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Hleihel R, Skayneh H, de Thé H, Hermine O, Bazarbachi A. Primary cells from patients with adult T cell leukemia/lymphoma depend on HTLV-1 Tax expression for NF-κB activation and survival. Blood Cancer J 2023; 13:67. [PMID: 37137914 PMCID: PMC10156663 DOI: 10.1038/s41408-023-00841-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2023] [Revised: 04/13/2023] [Accepted: 04/19/2023] [Indexed: 05/05/2023] Open
Abstract
Adult T cell leukemia/lymphoma (ATL) is an aggressive malignancy secondary to chronic infection with human T cell leukemia virus type 1 (HTLV-1). The viral oncoprotein Tax initiates T cell transformation through activation of critical cellular pathways, including NF-κB. Unexpectedly, Tax protein is not detectable in most ATL cells, in contrast to the HTLV-1 HBZ protein which antagonizes Tax effects. Here, we demonstrate that primary ATL cells from patients with acute or chronic ATL express very low levels of Tax mRNA and protein. Critically, survival of these primary ATL cells is dependent on continued Tax expression. Mechanistically, Tax extinction results in reversal of NF-κB activation, P53/PML activation and apoptosis. Tax drives interleukin-10 (IL-10) expression and recombinant IL-10 rescues the survival of tax-depleted primary ATL cells. These results demonstrate the critical role of continued Tax and IL-10 expression for the survival of primary ATL cells, highlighting their relevance as therapeutic targets.
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Affiliation(s)
- Rita Hleihel
- Department of Internal Medicine, Faculty of Medicine, American University of Beirut, Beirut, Lebanon
- Department of Anatomy, Cell Biology and Physiological Sciences, Faculty of Medicine, American University of Beirut, Beirut, Lebanon
| | - Hala Skayneh
- Department of Internal Medicine, Faculty of Medicine, American University of Beirut, Beirut, Lebanon
- Department of Anatomy, Cell Biology and Physiological Sciences, Faculty of Medicine, American University of Beirut, Beirut, Lebanon
| | - Hugues de Thé
- INSERM UMR 944, CNRS UMR 7212, Institut Universitaire d'Hématologie, Université Paris-Cité, Hôpital St. Louis 1, Paris, France
- Service d'Hématologie, Assistance Publique, Hôpital St. Louis 1, Paris, France
- College de France, PSL research University, Paris, France
| | - Olivier Hermine
- Institut Imagine-INSERM U1163, Necker Hospital, University of Paris, Paris, France
- Department of Hematology, Necker Hospital, University of Paris, Assistance Publique Hôpitaux de Paris, Paris, France
| | - Ali Bazarbachi
- Department of Internal Medicine, Faculty of Medicine, American University of Beirut, Beirut, Lebanon.
- Department of Anatomy, Cell Biology and Physiological Sciences, Faculty of Medicine, American University of Beirut, Beirut, Lebanon.
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2
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Lee SY, Miller KM, Kim JJ. Clinical and Mechanistic Implications of R-Loops in Human Leukemias. Int J Mol Sci 2023; 24:ijms24065966. [PMID: 36983041 PMCID: PMC10052022 DOI: 10.3390/ijms24065966] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2023] [Revised: 03/17/2023] [Accepted: 03/20/2023] [Indexed: 03/30/2023] Open
Abstract
Genetic mutations or environmental agents are major contributors to leukemia and are associated with genomic instability. R-loops are three-stranded nucleic acid structures consisting of an RNA-DNA hybrid and a non-template single-stranded DNA. These structures regulate various cellular processes, including transcription, replication, and DSB repair. However, unregulated R-loop formation can cause DNA damage and genomic instability, which are potential drivers of cancer including leukemia. In this review, we discuss the current understanding of aberrant R-loop formation and how it influences genomic instability and leukemia development. We also consider the possibility of R-loops as therapeutic targets for cancer treatment.
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Affiliation(s)
- Seo-Yun Lee
- Department of Life Science and Multidisciplinary, Genome Institute, Hallym University, Chuncheon 24252, Republic of Korea
| | - Kyle M Miller
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX 78712, USA
| | - Jae-Jin Kim
- Department of Life Science and Multidisciplinary, Genome Institute, Hallym University, Chuncheon 24252, Republic of Korea
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3
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Ramanayake S, Moulding DA, Tanaka Y, Singh A, Bangham CRM. Dynamics and consequences of the HTLV-1 proviral plus-strand burst. PLoS Pathog 2022; 18:e1010774. [PMID: 36441826 PMCID: PMC9731428 DOI: 10.1371/journal.ppat.1010774] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2022] [Revised: 12/08/2022] [Accepted: 11/15/2022] [Indexed: 11/30/2022] Open
Abstract
Expression of the transcriptional transactivator protein Tax, encoded on the proviral plus-strand of human T-cell leukaemia virus type 1 (HTLV-1), is crucial for the replication of the virus, but Tax-expressing cells are rarely detected in fresh blood ex vivo. The dynamics and consequences of the proviral plus-strand transcriptional burst remain insufficiently characterised. We combined time-lapse live-cell imaging, single-cell tracking and mathematical modelling to study the dynamics of Tax expression at single-cell resolution in two naturally-infected, non-malignant T-cell clones transduced with a short-lived enhanced green fluorescent protein (d2EGFP) Tax reporter system. Five different patterns of Tax expression were observed during the 30-hour observation period; the distribution of these patterns differed between the two clones. The mean duration of Tax expression in the two clones was 94 and 417 hours respectively, estimated from mathematical modelling of the experimental data. Tax expression was associated with a transient slowing in cell-cycle progression and proliferation, increased apoptosis, and enhanced activation of the DNA damage response pathways. Longer-term follow-up (14 days) revealed an increase in the proportion of proliferating cells and a decrease in the fraction of apoptotic cells as the cells ceased Tax expression, resulting in a greater net expansion of the initially Tax-positive population. Time-lapse live-cell imaging showed enhanced cell-to-cell adhesion among Tax-expressing cells, and decreased cell motility of Tax-expressing cells at the single-cell level. The results demonstrate the within-clone and between-clone heterogeneity in the dynamics and patterns of HTLV-1 plus-strand transcriptional bursts and the balance of positive and negative consequences of the burst for the host cell.
