger-like motif, which is conserved among all retroviruses. To study the function of the HHCC domain of Moloney murine leukemia virus IN, the first N-terminal 105 residues were expressed independently. This HHCC domain protein is found to complement a completely nonoverlapping construct lacking the HHCC domain for strand transfer, 3' processing and coordinated disintegration reactions, revealing trans interactions among IN domains. The HHCC domain protein binds zinc at a 1:1 ratio and changes its conformation upon binding to zinc. The presence of zinc within the HHCC domain stimulates selective integration processes. Zinc promotes the dimerization of the HHCC domain and protects it from N-ethylmaleimide modification. These studies dissect and define the requirement for the HHCC domain, the exact function of which remains unknown.
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Affiliation(s)
- F Yang
- Department of Biochemistry, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA
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20
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King PJ, Robinson WE. Resistance to the anti-human immunodeficiency virus type 1 compound L-chicoric acid results from a single mutation at amino acid 140 of integrase. J Virol 1998; 72:8420-4. [PMID: 9733896 PMCID: PMC110234 DOI: 10.1128/jvi.72.10.8420-8424.1998] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/1998] [Accepted: 06/24/1998] [Indexed: 11/20/2022] Open
Abstract
L-Chicoric acid is an inhibitor of human immunodeficiency virus type 1 (HIV-1) integrase in vitro and of HIV-1 replication in tissue culture. Following 3 months of selection in the presence of increasing concentrations of L-chicoric acid, HIV-1 was completely resistant to the compound. Introduction of the mutant integrase containing a single glycine-to-serine amino acid change at position 140 into the native, L-chicoric acid-sensitive virus demonstrated that this change was sufficient to confer resistance to L-chicoric acid. These results confirm through natural selection previous biochemical studies showing that L-chicoric acid inhibits integrase and that the drug is likely to interact at residues near the catalytic triad in the integrase active site.
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Affiliation(s)
- P J King
- Departments of Microbiology and Molecular Genetics, University of California, Irvine, California 92697, USA
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21
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Donzella GA, Leon O, Roth MJ. Implication of a central cysteine residue and the HHCC domain of Moloney murine leukemia virus integrase protein in functional multimerization. J Virol 1998; 72:1691-8. [PMID: 9445080 PMCID: PMC124658 DOI: 10.1128/jvi.72.2.1691-1698.1998] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Moloney murine leukemia virus (M-MuLV) IN-IN protein interactions important for catalysis of strand transfer and unimolecular and bimolecular disintegration reactions were investigated by using a panel of chemically modified M-MuLV IN proteins. Functional complementation of an HHCC-deleted protein (Ndelta105) by an independent HHCC domain (Cdelta232) was severely compromised by NEM modification of either subunit. Productive Ndelta105 IN-DNA interactions with a disintegration substrate lacking a long terminal repeat 5'-single-stranded tail also required complementation by a functional HHCC domain. Virus encoding the C209A M-MuLV IN mutation exhibited delayed virion production and replication kinetics.
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Affiliation(s)
- G A Donzella
- Department of Biochemistry, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, Piscataway 08854, USA
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22
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Abstract
The integrase protein of retroviruses catalyzes the insertion of the viral DNA into the genomes of the cells that they infect. Integrase is necessary and sufficient for this recombination reaction in vitro; however, the enzyme's activity appears to be modulated in vivo by viral and cellular components included in the nucleoprotein pre-integration complex. In addition to integrase, cis-acting sequences at the ends of the viral DNA are important for integration. Solution of the structures of the isolated N- and C-terminal domains of HIV-1 integrase by nuclear magnetic resonance (NMR) and the available crystal structures of the catalytic core domains from human immunodeficiency virus type-1 (HIV-1) and avian sarcoma virus (ASV) integrases are providing a structural basis for understanding some aspects of the integration reaction. The role of the evolutionarily conserved acidic amino acids in the D,D(35)E motif as metal-coordinating residues that are critical for catalysis, has been confirmed by the metal-integrase (core domain) complexes of ASV integrase. The central role that integrase plays in the life cycle of the virus makes it an attractive target for the design of drugs against retroviral diseases such as AIDS. To this end, several compounds have been screened for inhibitory effects against HIV-1 integrase. These include DNA intercalators, peptides, RNA ligands, and small organic compounds such as bis-catechols, flavones, and hydroxylated arylamides. Although the published inhibitors are not very potent, they serve as valuable leads for the development of the next generation of tight-binding analogues that are more specific to integrase. In addition, new approaches are being developed, exemplified by intracellular immunization studies with conformation-sensitive inhibitory monoclonal antibodies against HIV-1 integrase. Increased knowledge of the mechanism of retroviral DNA integration should provide new strategies for the design of effective antivirals that inhibit integrase in the future.
