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Hobbs M, King A, Salinas R, Chen Z, Tsangaras K, Greenwood AD, Johnson RN, Belov K, Wilkins MR, Timms P. Long-read genome sequence assembly provides insight into ongoing retroviral invasion of the koala germline. Sci Rep 2017; 7:15838. [PMID: 29158564 PMCID: PMC5696478 DOI: 10.1038/s41598-017-16171-1] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Accepted: 11/07/2017] [Indexed: 12/18/2022] Open
Abstract
The koala retrovirus (KoRV) is implicated in several diseases affecting the koala (Phascolarctos cinereus). KoRV provirus can be present in the genome of koalas as an endogenous retrovirus (present in all cells via germline integration) or as exogenous retrovirus responsible for somatic integrations of proviral KoRV (present in a limited number of cells). This ongoing invasion of the koala germline by KoRV provides a powerful opportunity to assess the viral strategies used by KoRV in an individual. Analysis of a high-quality genome sequence of a single koala revealed 133 KoRV integration sites. Most integrations contain full-length, endogenous provirus; KoRV-A subtype. The second most frequent integrations contain an endogenous recombinant element (recKoRV) in which most of the KoRV protein-coding region has been replaced with an ancient, endogenous retroelement. A third set of integrations, with very low sequence coverage, may represent somatic cell integrations of KoRV-A, KoRV-B and two recently designated additional subgroups, KoRV-D and KoRV-E. KoRV-D and KoRV-E are missing several genes required for viral processing, suggesting they have been transmitted as defective viruses. Our results represent the first comprehensive analyses of KoRV integration and variation in a single animal and provide further insights into the process of retroviral-host species interactions.
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Affiliation(s)
- Matthew Hobbs
- Australian Museum Research Institute, Australian Museum, 1 William Street Sydney, NSW, 2010, Australia
| | - Andrew King
- Australian Museum Research Institute, Australian Museum, 1 William Street Sydney, NSW, 2010, Australia
| | - Ryan Salinas
- Systems Biology Initiative, School of Biotechnology and Biomolecular Sciences, University of New South Wales, NSW, 2052, Australia
| | - Zhiliang Chen
- Systems Biology Initiative, School of Biotechnology and Biomolecular Sciences, University of New South Wales, NSW, 2052, Australia
| | - Kyriakos Tsangaras
- Department of Wildlife Diseases, Leibniz Institute for Zoo and Wildlife Research, Berlin, Germany.,Department of Translational Genetics, The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus
| | - Alex D Greenwood
- Department of Wildlife Diseases, Leibniz Institute for Zoo and Wildlife Research, Berlin, Germany.,Department of Veterinary Medicine, Freie Universität Berlin, Berlin, Germany
| | - Rebecca N Johnson
- Australian Museum Research Institute, Australian Museum, 1 William Street Sydney, NSW, 2010, Australia
| | - Katherine Belov
- School of Life and Environmental Sciences, University of Sydney, Sydney, NSW 2006, Australia
| | - Marc R Wilkins
- Systems Biology Initiative, School of Biotechnology and Biomolecular Sciences, University of New South Wales, NSW, 2052, Australia.,Ramaciotti Centre for Genomics, University of New South Wales, NSW, 2052, Australia
| | - Peter Timms
- Faculty of Science, Health, Education & Engineering, University of the Sunshine Coast, Locked Bag 4, Maroochydore DC, Qld, 4558, Australia.
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2
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Weber EL, Cannon PM. Promoter Choice for Retroviral Vectors: Transcriptional Strength Versus Trans-Activation Potential. Hum Gene Ther 2007; 18:849-60. [PMID: 17767401 DOI: 10.1089/hum.2007.067] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Gene expression from retroviral vectors can be driven by either the retroviral long terminal repeat (LTR) promoter or by cellular or viral promoters located internally in an LTR-deleted self-inactivating vector design. Adverse events in a gene therapy clinical trial for X-linked severe combined immune deficiency have led to the realization that the enhancer/promoter elements contained within integrated vectors may also act outside the vector genome to trans-activate host genes. Ideally, the gene expression system chosen for a vector should possess a low probability of trans-activation while still being able to support adequate levels of transgene expression. However, the parameters that define these specific characteristics are unknown. To gain insight into the mechanism of trans-activation, we compared a panel of commonly used retroviral LTRs and cellular and viral promoters for their ability to drive gene expression and to trans-activate a nearby minimal promoter in three different cell lines. These studies identified two elements, the cytomegalovirus enhancer/chicken beta-actin (CAG) and elongation factor (EF)-1alpha promoters, as being of potential value for use in vectors targeting lymphoid cells, as these elements exhibited both high levels of reporter gene expression and relatively low levels of trans-activation in T cells.
