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Mohanty S, Suklabaidya S, Lavorgna A, Ueno T, Fujisawa JI, Ngouth N, Jacobson S, Harhaj EW. The tyrosine kinase KDR is essential for the survival of HTLV-1-infected T cells by stabilizing the Tax oncoprotein. Nat Commun 2024; 15:5380. [PMID: 38918393 PMCID: PMC11199648 DOI: 10.1038/s41467-024-49737-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2023] [Accepted: 06/18/2024] [Indexed: 06/27/2024] Open
Abstract
Human T-cell leukemia virus type 1 (HTLV-1) infection is linked to the development of adult T-cell leukemia/lymphoma (ATLL) and the neuroinflammatory disease, HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). The HTLV-1 Tax oncoprotein regulates viral gene expression and persistently activates NF-κB to maintain the viability of HTLV-1-infected T cells. Here, we utilize a kinome-wide shRNA screen to identify the tyrosine kinase KDR as an essential survival factor of HTLV-1-transformed cells. Inhibition of KDR specifically induces apoptosis of Tax expressing HTLV-1-transformed cell lines and CD4 + T cells from HAM/TSP patients. Furthermore, inhibition of KDR triggers the autophagic degradation of Tax resulting in impaired NF-κB activation and diminished viral transmission in co-culture assays. Tax induces the expression of KDR, forms a complex with KDR, and is phosphorylated by KDR. These findings suggest that Tax stability is dependent on KDR activity which could be exploited as a strategy to target Tax in HTLV-1-associated diseases.
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Affiliation(s)
- Suchitra Mohanty
- Department of Microbiology and Immunology, Penn State College School of Medicine, Hershey, PA, USA
| | - Sujit Suklabaidya
- Department of Microbiology and Immunology, Penn State College School of Medicine, Hershey, PA, USA
| | - Alfonso Lavorgna
- Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins School of Medicine, Baltimore, MD, USA
- Millipore-Sigma, Rockville, MD, USA
| | - Takaharu Ueno
- Department of Microbiology, Kansai Medical University, Osaka, Japan
| | | | - Nyater Ngouth
- Viral Immunology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - Steven Jacobson
- Viral Immunology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - Edward W Harhaj
- Department of Microbiology and Immunology, Penn State College School of Medicine, Hershey, PA, USA.
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Gene Expression Landscape of Chronic Myeloid Leukemia K562 Cells Overexpressing the Tumor Suppressor Gene PTPRG. Int J Mol Sci 2022; 23:ijms23179899. [PMID: 36077295 PMCID: PMC9456469 DOI: 10.3390/ijms23179899] [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: 06/30/2022] [Revised: 08/09/2022] [Accepted: 08/15/2022] [Indexed: 11/24/2022] Open
Abstract
This study concerns the analysis of the modulation of Chronic Myeloid Leukemia (CML) cell model K562 transcriptome following transfection with the tumor suppressor gene encoding for Protein Tyrosine Phosphatase Receptor Type G (PTPRG) and treatment with the tyrosine kinase inhibitor (TKI) Imatinib. Specifically, we aimed at identifying genes whose level of expression is altered by PTPRG modulation and Imatinib concentration. Statistical tests as differential expression analysis (DEA) supported by gene set enrichment analysis (GSEA) and modern methods of ontological term analysis are presented along with some results of current interest for forthcoming experimental research in the field of the transcriptomic landscape of CML. In particular, we present two methods that differ in the order of the analysis steps. After a gene selection based on fold-change value thresholding, we applied statistical tests to select differentially expressed genes. Therefore, we applied two different methods on the set of differentially expressed genes. With the first method (Method 1), we implemented GSEA, followed by the identification of transcription factors. With the second method (Method 2), we first selected the transcription factors from the set of differentially expressed genes and implemented GSEA on this set. Method 1 is a standard method commonly used in this type of analysis, while Method 2 is unconventional and is motivated by the intention to identify transcription factors more specifically involved in biological processes relevant to the CML condition. Both methods have been equipped in ontological knowledge mining and word cloud analysis, as elements of novelty in our analytical procedure. Data analysis identified RARG and CD36 as a potential PTPRG up-regulated genes, suggesting a possible induction of cell differentiation toward an erithromyeloid phenotype. The prediction was confirmed at the mRNA and protein level, further validating the approach and identifying a new molecular mechanism of tumor suppression governed by PTPRG in a CML context.
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Characterizing the Interaction between the HTLV-1 Transactivator Tax-1 with Transcription Elongation Factor ELL2 and Its Impact on Viral Transactivation. Int J Mol Sci 2021; 22:ijms222413597. [PMID: 34948391 PMCID: PMC8705299 DOI: 10.3390/ijms222413597] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Revised: 12/12/2021] [Accepted: 12/15/2021] [Indexed: 11/16/2022] Open
Abstract
The human T-cell leukemia virus type 1 (HTLV-1)-encoded transactivator and oncoprotein Tax-1 is essential for HTLV-1 replication. We recently found that Tax-1 interacts with transcription elongation factor for RNA polymerase II 2, ELL2, which enhances Tax-1-mediated transactivation of the HTLV-1 promotor. Here, we characterize the Tax-1:ELL2 interaction and its impact on viral transactivation by confocal imaging, co-immunoprecipitation, and luciferase assays. We found that Tax-1 and ELL2 not only co-precipitate, but also co-localize in dot-like structures in the nucleus. Tax-1:ELL2 complex formation occurred independently of Tax-1 point mutations, which are crucial for post translational modifications (PTMs) of Tax-1, suggesting that these PTMs are irrelevant for Tax-1:ELL2 interaction. In contrast, Tax-1 deletion mutants lacking either N-terminal (aa 1-37) or C-terminal regions (aa 150-353) of Tax-1 were impaired in interacting with ELL2. Contrary to Tax-1, the related, non-oncogenic Tax-2B from HTLV-2B did not interact with ELL2. Finally, we found that ELL2-R1 (aa 1-353), which carries an RNA polymerase II binding domain, and ELL2-R3 (aa 515-640) are sufficient to interact with Tax-1; however, only ELL2-truncations expressing R1 could enhance Tax-1-mediated transactivation of the HTLV-1 promoter. Together, this study identifies domains in Tax-1 and ELL2 being required for Tax-1:ELL2 complex formation and for viral transactivation.
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Mohanty S, Harhaj EW. Mechanisms of Oncogenesis by HTLV-1 Tax. Pathogens 2020; 9:E543. [PMID: 32645846 PMCID: PMC7399876 DOI: 10.3390/pathogens9070543] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Revised: 06/24/2020] [Accepted: 07/01/2020] [Indexed: 01/23/2023] Open
Abstract
The human T-cell lymphotropic virus type 1 (HTLV-1) is the etiological agent of adult T-cell leukemia/lymphoma (ATLL), a neoplasm of CD4+CD25+ T cells that occurs in 2-5% of infected individuals after decades of asymptomatic latent infection. Multiple HTLV-1-encoded regulatory proteins, including Tax and HTLV-1 basic leucine zipper factor (HBZ), play key roles in viral persistence and latency. The HTLV-1 Tax oncoprotein interacts with a plethora of host cellular proteins to regulate viral gene expression and also promote the aberrant activation of signaling pathways such as NF-κB to drive clonal proliferation and survival of T cells bearing the HTLV-1 provirus. Tax undergoes various post-translational modifications such as phosphorylation and ubiquitination that regulate its function and subcellular localization. Tax shuttles in different subcellular compartments for the activation of anti-apoptotic genes and deregulates the cell cycle with the induction of DNA damage for the accumulation of genomic instability that can result in cellular immortalization and malignant transformation. However, Tax is highly immunogenic and therefore HTLV-1 has evolved numerous strategies to tightly regulate Tax expression while maintaining the pool of anti-apoptotic genes through HBZ. In this review, we summarize the key findings on the oncogenic mechanisms used by Tax that set the stage for the development of ATLL, and the strategies used by HTLV-1 to tightly regulate Tax expression for immune evasion and viral persistence.