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Affiliation(s)
- E Asante-Appiah
- Institute for Cancer Research, Fox Chase Cancer Center, Philadelphia, PA 19111, USA
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23
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List J, Haase AT. Integration of visna virus DNA occurs and may be necessary for productive infection. Virology 1997; 237:189-97. [PMID: 9356331 DOI: 10.1006/viro.1997.8785] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Proviral integration is thought to be an obligate step of the retroviral replication cycle but the lentivirus visna has been reported to replicate in sheep choroid plexus (SCP) cultures in the absence of proviral integration. Because of new evidence that visna virus has a functional integrase, we reexamined visna virus infection of SCP cultures and found that proviral integration does indeed occur in this setting. While the majority of viral DNA remains unintegrated, integrated proviruses arise early in infection and accumulate over time. The sequences of the resulting host-virus DNA junctions show that, like other retroviruses, visna loses terminal nucleotides from its DNA upon integration. However, unlike other retroviruses, in over half the host-U3 junctions analyzed only a single nucleotide was lost such that the universally conserved CA dinucleotide, two nucleotides from the end of unintegrated viral DNA, did not directly abut host sequences in the provirus. We analyzed the role of integration in visna replication by introducing a series of five mutations into the integrase gene of molecularly cloned visna virus LV1-1KS1. Each mutation abolished viral replication, suggesting that integration may be an obligatory step in replication. We also documented productive infection of SCP cultures in which cell division had been blocked by g-irradiation. The ability of visna to integrate and to replicate in nondividing cells points to the possible utility of visna-based vectors for gene transfer into differentiated cells.
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Affiliation(s)
- J List
- Department of Microbiology, University of Minnesota, 420 Delaware Street S.E., Minneapolis, Minnesota 55455, USA
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24
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Jonsson CB, Donzella GA, Gaucan E, Smith CM, Roth MJ. Functional domains of Moloney murine leukemia virus integrase defined by mutation and complementation analysis. J Virol 1996; 70:4585-97. [PMID: 8676485 PMCID: PMC190395 DOI: 10.1128/jvi.70.7.4585-4597.1996] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Retroviral integrases perform two catalytic steps, 3' processing and strand transfer, that result in the stable insertion of the retroviral DNA into the host genome. Mutant M-MuLV integrases were constructed to define the functional domains important for 3' processing, strand transfer, and disintegration by in vitro assays. N-terminal mutants had no detectable 3' processing activity, and only one mutant which lacks the HHCC domain, Ndelta105, had strand transfer activity. Strand transfer mediated by Ndelta105 showed preference for one site in the target DNA. Disintegration activity of N-terminal mutants decreased only minimally. In contrast, all C-terminal mutants truncated by more than 28 amino acids had no integration or disintegration activity. Activity on a single-strand disintegration substrate did not require a functional HHCC domain but did require most of the C-terminal region. Complementation analysis found that the HHCC region alone was able to function in trans to a promoter containing only the DD(35)E and C-terminal regions and to enhance integration site selection. Increasing the reducing conditions or adding the HHCC domain to Ndelta105 reaction mixtures restored the wild-type strand transfer activity and range of target sites. The reducing agent affected Cys-209 in the DD(35)E region. The presence of C-209 was required for complementation of Ndelta105 by the HHCC region.