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Affiliation(s)
- Erin L Weber
- Saban Research Institute of Childrens Hospital Los Angeles, Los Angeles, CA 90027, USA
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3
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Cordelier P, Strayer DS. Using gene delivery to protect HIV-susceptible CNS cells: inhibiting HIV replication in microglia. Virus Res 2006; 118:87-97. [PMID: 16414141 DOI: 10.1016/j.virusres.2005.11.016] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2005] [Revised: 11/04/2005] [Accepted: 11/18/2005] [Indexed: 01/13/2023]
Abstract
Antiretroviral chemotherapy penetrates the CNS poorly. CNS HIV, thus sheltered, may injure the brain and complicate control of systemic HIV infection. Microglial cells play a major role in HIV persistence in the CNS but are rarely targeted for gene delivery. Because recombinant SV40 vectors (rSV40s) transduce other phagocytic cells efficiently, we tested rSV40 delivery of anti-HIV genetic therapy to microglial cells. Microglia prepared as enriched cultures from human fetal brain, were transduced with marker vectors, SV(RFP) and SV(Nef/FLAG), respectively, carrying DsRed and HIV-1 Nef bearing a FLAG epitope. By immunostaining and FACS, 95% of unselected cells expressed the transgenes, without detectable toxicity. Microglia were transduced with SV(AT), carrying human alpha1-antitrypsin (alpha1AT), which blocks Env and Gag processing. SV(AT)-treated microglia strongly resisted challenge with HIV-1BaL, even when microglia were transduced with SV(AT) following HIV challenge. Thus, rSV40s effectively transduce microglia and protect them from HIV.
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Affiliation(s)
- Pierre Cordelier
- Department of Pathology, Jefferson Medical College, 1020 Locust Street, Room 251, Philadelphia, PA 19107, USA
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4
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Sørensen KD, Quintanilla-Martinez L, Kunder S, Schmidt J, Pedersen FS. Mutation of all Runx (AML1/core) sites in the enhancer of T-lymphomagenic SL3-3 murine leukemia virus unmasks a significant potential for myeloid leukemia induction and favors enhancer evolution toward induction of other disease patterns. J Virol 2004; 78:13216-31. [PMID: 15542674 PMCID: PMC524987 DOI: 10.1128/jvi.78.23.13216-13231.2004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
SL3-3 murine leukemia virus is a potent inducer of T-lymphomas in mice. Using inbred NMRI mice, it was previously reported that a mutant of SL3-3 with all enhancer Runx (AML1/core) sites disrupted by 3-bp mutations (SL3-3dm) induces predominantly non-T-cell tumors with severely extended latency (S. Ethelberg, J. Lovmand, J. Schmidt, A. Luz, and F. S. Pedersen, J. Virol. 71:7273-7280, 1997). By use of three-color flow cytometry and molecular and histopathological analyses, we have now performed a detailed phenotypic characterization of SL3-3- and SL3-3dm-induced tumors in this mouse strain. All wild-type induced tumors had clonal T-cell receptor beta rearrangements, and the vast majority were CD3(+) CD4(+) CD8(-) T-lymphomas. Such a consistent phenotypic pattern is unusual for murine leukemia virus-induced T-lymphomas. The mutant virus induced malignancies of four distinct hematopoietic lineages: myeloid, T lymphoid, B lymphoid, and erythroid. The most common disease was myeloid leukemia with maturation. Thus, mutation of all Runx motifs in the enhancer of SL3-3 severely impedes viral T-lymphomagenicity and thereby discloses a considerable and formerly unappreciated potential of this virus for myeloid leukemia induction. Proviral enhancers with complex structural alterations (deletions, insertions, and/or duplications) were found in most SL3-3dm-induced T-lymphoid tumors and immature myeloid leukemias but not in any cases of myeloid leukemia with maturation, mature B-lymphoma, or erythroleukemia. Altogether, our results indicate that the SL3-3dm enhancer in itself promotes induction of myeloid leukemia with maturation but that structural changes may arise in vivo and redirect viral disease specificity to induction of T-lymphoid or immature myeloid leukemias, which typically develop with moderately shorter latencies.
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Affiliation(s)
- Karina Dalsgaard Sørensen
- Department of Molecular Biology, University of Aarhus, C. F. Møllers Allé, Bldg. 130, DK-8000 Aarhus C, Denmark
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5
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Ma SL, Lovmand J, Sørensen AB, Luz A, Schmidt J, Pedersen FS. Triple basepair changes within and adjacent to the conserved YY1 motif upstream of the U3 enhancer repeats of SL3-3 murine leukemia virus cause a small but significant shortening of latency of T-lymphoma induction. Virology 2003; 313:638-44. [PMID: 12954229 DOI: 10.1016/s0042-6822(03)00379-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A highly conserved sequence upstream of the transcriptional enhancer in the U3 of murine leukemia viruses (MLVs) was reported to mediate negative regulation of their expression. In transient expression studies, negative regulation was reported to be conferred by coexpression of the transcription factor YY1, which binds to a motif in the upstream conserved region (UCR). To address the function of the UCR and its YY1-motif in an in vivo model of MLV-host interactions we introduced six consecutive triple basepair mutations into this region of the potent T-lymphomagenic SL3-3 MLV. We report that all mutants have retained their replication competence and that they all, like the SL3-3 wild type (wt), induce T-cell lymphomas when injected into newborn mice of the SWR strain. However, all mutants induced disease with slightly shorter latency periods than the wt SL3-3, suggesting that the YY1 motif as well as its immediate context in the UCR have a negative effect on the pathogenicity of the virus. This result may have implications for the design of retroviral vectors.