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Affiliation(s)
| | - Edward W. Harhaj
- Department of Microbiology and Immunology, Penn State College of Medicine, Hershey, PA 17033, USA;
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5
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Araújo THA, Barreto FK, Menezes ADL, Lima CPSD, Oliveira RSD, Lemos PDS, Galvão-Castro B, Kashima S, Farre L, Bittencourt AL, Carvalho EMD, Santos LA, Rego FFDA, Mota-Miranda ACA, Nunes MRT, Alcântara LCJ. Complete genome sequence of human T-cell lymphotropic type 1 from patients with different clinical profiles, including infective dermatitis. INFECTION GENETICS AND EVOLUTION 2019; 79:104166. [PMID: 31883457 DOI: 10.1016/j.meegid.2019.104166] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Revised: 12/16/2019] [Accepted: 12/24/2019] [Indexed: 12/12/2022]
Abstract
The HTLV-1 is the first human retrovirus and is associated with several clinical syndromes, however, the pathogenesis of these clinical manifestations is still not fully understood. Furthermore, there are few complete genomes publicly available, about 0.12 complete genomes per 10,000 infected individuals and the databases have a major deficiency of sequences information. This study generated and characterized 31 HTLV-1 complete genomes sequences derived from individuals with Tropical Spastic Paraparesis/HTLV-1-Associated Myelopathy (TSP/HAM), Adult T-cell leukemia/lymphoma (ATL), infective dermatitis associated to HTLV-1 (IDH) and asymptomatic patients. These sequences are associated to clinical and epidemiological information about the patients. The sequencing data generated on Ion Torrent PGM platform were assembled and mapped against the reference HTLV-1 genome. These sequences were genotyped as Cosmopolitan subtype, Transcontinental subgroup. We identified the variants in the coding regions of the genome of the different clinical profiles, however, no statistical relation was detected. This study contributed to increase of HTLV-1 complete genomes in the world. Furthermore, to better investigate the contribution of HTLV-1 mutations for the disease outcome it is necessary to evaluate the interaction of the viral genome and characteristics of the human host.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Lourdes Farre
- Fundação Oswaldo Cruz, Brazil; Catalan Institute of Oncology, Bellvitge Biomedical Research Institute, Barcelona, Spain
| | | | | | - Luciane Amorim Santos
- Fundação Oswaldo Cruz, Brazil; Escola Bahiana de Medicina e Saúde Pública Salvador, Brazil
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Martinez MP, Al-Saleem J, Green PL. Comparative virology of HTLV-1 and HTLV-2. Retrovirology 2019; 16:21. [PMID: 31391116 PMCID: PMC6686503 DOI: 10.1186/s12977-019-0483-0] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Accepted: 08/01/2019] [Indexed: 12/22/2022] Open
Abstract
Human T cell leukemia virus type 1 (HTLV-1) was the first discovered human retrovirus and the etiologic agent of adult T-cell leukemia and HTLV-1-associated myelopathy/tropical spastic paraparesis. Shortly after the discovery of HTLV-1, human T-cell leukemia virus type 2 (HTLV-2) was isolated from a patient with hairy cell leukemia. Despite possession of similar structural features to HTLV-1, HTLV-2 has not been definitively associated with lymphoproliferative disease. Since their discovery, studies have been performed with the goal of highlighting the differences between HTLV-1 and HTLV-2. A better understanding of these differences will shed light on the specific pathogenic mechanisms of HTLV-1 and lead to novel therapeutic targets. This review will compare and contrast the two oldest human retroviruses with regards to epidemiology, genomic structure, gene products, and pathobiology.
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Affiliation(s)
- Michael P Martinez
- Center for Retrovirus Research, The Ohio State University, Columbus, OH, USA.,Department of Veterinary Biosciences, The Ohio State University, Columbus, OH, USA
| | - Jacob Al-Saleem
- Center for Retrovirus Research, The Ohio State University, Columbus, OH, USA.,Department of Veterinary Biosciences, The Ohio State University, Columbus, OH, USA
| | - Patrick L Green
- Center for Retrovirus Research, The Ohio State University, Columbus, OH, USA. .,Department of Veterinary Biosciences, The Ohio State University, Columbus, OH, USA. .,Comprehensive Cancer Center, The Ohio State University, Columbus, OH, USA.
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7
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Chen L, Wang C, Luo J, Su W, Li M, Zhao N, Lyu W, Attaran H, He Y, Ding H, He H. Histone Deacetylase 1 Plays an Acetylation-Independent Role in Influenza A Virus Replication. Front Immunol 2017; 8:1757. [PMID: 29312300 PMCID: PMC5733105 DOI: 10.3389/fimmu.2017.01757] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Accepted: 11/27/2017] [Indexed: 12/21/2022] Open
Abstract
Influenza A viruses (IAVs) take advantage of the host acetylation system for their own benefit. Whether the nucleoprotein (NP) of IAVs undergoes acetylation and the interaction between the NP and the class I histone deacetylases (HDACs) were largely unknown. Here, we showed that the NP protein of IAV interacted with HDAC1, which downregulated the acetylation level of NP. Using mass spectrometry, we identified lysine 103 as an acetylation site of the NP. Compared with wild-type protein, two K103 NP mutants, K103A and K103R, enhanced replication efficiency of the recombinant viruses in vitro. We further demonstrated that HDAC1 facilitated viral replication via two paths: promoting the nuclear retention of NP and inhibiting TBK1-IRF3 pathway. Our results lead to a new mechanism for regulating NP acetylation, indicating that HDAC1 may be a possible target for antiviral drugs.
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Affiliation(s)
- Lin Chen
- National Research Center for Wildlife Born Diseases, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.,University of the Chinese Academy of Sciences, Beijing, China
| | - Chengmin Wang
- National Research Center for Wildlife Born Diseases, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Jing Luo
- National Research Center for Wildlife Born Diseases, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Wen Su
- National Research Center for Wildlife Born Diseases, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.,University of the Chinese Academy of Sciences, Beijing, China
| | - Meng Li
- National Research Center for Wildlife Born Diseases, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.,University of the Chinese Academy of Sciences, Beijing, China
| | - Na Zhao
- National Research Center for Wildlife Born Diseases, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.,University of the Chinese Academy of Sciences, Beijing, China
| | - Wenting Lyu
- National Research Center for Wildlife Born Diseases, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.,University of the Chinese Academy of Sciences, Beijing, China
| | - Hamidreza Attaran
- National Research Center for Wildlife Born Diseases, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Yapeng He
- National Research Center for Wildlife Born Diseases, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Hua Ding
- Department of Infectious Diseases, Hangzhou Center for Disease Control and Prevention, Hangzhou, China
| | - Hongxuan He
- National Research Center for Wildlife Born Diseases, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
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8
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Al-Saleem J, Kvaratskhelia M, Green PL. Methods for Identifying and Examining HTLV-1 HBZ Post-translational Modifications. Methods Mol Biol 2017; 1582:111-126. [PMID: 28357666 DOI: 10.1007/978-1-4939-6872-5_9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Post-translational modifications (PTMs) are chemical alterations to individual amino acids that alter a protein's conformation, stability, and/or function. Several pathogenic viruses have been shown to encode proteins with PTMs, including human T-cell leukemia virus type 1 (HTLV-1) Tax and Rex regulatory proteins. HTLV-1 basic leucine zipper protein (HBZ) was hypothesized to feature PTMs due to its functional activities and interactions with cellular transcription factors and acetyltransferases. Here, we describe the approach used to identify, via mass spectrometry, the PTMs of HBZ. In addition, we describe methods to determine the functional relevance of the identified PTMs.
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Affiliation(s)
- 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
| | - Mamuka Kvaratskhelia
- Center for Retrovirus Research, The Ohio State University, Columbus, OH, 43210, USA
- College of Pharmacy, 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.
- Compreshensive Cancer Center and Solove Research Institute, The Ohio State University, Columbus, OH, 43210, USA.
- Department of Molecular Virology, Immunology, and Medical Genetics, The Ohio State University, 127N Veterinary Medicine Academic Building, 1900 Coffey Rd, Columbus, OH, 43210, USA.