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Affiliation(s)
- C B Jonsson
- Department of Biochemistry, Robert W. Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway, New Jersey 08854, USA
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25
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Kirchner J, Sandmeyer SB. Ty3 integrase mutants defective in reverse transcription or 3'-end processing of extrachromosomal Ty3 DNA. J Virol 1996; 70:4737-47. [PMID: 8676501 PMCID: PMC190411 DOI: 10.1128/jvi.70.7.4737-4747.1996] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Ty3, a retroviruslike element in Saccharomyces cerevisiae, encodes an integrase (IN) which is essential for position-specific transposition. The Ty3 integrase contains the highly conserved His-Xaa(3-7)-His-Xaa(23-32)-Cys-Xaa(2)-Cys and Asp, Asp-Xaa(35)-Glu [D,D(35)E] motifs found in retroviral integrases. Mutations were introduced into the coding region for the Ty3 integrase to determine the effects in vivo of changes in conserved residues of the putative catalytic triad D,D(35)E and the nonconserved carboxyl-terminal region. Ty3 viruslike particles were found to be associated with significant amounts of linear DNA of the approximate size expected for a full-length reverse transcription product and with plus-strand strong-stop DNA. The full-length, preintegrative DNA has at each 3' end 2 bp that are removed prior to or during integration. Such 3'-end processing has not been observed for other retroviruslike elements. A mutation at either D-225 or E-261 of the Ty3 integrase blocked transposition and prevented processing of the 3' ends of Ty3 DNA in vivo, suggesting that the D,D(35)E region is part of the catalytic domain of Ty3 IN. Carboxyl-terminal deletions of integrase caused a dramatic reduction in the amount of Ty3 DNA in vivo and a decrease in reverse transcriptase activity in vitro but did not affect the apparent size or amount of the 55-kDa reverse transcriptase in viruslike particles. The 115-kDa viruslike particle protein, previously shown to react with antibodies to Ty3 integrase, was shown to be a reverse transcriptase-IN fusion protein. These results are consistent with a role for the integrase domain either in proper folding of reverse transcriptase or as part of a heterodimeric reverse transcriptase molecule.
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Affiliation(s)
- J Kirchner
- Howard Hughes Medical Institute, University of Washington, Seattle, Washington 98195-7370, USA
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26
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Donzella GA, Jonsson CB, Roth MJ. Coordinated disintegration reactions mediated by Moloney murine leukemia virus integrase. J Virol 1996; 70:3909-21. [PMID: 8648728 PMCID: PMC190269 DOI: 10.1128/jvi.70.6.3909-3921.1996] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The protein-DNA and protein-protein interactions important for function of the integrase (IN) protein of Moloney murine leukemia virus (M-MuLV) were investigated by using a coordinated-disintegration assay. A panel of M-MuLV IN mutants and substrate alterations highlighted distinctions between the intermolecular and intramolecular reactions of coordinated disintegration. Mispairing of the crossbone single-strand region and altered long terminal repeat (LTR) positioning affected the intermolecular, but not the intramolecular, reactions of coordinated disintegration. Partial components of the crossbone substrate were coordinated by M-MuLV IN, indicating a reliance on both LTR and target DNA determinants for substrate assembly. The intramolecular reaction was dependent on the presence of either the HHCC domain or a crossbone LTR 5' single-stranded tail. An M-MuLV IN mutant without the HHCC domain (Ndelta105) catalyzed reduced levels of double disintegration but not single disintegration. A separately purified HHCC domain protein (Cdelta232) stimulated double disintegration mediated by Ndelta105, suggesting a role of the N-terminal HHCC domain in stable IN-IN and IN-DNA interactions. Significantly, crossbone substrates lacking the LTR 5' tails were not recognized by the fingerless Ndelta105 protein. Collectively, these data suggest similar roles of the HHCC domain and 5' LTR tail in substrate recognition and modulation of IN activity.
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Affiliation(s)
- G A Donzella
- Department of Biochemistry, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, Piscataway 08854, USA
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27
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Kameoka M, Kimura T, Okada Y, Fujinaga K, Nakaya T, Takahashi H, Kishi M, Ikuta K. High susceptibility of U937-derived subclones to human immunodeficiency virus type 1 infection correlates with accumulation of unintegrated circular viral DNA. Virus Genes 1996; 12:117-29. [PMID: 8879128 DOI: 10.1007/bf00572950] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Our previous report showed that U937-derived subclones were differentiated into at least three types (high, middle, and low types), even in the subclones expressing similar levels of surface CD4, in terms of the kinetics of the appearance of viral antigens and virus production after infection with human immunodeficiency virus type 1 (HIV-1). Here we showed the evidence that high susceptibility to HIV-1 infection, which was confirmed by the profound expression of viral messages and antigens, was exclusively associated with a high number of the unintegrated extrachromosomal form of viral DNA, but not with the amounts of adsorbed virus RNA nor those of integrated DNA form. The difference in the amounts of extrachromosomal form of viral DNA was also observed in the culture with 3'-azido-3'-deoxythymidine (AZT), indicating that the susceptibility is essentially unrelated to multiple infection events. Thus, the susceptibility of U937-derived subclones to HIV-1 infection seems to be affected by the occurrence of specific events involved in the accumulation of unintegrated viral DNA after viral adsorption.
