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Garamszegi S, Yen JY, Honko AN, Geisbert JB, Rubins KH, Geisbert TW, Xia Y, Hensley LE, Connor JH. Transcriptional correlates of disease outcome in anticoagulant-treated non-human primates infected with ebolavirus. PLoS Negl Trop Dis 2014; 8:e3061. [PMID: 25079789 PMCID: PMC4117489 DOI: 10.1371/journal.pntd.0003061] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Accepted: 06/18/2014] [Indexed: 01/26/2023] Open
Abstract
Ebola virus (EBOV) infection in humans and non-human primates (NHPs) is highly lethal, and there is limited understanding of the mechanisms associated with pathogenesis and survival. Here, we describe a transcriptomic analysis of NHPs that survived lethal EBOV infection, compared to NHPs that did not survive. It has been previously demonstrated that anticoagulant therapeutics increase the survival rate in EBOV-infected NHPs, and that the characteristic transcriptional profile of immune response changes in anticoagulant-treated NHPs. In order to identify transcriptional signatures that correlate with survival following EBOV infection, we compared the mRNA expression profile in peripheral blood mononuclear cells from EBOV-infected NHPs that received anticoagulant treatment, to those that did not receive treatment. We identified a small set of 20 genes that are highly confident predictors and can accurately distinguish between surviving and non-surviving animals. In addition, we identified a larger predictive signature of 238 genes that correlated with disease outcome and treatment; this latter signature was associated with a variety of host responses, such as the inflammatory response, T cell death, and inhibition of viral replication. Notably, among survival-associated genes were subsets of genes that are transcriptionally regulated by (1) CCAAT/enhancer-binding protein alpha, (2) tumor protein 53, and (3) megakaryoblastic leukemia 1 and myocardin-like protein 2. These pathways merit further investigation as potential transcriptional signatures of host immune response to EBOV infection.
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Affiliation(s)
- Sara Garamszegi
- Bioinformatics Program, Boston University, Boston, Massachusetts, University of America
| | - Judy Y. Yen
- Department of Microbiology, School of Medicine, Boston University, Boston, Massachusetts, University of America
- National Emerging Infectious Diseases Laboratories, Boston University, Boston, Massachusetts, University of America
| | - Anna N. Honko
- U.S. Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, Maryland, United States of America
| | - Joan B. Geisbert
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Kathleen H. Rubins
- National Aeronautics and Space Administration, Houston, Texas, United States of America
| | - Thomas W. Geisbert
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Yu Xia
- Bioinformatics Program, Boston University, Boston, Massachusetts, University of America
- Department of Bioengineering, McGill University, Montreal, Canada
| | - Lisa E. Hensley
- Integrated Research Facility at Fort Detrick, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Fort Detrick, Frederick, Maryland, United States of America
| | - John H. Connor
- Bioinformatics Program, Boston University, Boston, Massachusetts, University of America
- Department of Microbiology, School of Medicine, Boston University, Boston, Massachusetts, University of America
- National Emerging Infectious Diseases Laboratories, Boston University, Boston, Massachusetts, University of America
- * E-mail:
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Zhao T, Coutts A, Xu L, Yu J, Ohshima K, Matsuoka M. HTLV-1 bZIP factor supports proliferation of adult T cell leukemia cells through suppression of C/EBPα signaling. Retrovirology 2013; 10:159. [PMID: 24359396 PMCID: PMC3880043 DOI: 10.1186/1742-4690-10-159] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2013] [Accepted: 12/11/2013] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND Human T-cell leukemia virus type 1 (HTLV-1) is an oncogenic retrovirus etiologically associated with adult T-cell leukemia (ATL). The HTLV-1 bZIP factor (HBZ), which is encoded by minus strand of provirus, is expressed in all ATL cases and supports the proliferation of ATL cells. However, the precise mechanism of growth promoting activity of HBZ is poorly understood. RESULTS In this study, we showed that HBZ suppressed C/EBPα signaling activation induced by either Tax or C/EBPα. As mechanisms of HBZ-mediated C/EBPα inhibition, we found that HBZ physically interacted with C/EBPα and diminished its DNA binding capacity. Luciferase and immunoprecipitation assays revealed that HBZ repressed C/EBPα activation in a Smad3-dependent manner. In addition, C/EBPα was overexpressed in HTLV-1 infected cell lines and fresh ATL cases. HBZ was able to induce C/EBPα transcription by enhancing its promoter activity. Finally, HBZ selectively modulated the expression of C/EBPα target genes, leading to the impairment of C/EBPα-mediated cell growth suppression. CONCLUSION HBZ, by suppressing C/EBPα signaling, supports the proliferation of HTLV-1 infected cells, which is thought to be critical for oncogenesis.