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Affiliation(s)
- Saumya Ramanayake
- Department of Infectious Diseases, Faculty of Medicine, Imperial College London, London, United Kingdom
| | - Dale A. Moulding
- Light Microscopy Core Facility, Great Ormond Street Institute of Child Health, University College London, London, United Kingdom
| | - Yuetsu Tanaka
- Department of Infectious Disease and Immunology, Okinawa-Asia Research Center of Medical Science, Faculty of Medicine, University of the Ryukyus, Nishihara, Okinawa, Japan
| | - Abhyudai Singh
- Department of Electrical and Computer Engineering, University of Delaware, Newark, Delaware, United States of America
| | - Charles R. M. Bangham
- Department of Infectious Diseases, Faculty of Medicine, Imperial College London, London, United Kingdom
- * E-mail:
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4
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El Hajj H, Bazarbachi A. Interplay between innate immunity and the viral oncoproteins Tax and HBZ in the pathogenesis and therapeutic response of HTLV-1 associated adult T cell leukemia. Front Immunol 2022; 13:957535. [PMID: 35935975 PMCID: PMC9352851 DOI: 10.3389/fimmu.2022.957535] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Accepted: 06/27/2022] [Indexed: 11/24/2022] Open
Abstract
The Human T-cell Leukemia virus type 1 (HTLV-1) causes an array of pathologies, the most aggressive of which is adult T-cell leukemia (ATL), a fatal blood malignancy with dismal prognosis. The progression of these diseases is partly ascribed to the failure of the immune system in controlling the spread of virally infected cells. HTLV-1 infected subjects, whether asymptomatic carriers or symptomatic patients are prone to opportunistic infections. An increasing body of literature emphasizes the interplay between HTLV-1, its associated pathologies, and the pivotal role of the host innate and adoptive immune system, in shaping the progression of HTLV-1 associated diseases and their response to therapy. In this review, we will describe the modalities adopted by the malignant ATL cells to subvert the host innate immune response with emphasis on the role of the two viral oncoproteins Tax and HBZ in this process. We will also provide a comprehensive overview on the function of innate immunity in the therapeutic response to chemotherapy, anti-viral or targeted therapies in the pre-clinical and clinical settings.
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Affiliation(s)
- Hiba El Hajj
- Department of Experimental Pathology, Immunology and Microbiology, Faculty of Medicine, American University of Beirut, Beirut, Lebanon
| | - Ali Bazarbachi
- Department of Internal Medicine, Faculty of Medicine, American University of Beirut, Beirut, Lebanon
- Department of Anatomy, Cell Biology and Physiological Sciences, Faculty of Medicine, American University of Beirut, Beirut, Lebanon
- *Correspondence: Ali Bazarbachi,
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5
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NF-κB-Induced R-Loops and Genomic Instability in HTLV-1-Infected and Adult T-Cell Leukemia Cells. Viruses 2022; 14:v14050877. [PMID: 35632619 PMCID: PMC9147355 DOI: 10.3390/v14050877] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Revised: 04/20/2022] [Accepted: 04/21/2022] [Indexed: 02/04/2023] Open
Abstract
Human T-cell leukemia virus type 1 (HTLV-1) is a human delta retrovirus that causes adult T-cell leukemia/lymphoma (ATL) in 3–5% of the infected population after decades of clinical latency. HTLV-1 Tax is a potent activator of IKK/NF-κB and a clastogen. While NF-κB activities are associated with cell survival and proliferation, constitutive NF-κB activation (NF-κB hyperactivation) by Tax leads to senescence and oncogenesis. Until recently, the mechanisms underlying the DNA damage and senescence induced by Tax and NF-κB were unknown. Current data indicate that NF-κB hyperactivation by Tax causes the accumulation of a nucleic acid structure known as an R-loop. R-loop excision by the transcription-coupled nucleotide excision repair (TC-NER) endonucleases, Xeroderma pigmentosum F (XPF), and XPG, in turn, promotes DNA double-strand breaks (DSBs). NF-κB blockade prevents Tax-induced R-loop accumulation, DNA damage, and senescence. In the same vein, the silencing of XPF and XPG mitigates Tax senescence, while deficiency in either or both frequently occurs in ATL of all types. ATL cells maintain constitutively active NF-κB, accumulate R-loops, and resist Tax-induced senescence. These results suggest that ATL cells must have acquired adaptive changes to prevent senescence and benefit from the survival and proliferation advantages conferred by Tax and NF-κB. In this review, the roles of R-loops in Tax- and NF-κB-induced DNA DSBs, senescence, and ATL development, and the epigenetic and genetic alterations that arise in ATL to reduce R-loop-associated DNA damage and avert senescence will be discussed.
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He Y, Pasupala N, Zhi H, Dorjbal B, Hussain I, Shih HM, Bhattacharyya S, Biswas R, Miljkovic M, Semmes OJ, Waldmann TA, Snow AL, Giam CZ. NF-κB-induced R-loop accumulation and DNA damage select for nucleotide excision repair deficiencies in adult T cell leukemia. Proc Natl Acad Sci U S A 2021; 118:e2005568118. [PMID: 33649200 PMCID: PMC7958262 DOI: 10.1073/pnas.2005568118] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Constitutive NF-κB activation (NF-κBCA) confers survival and proliferation advantages to cancer cells and frequently occurs in T/B cell malignancies including adult T cell leukemia (ATL) caused by human T-cell leukemia virus type 1 (HTLV-1). Counterintuitively, NF-κBCA by the HTLV-1 transactivator/oncoprotein Tax induces a senescence response, and HTLV-1 infections in culture mostly result in senescence or cell-cycle arrest due to NF-κBCA How NF-κBCA induces senescence, and how ATL cells maintain NF-κBCA and avert senescence, remain unclear. Here we report that NF-κBCA by Tax increases R-loop accumulation and DNA double-strand breaks, leading to senescence. R-loop reduction via RNase H1 overexpression, and short hairpin RNA silencing of two transcription-coupled nucleotide excision repair (TC-NER) endonucleases that are critical for R-loop excision-Xeroderma pigmentosum F (XPF) and XPG-attenuate Tax senescence, enabling HTLV-1-infected cells to proliferate. Our data indicate that ATL cells are often deficient in XPF, XPG, or both and are hypersensitive to ultraviolet irradiation. This TC-NER deficiency is found in all ATL types. Finally, ATL cells accumulate R-loops in abundance. Thus, TC-NER deficits are positively selected during HTLV-1 infection because they facilitate the outgrowth of infected cells initially and aid the proliferation of ATL cells with NF-κBCA later. We suggest that TC-NER deficits and excess R-loop accumulation represent specific vulnerabilities that may be targeted for ATL treatment.