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Affiliation(s)
- Shi Liang Ma
- Department of Molecular Biology, University of Aarhus, Aarhus, Denmark
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6
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Abujamra AL, Faller DV, Ghosh SK. Mutations that abrogate transactivational activity of the feline leukemia virus long terminal repeat do not affect virus replication. Virology 2003; 309:294-305. [PMID: 12758176 DOI: 10.1016/s0042-6822(03)00069-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The U3 region of the LTR of oncogenic Moloney murine leukemia virus (Mo-MuLV) and feline leukemia viruses (FeLV) have been previously reported to activate expression of specific cellular genes in trans, such as MHC class I, collagenase IV, and MCP-1, in an integration-independent manner. It has been suggested that transactivation of these specific cellular genes by leukemia virus U3-LTR may contribute to the multistage process of leukemogenesis. The U3-LTR region, necessary for gene transactivational activity, also contains multiple transcription factor-binding sites that are essential for normal virus replication. To dissect the promoter activity and the gene transactivational activity of the U3-LTR, we conducted mutational analysis of the U3-LTR region of FeLV-A molecular clone 61E. We identified minimal nucleotide substitution mutants on the U3 LTR that did not disturb transcription factor-binding sites but abrogated its ability to transactivate the collagenase gene promoter. To determine if these mutations actually have altered any uncharacterized important transcription factor-binding site, we introduced these U3-LTR mutations into the full-length infectious molecular clone 61E. We demonstrate that the mutant virus was replication competent but could not transactivate cellular gene expression. These results thus suggest that the gene transactivational activity is a distinct property of the LTR and possibly not related to its promoter activity. The cellular gene transactivational activity-deficient mutant FeLV generated in this study may also serve as a valuable reagent for testing the biological significance of LTR-mediated cellular gene activation in the tumorigenesis caused by leukemia viruses.
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Affiliation(s)
- Ana L Abujamra
- Cancer Research Center, Boston University School of Medicine, Boston, MA 02118, USA
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7
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Wilson CA, Laeeq S, Ritzhaupt A, Colon-Moran W, Yoshimura FK. Sequence analysis of porcine endogenous retrovirus long terminal repeats and identification of transcriptional regulatory regions. J Virol 2003; 77:142-9. [PMID: 12477819 PMCID: PMC140639 DOI: 10.1128/jvi.77.1.142-149.2003] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Porcine cells express endogenous retroviruses, some of which are infectious for human cells. To better understand the replication of these porcine endogenous retroviruses (PERVs) in cells of different types and animal species, we have performed studies of the long terminal repeat (LTR) region of known gammaretroviral isolates of PERV. Nucleotide sequence determination of the LTRs of PERV-NIH, PERV-C, PERV-A, and PERV-B revealed that the PERV-A and PERV-B LTRs are identical, whereas the PERV-NIH and PERV-C LTRs have significant sequence differences in the U3 region between each other and with the LTRs of PERV-A and PERV-B. Sequence analysis revealed a similar organization of basal promoter elements compared with other gammaretroviruses, including the presence of enhancer-like repeat elements. The sequences of the PERV-NIH and PERV-C repeat element are similar to that of the PERV-A and PERV-B element with some differences in the organization of these repeats. The sequence of the PERV enhancer-like repeat elements differs significantly from those of other known gammaretroviral enhancers. The transcriptional activities of the PERV-A, PERV-B, and PERV-C LTRs relative to each other were similar in different cell types of different animal species as determined by transient expression assays. On the other hand, the PERV-NIH LTR was considerably weaker in these cell types. The transcriptional activity of all PERV LTRs was considerably lower in porcine ST-IOWA cells than in cell lines from other species. Deletion mutant analysis of the LTR of a PERV-NIH isolate identified regions that transactivate or repress transcription depending on the cell type.
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Affiliation(s)
- Carolyn A Wilson
- Division of Cellular and Gene Therapies, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland 20892, USA
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8
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Yoshimura FK, Wang T. Role of the LTR region between the enhancer and promoter in mink cell focus-forming murine leukemia virus pathogenesis. Virology 2001; 283:121-31. [PMID: 11312668 DOI: 10.1006/viro.2001.0879] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Long terminal repeat (LTR) sequences are important determinants of mink cell focus-forming (MCF) murine leukemia virus pathogenesis. These sequences include the enhancer and sequences between the enhancer and promoter (DEN). In a previous study we showed that a virus missing the DEN region in its LTR was severely attenuated in its ability to induce thymic lymphoma. In this study we observed that a virus with an LTR consisting of DEN but no enhancer sequences was pathogenic. We compared the pathogenicity of this DEN virus with other LTR mutant MCF13 viruses that contained a single enhancer (1R) or a single enhancer plus DEN (1R + DEN). All LTR mutant viruses generated thymic lymphoma, however, at a much lower incidence and with a longer latency compared with wild-type (WT) MCF13 virus. DEN virus replication in the thymus was the lowest compared with the 1R and 1R + DEN viruses. Viral replication in a different thymic subpopulation could not explain the decreased pathogenicity of the LTR mutant viruses compared with WT virus. However, lower levels of mutant virus replication in the thymus compared with WT during the preleukemic period may contribute to the attenuation of pathogenicity. The phenotype of tumors induced by the mutant viruses was similar and differed from tumors induced by WT virus by the presence of CD3(-)CD4(-)CD8(-) cells. Analysis of LTR sequences of infectious virus rescued from tumors induced by the 1R and 1R + DEN viruses showed that amplification of enhancer sequences had occurred during tumor development. The lack of DEN virus expression by tumor cells led us to propose that DEN sequences may play a role at an early step in tumorigenesis.