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Affiliation(s)
- Tiejun Zhao
- College of Chemistry and Life Sciences, Zhejiang Normal University, 688 Yingbin Road, Jinhua, Zhejiang 321004, China
- Laboratory of Virus Control, Institute for Virus Research, Kyoto University, 53 Shogoin Kawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan
| | - Aaron Coutts
- Laboratory of Virus Control, Institute for Virus Research, Kyoto University, 53 Shogoin Kawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan
- Present address: School of Medicine, The University of Queensland, Herston 4006, Australia
| | - Lingling Xu
- College of Chemistry and Life Sciences, Zhejiang Normal University, 688 Yingbin Road, Jinhua, Zhejiang 321004, China
| | - Juntao Yu
- College of Chemistry and Life Sciences, Zhejiang Normal University, 688 Yingbin Road, Jinhua, Zhejiang 321004, China
| | - Koichi Ohshima
- Department of Pathology, School of Medicine, Kurume University, 67 Asahimachi, Kurume, Fukuoka 830-0011, Japan
| | - Masao Matsuoka
- Laboratory of Virus Control, Institute for Virus Research, Kyoto University, 53 Shogoin Kawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan
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3
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Forlani G, Abdallah R, Accolla RS, Tosi G. The MHC-II transactivator CIITA, a restriction factor against oncogenic HTLV-1 and HTLV-2 retroviruses: similarities and differences in the inhibition of Tax-1 and Tax-2 viral transactivators. Front Microbiol 2013; 4:234. [PMID: 23986750 PMCID: PMC3749491 DOI: 10.3389/fmicb.2013.00234] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Accepted: 07/30/2013] [Indexed: 11/13/2022] Open
Abstract
The activation of CD4(+) T helper cells is strictly dependent on the presentation of antigenic peptides by MHC class II (MHC-II) molecules. MHC-II expression is primarily regulated at the transcriptional level by the AIR-1 gene product CIITA (class II transactivator). Thus, CIITA plays a pivotal role in the triggering of the adaptive immune response against pathogens. Besides this well known function, we recently found that CIITA acts as an endogenous restriction factor against HTLV-1 (human T cell lymphotropic virus type 1) and HTLV-2 oncogenic retroviruses by targeting their viral transactivators Tax-1 and Tax-2, respectively. Here we review our findings on CIITA-mediated inhibition of viral replication and discuss similarities and differences in the molecular mechanisms by which CIITA specifically counteracts the function of Tax-1 and Tax-2 molecules. The dual function of CIITA as a key regulator of adaptive and intrinsic immunity represents a rather unique example of adaptation of host-derived factors against pathogen infections during evolution.