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Affiliation(s)
- Yunlong He
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, MD 20814
| | - Nagesh Pasupala
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, MD 20814
| | - Huijun Zhi
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, MD 20814
| | - Batsuhk Dorjbal
- Department of Pharmacology and Molecular Therapeutics, Uniformed Services University of the Health Sciences, Bethesda, MD 20814
| | - Imran Hussain
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, MD 20814
| | - Hsiu-Ming Shih
- Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan
- Institute of Molecular and Genomic Medicine, National Health Research Institutes, Miaoli County 350, Taiwan
| | - Sharmistha Bhattacharyya
- Department of Anatomy, Physiology, and Genetics, Uniformed Services University of the Health Sciences, Bethesda, MD 20814
| | - Roopa Biswas
- Department of Anatomy, Physiology, and Genetics, Uniformed Services University of the Health Sciences, Bethesda, MD 20814
| | - Milos Miljkovic
- Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892
| | - Oliver John Semmes
- Department of Microbiology and Molecular Cell Biology, Eastern Virginia Medical School, Norfolk, VA 23501
- The Leroy T. Canoles Jr. Cancer Research Center, Eastern Virginia Medical School, Norfolk, VA 23501
| | - Thomas A Waldmann
- Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892
| | - Andrew L Snow
- Department of Pharmacology and Molecular Therapeutics, Uniformed Services University of the Health Sciences, Bethesda, MD 20814
| | - Chou-Zen Giam
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, MD 20814;
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7
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Abstract
Human T-cell leukemia virus type 1 (HTLV-1) was discovered in 1980 as the first, and to date, the only retrovirus that causes human cancer. While HTLV-1 infection is generally asymptomatic, 3-5% of infected individuals develop a T cell neoplasm known as adult T cell leukemia/lymphoma (ATL) decades after infection. Since its discovery, HTLV-1 has served as a model for understanding retroviral oncogenesis, transcriptional regulation, cellular signal transduction, and cell-associated viral infection and spread. Much of the initial research was focused on the viral trans-activator/oncoprotein, Tax. Over the past decade, the study of HTLV-1 has entered the genomic era. With the development of new systems for studying HTLV-1 infection and pathogenesis, the completion of the whole genome, exome and transcriptome sequencing analyses of ATL, and the discovery of HBZ as another HTLV-1 oncogene, many established concepts about how HTLV-1 infects, persists and causes disease have undergone substantial revision. This chapter seeks to integrate our current understanding of the mechanisms of action of Tax and HBZ with the comprehensive genomic information of ATL to provide an overview of how HTLV-1 infects, replicates and causes leukemia.
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Herbein G, Nehme Z. Polyploid Giant Cancer Cells, a Hallmark of Oncoviruses and a New Therapeutic Challenge. Front Oncol 2020; 10:567116. [PMID: 33154944 PMCID: PMC7591763 DOI: 10.3389/fonc.2020.567116] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Accepted: 09/11/2020] [Indexed: 12/19/2022] Open
Abstract
Tumors are renowned as intricate systems that harbor heterogeneous cancer cells with distinctly diverse molecular signatures, sizes and genomic contents. Among those various genomic clonal populations within the complex tumoral architecture are the polyploid giant cancer cells (PGCC). Although described for over a century, PGCC are increasingly being recognized for their prominent role in tumorigenesis, metastasis, therapy resistance and tumor repopulation after therapy. A shared characteristic among all tumors triggered by oncoviruses is the presence of polyploidy. Those include Human Papillomaviruses (HPV), Epstein Barr Virus (EBV), Hepatitis B and C viruses (HBV and HCV, respectively), Human T-cell lymphotropic virus-1 (HTLV-1), Kaposi's sarcoma herpesvirus (KSHV) and Merkel polyomavirus (MCPyV). Distinct viral proteins, for instance Tax for HTLV-1 or HBx for HBV have demonstrated their etiologic role in favoring the appearance of PGCC. Different intriguing biological mechanisms employed by oncogenic viruses, in addition to viruses with high oncogenic potential such as human cytomegalovirus, could support the generation of PGCC, including induction of endoreplication, inactivation of tumor suppressors, development of hypoxia, activation of cellular senescence and others. Interestingly, chemoresistance and radioresistance have been reported in the context of oncovirus-induced cancers, for example KSHV and EBV-associated lymphomas and high-risk HPV-related cervical cancer. This points toward a potential linkage between the previously mentioned players and highlights PGCC as keystone cancer cells in virally-induced tumors. Subsequently, although new therapeutic approaches are actively needed to fight PGCC, attention should also be drawn to reveal the relationship between PGCC and oncoviruses, with the ultimate goal of establishing effective therapeutic platforms for treatment of virus-associated cancers. This review discusses the presence of PGCCs in tumors induced by oncoviruses, biological mechanisms potentially favoring their appearance, as well as their consequent implication at the clinical and therapeutic level.
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Affiliation(s)
- Georges Herbein
- Pathogens & Inflammation/EPILAB Laboratory, EA 4266, University of Franche-Comté, Université Bourgogne Franche-Comté (UBFC), Besançon, France.,Department of Virology, CHRU Besancon, Besançon, France
| | - Zeina Nehme
- Pathogens & Inflammation/EPILAB Laboratory, EA 4266, University of Franche-Comté, Université Bourgogne Franche-Comté (UBFC), Besançon, France.,Faculty of Sciences, Lebanese University, Beirut, Lebanon
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9
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Levy D, Ferreira MCMR, Reichert CO, de Almeida LV, Brocardo G, Lage LAPC, Culler HF, Nukui Y, Bydlowski SP, Pereira J. Cell Cycle Changes, DNA Ploidy, and PTTG1 Gene Expression in HTLV-1 Patients. Front Microbiol 2020; 11:1778. [PMID: 32793179 PMCID: PMC7393187 DOI: 10.3389/fmicb.2020.01778] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Accepted: 07/07/2020] [Indexed: 11/13/2022] Open
Abstract
Human T-cell lymphotropic virus type-1 (HTLV-1) is a pathogenic retrovirus that is associated with adult T-cell leukemia/lymphoma (ATL). Genetic instability is the hallmark of ATL. Cell cycle progression is needed for virus particle reproduction. HTLV-1 encoded Tax protein ultimately disrupts the mitotic spindle checkpoint, leading to incorrect chromosome segregation, resulting in aneuploidy. Cell cycle abnormalities have been described in T cells transfected with HTLV-1 virus in vitro, but not in HTLV-1 asymptomatic carriers. PTTG1 and HTLV-1 viral protein Tax exhibit a cooperative transforming activity. Overexpressed PTTG1 results in chromosome instability and aneuploidy, which has been suggested as a mechanism underlying PTTG1 transforming activity. Here we aimed to investigate cell cycle, DNA ploidy and PTTG1 mRNA expression in CD4+ and CD8+ T cells in healthy subjects (HS), HTLV-1 asymptomatic carriers and ATL patients. We have identified that HTLV-1 asymptomatic carriers have shown DNA aneuploidy and cell cycle arrest at cell cycle phase G0/G1 in CD4+ T cells. CD8+ T cells of HTLV-1 asymptomatic carriers also demonstrated DNA aneuploidy but without alteration in cell cycle. In ATL, CD4+ and CD8+ T cells present a higher number of cells in cell cycle S-phase and PTTG1 overexpression. These studies provide insight into malignant transformation of HTLV-1 asymptomatic carriers to ATL patients.
