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Bellon M, Nicot C. HTLV-1 Tax Tug-of-War: Cellular Senescence and Death or Cellular Transformation. Pathogens 2024; 13:87. [PMID: 38276160 PMCID: PMC10820833 DOI: 10.3390/pathogens13010087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Revised: 01/11/2024] [Accepted: 01/15/2024] [Indexed: 01/27/2024] Open
Abstract
Human T cell leukemia virus type 1 (HTLV-1) is a retrovirus associated with a lymphoproliferative disease known as adult T cell leukemia/lymphoma (ATLL). HTLV-1 infection efficiently transforms human T cells in vivo and in vitro. The virus does not transduce a proto-oncogene, nor does it integrate into tumor-promoting genomic sites. Instead, HTLV-1 uses a random mutagenesis model, resulting in cellular transformation. Expression of the viral protein Tax is critical for the immortalization of infected cells by targeting specific cellular signaling pathways. However, Tax is highly immunogenic and represents the main target for the elimination of virally infected cells by host cytotoxic T cells (CTLs). In addition, Tax expression in naïve cells induces pro-apoptotic signals and has been associated with the induction of non-replicative cellular senescence. This review will explore these conundrums and discuss the mechanisms used by the Tax viral oncoprotein to influence life-and-death cellular decisions and affect HTLV-1 pathogenesis.
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Affiliation(s)
| | - Christophe Nicot
- Department of Pathology and Laboratory Medicine, University of Kansas Medical Center, 3901 Rainbow Blvd, Kansas City, KS 66160, USA;
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2
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Permatasari HK, Nakahata S, Ichikawa T, Fauzi YR, Kiyonari H, Shide K, Kameda T, Shimoda K, Ono M, Taki T, Taniwaki M, Futakuchi M, Morishita K. Oncogenic isoform switch of tumor suppressor BCL11B in adult T-cell leukemia/lymphoma. Exp Hematol 2022; 111:41-49. [PMID: 35421541 DOI: 10.1016/j.exphem.2022.04.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 04/05/2022] [Accepted: 04/06/2022] [Indexed: 11/28/2022]
Abstract
B-cell leukemia/lymphoma 11B (BCL11B) is a transcription factor important for T-cell development and acts as a tumor suppressor gene in T-cell acute lymphoblastic leukemia. Here, we identified BCL11B as a candidate leukemia-associated gene in human T-cell leukemia virus type 1 (HTLV-1)-induced adult T-cell leukemia/lymphoma (ATLL). Interestingly, the short-form lacking exon 3 (BCL11B/S) protein was more highly expressed than the full-length BCL11B (BCL11B/L) in leukemic cells from most of the ATLL patients, although expression ratios of BCL11B/L to BCL11B/S were almost equally expressed in control CD4+ T cells. BCL11B/S and BCL11B/L exhibited distinct subcellular localization and differential effects on cellular growth; BCL11B/L expression showed nuclear localization and inhibited cell growth in ATLL cells, whereas BCL11B/S showed nucleo-cytoplasmic distribution and accelerated cell growth. Furthermore, BCL11B/S expression accelerated the development of T-cell leukemia/lymphomas in transgenic mice carrying HTLV-1/HBZ, a critical viral factor in leukemogenesis, whereas these phenotypes did not occur in the double transgenic mice carrying BCL11B/L and HTLV-1/HBZ. In HTLV-1-infected T-cell lines, BCL11B expression is downregulated by HTLV-1/Tax, a viral factor necessary at the early stage of leukemogenesis. These results suggest that downregulation of BCL11B/L expression and upregulation of BCL11B/S may contribute to the development and progression of ATLL.
