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Smith S, Seth J, Midkiff A, Stahl R, Syu YC, Shkriabai N, Kvaratskhelia M, Musier-Forsyth K, Jain P, Green PL, Panfil AR. The Pleiotropic Effects of YBX1 on HTLV-1 Transcription. Int J Mol Sci 2023; 24:13119. [PMID: 37685922 PMCID: PMC10487795 DOI: 10.3390/ijms241713119] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Revised: 08/18/2023] [Accepted: 08/21/2023] [Indexed: 09/10/2023] Open
Abstract
HTLV-1 is an oncogenic human retrovirus and the etiologic agent of the highly aggressive ATL malignancy. Two viral genes, Tax and Hbz, are individually linked to oncogenic transformation and play an important role in the pathogenic process. Consequently, regulation of HTLV-1 gene expression is a central feature in the viral lifecycle and directly contributes to its pathogenic potential. Herein, we identified the cellular transcription factor YBX1 as a binding partner for HBZ. We found YBX1 activated transcription and enhanced Tax-mediated transcription from the viral 5' LTR promoter. Interestingly, YBX1 also interacted with Tax. shRNA-mediated loss of YBX1 decreased transcript and protein abundance of both Tax and HBZ in HTLV-1-transformed T-cell lines, as well as Tax association with the 5' LTR. Conversely, YBX1 transcriptional activation of the 5' LTR promoter was increased in the absence of HBZ. YBX1 was found to be associated with both the 5' and 3' LTRs in HTLV-1-transformed and ATL-derived T-cell lines. Together, these data suggest that YBX1 positively influences transcription from both the 5' and 3' promoter elements. YBX1 is able to interact with Tax and help recruit Tax to the 5' LTR. However, through interactions with HBZ, YBX1 transcriptional activation of the 5' LTR is repressed.
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Affiliation(s)
- Susan Smith
- Center for Retrovirus Research, Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210, USA; (S.S.); (J.S.); (A.M.)
| | - Jaideep Seth
- Center for Retrovirus Research, Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210, USA; (S.S.); (J.S.); (A.M.)
| | - Amanda Midkiff
- Center for Retrovirus Research, Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210, USA; (S.S.); (J.S.); (A.M.)
| | - Rachel Stahl
- Center for Retrovirus Research, Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210, USA; (S.S.); (J.S.); (A.M.)
| | - Yu-Ci Syu
- Center for Retrovirus Research, Department of Chemistry and Biochemistry, Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA; (Y.-C.S.); (K.M.-F.)
| | - Nikoloz Shkriabai
- Division of Infectious Diseases, Anschutz Medical Campus, University of Colorado School of Medicine, Aurora, CO 80045, USA; (N.S.); (M.K.)
| | - Mamuka Kvaratskhelia
- Division of Infectious Diseases, Anschutz Medical Campus, University of Colorado School of Medicine, Aurora, CO 80045, USA; (N.S.); (M.K.)
| | - Karin Musier-Forsyth
- Center for Retrovirus Research, Department of Chemistry and Biochemistry, Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA; (Y.-C.S.); (K.M.-F.)
| | - Pooja Jain
- Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, PA 19129, USA;
| | - Patrick L. Green
- Center for Retrovirus Research, Comprehensive Cancer Center and Solove Research Institute, Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210, USA;
| | - Amanda R. Panfil
- Center for Retrovirus Research, Comprehensive Cancer Center and Solove Research Institute, Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210, USA;
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Maksimova V, Wilkie T, Smith S, Phelps C, Melvin C, Yu L, Niewiesk S, Green PL, Panfil AR. HTLV-1 Hbz protein, but not hbz mRNA secondary structure, is critical for viral persistence and disease development. PLoS Pathog 2023; 19:e1011459. [PMID: 37327244 DOI: 10.1371/journal.ppat.1011459] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Accepted: 06/05/2023] [Indexed: 06/18/2023] Open
Abstract
Human T-cell leukemia virus type 1 (HTLV-1) is the etiologic cause of adult T-cell leukemia/lymphoma (ATL) and encodes a viral oncoprotein (Hbz) that is consistently expressed in asymptomatic carriers and ATL patients, suggesting its importance in the development and maintenance of HTLV-1 leukemic cells. Our previous work found Hbz protein is dispensable for virus-mediated T-cell immortalization but enhances viral persistence. We and others have also shown that hbz mRNA promotes T-cell proliferation. In our current studies, we evaluated the role of hbz mRNA on HTLV-1-mediated immortalization in vitro as well as in vivo persistence and disease development. We generated mutant proviral clones to examine the individual contributions of hbz mRNA, hbz mRNA secondary structure (stem-loop), and Hbz protein. Wild-type (WT) and all mutant viruses produced virions and immortalized T-cells in vitro. Viral persistence and disease development were also evaluated in vivo by infection of a rabbit model and humanized immune system (HIS) mice, respectively. Proviral load and sense and antisense viral gene expression were significantly lower in rabbits infected with mutant viruses lacking Hbz protein compared to WT or virus with an altered hbz mRNA stem-loop (M3 mutant). HIS mice infected with Hbz protein-deficient viruses showed significantly increased survival times compared to animals infected with WT or M3 mutant virus. Altered hbz mRNA secondary structure, or loss of hbz mRNA or protein, has no significant effect on T-cell immortalization induced by HTLV-1 in vitro; however, the Hbz protein plays a critical role in establishing viral persistence and leukemogenesis in vivo.