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Affiliation(s)
- Debora Levy
- Lipids, Oxidation and Cell Biology Team, Laboratory of Immunology (LIM19), School of Medicine, Heart Institute (InCor), University of São Paulo, São Paulo, Brazil
| | - Mari Cleia M R Ferreira
- Department of Hematology, Hemotherapy and Cell Therapy, School of Medicine, University of São Paulo, São Paulo, Brazil
| | - Cadiele O Reichert
- Lipids, Oxidation and Cell Biology Team, Laboratory of Immunology (LIM19), School of Medicine, Heart Institute (InCor), University of São Paulo, São Paulo, Brazil
| | - Lis Vilela de Almeida
- Department of Hematology, Hemotherapy and Cell Therapy, School of Medicine, University of São Paulo, São Paulo, Brazil
| | - Graciela Brocardo
- Department of Hematology, Hemotherapy and Cell Therapy, School of Medicine, University of São Paulo, São Paulo, Brazil
| | - Luis Alberto P C Lage
- Department of Hematology, Hemotherapy and Cell Therapy, School of Medicine, University of São Paulo, São Paulo, Brazil
| | - Hebert F Culler
- Department of Hematology, Hemotherapy and Cell Therapy, School of Medicine, University of São Paulo, São Paulo, Brazil
| | - Youko Nukui
- Pro-Sangue Foundation, Department of Hematology, Hemotherapy and Cell Therapy, School of Medicine, University of São Paulo, São Paulo, Brazil
| | - Sergio P Bydlowski
- Lipids, Oxidation and Cell Biology Team, Laboratory of Immunology (LIM19), School of Medicine, Heart Institute (InCor), University of São Paulo, São Paulo, Brazil
| | - Juliana Pereira
- Laboratory of Medical Investigation on Pathogenesis and Targeted Therapy in Onco-Immuno-Hematology (LIM-31), School of Medicine, University of São Paulo, São Paulo, Brazil
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Witte R, Andriasyan V, Georgi F, Yakimovich A, Greber UF. Concepts in Light Microscopy of Viruses. Viruses 2018; 10:E202. [PMID: 29670029 PMCID: PMC5923496 DOI: 10.3390/v10040202] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Revised: 04/12/2018] [Accepted: 04/16/2018] [Indexed: 12/11/2022] Open
Abstract
Viruses threaten humans, livestock, and plants, and are difficult to combat. Imaging of viruses by light microscopy is key to uncover the nature of known and emerging viruses in the quest for finding new ways to treat viral disease and deepening the understanding of virus–host interactions. Here, we provide an overview of recent technology for imaging cells and viruses by light microscopy, in particular fluorescence microscopy in static and live-cell modes. The review lays out guidelines for how novel fluorescent chemical probes and proteins can be used in light microscopy to illuminate cells, and how they can be used to study virus infections. We discuss advantages and opportunities of confocal and multi-photon microscopy, selective plane illumination microscopy, and super-resolution microscopy. We emphasize the prevalent concepts in image processing and data analyses, and provide an outlook into label-free digital holographic microscopy for virus research.
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Affiliation(s)
- Robert Witte
- Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.
| | - Vardan Andriasyan
- Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.
| | - Fanny Georgi
- Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.
| | - Artur Yakimovich
- MRC Laboratory for Molecular Cell Biology, University College London, Gower St., London WC1E 6BT, UK.
| | - Urs F Greber
- Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.
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11
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Marziali F, Bugnon Valdano M, Brunet Avalos C, Moriena L, Cavatorta AL, Gardiol D. Interference of HTLV-1 Tax Protein with Cell Polarity Regulators: Defining the Subcellular Localization of the Tax-DLG1 Interaction. Viruses 2017; 9:E355. [PMID: 29168728 PMCID: PMC5744130 DOI: 10.3390/v9120355] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 11/15/2017] [Accepted: 11/21/2017] [Indexed: 12/17/2022] Open
Abstract
Human T cell leukemia virus (HTLV)-1 Tax (Tax) protein is very important in viral replication and cell transformation. Tax localizes in the nucleus and cytoplasm in association with organelles. Some activities of Tax depend on interactions with PDZ (PSD-95/Discs Large/Z0-1) domain-containing proteins such as Discs large protein 1 (DLG1) which is involved in cell polarity and proliferation. The DLG1 interaction results in a cytoplasmic co-localization pattern resembling vesicular aggregates, the nature of which is still unknown. To further explore the role of PDZ proteins in HTLV-1 cell transformation, we deeply investigated the Tax-DLG1 association. By fluorescence resonance energy transfer (FRET), we detected, for the first time, the direct binding of Tax to DLG1 within the cell. We showed that the interaction specifically affects the cellular distribution of not only DLG1, but also Tax. After studying different cell structures, we demonstrated that the aggregates distribute into the Golgi apparatus in spatial association with the microtubule-organizing center (MTOC). This study contributes to understand the biological significance of Tax-PDZ interactions.
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Affiliation(s)
- Federico Marziali
- Instituto de Biología Molecular y Celular de Rosario-CONICET, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, 2000 Rosario, Argentina.
| | - Marina Bugnon Valdano
- Instituto de Biología Molecular y Celular de Rosario-CONICET, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, 2000 Rosario, Argentina.
| | - Clarisse Brunet Avalos
- Instituto de Biología Molecular y Celular de Rosario-CONICET, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, 2000 Rosario, Argentina.
| | - Lucía Moriena
- Instituto de Biología Molecular y Celular de Rosario-CONICET, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, 2000 Rosario, Argentina.
| | - Ana Laura Cavatorta
- Instituto de Biología Molecular y Celular de Rosario-CONICET, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, 2000 Rosario, Argentina.
| | - Daniela Gardiol
- Instituto de Biología Molecular y Celular de Rosario-CONICET, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, 2000 Rosario, Argentina.
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12
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Larsen SE, Bilenkin A, Tarasenko TN, Arjunaraja S, Stinson JR, McGuire PJ, Snow AL. Sensitivity to Restimulation-Induced Cell Death Is Linked to Glycolytic Metabolism in Human T Cells. THE JOURNAL OF IMMUNOLOGY 2016; 198:147-155. [PMID: 27852741 DOI: 10.4049/jimmunol.1601218] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Accepted: 10/21/2016] [Indexed: 12/27/2022]
Abstract
Restimulation-induced cell death (RICD) regulates immune responses by restraining effector T cell expansion and limiting nonspecific damage to the host. RICD is triggered by re-engagement of the TCR on a cycling effector T cell, resulting in apoptosis. It remains unclear how RICD sensitivity is calibrated in T cells derived from different individuals or subsets. In this study we show that aerobic glycolysis strongly correlates with RICD sensitivity in human CD8+ effector T cells. Reducing glycolytic activity or glucose availability rendered effector T cells significantly less sensitive to RICD. We found that active glycolysis specifically facilitates the induction of proapoptotic Fas ligand upon TCR restimulation, accounting for enhanced RICD sensitivity in highly glycolytic T cells. Collectively, these data indicate that RICD susceptibility is linked to metabolic reprogramming, and that switching back to metabolic quiescence may help shield T cells from RICD as they transition into the memory pool.
