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Pluta A, Willems L, Douville RN, Kuźmak J. Effects of Naturally Occurring Mutations in Bovine Leukemia Virus 5'-LTR and Tax Gene on Viral Transcriptional Activity. Pathogens 2020; 9:pathogens9100836. [PMID: 33066207 PMCID: PMC7656303 DOI: 10.3390/pathogens9100836] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2020] [Revised: 10/05/2020] [Accepted: 10/09/2020] [Indexed: 01/28/2023] Open
Abstract
Bovine leukemia virus (BLV) is a deltaretrovirus infecting bovine B cells and causing enzootic bovine leucosis (EBL). The long terminal repeat (LTR) plays an indispensable role in viral gene expression. The BLV Tax protein acts as the main transactivator of LTR-driven transcription of BLV viral genes. The aim of this study was to analyze mutations in the BLV LTR region and tax gene to determine their association with transcriptional activity. LTRs were obtained from one hundred and six BLV isolates and analyzed for their genetic variability. Fifteen variants were selected and characterized based on mutations in LTR regulatory elements, and further used for in vitro transcription assays. Reporter vectors containing the luciferase gene under the control of each variant BLV promoter sequence, in addition to variant Tax expression vectors, were constructed. Both types of plasmids were used for cotransfection of HeLa cells and the level of luciferase activity was measured as a proxy of transcriptional activity. Marked differences in LTR promoter activity and Tax transactivation activity were observed amongst BLV variants. These results demonstrate that mutations in both the BLV LTR and tax gene can affect the promoter activity, which may have important consequences on proviral load, viral fitness, and transmissibility in BLV-infected cattle.
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Affiliation(s)
- Aneta Pluta
- Department of Biochemistry, National Veterinary Research Institute, 24-100 Puławy, Poland;
- Correspondence:
| | - Luc Willems
- Molecular and Cellular Epigenetics (Interdisciplinary Cluster for Applied Genoproteomics, GIGA) and Molecular Biology (TERRA), University of Liège (ULiège), 4000 Liege, Belgium;
| | - Renée N. Douville
- Department of Biology, The University of Winnipeg, Winnipeg, MB R3B 2E9, Canada;
- Department of Immunology, University of Manitoba, Winnipeg, MB R3E 0T5, Canada
| | - Jacek Kuźmak
- Department of Biochemistry, National Veterinary Research Institute, 24-100 Puławy, Poland;
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Regulation of Expression and Latency in BLV and HTLV. Viruses 2020; 12:v12101079. [PMID: 32992917 PMCID: PMC7601775 DOI: 10.3390/v12101079] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2020] [Revised: 09/20/2020] [Accepted: 09/21/2020] [Indexed: 12/14/2022] Open
Abstract
Human T-lymphotrophic virus type 1 (HTLV-1) and Bovine leukemia virus (BLV) belong to the Deltaretrovirus genus. HTLV-1 is the etiologic agent of the highly aggressive and currently incurable cancer adult T-cell leukemia (ATL) and a neurological disease HTLV-1-associated myelopathy (HAM)/tropical spastic paraparesis (TSP). BLV causes neoplastic proliferation of B cells in cattle: enzootic bovine leucosis (EBL). Despite the severity of these conditions, infection by HTLV-1 and BLV appear in most cases clinically asymptomatic. These viruses can undergo latency in their hosts. The silencing of proviral gene expression and maintenance of latency are central for the establishment of persistent infection, as well as for pathogenesis in vivo. In this review, we will present the mechanisms that control proviral activation and retroviral latency in deltaretroviruses, in comparison with other exogenous retroviruses. The 5′ long terminal repeats (5′-LTRs) play a main role in controlling viral gene expression. While the regulation of transcription initiation is a major mechanism of silencing, we discuss topics that include (i) the epigenetic control of the provirus, (ii) the cis-elements present in the LTR, (iii) enhancers with cell-type specific regulatory functions, (iv) the role of virally-encoded transactivator proteins, (v) the role of repressors in transcription and silencing, (vi) the effect of hormonal signaling, (vii) implications of LTR variability on transcription and latency, and (viii) the regulatory role of non-coding RNAs. Finally, we discuss how a better understanding of these mechanisms may allow for the development of more effective treatments against Deltaretroviruses.