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Affiliation(s)
- Happy Kurnia Permatasari
- Division of Tumor and Cellular Biochemistry, Department of Medical Sciences, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki 889-1692, Japan; Department of Biochemistry and Biomolecular, Faculty of Medicine, Universitas Brawijaya, 65145 Malang, East Java, Indonesia
| | - Shingo Nakahata
- Division of Tumor and Cellular Biochemistry, Department of Medical Sciences, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki 889-1692, Japan
| | - Tomonaga Ichikawa
- Division of Tumor and Cellular Biochemistry, Department of Medical Sciences, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki 889-1692, Japan
| | - Yanuar Rahmat Fauzi
- Division of Tumor and Cellular Biochemistry, Department of Medical Sciences, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki 889-1692, Japan
| | - Hiroshi Kiyonari
- Laboratory for Animal Resources and Genetic Engineering, RIKEN Center for Biosystems Dynamics Research, 2-2-3 Minatojima Minami-machi, Chuou-ku, Kobe 650-0047, Japan
| | - Kotaro Shide
- Division of Hematology, Diabetes, and Endocrinology, Department of Internal Medicine, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki 889-1692, Japan
| | - Takuro Kameda
- Division of Hematology, Diabetes, and Endocrinology, Department of Internal Medicine, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki 889-1692, Japan
| | - Kazuya Shimoda
- Division of Hematology, Diabetes, and Endocrinology, Department of Internal Medicine, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki 889-1692, Japan
| | - Masaya Ono
- Division of Chemotherapy and Clinical Research, National Cancer Center Research Institute, 5-1-1, Tsukiji, Chuo-ku, Tokyo 104-0045, Japan
| | - Tomohiko Taki
- Department of Molecular Diagnostics and Therapeutics, Kyoto Prefectural University of Medicine, 465 Kajii-cho, Kawaramachi-Hirokoji, Kamigyo-ku, Kyoto 602-8566, Japan; Center for Molecular Diagnostics and Therapeutics, Kyoto Prefectural University of Medicine, 465 Kajii-cho, Kawaramachi-Hirokoji, Kamigyo-ku, Kyoto 602-8566, Japan
| | - Masafumi Taniwaki
- Center for Molecular Diagnostics and Therapeutics, Kyoto Prefectural University of Medicine, 465 Kajii-cho, Kawaramachi-Hirokoji, Kamigyo-ku, Kyoto 602-8566, Japan
| | - Mitsuru Futakuchi
- Department of Pathology, Faculty of Medicine, Yamagata University, 2-2-2 Iida-nishi, Yamagata, 990-9585, Japan
| | - Kazuhiro Morishita
- Division of Tumor and Cellular Biochemistry, Department of Medical Sciences, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki 889-1692, Japan; Project for Advanced Medical Research and Development, Project Research Division, Frontier Science Research Center, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki, 889-1692, Japan.
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3
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Dysregulation of immune gene expression profiles during HTLV-1 infection. Meta Gene 2021. [DOI: 10.1016/j.mgene.2021.100944] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
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Kellogg C, Kouznetsova VL, Tsigelny IF. Implications of viral infection in cancer development. Biochim Biophys Acta Rev Cancer 2021; 1876:188622. [PMID: 34478803 DOI: 10.1016/j.bbcan.2021.188622] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2021] [Revised: 08/27/2021] [Accepted: 08/28/2021] [Indexed: 12/12/2022]
Abstract
Since the identification of the first human oncogenic virus in 1964, viruses have been studied for their potential role in aiding the development of cancer. Through the modulation of cellular pathways associated with proliferation, immortalization, and inflammation, viral proteins can mimic the effect of driver mutations and contribute to transformation. Aside from the modulation of signaling pathways, the insertion of viral DNA into the host genome and the deregulation of cellular miRNAs represent two additional mechanisms implicated in viral oncogenesis. In this review, we will discuss the role of twelve different viruses on cancer development and how these viruses utilize the abovementioned mechanisms to influence oncogenesis. The identification of specific mechanisms behind viral transformation of human cells could further elucidate the process behind cancer development.
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Affiliation(s)
- Caroline Kellogg
- REHS Program, San Diego Supercomputer Center, University of California, San Diego, CA, USA
| | - Valentina L Kouznetsova
- San Diego Supercomputer Center, University of California, San Diego, CA, USA; BiAna San Diego, CA, USA
| | - Igor F Tsigelny
- San Diego Supercomputer Center, University of California, San Diego, CA, USA; Department of Neurosciences, University of California, San Diego, CA, USA; BiAna San Diego, CA, USA.
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Kim Y, Mensah GA, Al Sharif S, Pinto DO, Branscome H, Yelamanchili SV, Cowen M, Erickson J, Khatkar P, Mahieux R, Kashanchi F. Extracellular Vesicles from Infected Cells Are Released Prior to Virion Release. Cells 2021; 10:cells10040781. [PMID: 33916140 PMCID: PMC8066806 DOI: 10.3390/cells10040781] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Revised: 03/24/2021] [Accepted: 03/29/2021] [Indexed: 12/29/2022] Open
Abstract
Here, we have attempted to address the timing of EV and virion release from virally infected cells. Uninfected (CEM), HIV-1-infected (J1.1), and human T cell leukemia virus-1 (HTLV-1)-infected (HUT102) cells were synchronized in G0. Viral latency was reversed by increasing gene expression with the addition of serum-rich media and inducers. Supernatants and cell pellets were collected post-induction at different timepoints and assayed for extracellular vesicle (EV) and autophagy markers; and for viral proteins and RNAs. Tetraspanins and autophagy-related proteins were found to be differentially secreted in HIV-1- and HTLV-1-infected cells when compared with uninfected controls. HIV-1 proteins were present at 6 h and their production increased up to 24 h. HTLV-1 proteins peaked at 6 h and plateaued. HIV-1 and HTLV-1 RNA production correlated with viral protein expression. Nanoparticle tracking analysis (NTA) showed increase of EV concentration over time in both uninfected and infected samples. Finally, the HIV-1 supernatant from the 6-h samples was found not to be infectious; however, the virus from the 24-h samples was successfully rescued and infectious. Overall, our data indicate that EV release may occur prior to viral release from infected cells, thereby implicating a potentially significant effect of EVs on uninfected recipient cells prior to subsequent viral infection and spread.