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Affiliation(s)
- Sasha E Larsen
- Department of Pharmacology and Molecular Therapeutics, Uniformed Services University of the Health Sciences, Bethesda, MD 20814; and
| | - Abegail Bilenkin
- Department of Pharmacology and Molecular Therapeutics, Uniformed Services University of the Health Sciences, Bethesda, MD 20814; and
| | - Tatiana N Tarasenko
- Metabolism, Infection and Immunity Unit, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892
| | - Swadhinya Arjunaraja
- Department of Pharmacology and Molecular Therapeutics, Uniformed Services University of the Health Sciences, Bethesda, MD 20814; and
| | - Jeffrey R Stinson
- Department of Pharmacology and Molecular Therapeutics, Uniformed Services University of the Health Sciences, Bethesda, MD 20814; and
| | - Peter J McGuire
- Metabolism, Infection and Immunity Unit, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892
| | - Andrew L Snow
- Department of Pharmacology and Molecular Therapeutics, Uniformed Services University of the Health Sciences, Bethesda, MD 20814; and
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Functional Comparison of HBZ and the Related APH-2 Protein Provides Insight into Human T-Cell Leukemia Virus Type 1 Pathogenesis. J Virol 2016; 90:3760-72. [PMID: 26819304 DOI: 10.1128/jvi.03113-15] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Accepted: 01/18/2016] [Indexed: 02/06/2023] Open
Abstract
UNLABELLED Human T-cell leukemia virus type 1 (HTLV-1) and type 2 (HTLV-2) are highly related retroviruses that transform T cells in vitro but have distinct pathological outcomes in vivo. HTLV-1 encodes a protein from the antisense strand of its proviral genome, the HTLV-1 basic leucine zipper factor (HBZ), which inhibits Tax-1-mediated viral transcription and promotes cell proliferation, a high proviral load, and persistence in vivo. In adult T-cell leukemia/lymphoma (ATL) cell lines and patient T cells, hbz is often the only viral gene expressed. The antisense strand of the HTLV-2 proviral genome also encodes a protein termed APH-2. Like HBZ, APH-2 is able to inhibit Tax-2-mediated viral transcription and is detectable in most primary lymphocytes from HTLV-2-infected patients. However, unlike HBZ, the loss of APH-2 in vivo results in increased viral replication and proviral loads, suggesting that HBZ and APH-2 modulate the virus and cellular pathways differently. Herein, we examined the effect of APH-2 on several known HBZ-modulated pathways: NF-κB (p65) transactivation, transforming growth factor β (TGF-β) signaling, and interferon regulatory factor 1 (IRF-1) transactivation. Like HBZ, APH-2 has the ability to inhibit p65 transactivation. Conversely, HBZ and APH-2 have divergent effects on TGF-β signaling and IRF-1 transactivation. Quantitative PCR and protein half-life experiments revealed a substantial disparity between HBZ and APH-2 transcript levels and protein stability, respectively. Taken together, our data further elucidate the functional differences between HBZ and APH-2 and how these differences can have profound effects on the survival of infected cells and, ultimately, pathogenesis. IMPORTANCE Human T-cell leukemia virus type 1 (HTLV-1) and type 2 (HTLV-2) are highly related retroviruses that have distinct pathological outcomes in infected hosts. Functional comparisons of HTLV-1 and HTLV-2 proteins provide a better understanding about how HTLV-1 infection is associated with disease and HTLV-2 infection is not. The HTLV genome antisense-strand genes hbz and aph-2 are often the only viral genes expressed in HTLV-infected T cells. Previously, our group found that HTLV-1 HBZ and HTLV-2 APH-2 had distinct effects in vivo and hypothesized that the differences in the interactions of HBZ and APH-2 with important cell signaling pathways dictate whether cells undergo proliferation, apoptosis, or senescence. Ultimately, these functional differences may affect how HTLV-1 causes disease but HTLV-2 generally does not. In the current study, we compared the effects of HBZ and APH-2 on several HTLV-relevant cellular pathways, including the TGF-β signaling, NF-κB activation, and IRF-1 transactivation pathways.
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Regulation of HTLV-1 tax stability, cellular trafficking and NF-κB activation by the ubiquitin-proteasome pathway. Viruses 2014; 6:3925-43. [PMID: 25341660 PMCID: PMC4213571 DOI: 10.3390/v6103925] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2014] [Revised: 10/15/2014] [Accepted: 10/21/2014] [Indexed: 12/22/2022] Open
Abstract
Human T-cell leukemia virus type 1 (HTLV-1) is a complex retrovirus that infects CD4+ T cells and causes adult T-cell leukemia/lymphoma (ATLL) in 3%–5% of infected individuals after a long latent period. HTLV-1 Tax is a trans-activating protein that regulates viral gene expression and also modulates cellular signaling pathways to enhance T-cell proliferation and cell survival. The Tax oncoprotein promotes T-cell transformation, in part via constitutive activation of the NF-κB transcription factor; however, the underlying mechanisms remain unknown. Ubiquitination is a type of post-translational modification that occurs in a three-step enzymatic cascade mediated by E1, E2 and E3 enzymes and regulates protein stability as well as signal transduction, protein trafficking and the DNA damage response. Emerging studies indicate that Tax hijacks the ubiquitin machinery to activate ubiquitin-dependent kinases and downstream NF-κB signaling. Tax interacts with the E2 conjugating enzyme Ubc13 and is conjugated on C-terminal lysine residues with lysine 63-linked polyubiquitin chains. Tax K63-linked polyubiquitination may serve as a platform for signaling complexes since this modification is critical for interactions with NEMO and IKK. In addition to NF-κB signaling, mono- and polyubiquitination of Tax also regulate its subcellular trafficking and stability. Here, we review recent advances in the diverse roles of ubiquitin in Tax function and how Tax usurps the ubiquitin-proteasome pathway to promote oncogenesis.
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15
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Jaworski E, Narayanan A, Van Duyne R, Shabbeer-Meyering S, Iordanskiy S, Saifuddin M, Das R, Afonso PV, Sampey GC, Chung M, Popratiloff A, Shrestha B, Sehgal M, Jain P, Vertes A, Mahieux R, Kashanchi F. Human T-lymphotropic virus type 1-infected cells secrete exosomes that contain Tax protein. J Biol Chem 2014; 289:22284-305. [PMID: 24939845 DOI: 10.1074/jbc.m114.549659] [Citation(s) in RCA: 112] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Human T-lymphotropic virus type 1 (HTLV-1) is the causative agent of adult T-cell leukemia and HTLV-1-associated myelopathy/tropical spastic paraparesis. The HTLV-1 transactivator protein Tax controls many critical cellular pathways, including host cell DNA damage response mechanisms, cell cycle progression, and apoptosis. Extracellular vesicles called exosomes play critical roles during pathogenic viral infections as delivery vehicles for host and viral components, including proteins, mRNA, and microRNA. We hypothesized that exosomes derived from HTLV-1-infected cells contain unique host and viral proteins that may contribute to HTLV-1-induced pathogenesis. We found exosomes derived from infected cells to contain Tax protein and proinflammatory mediators as well as viral mRNA transcripts, including Tax, HBZ, and Env. Furthermore, we observed that exosomes released from HTLV-1-infected Tax-expressing cells contributed to enhanced survival of exosome-recipient cells when treated with Fas antibody. This survival was cFLIP-dependent, with Tax showing induction of NF-κB in exosome-recipient cells. Finally, IL-2-dependent CTLL-2 cells that received Tax-containing exosomes were protected from apoptosis through activation of AKT. Similar experiments with primary cultures showed protection and survival of peripheral blood mononuclear cells even in the absence of phytohemagglutinin/IL-2. Surviving cells contained more phosphorylated Rb, consistent with the role of Tax in regulation of the cell cycle. Collectively, these results suggest that exosomes may play an important role in extracellular delivery of functional HTLV-1 proteins and mRNA to recipient cells.