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Rosewick N, Durkin K, Artesi M, Marçais A, Hahaut V, Griebel P, Arsic N, Avettand-Fenoel V, Burny A, Charlier C, Hermine O, Georges M, Van den Broeke A. Cis-perturbation of cancer drivers by the HTLV-1/BLV proviruses is an early determinant of leukemogenesis. Nat Commun 2017; 8:15264. [PMID: 28534499 PMCID: PMC5457497 DOI: 10.1038/ncomms15264] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2016] [Accepted: 03/14/2017] [Indexed: 12/12/2022] Open
Abstract
Human T-cell leukaemia virus type-1 (HTLV-1) and bovine leukaemia virus (BLV) infect T- and B-lymphocytes, respectively, provoking a polyclonal expansion that will evolve into an aggressive monoclonal leukaemia in ∼5% of individuals following a protracted latency period. It is generally assumed that early oncogenic changes are largely dependent on virus-encoded products, especially TAX and HBZ, while progression to acute leukaemia/lymphoma involves somatic mutations, yet that both are independent of proviral integration site that has been found to be very variable between tumours. Here, we show that HTLV-1/BLV proviruses are integrated near cancer drivers which they affect either by provirus-dependent transcription termination or as a result of viral antisense RNA-dependent cis-perturbation. The same pattern is observed at polyclonal non-malignant stages, indicating that provirus-dependent host gene perturbation contributes to the initial selection of the multiple clones characterizing the asymptomatic stage, requiring additional alterations in the clone that will evolve into full-blown leukaemia/lymphoma. Human T-cell leukaemia virus type-1 and bovine leukaemia virus infect T and B lymphocytes and lead to aggressive leukaemia. Here, the authors show these proviruses integrate near cancer drivers perturbing transcription termination or antisense RNA-dependent interaction, suggesting post-transcriptional mechanisms in some cases.
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Affiliation(s)
- Nicolas Rosewick
- Unit of Animal Genomics, GIGA-R, Université de Liège (ULg), Avenue de l'Hôpital 11, B34, Liège 4000, Belgium
| | - Keith Durkin
- Unit of Animal Genomics, GIGA-R, Université de Liège (ULg), Avenue de l'Hôpital 11, B34, Liège 4000, Belgium
| | - Maria Artesi
- Unit of Animal Genomics, GIGA-R, Université de Liège (ULg), Avenue de l'Hôpital 11, B34, Liège 4000, Belgium
| | - Ambroise Marçais
- Service d'hématologie, Hôpital Universitaire Necker, Université René Descartes, Assistance publique hôpitaux de Paris, 149-161 rue de Sèvres, Paris 75010, France
| | - Vincent Hahaut
- Unit of Animal Genomics, GIGA-R, Université de Liège (ULg), Avenue de l'Hôpital 11, B34, Liège 4000, Belgium
| | - Philip Griebel
- Vaccine and Infectious Disease Organization, VIDO-Intervac, University of Saskatchewan, 120 Veterinary Road, Saskatoon, Canada S7N 5E3
| | - Natasa Arsic
- Vaccine and Infectious Disease Organization, VIDO-Intervac, University of Saskatchewan, 120 Veterinary Road, Saskatoon, Canada S7N 5E3
| | - Véronique Avettand-Fenoel
- Laboratoire de Virologie, AP-HP, Hôpital Necker-Enfants Malades, Université Paris Descartes, Sorbonne Paris Cité, EA7327, 149 rue de Sèvres, Paris 75010, France
| | - Arsène Burny
- Laboratory of Experimental Hematology, Institut Jules Bordet, Université Libre de Bruxelles (ULB), Boulevard de Waterloo 121, Brussels 1000, Belgium
| | - Carole Charlier
- Unit of Animal Genomics, GIGA-R, Université de Liège (ULg), Avenue de l'Hôpital 11, B34, Liège 4000, Belgium
| | - Olivier Hermine
- Service d'hématologie, Hôpital Universitaire Necker, Université René Descartes, Assistance publique hôpitaux de Paris, 149-161 rue de Sèvres, Paris 75010, France.,INSERM U1163-ERL8254, Institut Imagine, 24 B Boulevard du Montparnasse, Paris 75010, France
| | - Michel Georges
- Unit of Animal Genomics, GIGA-R, Université de Liège (ULg), Avenue de l'Hôpital 11, B34, Liège 4000, Belgium
| | - Anne Van den Broeke
- Unit of Animal Genomics, GIGA-R, Université de Liège (ULg), Avenue de l'Hôpital 11, B34, Liège 4000, Belgium.,Laboratory of Experimental Hematology, Institut Jules Bordet, Université Libre de Bruxelles (ULB), Boulevard de Waterloo 121, Brussels 1000, Belgium
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Rose NJ, Lever AML. Rapamycin-induced inhibition of HTLV-I LTR activity is rescued by c-Myb. Retrovirology 2007; 4:24. [PMID: 17407584 PMCID: PMC1852806 DOI: 10.1186/1742-4690-4-24] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2007] [Accepted: 04/03/2007] [Indexed: 11/16/2022] Open
Abstract
Background Rapamycin is an immunosuppressive which represses translation of transcripts harbouring a polypyrimidine motif downstream of the mRNA cap site through the mammalian target of rapamycin complex. It inhibits the abnormal autologous proliferation of T-cell clones containing a transcriptionally active human T-lymphotropic virus, type I (HTLV-I) provirus, generated from infected subjects. We showed previously that this effect is independent of the polypyrimidine motifs in the viral long terminal repeat (LTR) R region suggesting that HTLV-I transcription, and not translation, is being affected. Here we studied whether rapamycin is having an effect on a specific transcription factor pathway. Further, we investigated whether mRNAs encoding transcription factors involved in HTLV-I transcriptional activation, specifically CREB, Ets and c-Myb, are implicated in the rapamycin-sensitivity of the HTLV-I LTR. Results An in vitro analysis of the role of SRE- and NF-κB-mediated transcription highlighted the latter as rapamycin sensitive. Over-expression of c-Myb reversed the rapamycin effect. Conclusion The sensitivity of HTLV-I transcription to rapamycin may be effected through an NF-κB-pathway associated with the rapamycin-sensitive mTORC1 cellular signalling network.