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9
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Zhang S, Cui X, Li J, Liang Z, Qiao W, Tan J. Lysine residues K66, K109, and K110 in the bovine foamy virus transactivator protein are required for transactivation and viral replication. Virol Sin 2016; 31:142-9. [PMID: 26980333 DOI: 10.1007/s12250-015-3652-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Accepted: 01/14/2016] [Indexed: 10/22/2022] Open
Abstract
Bovine foamy virus (BFV) is a complex retrovirus that infects cattle. Like all retroviruses, BFV encodes a transactivator Tas protein (BTas) that increases gene transcription from viral promoters. BFV encodes two promoters that can interact with BTas, a conserved promoter in the 5' long terminal repeat (LTR) and a unique internal promoter (IP). Our previous study showed that BTas is acetylated by p300 at residues K66, K109, and K110, which markedly enhanced the ability of BTas to bind to DNA. However, whether these residues are important for BFV replication was not determined. Therefore, in this study we provide direct evidence that BTas is required for BFV replication and demonstrate that residues K66, K109, and K110 are critical for BTas function and BFV replication. Full-length infectious clones were generated, which were BTas deficient or contained lysine to arginine (K→R) mutations at position 66, 109, and/or 110. In vivo data indicated that K→R mutations at positions 66, 109, and 110 in BTas impaired transactivation of both the LTR and IP promoters. In addition, the K→R mutations in full-length infectious clones reduced expression of viral proteins, and the triple mutant and BTas deletion completely abrogated viral replication. Taken together, these results indicate that lysine residues at positions 66, 109, and 110 in the BTas protein are crucial for BFV replication and suggest a potential role for BTas acetylation in regulating the viral life cycle.
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Affiliation(s)
- Suzhen Zhang
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Sciences, Nankai University, Tianjin, 300071, China
| | - Xiaoxu Cui
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Sciences, Nankai University, Tianjin, 300071, China
| | - Jing Li
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Sciences, Nankai University, Tianjin, 300071, China
| | - Zhibin Liang
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Sciences, Nankai University, Tianjin, 300071, China
| | - Wentao Qiao
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Sciences, Nankai University, Tianjin, 300071, China
| | - Juan Tan
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life Sciences, Nankai University, Tianjin, 300071, China.
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The Major Histocompatibility Complex Class II Transactivator CIITA Inhibits the Persistent Activation of NF-κB by the Human T Cell Lymphotropic Virus Type 1 Tax-1 Oncoprotein. J Virol 2016; 90:3708-21. [PMID: 26792751 DOI: 10.1128/jvi.03000-15] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Accepted: 01/18/2016] [Indexed: 01/05/2023] Open
Abstract
UNLABELLED Human T cell lymphotropic virus type 1 (HTLV-1) Tax-1, a key protein in HTLV-1-induced T cell transformation, deregulates diverse cell signaling pathways. Among them, the NF-κB pathway is constitutively activated by Tax-1, which binds to NF-κB proteins and activates the IκB kinase (IKK). Upon phosphorylation-dependent IκB degradation, NF-κB migrates into the nucleus, mediating Tax-1-stimulated gene expression. We show that the transcriptional regulator of major histocompatibility complex class II genes CIITA (class II transactivator), endogenously or ectopically expressed in different cells, inhibits the activation of the canonical NF-κB pathway by Tax-1 and map the region that mediates this effect. CIITA affects the subcellular localization of Tax-1, which is mostly retained in the cytoplasm, and this correlates with impaired migration of RelA into the nucleus. Cytoplasmic and nuclear mutant forms of CIITA reveal that CIITA exploits different strategies to suppress Tax-1-mediated NF-κB activation in both subcellular compartments. CIITA interacts with Tax-1 without preventing Tax-1 binding to both IKKγ and RelA. Nevertheless, CIITA affects Tax-1-induced IKK activity, causing retention of the inactive p50/RelA/IκB complex in the cytoplasm. Nuclear CIITA associates with Tax-1/RelA in nuclear bodies, blocking Tax-1-dependent activation of NF-κB-responsive genes. Thus, CIITA inhibits cytoplasmic and nuclear steps of Tax-1-mediated NF-κB activation. These results, together with our previous finding that CIITA acts as a restriction factor inhibiting Tax-1-promoted HTLV-1 gene expression and replication, indicate that CIITA is a versatile molecule that might also counteract Tax-1 transforming activity. Unveiling the molecular basis of CIITA-mediated inhibition of Tax-1 functions may be important in defining new strategies to control HTLV-1 spreading and oncogenic potential. IMPORTANCE HTLV-1 is the causative agent of human adult T cell leukemia-lymphoma (ATLL). The viral transactivator Tax-1 plays a central role in the onset of ATLL, mostly by deregulating the NF-κB pathway. We demonstrate that CIITA, a key regulator of adaptive immunity, suppresses Tax-1-dependent activation of NF-κB by acting at several levels: it retains most of Tax-1 and RelA in the cytoplasm and inhibits their residual functional activity in the nucleus. Importantly, this inhibition occurs in cells that are targets of HTLV-1 infection. These findings are of interest in the field of virology because they expand the current knowledge of the functional relationship between viral products and cellular interactors and provide the basis for a better understanding of the molecular countermeasures adopted by the host cell to antagonize HTLV-1 spreading and transforming properties. Within this framework, our results may contribute to the establishment of novel strategies against HTLV-1 infection and virus-dependent oncogenic transformation.
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Roles of HTLV-1 basic Zip Factor (HBZ) in Viral Chronicity and Leukemic Transformation. Potential New Therapeutic Approaches to Prevent and Treat HTLV-1-Related Diseases. Viruses 2015; 7:6490-505. [PMID: 26690203 PMCID: PMC4690875 DOI: 10.3390/v7122952] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Revised: 11/24/2015] [Accepted: 12/01/2015] [Indexed: 12/16/2022] Open
Abstract
More than thirty years have passed since human T-cell leukemia virus type 1 (HTLV-1) was described as the first retrovirus to be the causative agent of a human cancer, adult T-cell leukemia (ATL), but the precise mechanism behind HTLV-1 pathogenesis still remains elusive. For more than two decades, the transforming ability of HTLV-1 has been exclusively associated to the viral transactivator Tax. Thirteen year ago, we first reported that the minus strand of HTLV-1 encoded for a basic Zip factor factor (HBZ), and since then several teams have underscored the importance of this antisense viral protein for the maintenance of a chronic infection and the proliferation of infected cells. More recently, we as well as others have demonstrated that HBZ has the potential to transform cells both in vitro and in vivo. In this review, we focus on the latest progress in our understanding of HBZ functions in chronicity and cellular transformation. We will discuss the involvement of this paradigm shift of HTLV-1 research on new therapeutic approaches to treat HTLV-1-related human diseases.
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12
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SIRT1 Suppresses Human T-Cell Leukemia Virus Type 1 Transcription. J Virol 2015; 89:8623-31. [PMID: 26063426 DOI: 10.1128/jvi.01229-15] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Accepted: 06/02/2015] [Indexed: 12/11/2022] Open
Abstract
UNLABELLED Human T-cell leukemia virus type 1 (HTLV-1)-associated diseases are poorly treatable, and HTLV-1 vaccines are not available. High proviral load is one major risk factor for disease development. HTLV-1 encodes Tax oncoprotein, which activates transcription from viral long terminal repeats (LTR) and various types of cellular promoters. Counteracting Tax function might have prophylactic and therapeutic benefits. In this work, we report on the suppression of Tax activation of HTLV-1 LTR by SIRT1 deacetylase. The transcriptional activity of Tax on the LTR was largely ablated when SIRT1 was overexpressed, but Tax activation of NF-κB was unaffected. On the contrary, the activation of the LTR by Tax was boosted when SIRT1 was depleted. Treatment of cells with resveratrol shunted Tax activity in a SIRT1-dependent manner. The activation of SIRT1 in HTLV-1-transformed T cells by resveratrol potently inhibited HTLV-1 proviral transcription and Tax expression, whereas compromising SIRT1 by specific inhibitors augmented HTLV-1 mRNA expression. The administration of resveratrol also decreased the production of cell-free HTLV-1 virions from MT2 cells and the transmission of HTLV-1 from MT2 cells to uninfected Jurkat cells in coculture. SIRT1 associated with Tax in HTLV-1-transformed T cells. Treatment with resveratrol prevented the interaction of Tax with CREB and the recruitment of CREB, CRTC1, and p300 to Tax-responsive elements in the LTR. Our work demonstrates the negative regulatory function of SIRT1 in Tax activation of HTLV-1 transcription. Small-molecule activators of SIRT1 such as resveratrol might be considered new prophylactic and therapeutic agents in HTLV-1-associated diseases. IMPORTANCE Human T-cell leukemia virus type 1 (HTLV-1) causes a highly lethal blood cancer or a chronic debilitating disease of the spinal cord. Treatments are unsatisfactory, and vaccines are not available. Disease progression is associated with robust expression of HTLV-1 genes. Suppressing HTLV-1 gene expression might have preventive and therapeutic benefits. It is therefore critical that host factors controlling HTLV-1 gene expression be identified and characterized. This work reveals a new host factor that suppresses HTLV-1 gene expression and a natural compound that activates this suppression. Our findings not only provide new knowledge of the host control of HTLV-1 gene expression but also suggest a new strategy of using natural compounds for prevention and treatment of HTLV-1-associated diseases.