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Affiliation(s)
- Elizabeth Jaworski
- From the School of Systems Biology, National Center for Biodefense and Infectious Diseases, George Mason University, Manassas, Virginia 20110
| | - Aarthi Narayanan
- From the School of Systems Biology, National Center for Biodefense and Infectious Diseases, George Mason University, Manassas, Virginia 20110
| | - Rachel Van Duyne
- From the School of Systems Biology, National Center for Biodefense and Infectious Diseases, George Mason University, Manassas, Virginia 20110, the Department of Microbiology, Immunology, and Tropical Medicine and
| | - Shabana Shabbeer-Meyering
- From the School of Systems Biology, National Center for Biodefense and Infectious Diseases, George Mason University, Manassas, Virginia 20110
| | - Sergey Iordanskiy
- From the School of Systems Biology, National Center for Biodefense and Infectious Diseases, George Mason University, Manassas, Virginia 20110, the Department of Microbiology, Immunology, and Tropical Medicine and
| | - Mohammed Saifuddin
- From the School of Systems Biology, National Center for Biodefense and Infectious Diseases, George Mason University, Manassas, Virginia 20110
| | - Ravi Das
- From the School of Systems Biology, National Center for Biodefense and Infectious Diseases, George Mason University, Manassas, Virginia 20110
| | - Philippe V Afonso
- the Unité d'Epidémiologie et Physiopathologie des Virus Oncogènes, Département de Virologie, Institut Pasteur, F-75015 Paris, France, CNRS, UMR3569, F-75015 Paris, France, and
| | - Gavin C Sampey
- From the School of Systems Biology, National Center for Biodefense and Infectious Diseases, George Mason University, Manassas, Virginia 20110
| | - Myung Chung
- From the School of Systems Biology, National Center for Biodefense and Infectious Diseases, George Mason University, Manassas, Virginia 20110
| | - Anastas Popratiloff
- the Department of Chemistry, George Washington University, Washington, D. C. 20037
| | - Bindesh Shrestha
- Center for Microscopy and Image Analysis, George Washington University Medical Center, Washington, D. C. 20037
| | - Mohit Sehgal
- the Department of Microbiology and Immunology, Drexel Institute for Biotechnology and Virology Research, Drexel University College of Medicine, Doylestown, Pennsylvania 18902
| | - Pooja Jain
- the Department of Microbiology and Immunology, Drexel Institute for Biotechnology and Virology Research, Drexel University College of Medicine, Doylestown, Pennsylvania 18902
| | - Akos Vertes
- Center for Microscopy and Image Analysis, George Washington University Medical Center, Washington, D. C. 20037
| | - Renaud Mahieux
- the Equipe Oncogenèse Rétrovirale, Equipe labelisée "Ligue Nationale Contre le Cancer," International Center for Research in Infectiology, INSERM U1111-CNRS UMR5308, Ecole Normale Supérieure de Lyon, Université Lyon 1, Lyon 69364 Cedex 07, France
| | - Fatah Kashanchi
- From the School of Systems Biology, National Center for Biodefense and Infectious Diseases, George Mason University, Manassas, Virginia 20110,
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16
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Zhi H, Zahoor MA, Shudofsky AMD, Giam CZ. KSHV vCyclin counters the senescence/G1 arrest response triggered by NF-κB hyperactivation. Oncogene 2014; 34:496-505. [PMID: 24469036 PMCID: PMC4112183 DOI: 10.1038/onc.2013.567] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Revised: 11/20/2013] [Accepted: 11/29/2013] [Indexed: 12/19/2022]
Abstract
Many oncogenic viruses activate NF-κB as a part of their replicative cycles. We have shown recently that persistent and potentially oncogenic activation of NF-κB by the human T-lymphotropic virus 1 (HTLV-1) oncoprotein Tax immediately triggers a host senescence response mediated by cyclin-dependent kinase inhibitors: p21CIP1/WAF1 (p21) and p27Kip1 (p27) Here we demonstrate that RelA/NF-κB activation by Kaposi sarcoma herpesvirus (KSHV) latency protein vFLIP also leads to p21/p27 up-regulation and G1 cell cycle arrest. Remarkably, KSHV vCyclin, another latency protein co-expressed with vFLIP from a bicistronic latency-specific mRNA, was found to prevent the senescence and G1 arrest induced by HTLV-1 Tax and vFLIP respectively. This is due to the known ability of vCyclin/CDK6 complex to resist p21 and p27 inhibition and cause p27 degradation23. In KSHV-transformed BCBL-1 cells, sustained vFLIP expression with shRNA-mediated vCyclin depletion resulted in G1 arrest. The functional interdependence of vFLIP and vCyclin explains why they are co-translated from the same viral mRNA. Importantly, deregulation of the G1 cyclin-dependent kinase can facilitate chronic IKK/NF-κB activation.
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Affiliation(s)
- H Zhi
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, MD, USA
| | - M A Zahoor
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, MD, USA
| | - A M D Shudofsky
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, MD, USA
| | - C-Z Giam
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, MD, USA
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17
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NF-κB inhibition facilitates the establishment of cell lines that chronically produce human T-lymphotropic virus type 1 viral particles. J Virol 2014; 88:3496-504. [PMID: 24403591 DOI: 10.1128/jvi.02961-13] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Most human T-lymphotropic virus type 1 (HTLV-1)-infected HeLa and SupT1 cells cease proliferation and become senescent immediately after infection by HTLV-1 or transduction of the HTLV-1 tax gene. The cellular senescence response triggered by Tax is caused by hyperactivated NF-κB and mediated by cyclin-dependent kinase inhibitors, p21(CIP1/WAF1) and p27(KIP1). When NF-κB activity is blocked by a degradation-resistant form of IκBα, ΔN-IκBα, Tax-induced senescence is averted. Here, we show that NF-κB inhibition through the expression of ΔN-IκBα allows cells of a human osteosarcoma (HOS) cell line to be chronically infected by HTLV-1. Stable HTLV-1-producing HOS cell clones can be readily established and isolated. These clones continue to proliferate in culture; express Tax, Rex, Gag, and Env proteins persistently; and transmit HTLV-1 to naive HOS, SupT1, and Jurkat T reporter cell lines readily after cocultivation. As HOS cells are adherent to culture plates, infected T cells in suspension can be easily collected and characterized. The ease with which chronic and productive HTLV-1 infection can be established in cell culture through inhibition of NF-κB affords a useful means to examine in depth the molecular events of HTLV-1 replication and the mechanisms of action of viral genes. IMPORTANCE This paper describes a system for establishing cell lines that can be productively infected by human T-lymphotropic virus type 1 (HTLV-1) and can spread HTLV-1 to susceptible cells. Such a system can facilitate the study of HTLV-1 replication in cell culture.