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Affiliation(s)
- Nicola J Rose
- Division of Retrovirology, National Institute for Biological Standards and Control, Blanche Lane, South Mimms, Potters Bar, Hertfordshire EN6 3QG, UK
| | - Andrew ML Lever
- University of Cambridge Department of Medicine, Level 5, Addenbrooke's Hospital, Hills Road, Cambridge. CB2 2QQ, UK
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Lin HC, Hickey M, Hsu L, Medina D, Rabson AB. Activation of human T cell leukemia virus type 1 LTR promoter and cellular promoter elements by T cell receptor signaling and HTLV-1 Tax expression. Virology 2005; 339:1-11. [PMID: 15964046 DOI: 10.1016/j.virol.2005.05.015] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2004] [Revised: 02/11/2005] [Accepted: 05/12/2005] [Indexed: 11/25/2022]
Abstract
Human T cell leukemia virus 1 (HTLV-1) gene expression is regulated by both the viral Tax protein and by cellular transcriptional factors. We have previously shown that immune activation stimuli such as phorbol esters (PMA) and phytohemagglutinin (PHA) cooperate with HTLV-1 Tax expression to enhance HTLV-1 gene expression in infected T cells through increased activity of the HTLV-1 LTR. We now extend these studies to demonstrate roles for the T cell receptor complex, Lck, and Ras molecules in the coactivation of the HTLV-1 LTR by Tax and T cell activation stimuli. We also observe coactivation of Tax-responsive cellular promoter elements containing NF-kappaB and serum response factor (SRF) binding sites by Tax and T cell activation stimuli. These results suggest a model whereby T cell receptor stimulation and Tax expression coactivate HTLV-1 gene expression and cellular gene expression, enhancing activation of latent HTLV-1 and expression of cellular genes involved in disease pathogenesis.
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Affiliation(s)
- Hsin-Ching Lin
- The Cancer Institute of New Jersey, UMDNJ-Robert Wood Johnson Medical School, New Brunswick, NJ 08903, USA
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Koiwa T, Hamano-Usami A, Ishida T, Okayama A, Yamaguchi K, Kamihira S, Watanabe T. 5'-long terminal repeat-selective CpG methylation of latent human T-cell leukemia virus type 1 provirus in vitro and in vivo. J Virol 2002; 76:9389-97. [PMID: 12186921 PMCID: PMC136445 DOI: 10.1128/jvi.76.18.9389-9397.2002] [Citation(s) in RCA: 182] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
CpG methylation of the human T-cell leukemia virus type 1 (HTLV-1) long terminal repeat (LTR) has been implicated in proviral latency, but there is presently little information available regarding the pattern of LTR methylation and its effect on viral gene expression. To gain insight into the mechanisms of HTLV-1 latency, we have studied methylation of individual CpG sites in the U3-R region of the integrated proviral LTR by using bisulfite genomic sequencing methods. Surprisingly, our results reveal selective hypermethylation of the 5' LTR and accompanying hypomethylation of the 3' LTR in both latently infected cell lines and adult T-cell leukemia (ATL) cells having a complete provirus. Moreover, we observed a lack of CpG methylation in the LTRs of 5'-defective proviruses recovered from ATL samples, which is consistent with the selective hypomethylation of the 3' LTR. Thus, the integrated HTLV-1 provirus in these carriers appears to be hypermethylated in the 5' LTR and hypomethylated in the 3' LTR. These results, together with the observation that proviral gene expression is reactivated by 5-azacytidine in latently infected cell lines, indicate that selective hypermethylation of the HTLV-1 5' LTR is common both in vivo and in vitro. Thus, hypermethylation of the 5' LTR appears to be an important mechanism by which HTLV-1 gene expression is repressed during viral latency.
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Affiliation(s)
- Tsukasa Koiwa
- Division of Pathology, Department of Cancer Research, The Institute of Medical Science, The University of Tokyo, Tokyo 108-8639, Japan
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