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Affiliation(s)
- M Kameoka
- Section of Serology, Hokkaido University, Sapporo, Japan
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28
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Masuda T, Planelles V, Krogstad P, Chen IS. Genetic analysis of human immunodeficiency virus type 1 integrase and the U3 att site: unusual phenotype of mutants in the zinc finger-like domain. J Virol 1995; 69:6687-96. [PMID: 7474078 PMCID: PMC189578 DOI: 10.1128/jvi.69.11.6687-6696.1995] [Citation(s) in RCA: 138] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Retroviral integration is the step which leads to establishment of the provirus, cis- and trans-acting regions of the human immunodeficiency type 1 (HIV-1) retrovirus genome, including the attachment site (att) at the ends of the unintegrated viral DNA and the conserved domains within the integrase (IN) protein, have been identified as being important for integration. We investigated the role of each of these regions in the context of an infectious HIV-1 molecular clone through point mutagenesis of the att site and the zinc finger-like and catalytic domains of IN. The effect of each mutation on integration activity was examined by using a single-step infection system with envelope-pseudotype virus. The relative integration efficiency was estimated by monitoring the levels of viral DNA over time in the infected cells. The integration activities of catalytic domain point mutants and att site deletion mutants were estimated to be 0.5 and 5% of wild-type activity, respectively. However, in contrast with previous in vitro cell-free integration studies, alteration of the highly conserved CA dinucleotide resulted in a mutant which still retained 40% of wild-type integration activity. The relative levels of expression of each mutant, as measured by a luciferase reporter gene, correlated with levels of integration. This observation is consistent with those of previous studies indicating that integration is an obligatory step for retroviral gene expression. Interestingly, we found that three different HIV-1 constructs bearing point mutations in the zinc finger-like domain synthesized much lower levels of viral DNA after infection, suggesting impairment of these mutants before or at the initiation of reverse transcription. Western blot (immunoblot) analysis demonstrated wild-type levels of reverse transcriptase within the mutant virions. In vitro endogenous reverse transcription assays indicated that all three mutants in the zinc finger-like domain had wild-type levels of reverse transcriptase activity. These data indicate that in addition to integration, IN may have an effect on the proper course of events in the viral life cycle that precede integration.
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Affiliation(s)
- T Masuda
- Department of Microbiology & Immunology, UCLA School of Medicine 90095, USA
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29
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Engelman A, Englund G, Orenstein JM, Martin MA, Craigie R. Multiple effects of mutations in human immunodeficiency virus type 1 integrase on viral replication. J Virol 1995; 69:2729-36. [PMID: 7535863 PMCID: PMC188965 DOI: 10.1128/jvi.69.5.2729-2736.1995] [Citation(s) in RCA: 372] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The integration of a DNA copy of the human immunodeficiency virus type 1 (HIV-1) genome into a chromosome of an infected cell is a pivotal step in virus replication. Integration requires the activity of the virus-encoded integrase, which enters the cell as a component of the virion. Results of numerous mutagenesis studies have identified amino acid residues and protein domains of HIV-1 integrase critical for in vitro activity, but only a few of these mutants have been studied for their effects on HIV replication. We have introduced site-directed changes into an infectious DNA clone of HIV-1 and show that integrase mutations can affect virus replication at a variety of steps. We identified mutations that altered virion morphology, levels of particle-associated integrase and reverse transcriptase, and viral DNA synthesis. One replication-defective mutant virus which had normal morphology and protein composition displayed increased levels of circular viral DNA following infection of a T-cell line. This virus also had a significant titer in a CD4-positive indicator cell assay, which requires the viral Tat protein. Although unintegrated viral DNA can serve as a template for Tat expression in infected indicator cells, this level of expression is insufficient to support a spreading viral infection in CD4-positive lymphocytes.
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Affiliation(s)
- A Engelman
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland 20892, USA
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30
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Yoshinaga T, Fujiwara T. Different roles of bases within the integration signal sequence of human immunodeficiency virus type 1 in vitro. J Virol 1995; 69:3233-6. [PMID: 7707558 PMCID: PMC189032 DOI: 10.1128/jvi.69.5.3233-3236.1995] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
To investigate the roles of bases near the tips of each strand of the long terminal repeat of the human immunodeficiency virus type 1 in the integration reaction, we examined the efficiencies of both binding and integration activities of staggered-ended substrates and mismatched mutant substrates by the integration assay and the UV cross-linking assay. Our results suggest that some bases of the human immunodeficiency virus type 1 long terminal repeat are required primarily for binding, whereas others are more critical for later reaction steps in vitro.