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Affiliation(s)
- F K Yoshimura
- Department of Immunology and Microbiology, Wayne State University, 540 E. Canfield Ave., Detroit, MI 48201, USA.
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9
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Ghosh SK, Roy-Burman P, Faller DV. Long terminal repeat regions from exogenous but not endogenous feline leukemia viruses transactivate cellular gene expression. J Virol 2000; 74:9742-8. [PMID: 11000248 PMCID: PMC112408 DOI: 10.1128/jvi.74.20.9742-9748.2000] [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: 12/24/2022] Open
Abstract
We have previously reported that the long terminal repeat (LTR) region of feline leukemia viruses (FeLVs) can enhance expression of certain cellular genes such as the collagenase IV gene and MCP-1 in trans (S. K. Ghosh and D. V. Faller, J. Virol. 73:4931-4940, 1999). Genomic DNA of all healthy feline species also contains LTR-like sequences that are related to exogenous FeLV LTRs. In this study, we evaluated the cellular gene transactivational potential of these endogenous FeLV LTR sequences. Unlike their exogenous FeLV counterparts, neither nearly full-length endogenous FeLV molecular clones (CFE-6 and CFE-16) nor their isolated LTRs were able to activate collagenase IV gene or MCP-1 expression in transient transfection assays. We had also demonstrated previously that production of an RNA transcript from exogenous FeLV LTRs correlates with their transactivational activity. In the present study, we demonstrate that the endogenous FeLV LTRs do not generate LTR-specific RNA transcripts in the feline embryo fibroblast cell line AH927. Furthermore, infection of AH927 cells by an exogenous FeLV subgroup A virus did not induce production of such LTR-specific transcripts from the endogenous proviral genomes, although the LTR-specific transcripts from the exogenous virus were readily detected. Finally, LTR-specific transcripts were not generated in BALB/3T3 cells transiently transfected with isolated CFE-6 LTR, in contrast to transfections with LTRs from exogenous viruses. Our data thus suggest that the inability of endogenous FeLV LTRs in gene transactivation is not due to cell line specificity or presence of any upstream inhibitory cis-acting element. Endogenous, nonleukemogenic FeLV LTRs, therefore, do not transactivate cellular gene expression, and this property appears to be specific to exogenous, leukemogenic FeLVs.
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Affiliation(s)
- S K Ghosh
- Cancer Research Center, Boston University School of Medicine, Boston, Massachusetts 02118, USA.
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10
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Audit M, Déjardin J, Hohl B, Sidobre C, Hope TJ, Mougel M, Sitbon M. Introduction of a cis-acting mutation in the capsid-coding gene of moloney murine leukemia virus extends its leukemogenic properties. J Virol 1999; 73:10472-9. [PMID: 10559365 PMCID: PMC113102 DOI: 10.1128/jvi.73.12.10472-10479.1999] [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
Inoculation of newborn mice with the retrovirus Moloney murine leukemia virus (MuLV) results in the exclusive development of T lymphomas with gross thymic enlargement. The T-cell leukemogenic property of Moloney MuLV has been mapped to the U3 enhancer region of the viral promoter. However, we now describe a mutant Moloney MuLV which can induce the rapid development of a uniquely broad panel of leukemic cell types. This mutant Moloney MuLV with synonymous differences (MSD1) was obtained by introduction of nucleotide substitutions at positions 1598, 1599, and 1601 in the capsid gene which maintained the wild-type (WT) coding potential. Leukemias were observed in all MSD1-inoculated animals after a latency period that was shorter than or similar to that of WT Moloney MuLV. Importantly, though, only 56% of MSD1-induced leukemias demonstrated the characteristic thymoma phenotype observed in all WT Moloney MuLV leukemias. The remainder of MSD1-inoculated animals presented either with bona fide clonal erythroid or myelomonocytic leukemias or, alternatively, with other severe erythroid and unidentified disorders. Amplification and sequencing of U3 and capsid-coding regions showed that the inoculated parental MSD1 sequences were conserved in the leukemic spleens. This is the first report of a replication-competent MuLV lacking oncogenes which can rapidly lead to the development of such a broad range of leukemic cell types. Moreover, the ability of MSD1 to transform erythroid and myelomonocytic lineages is not due to changes in the U3 viral enhancer region but rather is the result of a cis-acting effect of the capsid-coding gag sequence.