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Affiliation(s)
- Yuriy Kim
- Laboratory of Molecular Virology, School of Systems Biology, George Mason University, Manassas, VA 20110, USA; (Y.K.); (G.A.M.); (S.A.S.); (D.O.P.); (H.B.); (M.C.); (J.E.); (P.K.)
| | - Gifty A. Mensah
- Laboratory of Molecular Virology, School of Systems Biology, George Mason University, Manassas, VA 20110, USA; (Y.K.); (G.A.M.); (S.A.S.); (D.O.P.); (H.B.); (M.C.); (J.E.); (P.K.)
| | - Sarah Al Sharif
- Laboratory of Molecular Virology, School of Systems Biology, George Mason University, Manassas, VA 20110, USA; (Y.K.); (G.A.M.); (S.A.S.); (D.O.P.); (H.B.); (M.C.); (J.E.); (P.K.)
| | - Daniel O. Pinto
- Laboratory of Molecular Virology, School of Systems Biology, George Mason University, Manassas, VA 20110, USA; (Y.K.); (G.A.M.); (S.A.S.); (D.O.P.); (H.B.); (M.C.); (J.E.); (P.K.)
| | - Heather Branscome
- Laboratory of Molecular Virology, School of Systems Biology, George Mason University, Manassas, VA 20110, USA; (Y.K.); (G.A.M.); (S.A.S.); (D.O.P.); (H.B.); (M.C.); (J.E.); (P.K.)
| | - Sowmya V. Yelamanchili
- Department of Anesthesiology, University of Nebraska Medical Center, Omaha, NE 68198, USA;
| | - Maria Cowen
- Laboratory of Molecular Virology, School of Systems Biology, George Mason University, Manassas, VA 20110, USA; (Y.K.); (G.A.M.); (S.A.S.); (D.O.P.); (H.B.); (M.C.); (J.E.); (P.K.)
| | - James Erickson
- Laboratory of Molecular Virology, School of Systems Biology, George Mason University, Manassas, VA 20110, USA; (Y.K.); (G.A.M.); (S.A.S.); (D.O.P.); (H.B.); (M.C.); (J.E.); (P.K.)
| | - Pooja Khatkar
- Laboratory of Molecular Virology, School of Systems Biology, George Mason University, Manassas, VA 20110, USA; (Y.K.); (G.A.M.); (S.A.S.); (D.O.P.); (H.B.); (M.C.); (J.E.); (P.K.)
| | - Renaud Mahieux
- International Center for Research in Infectiology, Retroviral Oncogenesis Laboratory, INSERM U1111-Université Claude Bernard Lyon 1, Ecole Normale Superieure de Lyon, Université de Lyon, Fondation Pour La Recherche Médicale, Labex Ecofect, 69007 Lyon, France;
| | - Fatah Kashanchi
- Laboratory of Molecular Virology, School of Systems Biology, George Mason University, Manassas, VA 20110, USA; (Y.K.); (G.A.M.); (S.A.S.); (D.O.P.); (H.B.); (M.C.); (J.E.); (P.K.)