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Affiliation(s)
- T Yoshinaga
- Shionogi Institute for Medical Science, Osaka, Japan
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31
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Taddeo B, Haseltine WA, Farnet CM. Integrase mutants of human immunodeficiency virus type 1 with a specific defect in integration. J Virol 1994; 68:8401-5. [PMID: 7966634 PMCID: PMC237311 DOI: 10.1128/jvi.68.12.8401-8405.1994] [Citation(s) in RCA: 74] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
A previous genetic analysis of the human immunodeficiency virus type 1 integrase protein failed to identify single amino acid substitutions that only block the integration of viral DNA (C.-G. Shin, B. Taddeo, W.A. Haseltine, and C.M. Farnet, J. Virol. 68:1633-1642, 1994). Additional substitutions of amino acids that are highly conserved among retroviral integrases were constructed in human immunodeficiency virus type 1 and analyzed for their effects on viral protein synthesis and processing, virion morphology, and viral DNA synthesis and integration in an attempt to identify mutants with a specific defect in integration. Four single amino acid substitutions resulted in replication defective viruses. Conservative, single amino acid substitutions of the two invariant aspartic acid residues found in all retroviral integrases prevented the integration of viral DNA and had no detectable effect on the other stages in the viral replication cycle, indicating that these mutants exhibited a specific defect in integration. Mutations at two positions, S-81 and P-109, blocked the integration of viral DNA but also resulted in the production of viral particles that exhibited reduced reverse transcriptase activity, suggesting additional defects in viral replication. Substitution of the highly conserved amino acid T66 had no effect on viral replication in a CD4+ human T-cell line. This analysis extends the range of possible phenotypes that may be produced by single amino acid substitutions in conserved residues of the integrase protein.
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Affiliation(s)
- B Taddeo
- Division of Human Retrovirology, Dana-Farber Cancer Institute, Boston, Massachusetts 02115
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32
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Yoshinaga T, Kimura-Ohtani Y, Fujiwara T. Detection and characterization of a functional complex of human immunodeficiency virus type 1 integrase and its DNA substrate by UV cross-linking. J Virol 1994; 68:5690-7. [PMID: 8057450 PMCID: PMC236971 DOI: 10.1128/jvi.68.9.5690-5697.1994] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
To analyze the association of the human immunodeficiency virus type 1 integrase (IN) protein with DNA substrates, we applied a shortwave UV cross-linking method to the in vitro integration system. Three photoadduct bands were detected on sodium dodecyl sulfate-polyacrylamide gels. The appearances of these photoadducts were examined with various substrates and under several incubation conditions. Our data suggest that one of these photoadducts is derived from the sequence- and strand-specific bound state of the early phase of the integration reaction before the 3' processing reaction. We also show that most of the photoadduct complexes are competent for integration even after UV irradiation.
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Affiliation(s)
- T Yoshinaga
- Shionogi Institute for Medical Science, Osaka, Japan
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33
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Cannon PM, Wilson W, Byles E, Kingsman SM, Kingsman AJ. Human immunodeficiency virus type 1 integrase: effect on viral replication of mutations at highly conserved residues. J Virol 1994; 68:4768-75. [PMID: 8035478 PMCID: PMC236416 DOI: 10.1128/jvi.68.8.4768-4775.1994] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Sequence comparisons of the integrase (IN) proteins from different retroviruses have identified several highly conserved residues. We have introduced mutations at 16 of these sites into the integrase gene of human immunodeficiency virus type 1 and analyzed the phenotypes of the resulting viruses. The viruses were all normal for p24 content and reverse transcriptase activity. In addition, all of the mutants could infect T-cell lines and undergo reverse transcription, as assessed by PCR analysis. Most of the mutant viruses also had normal Western blot (immunoblot) profiles, although three of the mutations resulted in reduced signals for IN relative to the wild type on the immunoblots and mutation of residue W235 completely abolished recognition of the protein by pooled sera from human immunodeficiency virus type 1-positive patients. Mutations that have previously been shown to abolish activity in in vitro studies produced noninfectious viruses. The substitution of W235 was notable in producing a noninfectious virus, despite previous reports of this residue being nonessential for IN activity in vitro (A.D. Leavitt, L. Shiue, and H.E. Varmus, J. Biol. Chem. 268:2113-2119, 1993). In addition, we have identified four highly conserved residues that can be mutated without any affect on viral replication in T-cell lines.