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MESH Headings
- 3T3 Cells
- Animals
- Capsid/genetics
- Capsid/physiology
- Cell Line
- Cell Transformation, Neoplastic
- Cell Transformation, Viral
- Friend murine leukemia virus/genetics
- Friend murine leukemia virus/physiology
- Gene Products, gag/genetics
- Gene Products, gag/physiology
- Genes, Viral
- Leukemia, Erythroblastic, Acute/classification
- Leukemia, Erythroblastic, Acute/pathology
- Leukemia, Erythroblastic, Acute/virology
- Leukemia, Myelomonocytic, Acute/classification
- Leukemia, Myelomonocytic, Acute/pathology
- Leukemia, Myelomonocytic, Acute/virology
- Mice
- Moloney murine leukemia virus/genetics
- Moloney murine leukemia virus/physiology
- Mutagenesis
- Retroviridae Infections/pathology
- Retroviridae Infections/virology
- Terminal Repeat Sequences
- Tumor Virus Infections/pathology
- Tumor Virus Infections/virology
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Affiliation(s)
- M Audit
- Institut de Génétique Moléculaire de Montpellier (IGMM), IFR24, CNRS-UMR5535, and Université Montpellier II, F-34293 Montpellier Cedex 5, France
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11
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Yoshimura FK, Wang T, Cankovic M. Sequences between the enhancer and promoter in the long terminal repeat affect murine leukemia virus pathogenicity and replication in the thymus. J Virol 1999; 73:4890-8. [PMID: 10233950 PMCID: PMC112532 DOI: 10.1128/jvi.73.6.4890-4898.1999] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
We previously showed that the 93-bp region between the enhancer and promoter (named DEN for downstream of enhancer) of the long terminal repeat (LTR) of the MCF13 murine leukemia virus is an important determinant of the ability of this virus to induce thymic lymphoma. In this study we observed that DEN plays a role in the regulation of virus replication in the thymus during the preleukemic period. A NF-kappaB site in the DEN region partially contributes to the effect of DEN on both lymphomagenicity and virus replication. To further study the effects of DEN and the NF-kappaB site on viral pathogenicity during the preleukemic period, we examined replication of wild-type and mutant viruses with a deletion of the NF-kappaB site or the entire DEN region in the thymus. Thymic lymphocytes which were infected with wild-type and mutant viruses were predominantly the CD3(-) CD4(+) CD8(+) and CD3(+) CD4(+) CD8(+) cells. The increase in infection by wild-type virus and both mutant viruses of these two subpopulations during the preleukemic period ranged from 9- to 84-fold, depending upon the time point and virus. The major difference between the wild-type and both mutant viruses was the lower rate and lower level of mutant virus replication in these thymic subpopulations. Significant differences in replication between wild-type and both mutant viruses were seen in the CD3(-) CD4(+) CD8(+) and CD3(-) CD4(-) CD8(-) subpopulations, suggesting that these thymic cell types are important targets for viral transformation.
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Affiliation(s)
- F K Yoshimura
- Department of Immunology and Microbiology and Karmanos Cancer Institute, Wayne State University, Detroit, Michigan 48201, USA.
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12
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Barat C, Rassart E. Nuclear factors that bind to the U3 region of two murine myeloid leukemia-inducing retroviruses, Cas-Br-E and Graffi. Virology 1998; 252:82-95. [PMID: 9875319 DOI: 10.1006/viro.1998.9435] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cas-Br-E and Graffi are two myeloid leukemia-inducing murine viruses. Cas-Br-E induces, in NIH-Swiss mice, mostly non-T, non-B leukemia composed of very immature cells with no specific characteristics (Bergeron et al. (1993). Leukemia 7, 954-962). The Graffi murine leukemia virus causes exclusively myeloid leukemia, but the tumor cells are clearly of granulocytic nature (Ru et al. (1993). J. Virol. 67, 4722). We were interested to understand the role of the long terminal repeat (LTR) U3 region in the myeloid specificity of these two retroviruses. We used DNase I footprinting and gel mobility shift assays to identify a number of protein binding sites within Cas-Br-E and Graffi U3 regions. The pattern of protected regions is highly similar for the two viruses. Some factors identified in other murine leukemia viruses, like the core binding factor, also bind to Cas-Br-E and Graffi LTR; however, other binding sites seem specific for these two viruses. Only one difference between them was noted, at the 5' end of the U3 region. Transcriptional activity of both LTRs was also analyzed in various cell lines and compared with other murine leukemia viruses. The results show a slight myeloid specificity for the two LTRs, and indicate that the Graffi enhancer is quite strong in a broad range of cell types.