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Affiliation(s)
- Victoria Maksimova
- Center for Retrovirus Research, Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio, United States
| | - Tasha Wilkie
- Center for Retrovirus Research, Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio, United States
| | - Susan Smith
- Center for Retrovirus Research, Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio, United States
| | - Cameron Phelps
- Center for Retrovirus Research, Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio, United States
| | - Corrine Melvin
- Center for Retrovirus Research, Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio, United States
| | - Lianbo Yu
- Department of Biomedical Informatics, College of Medicine, The Ohio State University, Columbus, Ohio, United States
| | - Stefan Niewiesk
- Center for Retrovirus Research, Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio, United States
| | - Patrick L Green
- Center for Retrovirus Research, Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio, United States
- Comprehensive Cancer Center and Solove Research Institute, The Ohio State University, Columbus, Ohio, United States
| | - Amanda R Panfil
- Center for Retrovirus Research, Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio, United States
- Comprehensive Cancer Center and Solove Research Institute, The Ohio State University, Columbus, Ohio, United States
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3
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Regulation of HTLV-1 Transformation. Biosci Rep 2022; 42:230803. [PMID: 35169839 PMCID: PMC8919135 DOI: 10.1042/bsr20211921] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Revised: 02/07/2022] [Accepted: 02/15/2022] [Indexed: 11/17/2022] Open
Abstract
Human T-cell leukemia virus type 1 (HTLV-1) is the only identified oncogenic human retrovirus. HTLV-1 infects approximately 5–10 million people worldwide and is the infectious cause of adult T-cell leukemia/lymphoma (ATL) and several chronic inflammatory diseases, including HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), dermatitis, and uveitis. Unlike other oncogenic retroviruses, HTLV-1 does not capture a cellular proto-oncogene or induce proviral insertional mutagenesis. HTLV-1 is a trans-activating retrovirus and encodes accessory proteins that induce cellular transformation over an extended period of time, upwards of several years to decades. Inarguably the most important viral accessory protein involved in transformation is Tax. Tax is a multifunctional protein that regulates several different pathways and cellular processes. This single viral protein is able to modulate viral gene expression, activate NF-κB signaling pathways, deregulate the cell cycle, disrupt apoptosis, and induce genomic instability. The summation of these processes results in cellular transformation and virus-mediated oncogenesis. Interestingly, HTLV-1 also encodes a protein called Hbz from the antisense strand of the proviral genome that counters many Tax functions in the infected cell, such as Tax-mediated viral transcription and NF-κB activation. However, Hbz also promotes cellular proliferation, inhibits apoptosis, and disrupts genomic integrity. In addition to viral proteins, there are other cellular factors such as MEF-2, superoxide-generating NAPDH oxidase 5-α (Nox5α), and PDLIM2 which have been shown to be critical for HTLV-1-mediated T-cell transformation. This review will highlight the important viral and cellular factors involved in HTLV-1 transformation and the available in vitro and in vivo tools used to study this complex process.
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Maksimova V, Smith S, Seth J, Phelps C, Niewiesk S, Satou Y, Green P, Panfil AR. HTLV-1 intragenic viral enhancer influences immortalization phenotype in vitro, but is dispensable for persistence and disease development in animal models. Front Immunol 2022; 13:954077. [PMID: 35958554 PMCID: PMC9359075 DOI: 10.3389/fimmu.2022.954077] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Accepted: 07/04/2022] [Indexed: 11/13/2022] Open
Abstract
Human T-cell leukemia virus type 1 (HTLV-1) is the causative infectious agent of adult T-cell leukemia/lymphoma (ATL) and chronic neurological disease. The disparity between silenced sense transcription versus constitutively active antisense (Hbz) transcription from the integrated provirus is not fully understood. The presence of an internal viral enhancer has recently been discovered in the Tax gene near the 3' long terminal repeat (LTR) of HTLV-1. In vitro, this enhancer has been shown to bind SRF and ELK-1 host transcription factors, maintain chromatin openness and viral gene transcription, and induce aberrant host gene transcription near viral integration sites. However, the function of the viral enhancer in the context of early HTLV-1 infection events remains unknown. In this study, we generated a mutant Enhancer virus (mEnhancer) and evaluated its effects on HTLV-1-mediated in vitro immortalization, establishment of persistent infection with an in vivo rabbit model, and disease development in a humanized immune system (HIS) mouse model. The mEnhancer virus was able to establish persistent infection in rabbits, and there were no significant differences in proviral load or HTLV-1-specific antibody responses over a 25-week study. However, rabbits infected with the mEnhancer virus had significantly decreased sense and antisense viral gene expression at 12-weeks post-infection. HIS mice infected with wt or mEnhancer virus showed similar disease progression, proviral load, and viral gene expression. While mEnhancer virus was able to sufficiently immortalize primary T-lymphocytes in cell culture, the immortalized cells had an altered phenotype (CD8+ T-cells), decreased proviral load, decreased sense and anti-sense gene expression, and altered cell cycle progression compared to HTLV-1.wt immortalized cells (CD4+ T-cells). These results suggest that the HTLV-1 enhancer element alone does not determine persistence or disease development but plays a pivotal role in regulating viral gene expression.