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Affiliation(s)
- P M Cannon
- Department of Biochemistry, University of Oxford, United Kingdom
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34
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Shin CG, Taddeo B, Haseltine WA, Farnet CM. Genetic analysis of the human immunodeficiency virus type 1 integrase protein. J Virol 1994; 68:1633-42. [PMID: 8107224 PMCID: PMC236621 DOI: 10.1128/jvi.68.3.1633-1642.1994] [Citation(s) in RCA: 106] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Single-amino-acid changes in a highly conserved central region of the human immunodeficiency virus type 1 (HIV-1) integrase protein were analyzed for their effects on viral protein synthesis, virion morphogenesis, and viral replication. Alteration of two amino acids that are invariant among retroviral integrases, D116 and E152 of HIV-1, as well as a mutation of the highly conserved amino acid S147 blocked viral replication in two CD4+ human T-cell lines. Mutations of four other highly conserved amino acids in the region had no detectable effect on viral replication, whereas mutations at two positions, N117 and Y143, resulted in viruses with a delayed-replication phenotype. Defects in virion precursor polypeptide processing, virion morphology, or viral DNA synthesis were observed for all of the replication-defective mutants, indicating that changes in integrase can have pleiotropic effects on viral replication.
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Affiliation(s)
- C G Shin
- Division of Human Retrovirology, Dana-Farber Cancer Institute, Boston, Massachusetts 02115
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35
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Viral long terminal repeat substrate binding characteristics of the human immunodeficiency virus type 1 integrase. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)41733-9] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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36
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Jonsson CB, Roth MJ. Role of the His-Cys finger of Moloney murine leukemia virus integrase protein in integration and disintegration. J Virol 1993; 67:5562-71. [PMID: 8350412 PMCID: PMC237959 DOI: 10.1128/jvi.67.9.5562-5571.1993] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Retroviral integrases mediate site-specific endonuclease and transesterification reactions in the absence of exogenous energy. The basis for the sequence specificity in these integrase-viral DNA recognition processes is unknown. Structural analogs of the disintegration substrate were made to analyze the disintegration reaction mechanism for the Moloney murine leukemia virus (M-MuLV) integrase (IN). Modifications in the target DNA portion of the disintegration substrate decreased enzymatic activity, while substitution of the highly conserved CA in the viral long terminal repeat portion had no effect on activity. The role of the His-Cys finger region in catalysis was addressed by N-ethylmaleimide (NEM) modification of the cysteine residues of M-MuLV IN as well as by mutations. Both integration activities, 3' processing, and strand transfer, were completely inhibited by NEM modification of M-MuLV IN, while disintegration activity was only partially sensitive. However, structural analogs of the disintegration substrates that were modified in the target DNA and had the conserved CA removed were not active with NEM-treated M-MuLV IN. In addition, mutants made in the His-Cys region of M-MuLV IN were examined and found to also be completely blocked in integration but not disintegration activity. These data suggest that the domains of M-MuLV IN that are required for the forward integration reaction substrate differ from those required for the reverse disintegration reaction substrate.
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Affiliation(s)
- C B Jonsson
- Department of Biochemistry, Robert Wood Johnson Medical School, University of Medicine and Dentistry, Piscataway, New Jersey 08854
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37
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Drelich M, Haenggi M, Mous J. Conserved residues Pro-109 and Asp-116 are required for interaction of the human immunodeficiency virus type 1 integrase protein with its viral DNA substrate. J Virol 1993; 67:5041-4. [PMID: 8392628 PMCID: PMC237894 DOI: 10.1128/jvi.67.8.5041-5044.1993] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The human immunodeficiency virus type 1 integrase protein can be specifically cross-linked to viral long terminal repeat substrate oligonucleotides in vitro by using UV light. Site-directed mutagenesis and deletion analyses were used to define the domains involved in the interaction of integrase with the viral DNA substrate. Our results showed that mutation of conserved residues Pro-109 and Asp-116, which are found to be critical for the endonuclease and integration activities of IN protein, abolished the ability of the protein to cross-link to its DNA substrate. Furthermore, deletion analysis experiments showed that removal of 39 amino acids from the amino terminus and deletion of 15 amino acids from the carboxyl terminus abolished DNA cross-linking.