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Affiliation(s)
- C Barat
- Département des Sciences Biologiques, Université du Québec à Montréal, Canada
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13
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Granger SW, Fan H. In vivo footprinting of the enhancer sequences in the upstream long terminal repeat of Moloney murine leukemia virus: differential binding of nuclear factors in different cell types. J Virol 1998; 72:8961-70. [PMID: 9765441 PMCID: PMC110313 DOI: 10.1128/jvi.72.11.8961-8970.1998] [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
The enhancer sequences in the Moloney murine leukemia virus (M-MuLV) long terminal repeat (LTR) are of considerable interest since they are crucial for virus replication and the ability of the virus to induce T lymphomas. While extensive studies have identified numerous nuclear factors that can potentially bind to M-MuLV enhancer DNA in vitro, it has not been made clear which of these factors are bound in vivo. To address this problem, we carried out in vivo footprinting of the M-MuLV enhancer in infected cells by in vivo treatment with dimethyl sulfate (DMS) followed by visualization through ligation-mediated PCR (LMPCR) and gel electrophoresis. In vivo DMS-LMPCR footprinting of the upstream LTR revealed evidence for factor binding at several previously characterized motifs. In particular, protection of guanines in the central LVb/Ets and Core sites within the 75-bp repeats was detected in infected NIH 3T3 fibroblasts, Ti-6 lymphoid cells, and thymic tumor cells. In contrast, factor binding at the NF-1 sites was found in infected fibroblasts but not in T-lymphoid cells. These results are consistent with the results of previous experiments indicating the importance of the LVb/Ets and Core sequences for many retroviruses and the biological importance especially of the NF-1 sites in fibroblasts and T-lymphoid cells. No evidence for factor binding to the glucocorticoid responsive element and LVa sites was found. Additional sites of protein binding included a region in the GC-rich sequences downstream of the 75-bp repeats (only in fibroblasts), a hypersensitive guanine on the minus strand in the LVc site (only in T-lymphoid cells), and a region upstream of the 75-bp repeats. These experiments provide concrete evidence for the differential in vivo binding of nuclear factors to the M-MuLV enhancers in different cell types.
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Affiliation(s)
- S W Granger
- Department of Molecular Biology and Biochemistry and Cancer Research Institute, University of California, Irvine, California 92697-3900, USA
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14
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Dickie P, Gazzinelli R, Chang LJ. Models of HIV type 1 proviral gene expression in wild-type HIV and MLV/HIV transgenic mice. AIDS Res Hum Retroviruses 1996; 12:1103-16. [PMID: 8844015 DOI: 10.1089/aid.1996.12.1103] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Two proviral HIV transgenic mouse models, one bearing wild-type HIV proviral DNA and the other a modified provirus in which the viral LTRs contained the core enhancer of the Moloney murine leukemia virus (MLV), were compared. The MLV/HIV chimeric LTR, in which the MLV enhancer replaced the NF-kappa B-binding motifs, was transcriptionally active in human and murine cells in vitro and virus containing the chimeric LTR was replication competent in human cell cultures. Transgenic mice derived from microinjections of chimeric MLV/HIV proviral DNA transcribed HIV genes at a greater frequency and at higher levels than wild-type HIV proviral transgenic mice. MLV/HIV mice were also more apt to develop disease; wasting, periocular infections, and a degenerative myopathy characterized the most predominant phenotype. The tissue specificities of the wild-type and chimeric LTRs in transgenic mice were remarkably similar, but a significant difference was apparent in lymphoid cells. Basal level and LPS-inducible HIV gene expression occurred in peritoneal and bone marrow-derived macrophages from wild-type HIV transgenic mice. In contrast, HIV gene expression in macrophages from MLV/HIV mice was undetectable, even following LPS induction. However, cultured splenocytes from MLV/HIV mice supported HIV proviral gene transcription better than splenocytes from HIV mice, particularly after induction with LPS or anti-IgD antibody but not with concanavalin A. These data suggest that in transgenic mice, the HIV and MLV/HIV LTRs display a differential tropism for macrophages and B cells, respectively. HIV and MLV/HIV transgenic mice represent alternative models amenable to in vivo studies of HIV gene regulation in lymphoid cells, the induction of HIV-related disease and the evaluation of anti-HIV therapies.
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Affiliation(s)
- P Dickie
- Laboratory of Molecular Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892-0460, USA
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Weng H, Choi SY, Faller DV. The Moloney leukemia retroviral long terminal repeat trans-activates AP-1-inducible genes and AP-1 transcription factor binding. J Biol Chem 1995; 270:13637-44. [PMID: 7775415 DOI: 10.1074/jbc.270.23.13637] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Moloney murine leukemia virus (Mo-MuLV) is a thymotropic and leukemogenic retrovirus which causes T lymphomas. The long terminal repeat (LTR) of Mo-MuLV affects the regulation of a number of cellular genes, including collagenase IV, monocyte chemoattractant protein-1, and c-jun genes, all of which contain 12-O-tetradecanoylphorbol-13-acetate-responsive element consensus sites within their promoters. We report here that Mo-MuLV stimulates the collagenase IV gene through transcription factor AP-1, and that the expression of a subgenomic portion of Mo-MuLV LTR alone is sufficient for this effect. Transient or stable expression of the viral LTR increases cellular AP-1 DNA binding activity. The collagenase IV 12-O-tetradecanoylphorbol-13-acetate-responsive element consensus sequence was shown to be required for this trans-activation. Deletions or mutations of this consensus site which abolished AP-1 binding also abolished trans-activation by the LTR. Transient or stable transfection of the viral LTR into cells stimulated c-jun gene expression, suggesting one mechanism whereby the viral LTR may induce cellular AP-1 activity. Thus, the Mo-MuLV LTR, through activation of the transcription factor AP-1, is capable of regulating cellular gene expression, including the induction of proto-oncogenes. This activity may be relevant to the mechanisms whereby retroviruses which do not contain oncogenes induce neoplasia.