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18
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Zane L, Jeang KT. HTLV-1 and leukemogenesis: virus-cell interactions in the development of adult T-cell leukemia. Recent Results Cancer Res 2014; 193:191-210. [PMID: 24008300 DOI: 10.1007/978-3-642-38965-8_11] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Human T-cell lymphotropic virus type 1 (HTLV-1) was originally discovered in the early 1980s. It is the first retrovirus to be unambiguously linked causally to a human cancer. HTLV-1 currently infects approximately 20 million people worldwide. In this chapter, we review progress made over the last 30 years in our understanding of HTLV-1 infection, replication, gene expression, and cellular transformation.
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Affiliation(s)
- Linda Zane
- Molecular Virology Section, Laboratory of Molecular Microbiology, The National Institutes of Allergy and Infectious Diseases, The National Institutes of Health, Bethesda, MD, 20892-0460, USA
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19
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Human T-cell leukemia virus type 1 Tax-deregulated autophagy pathway and c-FLIP expression contribute to resistance against death receptor-mediated apoptosis. J Virol 2013; 88:2786-98. [PMID: 24352466 DOI: 10.1128/jvi.03025-13] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
UNLABELLED The human T-cell leukemia virus type 1 (HTLV-1) Tax protein is considered to play a central role in the process that leads to adult T-cell leukemia/lymphoma (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). HTLV-1 Tax-expressing cells show resistance to apoptosis induced by Fas ligand (FasL) and tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL). The regulation of Tax on the autophagy pathway in HeLa cells and peripheral T cells was recently reported, but the function and underlying molecular mechanism of the Tax-regulated autophagy are not yet well defined. Here, we report that HTLV-1 Tax deregulates the autophagy pathway, which plays a protective role during the death receptor (DR)-mediated apoptosis of human U251 astroglioma cells. The cellular FLICE-inhibitory protein (c-FLIP), which is upregulated by Tax, also contributes to the resistance against DR-mediated apoptosis. Both Tax-induced autophagy and Tax-induced c-FLIP expression require Tax-induced activation of IκB kinases (IKK). Furthermore, Tax-induced c-FLIP expression is regulated through the Tax-IKK-NF-κB signaling pathway, whereas Tax-triggered autophagy depends on the activation of IKK but not the activation of NF-κB. In addition, DR-mediated apoptosis is correlated with the degradation of Tax, which can be facilitated by the inhibitors of autophagy. IMPORTANCE Our study reveals that Tax-deregulated autophagy is a protective mechanism for DR-mediated apoptosis. The molecular mechanism of Tax-induced autophagy is also illuminated, which is different from Tax-increased c-FLIP. Tax can be degraded via manipulation of autophagy and TRAIL-induced apoptosis. These results outline a complex regulatory network between and among apoptosis, autophagy, and Tax and also present evidence that autophagy represents a new possible target for therapeutic intervention for the HTVL-1 related diseases.
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20
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Sampey GC, Van Duyne R, Currer R, Das R, Narayanan A, Kashanchi F. Complex role of microRNAs in HTLV-1 infections. Front Genet 2012; 3:295. [PMID: 23251140 PMCID: PMC3523292 DOI: 10.3389/fgene.2012.00295] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2012] [Accepted: 11/29/2012] [Indexed: 12/15/2022] Open
Abstract
Human T-lymphotropic virus 1 (HTLV-1) was the first human retrovirus to be discovered and is the causative agent of adult T-cell leukemia/lymphoma (ATL) and the neurodegenerative disease HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). The importance of microRNA (miRNA) in the replicative cycle of several other viruses, as well as in the progression of associated pathologies, has been well established in the past decade. Moreover, involvement of miRNA alteration in the HTLV-1 life cycle, and in the progression of its related oncogenic and neurodegenerative diseases, has recently come to light. Several HTLV-1 derived proteins alter transcription factor functionalities, interact with chromatin remodelers, or manipulate components of the RNA interference (RNAi) machinery, thereby establishing various routes by which miRNA expression can be up- or down-regulated in the host cell. Furthermore, the mechanism of action through which dysregulation of host miRNAs affects HTLV-1 infected cells can vary substantially and include mRNA silencing via the RNA-induced silencing complex (RISC), transcriptional gene silencing, inhibition of RNAi components, and chromatin remodeling. These miRNA-induced changes can lead to increased cell survival, invasiveness, proliferation, and differentiation, as well as allow for viral latency. While many recent studies have successfully implicated miRNAs in the life cycle and pathogenesis of HTLV-1 infections, there are still significant outstanding questions to be addressed. Here we will review recent discoveries elucidating HTLV-1 mediated manipulation of host cell miRNA profiles and examine the impact on pathogenesis, as well as explore future lines of inquiry that could increase understanding in this field of study.
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Affiliation(s)
- Gavin C Sampey
- National Center for Biodefense and Infectious Diseases, School of Systems Biology, George Mason University Manassas, VA, USA
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21
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Currer R, Van Duyne R, Jaworski E, Guendel I, Sampey G, Das R, Narayanan A, Kashanchi F. HTLV tax: a fascinating multifunctional co-regulator of viral and cellular pathways. Front Microbiol 2012; 3:406. [PMID: 23226145 PMCID: PMC3510432 DOI: 10.3389/fmicb.2012.00406] [Citation(s) in RCA: 103] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2012] [Accepted: 11/12/2012] [Indexed: 12/18/2022] Open
Abstract
Human T-cell lymphotropic virus type 1 (HTLV-1) has been identified as the causative agent of adult T-cell leukemia (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). The virus infects between 15 and 20 million people worldwide of which approximately 2-5% develop ATL. The past 35 years of research have yielded significant insight into the pathogenesis of HTLV-1, including the molecular characterization of Tax, the viral transactivator, and oncoprotein. In spite of these efforts, the mechanisms of oncogenesis of this pleiotropic protein remain to be fully elucidated. In this review, we illustrate the multiple oncogenic roles of Tax by summarizing a recent body of literature that refines our understanding of cellular transformation. A focused range of topics are discussed in this review including Tax-mediated regulation of the viral promoter and other cellular pathways, particularly the connection of the NF-κB pathway to both post-translational modifications (PTMs) of Tax and subcellular localization. Specifically, recent research on polyubiquitination of Tax as it relates to the activation of the IkappaB kinase (IKK) complex is highlighted. Regulation of the cell cycle and DNA damage responses due to Tax are also discussed, including Tax interaction with minichromosome maintenance proteins and the role of Tax in chromatin remodeling. The recent identification of HTLV-3 has amplified the importance of the characterization of emerging viral pathogens. The challenge of the molecular determination of pathogenicity and malignant disease of this virus lies in the comparison of the viral transactivators of HTLV-1, -2, and -3 in terms of transformation and immortalization. Consequently, differences between the three proteins are currently being studied to determine what factors are required for the differences in tumorogenesis.