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Affiliation(s)
- Victoria Maksimova
- Department of Veterinary Biosciences, Center for Retrovirus Research, The Ohio State University, Columbus, OH, United States
| | - Susan Smith
- Department of Veterinary Biosciences, Center for Retrovirus Research, The Ohio State University, Columbus, OH, United States
| | - Jaideep Seth
- Department of Veterinary Biosciences, Center for Retrovirus Research, The Ohio State University, Columbus, OH, United States
| | - Cameron Phelps
- Department of Veterinary Biosciences, Center for Retrovirus Research, The Ohio State University, Columbus, OH, United States
| | - Stefan Niewiesk
- Department of Veterinary Biosciences, Center for Retrovirus Research, The Ohio State University, Columbus, OH, United States
| | - Yorifumi Satou
- Division of Genomics and Transcriptomics, Joint Research Center for Human Retrovirus Infection, Kumamoto University, Kumamoto, Japan
| | - Patrick L. Green
- Department of Veterinary Biosciences, Center for Retrovirus Research, The Ohio State University, Columbus, OH, United States
- Comprehensive Cancer Center and Solove Research Institute, The Ohio State University, Columbus, OH, United States
| | - Amanda R. Panfil
- Department of Veterinary Biosciences, Center for Retrovirus Research, The Ohio State University, Columbus, OH, United States
- Comprehensive Cancer Center and Solove Research Institute, The Ohio State University, Columbus, OH, United States
- *Correspondence: Amanda R. Panfil,
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5
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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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6
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Panfil AR, Green PL, Yoder KE. CRISPR Genome Editing Applied to the Pathogenic Retrovirus HTLV-1. Front Cell Infect Microbiol 2020; 10:580371. [PMID: 33425776 PMCID: PMC7785941 DOI: 10.3389/fcimb.2020.580371] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2020] [Accepted: 11/20/2020] [Indexed: 11/13/2022] Open
Abstract
CRISPR editing of retroviral proviruses has been limited to HIV-1. We propose human T-cell leukemia virus type 1 (HTLV-1) as an excellent model to advance CRISPR/Cas9 genome editing technologies against actively expressing and latent retroviral proviruses. HTLV-1 is a tumorigenic human retrovirus responsible for the development of both leukemia/lymphoma (ATL) and a neurological disease (HAM/TSP). The virus immortalizes and persists in CD4+ T lymphocytes that survive for the lifetime of the host. The most important drivers of HTLV-1-mediated transformation and proliferation are the tax and hbz viral genes. Tax, transcribed from the plus-sense or genome strand, is essential for de novo infection and cellular immortalization. Hbz, transcribed from the minus-strand, supports proliferation and survival of infected cells in both its protein and mRNA forms. Abrogating the function or expression of tax and/or hbz by genome editing and mutagenic double-strand break repair may disable HTLV-1-infected cell growth/survival and prevent immune modulatory effects and ultimately HTLV-1-associated disease. In addition, the HTLV-1 viral genome is highly conserved with remarkable sequence homogeneity, both within the same host and even among different HTLV isolates. This offers more focused guide RNA targeting. In addition, there are several well-established animal models for studying HTLV-1 infection in vivo as well as cell immortalization in vitro. Therefore, studies with HTLV-1 may provide a better basis to assess and advance in vivo genome editing against retroviral infections.
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Affiliation(s)
- Amanda R Panfil
- Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, OH, United States.,Center for Retrovirus Research, The Ohio State University, Columbus, OH, United States
| | - Patrick L Green
- Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, OH, United States.,Center for Retrovirus Research, The Ohio State University, Columbus, OH, United States
| | - Kristine E Yoder
- Center for Retrovirus Research, The Ohio State University, Columbus, OH, United States.,Department of Cancer Biology and Genetics, College of Medicine, The Ohio State University, Columbus, OH, United States
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7
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Wu W, Hatterschide J, Syu YC, Cantara WA, Blower RJ, Hanson HM, Mansky LM, Musier-Forsyth K. Human T-cell leukemia virus type 1 Gag domains have distinct RNA-binding specificities with implications for RNA packaging and dimerization. J Biol Chem 2018; 293:16261-16276. [PMID: 30217825 DOI: 10.1074/jbc.ra118.005531] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Revised: 09/13/2018] [Indexed: 12/14/2022] Open
Abstract
Human T-cell leukemia virus type 1 (HTLV-1) is the first retrovirus that has conclusively been shown to cause human diseases. In HIV-1, specific interactions between the nucleocapsid (NC) domain of the Gag protein and genomic RNA (gRNA) mediate gRNA dimerization and selective packaging; however, the mechanism for gRNA packaging in HTLV-1, a deltaretrovirus, is unclear. In other deltaretroviruses, the matrix (MA) and NC domains of Gag are both involved in gRNA packaging, but MA binds nucleic acids with higher affinity and has more robust chaperone activity, suggesting that this domain may play a primary role. Here, we show that the MA domain of HTLV-1, but not the NC domain, binds short hairpin RNAs derived from the putative gRNA packaging signal. RNA probing of the HTLV-1 5' leader and cross-linking studies revealed that the primer-binding site and a region within the putative packaging signal form stable hairpins that interact with MA. In addition to a previously identified palindromic dimerization initiation site (DIS), we identified a new DIS in HTLV-1 gRNA and found that both palindromic sequences bind specifically the NC domain. Surprisingly, a mutant partially defective in dimer formation in vitro exhibited a significant increase in RNA packaging into HTLV-1-like particles, suggesting that efficient RNA dimerization may not be strictly required for RNA packaging in HTLV-1. Moreover, the lifecycle of HTLV-1 and other deltaretroviruses may be characterized by NC and MA functions that are distinct from those of the corresponding HIV-1 proteins, but together provide the functions required for viral replication.