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13
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Bouchut A, Chawla AR, Jeffers V, Hudmon A, Sullivan WJ. Proteome-wide lysine acetylation in cortical astrocytes and alterations that occur during infection with brain parasite Toxoplasma gondii. PLoS One 2015; 10:e0117966. [PMID: 25786129 PMCID: PMC4364782 DOI: 10.1371/journal.pone.0117966] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Accepted: 11/20/2014] [Indexed: 01/22/2023] Open
Abstract
Lysine acetylation is a reversible post-translational modification (PTM) that has been detected on thousands of proteins in nearly all cellular compartments. The role of this widespread PTM has yet to be fully elucidated, but can impact protein localization, interactions, activity, and stability. Here we present the first proteome-wide survey of lysine acetylation in cortical astrocytes, a subtype of glia that is a component of the blood-brain barrier and a key regulator of neuronal function and plasticity. We identified 529 lysine acetylation sites across 304 proteins found in multiple cellular compartments that largely function in RNA processing/transcription, metabolism, chromatin biology, and translation. Two hundred and seventy-seven of the acetylated lysines we identified on 186 proteins have not been reported previously in any other cell type. We also mapped an acetylome of astrocytes infected with the brain parasite, Toxoplasma gondii. It has been shown that infection with T. gondii modulates host cell gene expression, including several lysine acetyltransferase (KAT) and deacetylase (KDAC) genes, suggesting that the host acetylome may also be altered during infection. In the T. gondii-infected astrocytes, we identified 34 proteins exhibiting a level of acetylation >2-fold and 24 with a level of acetylation <2-fold relative to uninfected astrocytes. Our study documents the first acetylome map for cortical astrocytes, uncovers novel lysine acetylation sites, and demonstrates that T. gondii infection produces an altered acetylome.
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Affiliation(s)
- Anne Bouchut
- Department of Pharmacology & Toxicology, Indiana University School of Medicine, Indianapolis, IN, 46202, United States of America
| | - Aarti R. Chawla
- Department of Biochemistry & Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, 46202, United States of America
| | - Victoria Jeffers
- Department of Pharmacology & Toxicology, Indiana University School of Medicine, Indianapolis, IN, 46202, United States of America
| | - Andy Hudmon
- Department of Biochemistry & Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, 46202, United States of America
| | - William J. Sullivan
- Department of Pharmacology & Toxicology, Indiana University School of Medicine, Indianapolis, IN, 46202, United States of America
- Department of Microbiology & Immunology, Indiana University School of Medicine, Indianapolis, IN, 46202, United States of America
- * E-mail:
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14
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Identification and characterization of HTLV-1 HBZ post-translational modifications. PLoS One 2014; 9:e112762. [PMID: 25389759 PMCID: PMC4229220 DOI: 10.1371/journal.pone.0112762] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Accepted: 10/14/2014] [Indexed: 11/19/2022] Open
Abstract
Human T-cell leukemia virus type-1 (HTLV-1) is estimated to infect 15–25 million people worldwide, with several areas including southern Japan and the Caribbean basin being endemic. The virus is the etiological agent of debilitating and fatal diseases, for which there is currently no long-term cure. In the majority of cases of leukemia caused by HTLV-1, only a single viral gene, hbz, and its cognate protein, HBZ, are expressed and their importance is increasingly being recognized in the development of HTLV-1-associated disease. We hypothesized that HBZ, like other HTLV-1 proteins, has properties and functions regulated by post-translational modifications (PTMs) that affect specific signaling pathways important for disease development. To date, PTM of HBZ has not been described. We used an affinity-tagged protein and mass spectrometry method to identify seven modifications of HBZ for the first time. We examined how these PTMs affected the ability of HBZ to modulate several pathways, as measured using luciferase reporter assays. Herein, we report that none of the identified PTMs affected HBZ stability or its regulation of tested pathways.
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15
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Medina F, Quintremil S, Alberti C, Barriga A, Cartier L, Puente J, Ramírez E, Ferreira A, Tanaka Y, Valenzuela MA. Tax posttranslational modifications and interaction with calreticulin in MT-2 cells and human peripheral blood mononuclear cells of human T cell lymphotropic virus type-I-associated myelopathy/tropical spastic paraparesis patients. AIDS Res Hum Retroviruses 2014; 30:370-9. [PMID: 24321043 DOI: 10.1089/aid.2013.0036] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The human retrovirus human T cell lymphotropic virus type-I (HTLV-1) is the etiologic agent of HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). Axonal degeneration in HAM/TSP patients occurs without neuron infection, with the secreted viral Tax protein proposed to be involved. We previously found that Tax secreted into the culture medium of MT-2 cells (HTLV-1-infected cell line) produced neurite retraction in neuroblastoma cells differentiated to neuronal type. To assess the relevance of Tax posttranslational modifications on this effect, we addressed the question of whether Tax secreted by MT-2 cells and peripheral blood mononuclear cells (PBMCs) of HTLV-1-infected subjects is modified. The interaction of Tax with calreticulin (CRT) that modulates intracellular Tax localization and secretion has been described. We studied Tax localization and modifications in MT-2 cells and its interaction with CRT. Intracellular Tax in MT-2 cells was assessed by flow cytometry, corresponding mainly to a 71-kDa protein followed by western blot. This protein reported as a chimera with gp21 viral protein-confirmed by mass spectrometry-showed no ubiquitination or SUMOylation. The Tax-CRT interaction was determined by confocal microscopy and coimmunoprecipitation. Extracellular Tax from HAM/TSP PBMCs is ubiquitinated according to western blot, and its interaction with CRT was shown by coimmunoprecipitation. A positive correlation between Tax and CRT secretion was observed in HAM/TSP PBMCs and asymptomatic carriers. For both proteins inhibitors and activators of secretion showed secretion through the endoplasmic reticulum-Golgi complex. Tax, present in PBMC culture medium, produced neurite retraction in differentiated neuroblastoma cells. These results suggest that Tax, whether ubiquitinated or not, is active for neurite retraction.
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Affiliation(s)
- Fernando Medina
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santiago, Chile
| | - Sebastian Quintremil
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santiago, Chile
| | - Carolina Alberti
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santiago, Chile
| | - Andres Barriga
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santiago, Chile
| | - Luis Cartier
- Departamento de Ciencias Neurológicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Javier Puente
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santiago, Chile
| | - Eugenio Ramírez
- Programa de Virología, Facultad de Medicina, Universidad de Chile, and Departamento de Virología, ISP, Santiago, Chile
| | - Arturo Ferreira
- Programa de Inmunologia, ICBM, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Yuetsu Tanaka
- Department of Immunology, Graduate School and Faculty of Medicine, University of the Ryukyus, Nishihara, Japan
| | - Maria Antonieta Valenzuela
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santiago, Chile
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16
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HSP90 protects the human T-cell leukemia virus type 1 (HTLV-1) tax oncoprotein from proteasomal degradation to support NF-κB activation and HTLV-1 replication. J Virol 2013; 87:13640-54. [PMID: 24109220 DOI: 10.1128/jvi.02006-13] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Human T-cell leukemia virus type 1 (HTLV-1) is the causative agent of adult T-cell leukemia (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). The HTLV-1 genome encodes the Tax protein that plays essential regulatory roles in HTLV-1 replication and oncogenic transformation of T lymphocytes. Despite intensive study of Tax, how Tax interfaces with host signaling pathways to regulate virus replication and drive T-cell proliferation and immortalization remains poorly understood. To gain new insight into the mechanisms of Tax function and regulation, we used tandem affinity purification and mass spectrometry to identify novel cellular Tax-interacting proteins. This screen identified heat shock protein 90 (HSP90) as a new binding partner of Tax. The interaction between HSP90 and Tax was validated by coimmunoprecipitation assays, and colocalization between the two proteins was observed by confocal microscopy. Treatment of HTLV-1-transformed cells with the HSP90 inhibitor 17-DMAG elicited proteasomal degradation of Tax in the nuclear matrix with concomitant inhibition of NF-κB and HTLV-1 long terminal repeat (LTR) activation. Knockdown of HSP90 by lentiviral shRNAs similarly provoked a loss of Tax protein in HTLV-1-transformed cells. Finally, treatment of HTLV-1-transformed cell lines with 17-DMAG suppressed HTLV-1 replication and promoted apoptotic cell death. Taken together, our results reveal that Tax is a novel HSP90 client protein and HSP90 inhibitors may exert therapeutic benefits for ATL and HAM/TSP patients.