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Affiliation(s)
- M Drelich
- Pharmaceutical Research New Technologies, F. Hoffmann-La Roche Ltd., Basel, Switzerland
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38
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Woerner AM, Marcus-Sekura CJ. Characterization of a DNA binding domain in the C-terminus of HIV-1 integrase by deletion mutagenesis. Nucleic Acids Res 1993; 21:3507-11. [PMID: 8346030 PMCID: PMC331452 DOI: 10.1093/nar/21.15.3507] [Citation(s) in RCA: 104] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The integrase (IN) protein of human immunodeficiency virus type 1 (HIV-1) catalyzes site-specific cleavage of 2 bases from the viral long terminal repeat (LTR) sequence yet it binds DNA with little DNA sequence specificity. We have previously demonstrated that the C-terminal half of IN (amino acids 154-288) possesses a DNA binding domain. In order to further characterize this region, a series of clones expressing truncated forms of IN as N-terminal fusion proteins in E.coli were constructed and analyzed by Southwestern blotting. Proteins containing amino acids 1-263, 1-248 and 170-288 retained the ability to bind DNA, whereas a protein containing amino acids 1-180 showed no detectable DNA binding. This defines a DNA binding domain contained within amino acids 180-248. This region contains an arrangement of 9 lysine and arginine residues each separated by 2-4 amino acids (KxxxKxxxKxxxxRxxxRxxRxxxxKxxxKxxxK), spanning amino acids 211-244, which is conserved in all HIV-1 isolates. A clone expressing full-length IN with a C-terminal fusion of 16 amino acids was able to bind DNA comparably to a cloned protein with a free C-terminus, and an IN-specific monoclonal antibody which recognizes an epitope contained within amino acids 264-279 was unable to block DNA binding, supporting the evidence that a region necessary for binding lies upstream of amino acid 264.
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Affiliation(s)
- A M Woerner
- Division of Viral Products, FDA, Bethesda, MD 20892
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39
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Site-directed mutagenesis of HIV-1 integrase demonstrates differential effects on integrase functions in vitro. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)53969-7] [Citation(s) in RCA: 137] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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40
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McEuen AR, Edwards B, Koepke KA, Ball AE, Jennings BA, Wolstenholme AJ, Danson MJ, Hough DW. Zinc binding by retroviral integrase. Biochem Biophys Res Commun 1992; 189:813-8. [PMID: 1472053 DOI: 10.1016/0006-291x(92)92275-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Zinc binding by integrase from Moloney murine leukaemia virus and a protein A fusion protein containing integrase from human immunodeficiency virus type 1 was demonstrated by a zinc blotting technique using 65ZnCl2. Autoradiography revealed a clear band that was absent from the appropriate controls. This band co-migrated with the major band in Coomassie-stained gels and in immunoblots. This binding activity was retained in the presence of competing divalent cations and was sensitive to oxidation. This is the first demonstration of zinc binding by intact retroviral integrase.
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Affiliation(s)
- A R McEuen
- Biochemistry Dept., University of Bath, U.K
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41
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LaFemina RL, Schneider CL, Robbins HL, Callahan PL, LeGrow K, Roth E, Schleif WA, Emini EA. Requirement of active human immunodeficiency virus type 1 integrase enzyme for productive infection of human T-lymphoid cells. J Virol 1992; 66:7414-9. [PMID: 1433523 PMCID: PMC240448 DOI: 10.1128/jvi.66.12.7414-7419.1992] [Citation(s) in RCA: 230] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The human immunodeficiency virus type 1 (HIV-1) integrase enzyme exhibits significant amino acid sequence conservation with integrase proteins of other retroviruses. We introduced specific amino acid substitutions at a number of the conserved residue positions of recombinant HIV-1 integrase. Some of these substitutions resulted in proteins which were not able to be purified in the same manner as the wild-type enzyme, and these were not studied further. The remaining mutant enzymes were assessed for their abilities to perform functions characteristic of the integrase protein. These included specific removal of the terminal dinucleotides from oligonucleotide substrates representative of the viral U5-long terminal repeat, nonspecific cleavage of oligonucleotide substrates, and mediation of the strand transfer (integration) reaction. Substitution at position 43, within the protein's zinc finger motif region, resulted in an enzyme with reduced specificity for cleavage of the terminal dinucleotide. In addition, a double substitution of aspartic acid and glutamine for valine and glutamic acid, respectively, at positions 151 and 152 within the D,D(35)E motif region rendered the integrase protein inactive for all of its functions. The introduction of this double substitution into an infectious HIV-1 provirus yielded a mutant virus that was incapable of productively infecting human T-lymphoid cells in culture.