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Affiliation(s)
| | | | - Roberto S. Accolla
- Laboratory of General Pathology and Immunology, Department of Surgical and Morphological Sciences, University of InsubriaVarese, Italy
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4
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Hieshima K, Nagakubo D, Shigeta A, Tanaka Y, Hoshino H, Tsukasaki K, Yamada Y, Yoshie O. c-Maf suppresses human T-cell leukemia virus type 1 Tax by competing for CREB-binding protein. Cancer Sci 2011; 102:890-4. [DOI: 10.1111/j.1349-7006.2011.01873.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
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5
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Liu Y, Nonnemacher MR, Wigdahl B. CCAAT/enhancer-binding proteins and the pathogenesis of retrovirus infection. Future Microbiol 2009; 4:299-321. [PMID: 19327116 DOI: 10.2217/fmb.09.4] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Previous studies indicate that two upstream CCAAT/enhancer-binding protein (C/EBP) sites and C/EBPbeta are required for subtype B HIV-1 gene expression in cells of the monocyte-macrophage lineage. The mechanisms of C/EBP regulation of HIV-1 transcription and replication remain unclear. This review focuses on studies concerning the role of C/EBP factors in HIV-1, human T-cell leukemia virus type 1, and SIV transcription in various cell types and tissues cultured in vitro, animal models and during human infection. The structure and function of the C/EBPbeta gene and the related protein isoforms are discussed along with the transcription factors, coactivators, viral proteins, cytokines and chemokines that affect C/EBP function.
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Affiliation(s)
- Yujie Liu
- Department of Microbiology & Immunology, Center for Molecular Virology & Neuroimmunology, Center for Cancer Biology, Philadelphia, PA 19129, USA
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6
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Lepoutre V, Jain P, Quann K, Wigdahl B, Khan ZK. Role of resident CNS cell populations in HTLV-1-associated neuroinflammatory disease. Front Biosci (Landmark Ed) 2009; 14:1152-68. [PMID: 19273122 DOI: 10.2741/3300] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Human T cell leukemia virus type 1 (HTLV-1), the first human retrovirus discovered, is the etiologic agent for a number of disorders; the two most common pathologies include adult T cell leukemia (ATL) and a progressive demyelinating neuroinflammatory disease, HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). The neurologic dysfunction associated with HAM/TSP is a result of viral intrusion into the central nervous system (CNS) and the generation of a hyperstimulated host response within the peripheral and central nervous system that includes expanded populations of CD4+ and CD8+ T cells and proinflammatory cytokines/chemokines in the cerebrospinal fluid (CSF). This robust, yet detrimental immune response likely contributes to the death of myelin producing oligodendrocytes and degeneration of neuronal axons. The mechanisms of neurological degeneration in HAM/TSP have yet to be fully delineated in vivo and may involve the immunogenic properties of the HTLV-1 transactivator protein Tax. This comprehensive review characterizes the available knowledge to date concerning the effects of HTLV-1 on CNS resident cell populations with emphasis on both viral and host factors contributing to the genesis of HAM/TSP.
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Affiliation(s)
- Veronique Lepoutre
- Department of Microbiology and Immunology, Institute for Molecular Medicine and Infectious Disease, Drexel University College of Medicine, Philadelphia, Pennsylvania 19102, USA
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7
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Boxus M, Twizere JC, Legros S, Dewulf JF, Kettmann R, Willems L. The HTLV-1 Tax interactome. Retrovirology 2008; 5:76. [PMID: 18702816 PMCID: PMC2533353 DOI: 10.1186/1742-4690-5-76] [Citation(s) in RCA: 195] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2008] [Accepted: 08/14/2008] [Indexed: 12/22/2022] Open
Abstract
The Tax1 oncoprotein encoded by Human T-lymphotropic virus type I is a major determinant of viral persistence and pathogenesis. Tax1 affects a wide variety of cellular signalling pathways leading to transcriptional activation, proliferation and ultimately transformation. To carry out these functions, Tax1 interacts with and modulates activity of a number of cellular proteins. In this review, we summarize the present knowledge of the Tax1 interactome and propose a rationale for the broad range of cellular proteins identified so far.
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Affiliation(s)
- Mathieu Boxus
- University Academia Wallonie-Europe, Molecular and Cellular Biology at FUSAGx, Gembloux, Belgium.