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Affiliation(s)
- Robert Currer
- National Center for Biodefense and Infectious Diseases, George Mason University Manassas, VA, USA
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22
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Mo M, Shahar S, Fleming SB, Mercer AA. How viruses affect the cell cycle through manipulation of the APC/C. Trends Microbiol 2012; 20:440-8. [PMID: 22727131 DOI: 10.1016/j.tim.2012.05.007] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Revised: 05/21/2012] [Accepted: 05/28/2012] [Indexed: 02/06/2023]
Abstract
Viruses frequently exploit host cell cycle machineries for their own benefit, often by targeting 'master switches' of cell cycle regulation. By doing so, they achieve maximum effect from minimal input. One such master switch is the anaphase promoting complex or cyclosome (APC/C), a multicomponent ubiquitin ligase and a dominant regulator of the cell cycle. A growing number of viruses have been shown to target the APC/C. Although differing strategies are employed, viral manipulation of the APC/C seems to serve a common purpose, namely, to create an environment supportive of viral replication. Here, the molecular mechanisms employed by these viruses are summarized and discussed.
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Affiliation(s)
- Min Mo
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9016, New Zealand
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23
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Boxus M, Willems L. How the DNA damage response determines the fate of HTLV-1 Tax-expressing cells. Retrovirology 2012; 9:2. [PMID: 22221708 PMCID: PMC3283471 DOI: 10.1186/1742-4690-9-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Accepted: 01/05/2012] [Indexed: 11/10/2022] Open
Abstract
How the Human T lymphotropic virus type 1 (HTLV-1) Tax protein stimulates proliferation while triggering cell cycle arrest and senescence remains puzzling. There is also a debate about the ability of Tax to activate or inhibit the DNA damage response. Here, we comment on these different activities and propose a conceptual rationale for the apparently conflicting observations.
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Affiliation(s)
- Mathieu Boxus
- National Fund for Scientific Research, Gembloux Agro-Bio Tech and Interdisciplinary Cluster for Applied Genoproteomics (GIGA), University of Liège, Belgium
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24
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Barrios CS, Abuerreish M, Lairmore MD, Castillo L, Giam CZ, Beilke MA. Recombinant human T-cell leukemia virus types 1 and 2 Tax proteins induce high levels of CC-chemokines and downregulate CCR5 in human peripheral blood mononuclear cells. Viral Immunol 2011; 24:429-39. [PMID: 22111594 DOI: 10.1089/vim.2011.0037] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Human T-cell leukemia viruses types 1 (HTLV-1) and 2 (HTLV-2) produce key transcriptional regulatory gene products, known as Tax1 and Tax2, respectively. Tax1 and Tax2 transactivate multiple host genes involved in cellular immune responses within the cellular microenvironment, including induction of genes encoding expression of CC-chemokines. It is speculated that HTLV Tax proteins may act as immune modulators. In this study, recombinant Tax1 and Tax2 proteins were tested for their effects on the viability of cultured peripheral blood mononuclear cells (PBMCs), and their ability to induce expression of CC-chemokines and to downregulate the level of CCR5 expression in PBMCs. PBMCs obtained from uninfected donors were cultured in a range of Tax1 and Tax2 concentrations (10-100 pM), and supernatant fluids were harvested at multiple time points for quantitative determinations of MIP-1α/CCL3, MIP-1β/CCL4, and RANTES/CCL5. Treatment of PBMCs with Tax1 and Tax2 proteins (100 pM) resulted in a significant increase in viability over a 7-d period compared to controls (p<0.01). Both Tax1 and Tax2 induced high levels of all three CC-chemokines over the dosing range compared to mock-treated controls (p<0.05). The gated population of lymphocytes treated with Tax2, as well as lymphocytes from HTLV-2-infected donors, showed a significantly lower percentage of CCR5-positive cells compared to those of uninfected donors and from mock-treated lymphocytes, respectively (p<0.05). These results suggest that Tax1 and Tax2 could promote innate immunity in the extracellular environment during HTLV-1 and HTLV-2 infections via CC-chemokine ligands and receptors.
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Affiliation(s)
- Christy S Barrios
- Infectious Diseases Division, Department of Medicine, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA
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25
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Polakowski N, Han H, Lemasson I. Direct inhibition of RNAse T2 expression by the HTLV-1 viral protein Tax. Viruses 2011; 3:1485-500. [PMID: 21994792 PMCID: PMC3185805 DOI: 10.3390/v3081485] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2011] [Accepted: 08/10/2011] [Indexed: 12/20/2022] Open
Abstract
Adult T-cell leukemia (ATL) is one of the primary diseases caused by Human T-cell Leukemia Virus type 1 (HTLV-1) infection. The virally-encoded Tax protein is believed to initiate early events in the development of this disease, as it is able to promote immortalization of T-cells and transformation of other cell types. These processes may be aided by the ability of the viral protein to directly deregulate expression of specific cellular genes through interactions with numerous transcriptional regulators. To identify gene promoters where Tax is localized, we isolated Tax-DNA complexes from an HTLV-1-infected T-cell line through a chromatin immunoprecipitation (ChIP) assay and used the DNA to probe a CpG island microarray. A site within the RNASET2 gene was found to be occupied by Tax. Real-time PCR analysis confirmed this result, and transient expression of Tax in uninfected cells led to the recruitment of the viral protein to the promoter. This event correlated with a decrease in the level of RNase T2 mRNA and protein, suggesting that Tax represses expression of this gene. Loss of RNase T2 expression occurs in certain hematological malignancies and other forms of cancer, and RNase T2 was recently reported to function as a tumor suppressor. Consequently, a reduction in the level of RNase T2 by Tax may play a role in ATL development.
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Affiliation(s)
- Nicholas Polakowski
- Authors to whom correspondence should be addressed; E-Mails: (N.P.); (I.L.); Tel.: +1-252-744-2711 or +1-252-744-2706; Fax: +1-252-744-3104
| | | | - Isabelle Lemasson
- Authors to whom correspondence should be addressed; E-Mails: (N.P.); (I.L.); Tel.: +1-252-744-2711 or +1-252-744-2706; Fax: +1-252-744-3104
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