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17
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Romanelli MG, Diani E, Bergamo E, Casoli C, Ciminale V, Bex F, Bertazzoni U. Highlights on distinctive structural and functional properties of HTLV Tax proteins. Front Microbiol 2013; 4:271. [PMID: 24058363 PMCID: PMC3766827 DOI: 10.3389/fmicb.2013.00271] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2013] [Accepted: 08/20/2013] [Indexed: 12/15/2022] Open
Abstract
Human T cell leukemia viruses (HTLVs) are complex human retroviruses of the Deltaretrovirus genus. Four types have been identified thus far, with HTLV-1 and HTLV-2 much more prevalent than HTLV-3 or HTLV-4. HTLV-1 and HTLV-2 possess strictly related genomic structures, but differ significantly in pathogenicity, as HTLV-1 is the causative agent of adult T cell leukemia and of HTLV-associated myelopathy/tropical spastic paraparesis, whereas HTLV-2 is not associated with neoplasia. HTLVs code for a protein named Tax that is responsible for enhancing viral expression and drives cell transformation. Much effort has been invested to dissect the impact of Tax on signal transduction pathways and to identify functional differences between the HTLV Tax proteins that may explain the distinct oncogenic potential of HTLV-1 and HTLV-2. This review summarizes our current knowledge of Tax-1 and Tax-2 with emphasis on their structure, role in activation of the NF-κB (nuclear factor kappa-B) pathway, and interactions with host factors.
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18
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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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19
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Shirinian M, Kfoury Y, Dassouki Z, El-Hajj H, Bazarbachi A. Tax-1 and Tax-2 similarities and differences: focus on post-translational modifications and NF-κB activation. Front Microbiol 2013; 4:231. [PMID: 23966989 PMCID: PMC3744011 DOI: 10.3389/fmicb.2013.00231] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2013] [Accepted: 07/29/2013] [Indexed: 11/13/2022] Open
Abstract
Although human T cell leukemia virus type 1 and 2 (HTLV-1 and HTLV-2) share similar genetic organization, they have major differences in their pathogenesis and disease manifestation. HTLV-1 is capable of transforming T lymphocytes in infected patients resulting in adult T cell leukemia/lymphoma whereas HTLV-2 is not clearly associated with lymphoproliferative diseases. Numerous studies have provided accumulating evidence on the involvement of the viral transactivators Tax-1 versus Tax-2 in T cell transformation. Tax-1 is a potent transcriptional activator of both viral and cellular genes. Tax-1 post-translational modifications and specifically ubiquitylation and SUMOylation have been implicated in nuclear factor-kappaB (NF-κB) activation and may contribute to its transformation capacity. Although Tax-2 has similar protein structure compared to Tax-1, the two proteins display differences both in their protein–protein interaction and activation of signal transduction pathways. Recent studies on Tax-2 have suggested ubiquitylation and SUMOylation independent mechanisms of NF-κB activation. In this present review, structural and functional differences between Tax-1 and Tax-2 will be summarized. Specifically, we will address their subcellular localization, nuclear trafficking and their effect on cellular regulatory proteins. A special attention will be given to Tax-1/Tax-2 post-translational modification such as ubiquitylation, SUMOylation, phosphorylation, acetylation, NF-κB activation, and protein–protein interactions involved in oncogenecity both in vivo and in vitro.
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Affiliation(s)
- Margret Shirinian
- Department of Internal Medicine, Faculty of Medicine, American University of Beirut Beirut, Lebanon
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20
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Lodewick J, Sampaio C, Boxus M, Rinaldi AS, Coulonval K, Willems L, Roger PP, Bex F. Acetylation at lysine 346 controls the transforming activity of the HTLV-1 Tax oncoprotein in the Rat-1 fibroblast model. Retrovirology 2013; 10:75. [PMID: 23880157 PMCID: PMC3734113 DOI: 10.1186/1742-4690-10-75] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2013] [Accepted: 07/18/2013] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND Transformation by the Tax oncoprotein of the human T cell leukemia virus type 1 (HTLV-1) is governed by actions on cellular regulatory signals, including modulation of specific cellular gene expression via activation of signaling pathways, acceleration of cell cycle progression via stimulation of cyclin-dependent kinase activity leading to retinoblastoma protein (pRb) hyperphosphorylation and perturbation of survival signals. These actions control early steps in T cell transformation and development of Adult T cell leukemia (ATL), an aggressive malignancy of HTLV-1 infected T lymphocytes. Post-translational modifications of Tax by phosphorylation, ubiquitination, sumoylation and acetylation have been implicated in Tax-mediated activation of the NF-κB pathway, a key function associated with Tax transforming potential. RESULTS In this study, we demonstrate that acetylation at lysine K(346) in the carboxy-terminal domain of Tax is modulated in the Tax nuclear bodies by the acetyltransferase p300 and the deacetylases HDAC5/7 and controls phosphorylation of the tumor suppressor pRb by Tax-cyclin D3-CDK4-p21(CIP) complexes. This property correlates with the inability of the acetylation deficient K(346)R mutant, but not the acetylation mimetic K(346)Q mutant, to promote anchorage-independent growth of Rat-1 fibroblasts. By contrast, acetylation at lysine K(346) had no effects on the ability of Tax carboxy-terminal PDZ-binding domain to interact with the tumor suppressor hDLG. CONCLUSIONS The identification of the acetyltransferase p300 and the deacetylase HDAC7 as enzymes modulating Tax acetylation points to new therapeutic targets for the treatment of HTLV-1 infected patients at risk of developing ATL.
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Affiliation(s)
- Julie Lodewick
- Institute for Microbiological Research J-M Wiame (IRMW), Laboratory of Microbiology, Université Libre de Bruxelles, 1, Avenue E, Gryson, Brussels, Belgium
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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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Human T cell leukemia virus type 2 tax-mediated NF-κB activation involves a mechanism independent of Tax conjugation to ubiquitin and SUMO. J Virol 2012; 87:1123-36. [PMID: 23135727 DOI: 10.1128/jvi.01792-12] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Permanent activation of the NF-κB pathway by the human T cell leukemia virus type 1 (HTLV-1) Tax (Tax1) viral transactivator is a key event in the process of HTLV-1-induced T lymphocyte immortalization and leukemogenesis. Although encoding a Tax transactivator (Tax2) that activates the canonical NF-κB pathway, HTLV-2 does not cause leukemia. These distinct pathological outcomes might be related, at least in part, to distinct NF-κB activation mechanisms. Tax1 has been shown to be both ubiquitinated and SUMOylated, and these two modifications were originally proposed to be required for Tax1-mediated NF-κB activation. Tax1 ubiquitination allows recruitment of the IKK-γ/NEMO regulatory subunit of the IKK complex together with Tax1 into centrosome/Golgi-associated cytoplasmic structures, followed by activation of the IKK complex and RelA/p65 nuclear translocation. Herein, we compared the ubiquitination, SUMOylation, and acetylation patterns of Tax2 and Tax1. We show that, in contrast to Tax1, Tax2 conjugation to endogenous ubiquitin and SUMO is barely detectable while both proteins are acetylated. Importantly, Tax2 is neither polyubiquitinated on lysine residues nor ubiquitinated on its N-terminal residue. Consistent with these observations, Tax2 conjugation to ubiquitin and Tax2-mediated NF-κB activation is not affected by overexpression of the E2 conjugating enzyme Ubc13. We further demonstrate that a nonubiquitinable, non-SUMOylable, and nonacetylable Tax2 mutant retains a significant ability to activate transcription from a NF-κB-dependent promoter after partial activation of the IKK complex and induction of RelA/p65 nuclear translocation. Finally, we also show that Tax2 does not interact with TRAF6, a protein that was shown to positively regulate Tax1-mediated activation of the NF-κB pathway.