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8
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Barbeau B, Mesnard JM. Does the HBZ gene represent a new potential target for the treatment of adult T-cell leukemia? Int Rev Immunol 2008; 26:283-304. [PMID: 18027202 DOI: 10.1080/08830180701690843] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Links between human T-cell leukemia virus type 1 and adult T-cell leukemia (ATL) were first suspected in 1980. Provirus integration has since been found in all ATL cells. Although the viral Tax protein is involved in the proliferation of the infected cells during the preleukemic stage, Tax expression is not systematically detected in primary leukemic cells. Recent studies found that the viral HBZ gene was always expressed in leukemic cells, suggesting its involvement in the progression of the infected cells toward malignancy. How could this new discovery be translated into possible new avenues for the prevention or treatment of ATL?
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Affiliation(s)
- Benoit Barbeau
- Département des Sciences Biologiques, Université du Québec à Montréal, Montréal, Canada
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9
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Pandya D, Rahman S, Wigdahl B, Khan ZK, Jain P. New insights into the pathogenesis, diagnosis and treatment of human T-cell leukemia virus type 1-induced disease. Future Virol 2007. [DOI: 10.2217/17460794.2.5.481] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
It has been over 25 years since the discovery of human T-cell leukemia virus type 1 (HTLV-1); however, the exact sequence of events that occur during primary infection, clinical latency or the development of disease remains unresolved. The advances in molecular virology and neuroimmunology have contributed significantly to our understanding of HTLV-1 pathogenesis, but also uncovered the complexity of the virus–host interaction both in the peripheral blood and the CNS. Here, we overview the general pathologic features of HTLV-1, molecular mechanisms of oncogenic transformation and characteristics of the host immune response during the associated neuroinflammatory process. We also discuss both current and new approaches in the diagnosis and therapy of HTLV-1 associated diseases – adult T-cell leukemia and HTLV-1-associated myelopathy/tropical spastic paraparesis. Finally, potentially important emerging areas of research that may have an impact on our understanding of the pathogenic mechanism have been briefly introduced.
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Affiliation(s)
- Devanshi Pandya
- Drexel University College of Medicine, Department of Microbiology & Immunology, and, Center for Cancer Biology, Institute for Molecular Medicine & Infectious Disease, Philadelphia, PA 19102, USA
| | - Saifur Rahman
- Drexel University College of Medicine, Department of Microbiology & Immunology, and, Center for Cancer Biology, Institute for Molecular Medicine & Infectious Disease, Philadelphia, PA 19102, USA
| | - Brian Wigdahl
- Drexel University College of Medicine, Department of Microbiology & Immunology, and, Center for Cancer Biology, Institute for Molecular Medicine & Infectious Disease, Philadelphia, PA 19102, USA
| | - Zafar K Khan
- Drexel University College of Medicine, Department of Microbiology & Immunology, and, Center for Cancer Biology, Institute for Molecular Medicine & Infectious Disease, Philadelphia, PA 19102, USA
| | - Pooja Jain
- Drexel University College of Medicine, Department of Microbiology & Immunology, Institute for Molecular Medicine & Infectious Disease, New College Building, Room 18311, 245 North 15th Street, Philadelphia, PA 19102, USA
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10
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Lemasson I, Lewis MR, Polakowski N, Hivin P, Cavanagh MH, Thébault S, Barbeau B, Nyborg JK, Mesnard JM. Human T-cell leukemia virus type 1 (HTLV-1) bZIP protein interacts with the cellular transcription factor CREB to inhibit HTLV-1 transcription. J Virol 2006; 81:1543-53. [PMID: 17151132 PMCID: PMC1797566 DOI: 10.1128/jvi.00480-06] [Citation(s) in RCA: 141] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The complex human T-cell leukemia virus type 1 (HTLV-1) retrovirus encodes several proteins that are unique to the virus within its 3'-end region. Among them, the viral transactivator Tax and posttranscriptional regulator Rex are well characterized, and both positively regulate HTLV-1 viral expression. Less is known about the other regulatory proteins encoded in this region of the provirus, including the recently discovered HBZ protein. HBZ has been shown to negatively regulate basal and Tax-dependent HTLV-1 transcription through its ability to interact with specific basic-leucine zipper (bZIP) proteins. In the present study, we found that HBZ reduces HTLV-1 transcription and virion production. We then characterized the interaction between HBZ and the cellular transcription factor CREB. CREB plays a critical role in Tax-mediated HTLV-1 transcription by forming a complex with Tax that binds to viral cyclic AMP-response elements (CREs) located within the viral promoter. We found that HBZ and CREB interact in vivo and directly in vitro, and this interaction occurs through the bZIP domain of each protein. We also found that CREM-Ia and ATF-1, which share significant homology in their bZIP domains with the bZIP domain of CREB, interact with HBZ-bZIP. The interaction between CREB and HBZ prevents CREB binding to the viral CRE elements in vitro and in vivo, suggesting that the reduction in HTLV-1 transcription by HBZ is partly due to the loss of CREB at the promoter. We also found that HBZ displaces CREB from a cellular CRE, suggesting that HBZ may deregulate CREB-dependent cellular gene expression.