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Affiliation(s)
- H Weng
- Cancer Research Center, Boston University School of Medicine, Massachusetts 02118, USA
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16
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Athas GB, Lobelle-Rich P, Levy LS. Function of a unique sequence motif in the long terminal repeat of feline leukemia virus isolated from an unusual set of naturally occurring tumors. J Virol 1995; 69:3324-32. [PMID: 7745680 PMCID: PMC189044 DOI: 10.1128/jvi.69.6.3324-3332.1995] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Feline leukemia virus (FeLV) proviruses have been characterized from naturally occurring non-B-cell, non-T-cell tumors occurring in the spleens of infected cats. These proviruses exhibit a unique sequence motif in the long terminal repeat (LTR), namely, a 21-bp tandem triplication beginning 25 bp downstream of the enhancer. The repeated finding of the triplication-containing LTR in non-B-cell, non-T-cell lymphomas of the spleen suggests that the unique LTR is an essential participant in the development of tumors of this particular phenotype. The nucleotide sequence of the triplication-containing LTR most closely resembles that of FeLV subgroup C. Studies performed to measure the ability of the triplication-containing LTR to modulate gene expression indicate that the 21-bp triplication provides transcriptional enhancer function to the LTR that contains it and that it substitutes at least in part for the duplication of the enhancer. The 21-bp triplication confers a bona fide enhancer function upon LTR-directed reporter gene expression; however, the possibility of a spacer function was not eliminated. The studies demonstrate further that the triplication-containing LTR acts preferentially in a cell-type-specific manner, i.e., it is 12-fold more active in K-562 cells than is an LTR lacking the triplication. A recombinant, infectious FeLV bearing the 21-bp triplication in U3 was constructed. Cells infected with the recombinant were shown to accumulate higher levels of viral RNA transcripts and virus particles in culture supernatants than did cells infected with the parental type. The triplication-containing LTR is implicated in the induction of tumors of a particular phenotype, perhaps through transcriptional regulation of the virus and/or adjacent cellular genes, in the appropriate target cell.
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Affiliation(s)
- G B Athas
- Department of Microbiology and Immunology, Tulane University School of Medicine, New Orleans, Louisiana 70112, USA
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Yoshimura FK, Diem K. Characterization of nuclear protein binding to a site in the long terminal repeat of a murine leukemia virus: comparison with the NFAT complex. J Virol 1995; 69:994-1000. [PMID: 7815567 PMCID: PMC188668 DOI: 10.1128/jvi.69.2.994-1000.1995] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
We previously identified a protein-binding site (MLPal) that is located downstream of the enhancer element in the long terminal repeat (LTR) of a mink cell focusing-forming (MCF) murine leukemia virus (F. K. Yoshimura, K. Diem, H. Chen, and J. Tupper, J. Virol. 67:2298-2304, 1993). We determined that the MLPal site regulates transcription specifically in T cells and affects the lymphomagenicity of the MCF isolate 13 murine leukemia virus with a single enhancer repeat in its LTR. In this report, we present evidence that two different proteins, a T-cell-specific protein and a ubiquitous protein, bind the MLPal site in a sequence-specific manner. By mutational analysis, we determined that the T-cell-specific and the ubiquitous proteins require different nucleotides in the MLPal sequence for DNA binding. By competitive electrophoretic mobility shift assays, we demonstrated that the T-cell-specific protein that binds MLPal is identical or similar to a protein from nonactivable T cells that interacts with the binding site of the nuclear factor of activated T cells (NFAT). Unlike the NFAT-binding site, however, the MLPal site does not bind proteins that are inducible by T-cell activation. We observed that the MLPal sequence is conserved in the LTRs of other mammalian retroviruses that cause T-cell diseases. Furthermore, the MLPal sequence is present in the transcriptional regulatory regions of cellular genes that either are expressed specifically in T cells or are commonly rearranged by provirus integration in thymic lymphomas. Thus, the MLPal-binding proteins may play a role in the transcriptional regulation not only of the MCF virus LTR but also of cellular genes involved in T-cell development.
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Affiliation(s)
- F K Yoshimura
- Department of Biological Structure, University of Washington, Seattle, Washington 98195
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18
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The long terminal repeats of a murine retrovirus encode a trans-activator for cellular genes. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)32075-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Chen H, Yoshimura FK. Identification of a region of a murine leukemia virus long terminal repeat with novel transcriptional regulatory activities. J Virol 1994; 68:3308-16. [PMID: 8151791 PMCID: PMC236821 DOI: 10.1128/jvi.68.5.3308-3316.1994] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The 93-bp region downstream of the enhancer (DEN) in the long terminal repeat (LTR) of the mink cell focus-forming virus (MCF13) has been shown to be important for transcriptional activation and viral lymphomagenicity (J. C. Tupper, H. Chen, E. F. Hays, G. C. Bristol, and F. K. Yoshimura, J. Virol. 66:7080-7088, 1992). In this report, we have further explored the role of the DEN region in transcriptional activation. We observed that it has enhancer-like abilities as well as some unique LTR properties. Transcriptional activation by the DEN region involved interactions with enhancer sequences that were either synergistic or additive, depending on the cell type. The most intriguing property of the DEN region is its ability to induce transcription in activated T cells. This activity is unique for the LTR in that no other LTR region can do this. We also examined the role of the DEN region in retroviral lymphomagenesis. We cloned and sequenced proviral LTRs integrated upstream of the cellular c-myc gene from DNA obtained from thymic tumors induced by DEN region deletion mutant viruses in AKR mice. We determined that for transcriptional activation of the c-myc proto-oncogene, enhancer sequences can substitute for the DEN region. This study identifies the significance of non-enhancer sequences in the LTR for the oncogenesis of the MCF13 retrovirus.