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23
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Bidoia C. Human T-lymphotropic virus proteins and post-translational modification pathways. World J Virol 2012; 1:115-30. [PMID: 24175216 PMCID: PMC3782272 DOI: 10.5501/wjv.v1.i4.115] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2011] [Revised: 06/04/2012] [Accepted: 07/13/2012] [Indexed: 02/05/2023] Open
Abstract
Cell life from the cell cycle to the signaling transduction and response to stimuli is finely tuned by protein post-translational modifications (PTMs). PTMs alter the conformation, the stability, the localization, and hence the pattern of interactions of the targeted protein. Cell pathways involve the activation of enzymes, like kinases, ligases and transferases, that, once activated, act on many proteins simultaneously, altering the state of the cell and triggering the processes they are involved in. Viruses enter a balanced system and hijack the cell, exploiting the potential of PTMs either to activate viral encoded proteins or to alter cellular pathways, with the ultimate consequence to perpetuate through their replication. Human T-lymphotropic virus type 1 (HTLV-1) is known to be highly oncogenic and associates with adult T-cell leukemia/lymphoma, HTLV-1-associated myelopathy/tropical spastic paraparesis and other inflammatory pathological conditions. HTLV-1 protein activity is controlled by PTMs and, in turn, viral activity is associated with the modulation of cellular pathways based on PTMs. More knowledge is acquired about the PTMs involved in the activation of its proteins, like Tax, Rex, p12, p13, p30, HTLV-I basic leucine zipper factor and Gag. However, more has to be understood at the biochemical level in order to counteract the associated fatal outcomes. This review will focus on known PTMs that directly modify HTLV-1 components and on enzymes whose activity is modulated by viral proteins.
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Affiliation(s)
- Carlo Bidoia
- Carlo Bidoia, Centre for Research in Infectious Diseases, School of Medicine and Medical Science, University College Dublin, Belfield, Dublin 4, Ireland
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24
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The multifaceted oncoprotein Tax: subcellular localization, posttranslational modifications, and NF-κB activation. Adv Cancer Res 2012; 113:85-120. [PMID: 22429853 DOI: 10.1016/b978-0-12-394280-7.00003-8] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The human T-cell lymphotropic virus type-I (HTLV-I) is the etiologic agent of adult T-cell leukemia/lymphoma (ATL) and of tropical spastic paraparesis/HTLV-I-associated myelopathy. Constitutive NF-κB activation by the viral oncoprotein Tax plays a crucial role in the induction and maintenance of cellular proliferation, transformation, and inhibition of apoptosis. In an attempt to provide a general view of the molecular mechanisms of constitutive Tax-induced NF-κB activation, we summarize in this review the recent body of literature that supports a major role for Tax posttranslational modifications, chiefly ubiquitination, and SUMOylation, in the NF-κB activity of Tax. These modifications indeed participate in the control of Tax subcellular localization and modulate its protein-protein interaction potential. Tax posttranslational modifications, which highlight the ability of HTLV-I to optimize its limited viral genome size, might represent an attractive target for the design of new therapies for ATL.
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25
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Chan JK, Greene WC. Dynamic roles for NF-κB in HTLV-I and HIV-1 retroviral pathogenesis. Immunol Rev 2012; 246:286-310. [DOI: 10.1111/j.1600-065x.2012.01094.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Abstract
Human T-cell lymphotropic virus type 1 (HTLV-1) is the etiological agent of adult T-cell leukemia/lymphoma (ATL), whereas the highly related HTLV-2 is not associated with ATL or other cancers. In addition to ATL leukemogenesis, studies of the HTLV viruses also provide an exceptional model for understanding basic pathogenic mechanisms of virus-host interactions and human oncogenesis. Accumulating evidence suggests that the viral regulatory protein Tax and host inflammatory transcription factor NF-κB are largely responsible for the different pathogenic potentials of HTLV-1 and HTLV-2. Here, we discuss the molecular mechanisms of HTLV-1 oncogenic pathogenesis with a focus on the interplay between the Tax oncoprotein and NF-κB pro-oncogenic signaling. We also outline some of the most intriguing and outstanding questions in the fields of HTLV and NF-κB. Answers to those questions will greatly advance our understanding of ATL leukemogenesis and other NF-κB-associated tumorigenesis and will help us design personalized cancer therapies.
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27
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Wang YE, Pernet O, Lee B. Regulation of the nucleocytoplasmic trafficking of viral and cellular proteins by ubiquitin and small ubiquitin-related modifiers. Biol Cell 2011; 104:121-38. [PMID: 22188262 PMCID: PMC3625690 DOI: 10.1111/boc.201100105] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2011] [Accepted: 11/22/2011] [Indexed: 12/29/2022]
Abstract
Nucleocytoplasmic trafficking of many cellular proteins is regulated by nuclear import/export signals as well as post-translational modifications such as covalent conjugation of ubiquitin and small ubiquitin-related modifiers (SUMOs). Ubiquitination and SUMOylation are rapid and reversible ways to modulate the intracellular localisation and function of substrate proteins. These pathways have been co-opted by some viruses, which depend on the host cell machinery to transport their proteins in and out of the nucleus. In this review, we will summarise our current knowledge on the ubiquitin/SUMO-regulated nuclear/subnuclear trafficking of cellular proteins and describe examples of viral exploitation of these pathways.
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Affiliation(s)
- Yao E Wang
- Department of Microbiology, Immunology, and Molecular Genetics, UCLA, Los Angeles, CA 90095, USA
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Chang R, Tan J, Xu F, Han H, Geng Y, Li Y, Qiao W. Lysine acetylation sites in bovine foamy virus transactivator BTas are important for its DNA binding activity. Virology 2011; 418:21-6. [PMID: 21813148 DOI: 10.1016/j.virol.2011.07.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2010] [Revised: 06/03/2011] [Accepted: 07/07/2011] [Indexed: 11/29/2022]
Abstract
Cellular acetylation signaling is important for viral gene regulation, particularly during the transactivation of retroviruses. The regulatory protein of bovine foamy virus (BFV), BTas, is a transactivator that augments viral gene transcription from both the long terminal repeat (LTR) promoter and the internal promoter (IP). In this study, we report that the histone acetyltransferase (HAT), p300, specifically acetylates BTas both in vivo and in vitro. Further studies demonstrated that BTas acetylation markedly enhances its transactivation activity. Mutagenesis analysis identified three lysines at positions 66, 109 and 110 in BTas that are acetylated by p300. The K110R mutant lost its binding to BFV promoter as well as its ability to activate BFV promoter. The acetylation of K66 and K109 may contribute to increased BTas binding ability. These results suggest that the p300-acetylated lysines of BTas are important for transactivation of BFV promoters and therefore have an important role in BFV replication.
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Affiliation(s)
- Rui Chang
- Key Laboratory of Molecular Microbiology and Biotechnology (Ministry of Education), College of Life Sciences, Nankai University, Tianjin 300071, China
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Lodewick J, Lamsoul I, Bex F. Move or die: the fate of the Tax oncoprotein of HTLV-1. Viruses 2011; 3:829-57. [PMID: 21994756 PMCID: PMC3185767 DOI: 10.3390/v3060829] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2011] [Revised: 05/31/2011] [Accepted: 06/01/2011] [Indexed: 12/12/2022] Open
Abstract
The HTLV-1 Tax protein both activates viral replication and is involved in HTLV-1-mediated transformation of T lymphocytes. The transforming properties of Tax include altering the expression of select cellular genes via activation of cellular pathways and perturbation of both cell cycle control mechanisms and apoptotic signals. The recent discovery that Tax undergoes a hierarchical sequence of posttranslational modifications that control its intracellular localization provides provocative insights into the mechanisms regulating Tax transcriptional and transforming activities.
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Affiliation(s)
- Julie Lodewick
- Institut de Recherches Microbiologiques J-M Wiame, Université Libre de Bruxelles, B-1070 Bruxelles, Belgium.
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30
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Bertazzoni U, Turci M, Avesani F, Di Gennaro G, Bidoia C, Romanelli MG. Intracellular localization and cellular factors interaction of HTLV-1 and HTLV-2 Tax proteins: similarities and functional differences. Viruses 2011; 3:541-560. [PMID: 21994745 PMCID: PMC3185761 DOI: 10.3390/v3050541] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2011] [Accepted: 04/26/2011] [Indexed: 12/24/2022] Open
Abstract
Human T-lymphotropic viruses type 1 (HTLV-1) and type 2 (HTLV-2) present very similar genomic structures but HTLV-1 is more pathogenic than HTLV-2. Is this difference due to their transactivating Tax proteins, Tax-1 and Tax-2, which are responsible for viral and cellular gene activation? Do Tax-1 and Tax-2 differ in their cellular localization and in their interaction pattern with cellular factors? In this review, we summarize Tax-1 and Tax-2 structural and phenotypic properties, their interaction with factors involved in signal transduction and their localization-related behavior within the cell. Special attention will be given to the distinctions between Tax-1 and Tax-2 that likely play an important role in their transactivation activity.