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Affiliation(s)
- Weixin Wu
- From the Department of Chemistry and Biochemistry, Center for Retrovirus Research, and Center for RNA Biology, The Ohio State University, Columbus Ohio 43210 and
| | - Joshua Hatterschide
- From the Department of Chemistry and Biochemistry, Center for Retrovirus Research, and Center for RNA Biology, The Ohio State University, Columbus Ohio 43210 and
| | - Yu-Ci Syu
- From the Department of Chemistry and Biochemistry, Center for Retrovirus Research, and Center for RNA Biology, The Ohio State University, Columbus Ohio 43210 and
| | - William A Cantara
- From the Department of Chemistry and Biochemistry, Center for Retrovirus Research, and Center for RNA Biology, The Ohio State University, Columbus Ohio 43210 and
| | | | - Heather M Hanson
- Institute for Molecular Virology.,Molecular, Cellular, Developmental Biology and Genetics Graduate Program, and
| | - Louis M Mansky
- Institute for Molecular Virology.,Molecular, Cellular, Developmental Biology and Genetics Graduate Program, and.,Masonic Cancer Center, University of Minnesota, Minneapolis, Minnesota 55455
| | - Karin Musier-Forsyth
- From the Department of Chemistry and Biochemistry, Center for Retrovirus Research, and Center for RNA Biology, The Ohio State University, Columbus Ohio 43210 and
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8
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Giam CZ, Semmes OJ. HTLV-1 Infection and Adult T-Cell Leukemia/Lymphoma-A Tale of Two Proteins: Tax and HBZ. Viruses 2016; 8:v8060161. [PMID: 27322308 PMCID: PMC4926181 DOI: 10.3390/v8060161] [Citation(s) in RCA: 99] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Revised: 05/31/2016] [Accepted: 06/01/2016] [Indexed: 12/19/2022] Open
Abstract
HTLV-1 (Human T-cell lymphotropic virus type 1) is a complex human delta retrovirus that currently infects 10–20 million people worldwide. While HTLV-1 infection is generally asymptomatic, 3%–5% of infected individuals develop a highly malignant and intractable T-cell neoplasm known as adult T-cell leukemia/lymphoma (ATL) decades after infection. How HTLV-1 infection progresses to ATL is not well understood. Two viral regulatory proteins, Tax and HTLV-1 basic zipper protein (HBZ), encoded by the sense and antisense viral transcripts, respectively, are thought to play indispensable roles in the oncogenic process of ATL. This review focuses on the roles of Tax and HBZ in viral replication, persistence, and oncogenesis. Special emphasis is directed towards recent literature on the mechanisms of action of these two proteins and the roles of Tax and HBZ in influencing the outcomes of HTLV-1 infection including senescence induction, viral latency and persistence, genome instability, cell proliferation, and ATL development. Attempts are made to integrate results from cell-based studies of HTLV-1 infection and studies of HTLV-1 proviral integration site preference, clonality, and clonal expansion based on high throughput DNA sequencing. Recent data showing that Tax hijacks key mediators of DNA double-strand break repair signaling—the ubiquitin E3 ligase, ring finger protein 8 (RNF8) and the ubiquitin E2 conjugating enzyme (UBC13)—to activate the canonical nuclear factor kappa-light-chain-enhancer of activated B-cells (NF-κB) and other signaling pathways will be discussed. A perspective on how the Tax-RNF8 signaling axis might impact genomic instability and how Tax may collaborate with HBZ to drive oncogenesis is provided.
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Affiliation(s)
- Chou-Zen Giam
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Rd., Bethesda, MD 20814, USA.
| | - Oliver John Semmes
- Department of Microbiology and Molecular Cell Biology, The Leroy T. Canoles Jr Cancer Research Center, Eastern Virginia Medical School, Norfolk, VA 23501, USA.
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9
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Panfil AR, Al-Saleem J, Howard CM, Mates JM, Kwiek JJ, Baiocchi RA, Green PL. PRMT5 Is Upregulated in HTLV-1-Mediated T-Cell Transformation and Selective Inhibition Alters Viral Gene Expression and Infected Cell Survival. Viruses 2015; 8:E7. [PMID: 26729154 PMCID: PMC4728567 DOI: 10.3390/v8010007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Revised: 12/11/2015] [Accepted: 12/18/2015] [Indexed: 11/16/2022] Open
Abstract
Human T-cell leukemia virus type-1 (HTLV-1) is a tumorigenic retrovirus responsible for development of adult T-cell leukemia/lymphoma (ATLL). This disease manifests after a long clinical latency period of up to 2-3 decades. Two viral gene products, Tax and HBZ, have transforming properties and play a role in the pathogenic process. Genetic and epigenetic cellular changes also occur in HTLV-1-infected cells, which contribute to transformation and disease development. However, the role of cellular factors in transformation is not completely understood. Herein, we examined the role of protein arginine methyltransferase 5 (PRMT5) on HTLV-1-mediated cellular transformation and viral gene expression. We found PRMT5 expression was upregulated during HTLV-1-mediated T-cell transformation, as well as in established lymphocytic leukemia/lymphoma cell lines and ATLL patient PBMCs. shRNA-mediated reduction in PRMT5 protein levels or its inhibition by a small molecule inhibitor (PRMT5i) in HTLV-1-infected lymphocytes resulted in increased viral gene expression and decreased cellular proliferation. PRMT5i also had selective toxicity in HTLV-1-transformed T-cells. Finally, we demonstrated that PRMT5 and the HTLV-1 p30 protein had an additive inhibitory effect on HTLV-1 gene expression. Our study provides evidence for PRMT5 as a host cell factor important in HTLV-1-mediated T-cell transformation, and a potential target for ATLL treatment.
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Affiliation(s)
- Amanda R Panfil
- Center for Retrovirus Research, The Ohio State University, Columbus, OH 43210, USA.
- Department of Veterinary Biosciences, The Ohio State University, Columbus, OH 43210, USA.
| | - Jacob Al-Saleem
- Center for Retrovirus Research, The Ohio State University, Columbus, OH 43210, USA.
- Department of Veterinary Biosciences, The Ohio State University, Columbus, OH 43210, USA.
| | - Cory M Howard
- Center for Retrovirus Research, The Ohio State University, Columbus, OH 43210, USA.
- Department of Veterinary Biosciences, The Ohio State University, Columbus, OH 43210, USA.
| | - Jessica M Mates
- Center for Microbial Interface Biology, The Ohio State University, Columbus, OH 43210, USA.
| | - Jesse J Kwiek
- Center for Retrovirus Research, The Ohio State University, Columbus, OH 43210, USA.
- Center for Microbial Interface Biology, The Ohio State University, Columbus, OH 43210, USA.
- Department of Microbiology and Department of Microbial Infection and Immunity, The Ohio State University, Columbus, OH 43210, USA.
| | - Robert A Baiocchi
- Division of Hematology, Department of Internal Medicine, The Ohio State University, Columbus, OH 43210, USA.
- Comprehensive Cancer Center and Solove Research Institute, The Ohio State University, Columbus, OH 43210, USA.
| | - Patrick L Green
- Center for Retrovirus Research, The Ohio State University, Columbus, OH 43210, USA.
- Department of Veterinary Biosciences, The Ohio State University, Columbus, OH 43210, USA.