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Affiliation(s)
- Isabelle Lemasson
- East Carolina University, Department of Microbiology and Immunology, Brody School of Medicine, 600 Moye Blvd., Greenville, NC 27834, USA.
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11
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Grant C, Nonnemacher M, Jain P, Pandya D, Irish B, Williams SC, Wigdahl B. CCAAT/enhancer-binding proteins modulate human T cell leukemia virus type 1 long terminal repeat activation. Virology 2006; 348:354-69. [PMID: 16458341 DOI: 10.1016/j.virol.2005.12.024] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2005] [Revised: 09/06/2005] [Accepted: 12/09/2005] [Indexed: 10/25/2022]
Abstract
CCAAT/enhancer-binding protein (C/EBP) basic region/leucine zipper (bZIP) transcription factors have been shown to form heterodimers with cAMP-responsive element binding protein 2 (CREB-2), a transcription factor involved in regulating basal and Tax-mediated transactivation of the human T cell leukemia virus type 1 (HTLV-1) long terminal repeat (LTR). In cells of the monocyte-macrophage lineage (proposed to play a role in HTLV-1 pathogenesis as an accessory target cell), several members of the C/EBP family are expressed at high levels and may have functional impact on both basal and Tax-mediated transactivation of the HTLV-1 LTR. Basal activation of the HTLV-1 LTR was enhanced by overexpression of C/EBPbeta, C/EBPdelta, or C/EBPepsilon, whereas transactivation of the LTR by Tax was inhibited by overexpression of C/EBPalpha and C/EBPbeta. Inhibition of Tax-mediated transactivation of the HTLV-1 LTR was co-activator-independent, did not require C/EBP binding to the Tax-responsive elements, and may involve heterodimerization with CREB factors.
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Affiliation(s)
- Christian Grant
- Department of Microbiology and Immunology, The Pennsylvania State University, College of Medicine, Hershey, 17033, USA
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12
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Abstract
Adult T-cell leukemia (ATL) is an aggressive hematologic malignancy caused by human T-cell leukemia virus type I (HTLV-1). Tax, encoded by the HTLV-1 pX region, has been recognized by its pleiotropic actions to play a critical role in leukemogenesis. Three highly conserved 21-bp repeat elements located within the long terminal repeat, commonly referred to as Tax-responsive element 1 (TRE-1), are critical to Tax-mediated viral transcriptional activation through complex interaction with cyclic AMP-responsive element binding protein (CREB), CBP/p300 and PCAF. Tax has also been shown to activate transcription from a number of critical cellular genes through the NF-kappaB and serum-responsive factor pathways. Tax transactivation has been attributed to the protein's interaction with transcription factors, chromatin remodeling complexes, cell cycle and repair genes. In this review, we will discuss some of the latest findings on this fascinating viral activator and highlight its regulation of cellular factors including CREB, p300/CBP and their effect on RNA polymerase II and chromatin remodeling, as well as its role in cytoplasmic and nuclear function. We will highlight the possible contribution of each factor, discuss Tax's critical peptide domains and highlight its post-transcriptional modifications. It is quite obvious that, collectively, Tax's effects on a wide variety of cellular targets cooperate in promoting cell proliferation and leukemogenesis. In addition, the post-transcriptional effects of Rex play an important role in virus replication. Understanding these interactions at a molecular level will facilitate the targeted development of drugs to effectively inhibit or treat ATL.