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Affiliation(s)
- Umberto Bertazzoni
- Department of Life and Reproduction Sciences, University of Verona, Strada le Grazie 8, 37134, Verona, Italy; E-Mails: (M.T.); (F.A.); (G.D.G.)
- Authors to whom correspondence should be addressed; E-Mails: (U.B.); (M.G.R); Tel.: +39-0458027182; Fax: +390458027180
| | - Marco Turci
- Department of Life and Reproduction Sciences, University of Verona, Strada le Grazie 8, 37134, Verona, Italy; E-Mails: (M.T.); (F.A.); (G.D.G.)
| | - Francesca Avesani
- Department of Life and Reproduction Sciences, University of Verona, Strada le Grazie 8, 37134, Verona, Italy; E-Mails: (M.T.); (F.A.); (G.D.G.)
| | - Gianfranco Di Gennaro
- Department of Life and Reproduction Sciences, University of Verona, Strada le Grazie 8, 37134, Verona, Italy; E-Mails: (M.T.); (F.A.); (G.D.G.)
| | - Carlo Bidoia
- Centre for Research in Infectious Diseases, University College Dublin, Belfield, Dublin 4, Ireland; E-Mail: (C.B.)
| | - Maria Grazia Romanelli
- Department of Life and Reproduction Sciences, University of Verona, Strada le Grazie 8, 37134, Verona, Italy; E-Mails: (M.T.); (F.A.); (G.D.G.)
- Authors to whom correspondence should be addressed; E-Mails: (U.B.); (M.G.R); Tel.: +39-0458027182; Fax: +390458027180
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31
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Legros S, Boxus M, Gatot JS, Van Lint C, Kruys V, Kettmann R, Twizere JC, Dequiedt F. The HTLV-1 Tax protein inhibits formation of stress granules by interacting with histone deacetylase 6. Oncogene 2011; 30:4050-62. [PMID: 21532619 DOI: 10.1038/onc.2011.120] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [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) is the causative agent of a fatal adult T-cell leukemia. Through deregulation of multiple cellular signaling pathways the viral Tax protein has a pivotal role in T-cell transformation. In response to stressful stimuli, cells mount a cellular stress response to limit the damage that environmental forces inflict on DNA or proteins. During stress response, cells postpone the translation of most cellular mRNAs, which are gathered into cytoplasmic mRNA-silencing foci called stress granules (SGs) and allocate their available resources towards the production of dedicated stress-management proteins. Here we demonstrate that Tax controls the formation of SGs and interferes with the cellular stress response pathway. In agreement with previous reports, we observed that Tax relocates from the nucleus to the cytoplasm in response to environmental stress. We found that the presence of Tax in the cytoplasm of stressed cells prevents the formation of SGs and counteracts the shutoff of specific host proteins. Unexpectedly, nuclear localization of Tax promotes spontaneous aggregation of SGs, even in the absence of stress. Mutant analysis revealed that the SG inhibitory capacity of Tax is independent of its transcriptional abilities but relies on its interaction with histone deacetylase 6, a critical component of SGs. Importantly, the stress-protective effect of Tax was also observed in the context of HTLV-1 infected cells, which were shown to be less prone to form SGs and undergo apoptosis under arsenite exposure. These observations identify Tax as the first virally encoded inhibitory component of SGs and unravel a new strategy developed by HTLV-1 to deregulate normal cell processes. We postulate that inhibition of the stress response pathway by Tax would favor cell survival under stressful conditions and may have an important role in HTLV-1-induced cellular transformation.
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Affiliation(s)
- S Legros
- Center for Molecular and Cellular Biology, Gembloux Agro-Bio Tech, University of Liège (ULg), Gembloux, Belgium
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32
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Ubiquitin-specific peptidase 20 targets TRAF6 and human T cell leukemia virus type 1 tax to negatively regulate NF-kappaB signaling. J Virol 2011; 85:6212-9. [PMID: 21525354 DOI: 10.1128/jvi.00079-11] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
NF-κB plays a key role in innate and acquired immunity. Its activity is regulated through intricate signaling networks. Persistent or excessive activation of NF-κB induces diseases, such as autoimmune disorders and malignant neoplasms. Infection by human T cell leukemia virus type 1 (HTLV-1) causes a fatal hematopoietic malignancy termed adult T cell leukemia (ATL). The HTLV-1 viral oncoprotein Tax functions pivotally in leukemogenesis through its potent activation of NF-κB. Recent findings suggest that protein ubiquitination is crucial for proper regulation of NF-κB signaling and for Tax activity. Here, we report that ubiquitin-specific peptidase USP20 deubiquitinates TRAF6 and Tax and suppresses interleukin 1β (IL-1β)- and Tax-induced NF-κB activation. Our results point to USP20 as a key negative regulator of Tax-induced NF-κB signaling.
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33
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Zhang J, Yamada O, Kida S, Matsushita Y, Yamaoka S, Chagan-Yasutan H, Hattori T. Identification of CD44 as a downstream target of noncanonical NF-κB pathway activated by human T-cell leukemia virus type 1-encoded Tax protein. Virology 2011; 413:244-52. [PMID: 21411116 DOI: 10.1016/j.virol.2011.02.021] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2010] [Revised: 01/21/2011] [Accepted: 02/24/2011] [Indexed: 12/16/2022]
Abstract
Our previous study showed Human T-cell leukemia virus type 1 Tax induces osteopontin (OPN) expression by transactivating its promoter. As an extension, we investigated here the possible influence of Tax on CD44, an important receptor for OPN. Co-expression of Tax, but not its NF-κB-defective mutant, significantly increased the reporter gene expression directed by CD44 promoter. Tax-mediated CD44 activation was largely diminished by disrupting an element similar to the noncanonical κβ site found in other IKKα target genes, and further, co-transfection of RelB siRNA abolished CD44 induction by Tax, suggesting an involvement of noncanonical NF-κB pathway in Tax-mediated transactivation. Consistently, chromatin immunoprecipitation revealed a specific interaction of CD44 promoter with RelB-containing complex. Together, these results indicate that D44 gene is one of the downstream target genes of aberrantly activated noncanonical NF-κB signaling by Tax, providing an additional line of evidence explaining how Tax-induced NF-κB signaling is integrated into a fate-determining cellular program.
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Affiliation(s)
- Jing Zhang
- Research and Development Center, FUSO Pharmaceutical Industries, LTD., 2-3-30 Morinomiya, Joto-ku, Osaka 536-8523, Japan
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34
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Human T-cell leukemia virus type 1 (HTLV-1) and leukemic transformation: viral infectivity, Tax, HBZ and therapy. Oncogene 2010; 30:1379-89. [PMID: 21119600 DOI: 10.1038/onc.2010.537] [Citation(s) in RCA: 201] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The human T-cell leukemia virus type 1 (HTLV-1) was the first retrovirus discovered to be causative of a human cancer, adult T-cell leukemia. The transforming entity of HTLV-1 has been attributed to the virally-encoded oncoprotein, Tax. Unlike the v-onc proteins encoded by other oncogenic animal retroviruses that transform cells, Tax does not originate from a c-onc counterpart. In this article, we review progress in our understanding of HTLV-1 infectivity, cellular transformation, anti-sense transcription and therapy, 30 years after the original discovery of this virus.
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35
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Jeang KT. HTLV-1 and adult T-cell leukemia: insights into viral transformation of cells 30 years after virus discovery. J Formos Med Assoc 2010; 109:688-93. [PMID: 20970064 DOI: 10.1016/s0929-6646(10)60112-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2010] [Revised: 08/02/2010] [Accepted: 08/02/2010] [Indexed: 12/22/2022] Open
Abstract
Human T-cell leukemia virus type 1 (HTLV-1), the etiological agent of adult T-cell leukemia, was the first human retrovirus to be isolated. It is now the 30(th) anniversary of the initial discovery of HTLV-1. This review discusses recent insights into the role of the HTLV-1 Tax oncoprotein in cellular proliferation and the abrogation of cellular checkpoints that lead to disease progression.
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Affiliation(s)
- Kuan-Teh Jeang
- National Institutes of Health, Bethesda, Maryland 20892, USA.