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Affiliation(s)
- H Chen
- Department of Biological Structure, School of Medicine, University of Washington, Seattle 98195
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Yoshimura FK, Diem K, Chen H, Tupper J. A protein-binding site with dyad symmetry in the long terminal repeat of the MCF13 murine leukemia virus that contributes to transcriptional activity in T lymphocytes. J Virol 1993; 67:2298-304. [PMID: 8383242 PMCID: PMC240375 DOI: 10.1128/jvi.67.4.2298-2304.1993] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
We have previously identified regions in the long terminal repeat (LTR) of the MCF13 murine leukemia virus (MLV) that contribute to transcriptional activity in different cell types. We have observed that enhancer sequences and a region that resides 3' of the enhancer make significant contributions to transcriptional activity in T lymphocytes (T. Hollon and F. K. Yoshimura, J. Virol. 63:3353-3361, 1989). In this report, we have focused on the region of the MCF13 LTR that is 3' of the enhancer to identify binding sites for proteins that may play a role in the regulation of transcription in T cells. By gel shift and DNA footprint analyses, we have identified a single protein-binding site (MLPal) that includes a nucleotide sequence with dyad symmetry. A synthetic double-stranded oligonucleotide corresponding to this protein-binding site formed a specific protein-DNA complex. Deletion of this protein-binding site from the wild-type LTR decreased transcriptional activity in T lymphocytes but not in fibroblasts as determined by a transient expression assay. The MLPal sequence by itself cannot augment transcription in T cells but is able to do so in conjunction with enhancer sequences.
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Affiliation(s)
- F K Yoshimura
- Department of Biological Structure, University of Washington, Seattle 98195
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Tupper JC, Chen H, Hays EF, Bristol GC, Yoshimura FK. Contributions to transcriptional activity and to viral leukemogenicity made by sequences within and downstream of the MCF13 murine leukemia virus enhancer. J Virol 1992; 66:7080-8. [PMID: 1331510 PMCID: PMC240380 DOI: 10.1128/jvi.66.12.7080-7088.1992] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
We have identified nucleotide sequences that regulate transcription in both a cell-type-specific and general manner in the long terminal repeat of the MCF13 murine leukemia virus. Besides the enhancer element, we have observed that the region between the enhancer and promoter (DEN) has a profound effect on transcription in different cell types. This effect, however, was dependent on the copy number of enhancer repeats and was detectable in the presence of a single repeat. When two enhancer repeats were present, the effect of DEN on transcription was abrogated except in T cells. DEN also makes a significant contribution to the leukemogenic property of the MCF13 retrovirus. Its deletion from the MCF13 virus dramatically reduced the incidence of thymic lymphoma and increased the latency of disease in comparison with the wild-type virus. This effect was most marked when one rather than two enhancer repeats was present in the mutant viruses. We also observed that the removal of one repeat alone remarkably reduced leukemogenicity by the MCF13 virus. A newly identified protein-binding site (MLPal) located within DEN affects transcription only in T cells, and its deletion attenuates the ability of an MCF13 virus with a single enhancer repeat to induce thymic lymphoma. This observation suggests that the MLPal protein-binding site contributes to the effect of the DEN region on T-cell-specific transcription and viral leukemogenicity. This study identifies the importance of nonenhancer sequences in the long terminal repeat for the oncogenesis of the MCF13 retrovirus.
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MESH Headings
- 3T3 Cells
- Animals
- Animals, Newborn
- Base Sequence
- Binding Sites
- Cell Line
- Chloramphenicol O-Acetyltransferase/genetics
- Chloramphenicol O-Acetyltransferase/metabolism
- DNA, Viral/genetics
- DNA-Binding Proteins/metabolism
- Enhancer Elements, Genetic
- Leukemia Virus, Murine/genetics
- Leukemia Virus, Murine/pathogenicity
- Leukemia, Experimental/microbiology
- Lymphoma/microbiology
- Mice
- Mice, Inbred AKR
- Molecular Sequence Data
- Muridae
- Mutagenesis, Site-Directed
- Oligodeoxyribonucleotides
- Recombinant Proteins/metabolism
- Repetitive Sequences, Nucleic Acid
- Restriction Mapping
- Sequence Deletion
- Thymus Neoplasms/microbiology
- Transcription, Genetic
- Transfection
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Affiliation(s)
- J C Tupper
- Department of Biological Structure, University of Washington, Seattle 98195
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