- Comprehensive Cancer Center and Solove Research Institute, The Ohio State University, Columbus, OH 43210, USA.
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10
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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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11
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O'Connor GM, Seich Al Basatena NK, Olavarria V, MacNamara A, Vine A, Ying Q, Hisada M, Galvão-Castro B, Asquith B, McVicar DW. In contrast to HIV, KIR3DS1 does not influence outcome in HTLV-1 retroviral infection. Hum Immunol 2012; 73:783-7. [PMID: 22609443 PMCID: PMC3402611 DOI: 10.1016/j.humimm.2012.05.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2011] [Revised: 04/30/2012] [Accepted: 05/08/2012] [Indexed: 12/14/2022]
Abstract
While most carriers of human T-cell leukemia virus type 1 (HTLV-1) remain asymptomatic throughout their lifetime, infection is associated with the development of adult T-cell leukemia (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). The exact parameters that determine these outcomes are unknown but are believed to include host genetic factors that control the immune response to infection. Host response to fellow retroviridae member HIV is influenced by the expression of members of the Killer Immunoglobulin Receptor (KIR) family including KIR3DS1. In this study we examined the association of KIR3DS1 with the outcome of HTLV-1 infection in three geographically distinct cohorts (Jamaican, Japanese and Brazilian). Despite increased prevalence of KIR3DS1 in the HAM/TSP patients of the Jamaican cohort, we found no evidence for a role of KIR3DS1 in influencing control of proviral load or disease outcome. This suggests that unlike HIV, KIR3DS1-mediated regulation of HTLV-1 infection does not occur, or is ineffective.
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MESH Headings
- Adolescent
- Adult
- Aged
- Aged, 80 and over
- Asymptomatic Diseases
- Brazil/epidemiology
- Child
- Cohort Studies
- Ethnicity
- Female
- Human T-lymphotropic virus 1/immunology
- Humans
- Jamaica/epidemiology
- Japan/epidemiology
- Leukemia-Lymphoma, Adult T-Cell/complications
- Leukemia-Lymphoma, Adult T-Cell/ethnology
- Leukemia-Lymphoma, Adult T-Cell/immunology
- Leukemia-Lymphoma, Adult T-Cell/virology
- Male
- Middle Aged
- Paraparesis, Tropical Spastic/complications
- Paraparesis, Tropical Spastic/ethnology
- Paraparesis, Tropical Spastic/immunology
- Paraparesis, Tropical Spastic/virology
- Prevalence
- Prognosis
- Receptors, KIR3DS1/genetics
- Receptors, KIR3DS1/immunology
- Spinal Cord Diseases/complications
- Spinal Cord Diseases/ethnology
- Spinal Cord Diseases/immunology
- Spinal Cord Diseases/virology
- Viral Load
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Affiliation(s)
- Geraldine M O'Connor
- Cancer and Inflammation Program, Laboratory of Experimental Immunology, NCI-Frederick, Frederick, MD 21702, USA.
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12
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Yeung ML, Jeang KT. Roles of miRNAs in virus-mediated cellular transformation: lessons from human T-cell leukemia virus type 1. Future Virol 2011. [DOI: 10.2217/fvl.11.109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
miRNAs are small noncoding RNAs of ˜18–25 nucleotides that contribute to the regulation of a diverse variety of biological pathways. Perturbed miRNA expression is seen in many diseases, including cancers. Here, we first discuss the oncogenic and tumor suppressor roles of miRNA, including the roles played by miRNAs in the replication of some oncogenic viruses. Next, using human T-cell leukemia virus type 1 as an example, we discuss the contributions of virus-induced miRNAs in human T-cell leukemia virus type 1-transformation of human cells. Finally, we briefly survey the therapeutic potential of miRNA mimics or anti-miRNAs, antagomirs, to reverse cancer phenotypes.
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Affiliation(s)
- Man Lung Yeung
- State Key Laboratory of Emerging Infectious Diseases, The University of Hong Kong, Hong Kong
- Research Centre of Infection & Immunology, The University of Hong Kong, Hong Kong
- Department of Microbiology, The University of Hong Kong, Hong Kong
- Carol Yu Centre for Infection, The University of Hong Kong, Hong Kong
| | - Kuan-Teh Jeang
- Molecular Virology Section, Laboratory of Molecular Microbiology National Institute of Allergy and Infectious Diseases, National Institutes of Health, Building 4, Room 306, 9000 Rockville Pike, Bethesda, MD 20892–0460, USA
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13
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Zheng ZM. Viral oncogenes, noncoding RNAs, and RNA splicing in human tumor viruses. Int J Biol Sci 2010; 6:730-55. [PMID: 21152115 PMCID: PMC2999850 DOI: 10.7150/ijbs.6.730] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2010] [Accepted: 11/27/2010] [Indexed: 12/13/2022] Open
Abstract
Viral oncogenes are responsible for oncogenesis resulting from persistent virus infection. Although different human tumor viruses express different viral oncogenes and induce different tumors, their oncoproteins often target similar sets of cellular tumor suppressors or signal pathways to immortalize and/or transform infected cells. Expression of the viral E6 and E7 oncogenes in papillomavirus, E1A and E1B oncogenes in adenovirus, large T and small t antigen in polyomavirus, and Tax oncogene in HTLV-1 are regulated by alternative RNA splicing. However, this regulation is only partially understood. DNA tumor viruses also encode noncoding RNAs, including viral microRNAs, that disturb normal cell functions. Among the determined viral microRNA precursors, EBV encodes 25 from two major clusters (BART and BHRF1), KSHV encodes 12 from a latent region, human polyomavirus MCV produce only one microRNA from the late region antisense to early transcripts, but HPVs appears to produce no viral microRNAs.