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36
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Tax ubiquitylation and SUMOylation control the dynamic shuttling of Tax and NEMO between Ubc9 nuclear bodies and the centrosome. Blood 2010; 117:190-9. [PMID: 20959607 DOI: 10.1182/blood-2010-05-285742] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The human T-lymphotropic virus type I oncoprotein Tax is critical for T-cell transformation, acting mainly through nuclear factor kappa B essential modulator (NEMO) binding and subsequent nuclear factor-κB activation. Tax localizes to Tax nuclear bodies and to the centrosome and is subjected to ubiquitylation and small ubiquitin-like modifier (SUMO)ylation, which are both necessary for complete transcriptional activation. Using the photoconvertible fluorophore Dendra-2 coupled with live video confocal microscopy, we show for the first time that the same Tax molecule shuttles among Tax nuclear bodies and between these nuclear bodies and the centrosome, depending on its posttranslational modifications. Ubiquitylation targets Tax to nuclear bodies to which NEMO is recruited and subsequently SUMOylated. We also demonstrate that Tax nuclear bodies contain the SUMOylation machinery including SUMO and the SUMO conjugating enzyme Ubc9, strongly suggesting that these nuclear bodies represent sites of active SUMOylation. Finally, both ubiquitylation and SUMOylation of Tax control NEMO targeting to the centrosome. Altogether, we are proposing a model where both ubiquitylation and SUMOylation of Tax control the shuttling of Tax and NEMO between the cytoplasmic and nuclear compartments.
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37
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Human T Lymphotropic Virus Type 1 (HTLV-1): Molecular Biology and Oncogenesis. Viruses 2010; 2:2037-2077. [PMID: 21994719 PMCID: PMC3185741 DOI: 10.3390/v2092037] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2010] [Revised: 08/25/2010] [Accepted: 09/15/2010] [Indexed: 12/13/2022] Open
Abstract
Human T lymphotropic viruses (HTLVs) are complex deltaretroviruses that do not contain a proto-oncogene in their genome, yet are capable of transforming primary T lymphocytes both in vitro and in vivo. There are four known strains of HTLV including HTLV type 1 (HTLV-1), HTLV-2, HTLV-3 and HTLV-4. HTLV-1 is primarily associated with adult T cell leukemia (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). HTLV-2 is rarely pathogenic and is sporadically associated with neurological disorders. There have been no diseases associated with HTLV-3 or HTLV-4 to date. Due to the difference in the disease manifestation between HTLV-1 and HTLV-2, a clear understanding of their individual pathobiologies and the role of various viral proteins in transformation should provide insights into better prognosis and prevention strategies. In this review, we aim to summarize the data accumulated so far in the transformation and pathogenesis of HTLV-1, focusing on the viral Tax and HBZ and citing appropriate comparisons to HTLV-2.
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38
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Shembade N, Harhaj EW. Role of post-translational modifications of HTLV-1 Tax in NF-κB activation. World J Biol Chem 2010; 1:13-20. [PMID: 21540989 PMCID: PMC3083931 DOI: 10.4331/wjbc.v1.i1.13] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2009] [Revised: 12/17/2009] [Accepted: 12/24/2009] [Indexed: 02/05/2023] Open
Abstract
Human T-cell leukemia virus type 1 (HTLV-1), the first human retrovirus discovered, is the etiological agent of adult-T-cell leukemia/lymphoma. The HTLV-1 encoded Tax protein is a potent oncoprotein that deregulates gene expression by constitutively activating nuclear factor-κB (NF-κB). Tax activation of NF-κB is critical for the immortalization and survival of HTLV-1-infected T cells. In this review, we summarize the present knowledge on mechanisms underlying Tax-mediated NF-κB activation, with an emphasis on post-translational modifications of Tax.
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Affiliation(s)
- Noula Shembade
- Noula Shembade, Edward W Harhaj, Department of Microbiology and Immunology, Sylvester Comprehensive Cancer Center, University of Miami, Miller School of Medicine, Miami, FL 33136, United States
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39
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Chen S, Feng B, George B, Chakrabarti R, Chen M, Chakrabarti S. Transcriptional coactivator p300 regulates glucose-induced gene expression in endothelial cells. Am J Physiol Endocrinol Metab 2010; 298:E127-37. [PMID: 19903865 DOI: 10.1152/ajpendo.00432.2009] [Citation(s) in RCA: 126] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Sustained hyperglycemia in diabetes causes alteration of a large number of transcription factors and mRNA transcripts, leading to tissue damage. We investigated whether p300, a transcriptional coactivator with histone acetyl transferase activity, regulates glucose-induced activation of transcription factors and subsequent upregulation of vasoactive factors and extracellular matrix (ECM) proteins in human umbilical vein endothelial cells (HUVECs). HUVECs were incubated in varied glucose concentrations and were studied after p300 small interfering RNA (siRNA) transfection, p300 overexpression, or incubation with the p300 inhibitor curcumin. Histone H2AX phosphorylation and lysine acetylation were examined for oxidative DNA damage and p300 activation. Screening for transcription factors was performed with the Luminex system. Alterations of selected transcription factors were validated. mRNA expression of p300, endothelin-1 (ET-1), vascular endothelial growth factor (VEGF), and fibronectin (FN) and its splice variant EDB(+)FN and FN protein production were analyzed. HUVECs in 25 mmol/l glucose showed increased p300 production accompanied by increased binding of p300 to ET-1 and FN promoters, augmented histone acetylation, H2AX phosphorylation, activation of multiple transcription factors, and increased mRNA expression of vasoactive factors and ECM proteins. p300 overexpression showed a glucose-like effect on the mRNA expression of ET-1, VEGF, and FN. Furthermore, siRNA-mediated p300 blockade or chemical inhibitor of p300 prevented such glucose-induced changes. Similar mRNA upregulation was also seen in the organ culture of vascular tissues, which was prevented by p300 siRNA transfection. Data from these studies suggest that glucose-induced p300 upregulation is an important upstream epigenetic mechanism regulating gene expression of vasoactive factors and ECM proteins in endothelial cells and is a potential therapeutic target for diabetic complications.
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Affiliation(s)
- Shali Chen
- Department of Pathology, University of Western Ontario, Schulich School of Medicine, London, Ontario, Canada
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40
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Distinct functions of HTLV-1 Tax1 from HTLV-2 Tax2 contribute key roles to viral pathogenesis. Retrovirology 2009; 6:117. [PMID: 20017952 PMCID: PMC2806368 DOI: 10.1186/1742-4690-6-117] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2009] [Accepted: 12/17/2009] [Indexed: 12/17/2022] Open
Abstract
While the human T-cell leukemia virus type 1 (HTLV-1) is the etiologic agent of adult T-cell leukemia/lymphoma (ATL), to date, its close relative HTLV-2 is not associated with ATL or other types of malignancies. Accumulating evidence shows that HTLV-1 Tax1 and HTLV-2 Tax2 have many shared activities, but the two proteins have a limited number of significantly distinct activities, and these distinctions appear to play key roles in HTLV-1 specific pathogenesis. In this review, we summarize the functions of Tax1 associated with cell survival, cell proliferation, persistent infection as well as pathogenesis. We emphasize special attention to distinctions between Tax1 and Tax2.
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41
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Journo C, Douceron E, Mahieux R. HTLV gene regulation: because size matters, transcription is not enough. Future Microbiol 2009; 4:425-40. [PMID: 19416012 DOI: 10.2217/fmb.09.13] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Despite being discovered in animals in the early 20th century, the scientific interest in retroviruses was boosted with the discovery of human retroviruses (human T-leukemia/lymphoma virus [HTLV] and HIV), which are responsible for significant morbidity and mortality. HTLV was identified more than 25 years ago as the etiological agent of adult T-cell leukemia/lymphoma. It was then shown to be a complex retrovirus, given that it not only encodes the characteristic retroviral Gag, Pol and Env proteins, but also regulatory and accessory proteins. Since the first studies documenting the role of these proteins in viral expression, the picture has become increasingly more complex. Indeed, owing to the limited size of its genome that contains overlapping open-reading frames, HTLV has evolved unique ways to regulate its expression. Retroviral expression was originally thought to be mainly controlled through the regulation of transcription from the 5 long-terminal repeats, but we now know that the 3 long-terminal repeats also serve as promoters. Regulation of splicing and mRNA export, and post-translational modifications of viral protein also play a major role. This review discusses the latest insights gained into the field of HTLV gene expression.
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Affiliation(s)
- Chloé Journo
- Equipe Oncogenèse Rétrovirale, INSERM-U758 Virologie Humaine, 69364 Lyon Cedex 07, France
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