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Affiliation(s)
- Fatah Kashanchi
- Department of Biochemistry and Molecular Biology, The George Washington University School of Medicine, 2300 Eye St, NW, Ross Hall, Washington, DC, USA.
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13
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Forgacs E, Gupta SK, Kerry JA, Semmes OJ. The bZIP transcription factor ATFx binds human T-cell leukemia virus type 1 (HTLV-1) Tax and represses HTLV-1 long terminal repeat-mediated transcription. J Virol 2005; 79:6932-9. [PMID: 15890932 PMCID: PMC1112100 DOI: 10.1128/jvi.79.11.6932-6939.2005] [Citation(s) in RCA: 14] [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
The human T-cell leukemia virus type 1 (HTLV-1) viral protein Tax is a transactivator of transcription driven by the cognate viral long terminal repeat (LTR). Tax exerts its effect through three nonidentical copies of the Tax-responsive element (TxRE), a member of the asymmetric cyclic AMP response element (CRE) family of enhancer sequences. Transactivation is mediated via interaction of Tax with members of the CREB/ATF family bound to TxRE. We have identified a cellular repressor of transcription, activating transcription factor x (ATFx), as a novel Tax-binding protein. In addition to binding directly to Tax we show by electrophoretic mobility shift assay that ATFx binds to the TxRE enhancer element via the bZIP domain. The functional impact of this bridging interaction results in repression of both basal and Tax-induced transcription from the HTLV-1 LTR. ATFx is unique among ATF family of proteins in that it is cell cycle regulated and exerts a tight repressive control over apoptotic signaling. We propose that recruitment of ATFx to the HTLV-1 LTR serves to link viral transcription with critical events in cellular homeostasis.
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Affiliation(s)
- Eva Forgacs
- Department of Microbiology and Molecular Cell Biology, Eastern Virginia Medical School, Norfolk, VA, USA
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Hivin P, Frédéric M, Arpin-André C, Basbous J, Gay B, Thébault S, Mesnard JM. Nuclear localization of HTLV-I bZIP factor (HBZ) is mediated by three distinct motifs. J Cell Sci 2005; 118:1355-62. [PMID: 15755797 DOI: 10.1242/jcs.01727] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The genome of the human T-cell leukemia virus type I (HTLV-I) codes for a basic leucine zipper protein, HBZ, capable of repressing JUN activity and viral transcription. Transient expression in mammalian cells showed that HBZ was targeted to the nucleus, where it accumulated in nuclear speckles. By using a complementary set of deletion mutants, we report here that the nuclear targeting of HBZ is mediated by three distinct nuclear localization signals and that at least two are necessary for the translocation of HBZ to the nucleus. Moreover, the resulting mutant proteins distribute throughout the nucleoplasm and/or into the nucleoli, whereas the wild-type HBZ exclusively accumulates in nuclear speckles, suggesting that the integrity of the protein is required for its speckle localization. We also demonstrate that the HBZ-containing speckles do not correspond to Cajal bodies, splicing factor compartments, or promyelocytic leukemia oncoprotein bodies. Unexpectedly, by using immunogold electron microscopy, we found HBZ localized to heterochromatin. Until now, such characteristics had never been described for a transcription factor and could explain the inhibitory activity of HBZ.
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Affiliation(s)
- Patrick Hivin
- Laboratoire Infections Rétrovirales et Signalisation Cellulaire, CNRS/UM I UMR 5121/IFR 122, Institut de Biologie, 34960 Montpellier Cedex 2, France
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