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Affiliation(s)
- Zhi-Ming Zheng
- Tumor Virus RNA Biology Laboratory, HIV and AIDS Malignancy Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
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14
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Gulzar N, Shroff A, Buberoglu B, Klonowska D, Kim JE, Copeland KFT. Properties of HTLV-I transformed CD8+ T-cells in response to HIV-1 infection. Virology 2010; 406:302-11. [PMID: 20708209 DOI: 10.1016/j.virol.2010.07.029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2010] [Revised: 05/06/2010] [Accepted: 07/20/2010] [Indexed: 10/19/2022]
Abstract
HIV-1 infection studies of primary CD8(+) T-cells are hampered by difficulty in obtaining a significant number of targets for infection and low levels of productive infection. Further, there exists a paucity of CD8-expressing T-cell lines to address questions pertaining to the study of CD8(+) T-cells in the context of HIV-1 infection. In this study, a set of CD8(+) T-cell clones were originated through HTLV-I transformation in vitro, and the properties of these cells were examined. The clones were susceptible to T-cell tropic strains of the virus and exhibited HIV-1 production 20-fold greater than primary CD4(+) T-cells. Productive infection resulted in a decrease in expression of CD8 and CXCR4 molecules on the surface of the CD8(+) T-cell clones and antibodies to these molecules abrogated viral binding and replication. These transformed cells provide an important tool in the study of CD8(+) T-cells and may provide important insights into the mechanism(s) behind HIV-1 induced CD8(+) T-cell dysfunction.
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Affiliation(s)
- N Gulzar
- National HIV and Retrovirology Laboratories, Public Health Agency of Canada, Ottawa, Canada
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15
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Kinjo T, Ham-Terhune J, Peloponese JM, Jeang KT. Induction of reactive oxygen species by human T-cell leukemia virus type 1 tax correlates with DNA damage and expression of cellular senescence marker. J Virol 2010; 84:5431-7. [PMID: 20219913 PMCID: PMC2863840 DOI: 10.1128/jvi.02460-09] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2009] [Accepted: 02/27/2010] [Indexed: 01/29/2023] Open
Abstract
Human T-cell leukemia virus type 1 (HTLV-1) Tax affects cellular genomic stability and senescence. As yet, the mechanism(s) for these events caused by Tax is incompletely understood. Here, we show that Tax expression in primary human cells induces reactive oxygen species (ROS), which elicits DNA damage and the expression of senescence marker. Treatment with a ROS scavenger or knockdown of Tax expression by small interfering RNA (siRNA) abrogated Tax-induced DNA damage and the expression of senescence marker. Our data suggest that ROS induction explains Tax-induced cellular DNA damage and cellular senescence.
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Affiliation(s)
- Takao Kinjo
- Molecular Virology Section, Laboratory of Molecular Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, Division of Pathology and Cell Biology, Graduate School and Faculty of Medicine, University of the Ryukyus, Okinawa 903-0215, Japan, Division of Morphological Pathology, Department of Basic Laboratory Sciences, School of Health Sciences, University of the Ryukyus, Okinawa 903-0215, Japan, CNRS and Université Montpellier 1, UM5236, Centre d'Études d'Agents Pathogènes et Biotechnologies pour la Santé (CPBS), Montpellier F-34965, France, CPBS, Université Montpellier 2, Montpellier F-34095, France
| | - Julia Ham-Terhune
- Molecular Virology Section, Laboratory of Molecular Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, Division of Pathology and Cell Biology, Graduate School and Faculty of Medicine, University of the Ryukyus, Okinawa 903-0215, Japan, Division of Morphological Pathology, Department of Basic Laboratory Sciences, School of Health Sciences, University of the Ryukyus, Okinawa 903-0215, Japan, CNRS and Université Montpellier 1, UM5236, Centre d'Études d'Agents Pathogènes et Biotechnologies pour la Santé (CPBS), Montpellier F-34965, France, CPBS, Université Montpellier 2, Montpellier F-34095, France
| | - Jean-Marie Peloponese
- Molecular Virology Section, Laboratory of Molecular Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, Division of Pathology and Cell Biology, Graduate School and Faculty of Medicine, University of the Ryukyus, Okinawa 903-0215, Japan, Division of Morphological Pathology, Department of Basic Laboratory Sciences, School of Health Sciences, University of the Ryukyus, Okinawa 903-0215, Japan, CNRS and Université Montpellier 1, UM5236, Centre d'Études d'Agents Pathogènes et Biotechnologies pour la Santé (CPBS), Montpellier F-34965, France, CPBS, Université Montpellier 2, Montpellier F-34095, France
| | - Kuan-Teh Jeang
- Molecular Virology Section, Laboratory of Molecular Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, Division of Pathology and Cell Biology, Graduate School and Faculty of Medicine, University of the Ryukyus, Okinawa 903-0215, Japan, Division of Morphological Pathology, Department of Basic Laboratory Sciences, School of Health Sciences, University of the Ryukyus, Okinawa 903-0215, Japan, CNRS and Université Montpellier 1, UM5236, Centre d'Études d'Agents Pathogènes et Biotechnologies pour la Santé (CPBS), Montpellier F-34965, France, CPBS, Université Montpellier 2, Montpellier F-34095, France
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16
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Kinetic analysis of human T-cell leukemia virus type 1 gene expression in cell culture and infected animals. J Virol 2009; 83:3788-97. [PMID: 19193802 DOI: 10.1128/jvi.02315-08] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Human T-cell leukemia virus type 1 (HTLV-1) infection causes adult T-cell leukemia and is associated with a variety of lymphocyte-mediated disorders. It has been hypothesized that a highly regulated pattern of HTLV-1 gene expression is critical for virus survival and disease pathogenesis. In this study, real-time reverse transcriptase PCR was used to determine the kinetics of viral gene expression in cells transiently transfected with an HTLV-1 proviral plasmid, in newly infected human peripheral blood mononuclear cells (PBMCs), and in PBMCs from newly infected rabbits. The HTLV-1 gene expression profiles in transiently transfected and infected cells were similar; over time, all transcripts increased and then maintained stable levels. gag/pol, tax/rex, and env mRNA were detected first and at the highest levels, whereas the expression levels of the accessory genes, including the antisense Hbz, were significantly lower than the tax/rex levels (ranging from 1 to 4 logs depending on the specific mRNA). In infected rabbits, tax/rex and gag/pol mRNA levels peaked early after inoculation and progressively decreased, which correlated inversely with the proviral load and host antibody response against viral proteins. Interestingly, Hbz mRNA was detectable at 1 week postinfection and increased and stabilized. The expression levels of all other HTLV-1 genes in infected rabbit PBMCs were at or below our limit of detection. This analysis provides insight into viral gene expression under various in vitro and in vivo experimental conditions. Our in vivo data indicate that in infected rabbits, Hbz mRNA expression over time directly correlates with the proviral load, which provides the first evidence linking Hbz expression to proviral load and the survival of the virus-infected cell in the host.