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Affiliation(s)
- R L LaFemina
- Merck Research Laboratories, West Point, Pennsylvania 19486
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42
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Fitzgerald ML, Vora AC, Zeh WG, Grandgenett DP. Concerted integration of viral DNA termini by purified avian myeloblastosis virus integrase. J Virol 1992; 66:6257-63. [PMID: 1328665 PMCID: PMC240116 DOI: 10.1128/jvi.66.11.6257-6263.1992] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Concerted integration of retroviral DNA termini, which produces a characteristic duplication of sequences at the integration site and formation of the proviral state, is a necessary step of the retroviral life cycle. We investigated the pairwise integration reaction catalyzed by purified avian retrovirus integrase by measuring the response to solution parameters and how the sequences of the viral termini, which comprise the avian imperfect inverted repeat, affect the reaction. When we optimized the reaction, an efficiency was achieved which approached that measured in systems using cytoplasmic extracts from virus-infected cells. The response of purified avian integrase to solution parameters was similar to that of the integration activity derived from cellular extracts. For strand transfer, the U3 viral terminal sequences were preferred to those of the U5 termini, a result we previously showed for the trimming reaction. That the sequence preference was the same for trimming and strand transfer may be further evidence that only one catalytic site is used for both reactions. A significant number of integration sites were sequenced. Interesting trends were found for the fidelity of the host duplications to the avian 6-bp duplication size, the clustering of the integration sites in the nonessential region of the lambda host DNA, and the sequence characteristics of the duplication sites.
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Affiliation(s)
- M L Fitzgerald
- Institute for Molecular Virology, St. Louis University Medical Center, Missouri 63110
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43
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Murphy JE, Goff SP. A mutation at one end of Moloney murine leukemia virus DNA blocks cleavage of both ends by the viral integrase in vivo. J Virol 1992; 66:5092-5. [PMID: 1629963 PMCID: PMC241375 DOI: 10.1128/jvi.66.8.5092-5095.1992] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The integration of retroviral DNA proceeds through two steps: trimming of the termini to expose new 3' OH ends, and the transfer of those ends to the phosphates of target DNA. We have examined the ability of the Moloney murine leukemia virus integrase protein (IN) to trim the termini of the preintegrative DNA of mutant viruses with alterations in the U3 inverted repeat. The mutant terminus of one replication-defective viral DNA, containing a 7-bp deletion in the U3 inverted repeat, was not trimmed to produce the normal recessed end. Remarkably, the other terminus of this mutant DNA was also not trimmed, even though its sequence is wild type. This finding suggests that the IN protein requires the presence of two good ends before becoming properly activated to trim either one.
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Affiliation(s)
- J E Murphy
- Department of Biochemistry and Molecular Biophysics, Columbia University College of Physicians and Surgeons, New York, New York 10032
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44
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Mumm SR, Hippenmeyer PJ, Grandgenett DP. Characterization of a stable eukaryotic cell line expressing the Rous sarcoma virus integrase. Virology 1992; 189:500-10. [PMID: 1322585 DOI: 10.1016/0042-6822(92)90574-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The Rous sarcoma virus integration protein (IN) is required for efficient integration of viral DNA into the host genome. IN was expressed in mouse C127 cells using a bovine papillomavirus vector. This system utilizes the mouse metallothionein promoter and the SV40 late polyadenylation signal for efficient expression of IN. A stable cell line derived from a single hygromycin-resistant colony was characterized. The expression of IN increased significantly upon Zn2+ induction of the metallothionein promoter, but did not respond to "superinduction" protocols. Full-length nonphosphorylated IN was the major product of expression. A minor product resulting from initiation of translation at an internal Met codon was also produced. The expressed IN did not exhibit the polypeptide heterogeneity at its COOH-terminus nor phosphorylation as is seen when IN is immunoprecipitated from virions. Using subcellular fractionation and indirect immunofluorescence, IN was primarily localized to nuclei and in some cells appeared to concentrate at discrete loci within the nuclei.
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Affiliation(s)
- S R Mumm
- St. Louis University Medical Center, Institute for Molecular Virology, Missouri 63110
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45
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Mutational analysis of the carboxyl terminus of the Moloney murine leukemia virus integration protein. J Virol 1991; 65:2141-5. [PMID: 2002557 PMCID: PMC240092 DOI: 10.1128/jvi.65.4.2141-2145.1991] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The integration protein (IN) is required for retrovirus DNA integration into the host DNA. The function of the C terminus of the Moloney murine leukemia virus IN protein was examined. The terminal 28 amino acids were found to be nonessential. A linker insertion at position 6025, within a 36-amino-acid insertion not found in any other retrovirus, also produced viable virus.
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