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17
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Yeung ML, Yasunaga JI, Bennasser Y, Dusetti N, Harris D, Ahmad N, Matsuoka M, Jeang KT. Roles for microRNAs, miR-93 and miR-130b, and tumor protein 53-induced nuclear protein 1 tumor suppressor in cell growth dysregulation by human T-cell lymphotrophic virus 1. Cancer Res 2008; 68:8976-85. [PMID: 18974142 DOI: 10.1158/0008-5472.can-08-0769] [Citation(s) in RCA: 153] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A role for microRNAs (miRNA) in human T-cell leukemia virus 1 (HTLV-1)-mediated cellular transformation has not been described. Here, we profiled miRNA expression in HTLV-1-transformed human T-cell lines and primary peripheral blood mononuclear cells from adult T-cell leukemia patients. Analyses of 11 different profiles revealed six miRNAs that were consistently up-regulated. Two of the up-regulated miRNAs (miR-93 and miR-130b) target the 3' untranslated region (3'UTR) of the mRNA for a tumor suppressor protein, tumor protein 53-induced nuclear protein 1 (TP53INP1). A low expression level of TP53INP1 protein was found in HTLV-1-transformed cells. Additionally, when antagomirs were used to knock down miR-93 and miR-130b in these cells, the expression of TP53INP1 was increased, suggesting that the latter is regulated inside cells by the former. A role for TP53INP1 in regulating cell growth was established by experiments that showed that enhanced TP53INP1 expression increased apoptosis. Collectively, the findings implicate a miR-93/miR-130b-TP53INP1 axis that affects the proliferation and survival of HTLV-1-infected/transformed cells.
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Affiliation(s)
- Man Lung Yeung
- Molecular Virology Section, Laboratory of Molecular Microbiology, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, Maryland, USA
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18
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Sheleg SV, Peloponese JM, Chi YH, Li Y, Eckhaus M, Jeang KT. Evidence for cooperative transforming activity of the human pituitary tumor transforming gene and human T-cell leukemia virus type 1 Tax. J Virol 2007; 81:7894-901. [PMID: 17507465 PMCID: PMC1951308 DOI: 10.1128/jvi.00555-07] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Aneuploidy is frequent in cancers. Recently it was found that pituitary tumor transforming gene (PTTG; also called Pds1p or securin) is overexpressed in many different tumors. Human T-cell leukemia virus type 1 (HTLV-1) is a retrovirus that primarily infects CD4+ T lymphocytes and causes adult T-cell leukemia. Here, we report that overexpression of human PTTG cooperated with the HTLV-I Tax oncoprotein in cellular transformation. Coexpression of Tax and PTTG enhanced chromosomal instability and neoplastic changes to levels greater than overexpression of either factor singularly. Cells that overexpressed both PTTG and Tax induced tumors more robustly in nude mice than cells that expressed either PTTG alone or Tax alone.
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Affiliation(s)
- Sergey V Sheleg
- Molecular Virology Section, Laboratory of Molecular Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
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19
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Younis I, Yamamoto B, Phipps A, Green PL. Human T-cell leukemia virus type 1 expressing nonoverlapping tax and rex genes replicates and immortalizes primary human T lymphocytes but fails to replicate and persist in vivo. J Virol 2006; 79:14473-81. [PMID: 16282446 PMCID: PMC1287553 DOI: 10.1128/jvi.79.23.14473-14481.2005] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Human T-cell leukemia virus type 1 (HTLV-1) is an oncogenic retrovirus associated primarily with adult T-cell leukemia and neurological disease. HTLV-1 encodes the positive trans-regulatory proteins Tax and Rex, both of which are essential for viral replication. Tax activates transcription initiation from the viral long terminal repeat and modulates the transcription or activity of a number of cellular genes. Rex regulates gene expression posttranscriptionally by facilitating the cytoplasmic expression of incompletely spliced viral mRNAs. Tax and Rex mutants have been identified that have defective activities or impaired biochemical properties associated with their function. To ultimately determine the contribution of specific protein activities on viral replication and cellular transformation of primary T cells, mutants need to be characterized in the context of an infectious molecular clone. Since the tax and rex genes are in partially overlapping reading frames, mutation in one gene frequently disrupts the other, confounding interpretation of mutational analyses in the context of the virus. Here we generated and characterized a unique proviral clone (H1IT) in which the tax and rex genes were separated by expressing Tax from an internal ribosome entry site. We showed that H1IT expresses both functional Tax and Rex. In short- and long-term coculture assays, H1IT was competent to infect and immortalize primary human T cells similar to wild-type HTLV-1. In contrast, H1IT failed to efficiently replicate and persist in inoculated rabbits, thus emphasizing the importance of temporal and quantitative regulation of specific mRNA for viral survival in vivo.
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Affiliation(s)
- Ihab Younis
- Department of Veterinary Biosciences, The Ohio State University, Columbus, OH 43210, USA
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20
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Arnold J, Yamamoto B, Li M, Phipps AJ, Younis I, Lairmore MD, Green PL. Enhancement of infectivity and persistence in vivo by HBZ, a natural antisense coded protein of HTLV-1. Blood 2006; 107:3976-82. [PMID: 16424388 PMCID: PMC1895283 DOI: 10.1182/blood-2005-11-4551] [Citation(s) in RCA: 152] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Natural antisense viral transcripts have been recognized in retroviruses, including human T-cell leukemia virus type 1 (HTLV-1), HIV-1, and feline immunodeficiency virus (FIV), and have been postulated to encode proteins important for the infection cycle and/or pathogenesis of the virus. The antisense strand of the HTLV-1 genome encodes HBZ, a novel nuclear basic region leucine zipper (b-ZIP) protein that in overexpression assays down-regulates Tax oncoprotein-induced viral transcription. Herein, we investigated the contribution of HBZ to HTLV-1-mediated immortalization of primary T lymphocytes in vitro and HTLV-1 infection in a rabbit animal model. HTLV-1 HBZ mutant viruses were generated and evaluated for viral gene expression, protein production, and immortalization capacity. Biologic properties of HBZ mutant viruses in vitro were indistinguishable from wild-type HTLV-1, providing the first direct evidence that HBZ is dispensable for viral replication and cellular immortalization. Rabbits inoculated with irradiated cells expressing HTLV-1 HBZ mutant viruses became persistently infected. However, these rabbits displayed a decreased antibody response to viral gene products and reduced proviral copies in peripheral blood mononuclear cells (PBMCs) as compared with wild-type HTLV-1-infected animals. Our findings indicated that HBZ was not required for in vitro cellular immortalization, but enhanced infectivity and persistence in inoculated rabbits. This study demonstrates that retroviruses use negative-strand-encoded proteins in the establishment of chronic viral infections.
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Affiliation(s)
- Joshua Arnold
- Department of Veterinary Biosciences, The Ohio State University, 1925 Coffey Road, Columbus, OH 43210, USA
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21
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Abstract
Acute T-lymphoproliferative syndromes are caused by herpesvirus saimiri (HVS) and ateles in neotropical primates; by alcelaphine herpesvirus-1 and ovine herpesvirus-2 strains in domestic cattle and other ungulates; and by the α-herpesvirus of Marek's disease in chickens. T-cell lymphoproliferation caused by these herpesviruses has short incubation periods and a rapid course when compared with retroviral disease. The B-lymphotropic Epstein–Barr virus (EBV) is also associated with some human T-cell malignancies. Analogous to EBV in B cells, HVS isolates of the subgroup C are uniquely capable of transforming human and Old World primate T lymphocytes to continuous growth in cell culture and can provide useful tools for T-cell immunology or gene transfer. Signal transduction pathways stimulated by the viral oncoproteins seem to converge at related cellular effector proteins, in total providing a proproliferative signal. However, the viral oncoproteins most likely evolved to evade immune recognition and to support persistent infection in the natural host, where these viruses are frequently apathogenic.
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Affiliation(s)
- Armin Ensser
- Friedrich-Alexander-Universität Erlangen-Nürnberg, Institut für Klinische und Molekulare Virologie, Schlossgarten 4, 91054 Erlangen, Germany
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22
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Azran I, Schavinsky-Khrapunsky Y, Aboud M. Role of Tax protein in human T-cell leukemia virus type-I leukemogenicity. Retrovirology 2004; 1:20. [PMID: 15310405 PMCID: PMC514576 DOI: 10.1186/1742-4690-1-20] [Citation(s) in RCA: 123] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2004] [Accepted: 08/13/2004] [Indexed: 11/17/2022] Open
Abstract
HTLV-1 is the etiological agent of adult T-cell leukemia (ATL), the neurological syndrome TSP/HAM and certain other clinical disorders. The viral Tax protein is considered to play a central role in the process leading to ATL. Tax modulates the expression of many viral and cellular genes through the CREB/ATF-, SRF- and NF-κB-associated pathways. In addition, Tax employs the CBP/p300 and p/CAF co-activators for implementing the full transcriptional activation competence of each of these pathways. Tax also affects the function of various other regulatory proteins by direct protein-protein interaction. Through these activities Tax sets the infected T-cells into continuous uncontrolled replication and destabilizes their genome by interfering with the function of telomerase and topoisomerase-I and by inhibiting DNA repair. Furthermore, Tax prevents cell cycle arrest and apoptosis that would otherwise be induced by the unrepaired DNA damage and enables, thereby, accumulation of mutations that can contribute to the leukemogenic process. Together, these capacities render Tax highly oncogenic as reflected by its ability to transform rodent fibroblasts and primary human T-cells and to induce tumors in transgenic mice. In this article we discuss these effects of Tax and their apparent contribution to the HTLV-1 associated leukemogenic process. Notably, however, shortly after infection the virus enters into a latent state, in which viral gene expression is low in most of the HTLV-1 carriers' infected T-cells and so is the level of Tax protein, although rare infected cells may still display high viral RNA. This low Tax level is evidently insufficient for exerting its multiple oncogenic effects. Therefore, we propose that the latent virus must be activated, at least temporarily, in order to elevate Tax to its effective level and that during this transient activation state the infected cells may acquire some oncogenic mutations which can enable them to further progress towards ATL even if the activated virus is re-suppressed after a while. We conclude this review by outlining an hypothetical flow of events from the initial virus infection up to the ultimate ATL development and comment on the risk factors leading to ATL development in some people and to TSP/HAM in others.
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Affiliation(s)
- Inbal Azran
- Department of Microbiology and Immunology and Cancer Research Center, Faculty of Health Sciences, Ben Gurion University of the Negev, Beer Sheva 84105, Israel
| | - Yana Schavinsky-Khrapunsky
- Department of Microbiology and Immunology and Cancer Research Center, Faculty of Health Sciences, Ben Gurion University of the Negev, Beer Sheva 84105, Israel
| | - Mordechai Aboud
- Department of Microbiology and Immunology and Cancer Research Center, Faculty of Health Sciences, Ben Gurion University of the Negev, Beer Sheva 84105, Israel
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