- Correspondence: ; Tel.: +703-993-9160; Fax: +703-993-7022
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Mohanty S, Han T, Choi YB, Lavorgna A, Zhang J, Harhaj EW. The E3/E4 ubiquitin conjugation factor UBE4B interacts with and ubiquitinates the HTLV-1 Tax oncoprotein to promote NF-κB activation. PLoS Pathog 2020; 16:e1008504. [PMID: 33362245 PMCID: PMC7790423 DOI: 10.1371/journal.ppat.1008504] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Revised: 01/07/2021] [Accepted: 11/13/2020] [Indexed: 11/18/2022] Open
Abstract
Human T-cell leukemia virus type 1 (HTLV-1) is the etiological agent of adult T-cell leukemia/lymphoma (ATLL), and the neurological disease HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). The HTLV-1 Tax protein persistently activates the NF-κB pathway to enhance the proliferation and survival of HTLV-1 infected T cells. Lysine 63 (K63)-linked polyubiquitination of Tax provides an important regulatory mechanism that promotes Tax-mediated interaction with the IKK complex and activation of NF-κB; however, the host proteins regulating Tax ubiquitination are largely unknown. To identify new Tax interacting proteins that may regulate its ubiquitination we conducted a yeast two-hybrid screen using Tax as bait. This screen yielded the E3/E4 ubiquitin conjugation factor UBE4B as a novel binding partner for Tax. Here, we confirmed the interaction between Tax and UBE4B in mammalian cells by co-immunoprecipitation assays and demonstrated colocalization by proximity ligation assay and confocal microscopy. Overexpression of UBE4B specifically enhanced Tax-induced NF-κB activation, whereas knockdown of UBE4B impaired Tax-induced NF-κB activation and the induction of NF-κB target genes in T cells and ATLL cell lines. Furthermore, depletion of UBE4B with shRNA resulted in apoptotic cell death and diminished the proliferation of ATLL cell lines. Finally, overexpression of UBE4B enhanced Tax polyubiquitination, and knockdown or CRISPR/Cas9-mediated knockout of UBE4B attenuated both K48- and K63-linked polyubiquitination of Tax. Collectively, these results implicate UBE4B in HTLV-1 Tax polyubiquitination and downstream NF-κB activation. Infection with the retrovirus HTLV-1 leads to the development of either CD4+CD25+ leukemia/lymphoma (ATLL) or a demyelinating neuroinflammatory disease (HAM/TSP) in a subset of infected individuals. The HTLV-1 Tax protein is a regulatory protein which regulates viral gene expression and persistently activates cellular signaling pathways such as NF-κB to drive the clonal expansion and longevity of HTLV-1 infected CD4+ T cells. Polyubiquitination of Tax is a key mechanism of NF-κB activation by assembling and activating IκB kinase (IKK) signaling complexes; however, the host factors regulating Tax ubiquitination have remained elusive. Here, we have identified the E3/E4 ubiquitin conjugation factor UBE4B as a novel Tax binding protein that promotes both K48- and K63-linked polyubiquitination of Tax. Knockdown or knockout of UBE4B impairs Tax-induced NF-κB activation and triggers apoptosis of HTLV-1-transformed cells. Therefore, UBE4B is an integral host factor that supports HTLV-1 Tax polyubiquitination, NF-κB activation and cell survival.
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Affiliation(s)
- Suchitra Mohanty
- Department of Microbiology and Immunology, Penn State College School of Medicine, Hershey, Pennsylvania, United States of America
| | - Teng Han
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America
- Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America
| | - Young Bong Choi
- Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America
| | - Alfonso Lavorgna
- Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America
| | - Jiawen Zhang
- Department of Microbiology and Immunology, Penn State College School of Medicine, Hershey, Pennsylvania, United States of America
| | - Edward William Harhaj
- Department of Microbiology and Immunology, Penn State College School of Medicine, Hershey, Pennsylvania, United States of America
- Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America
- * E-mail:
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7
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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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The human T-cell leukemia virus type-1 tax oncoprotein dissociates NF-κB p65 RelA-Stathmin complexes and causes catastrophic mitotic spindle damage and genomic instability. Virology 2019; 535:83-101. [PMID: 31299491 DOI: 10.1016/j.virol.2019.07.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 06/21/2019] [Accepted: 07/02/2019] [Indexed: 12/23/2022]
Abstract
Genomic instability is a hallmark of many cancers; however, the molecular etiology of chromosomal dysregulation is not well understood. The human T-cell leukemia virus type-1 (HTLV-1) oncoprotein Tax activates NF-κB-signaling and induces DNA-damage and aberrant chromosomal segregation through diverse mechanisms which contribute to viral carcinogenesis. Intriguingly, Stathmin/oncoprotein-18 (Op-18) depolymerizes tubulin and interacts with the p65RelA subunit and functions as a cofactor for NF-κB-dependent transactivation. We thus hypothesized that the dissociation of p65RelA-Stathmin/Op-18 complexes by Tax could lead to the catastrophic destabilization of microtubule (MT) spindle fibers during mitosis and provide a novel mechanistic link between NF-κB-signaling and genomic instability. Here we report that the inhibition of Stathmin expression by the retroviral latency protein, p30II, or knockdown with siRNA-stathmin, dampens Tax-mediated NF-κB transactivation and counters Tax-induced genomic instability and cytotoxicity. The Tax-G148V mutant, defective for NF-κB activation, exhibited reduced p65RelA-Stathmin binding and diminished genomic instability and cytotoxicity. Dominant-negative inhibitors of NF-κB also prevented Tax-induced multinucleation and apoptosis. Moreover, cell clones containing the infectious HTLV-1 ACH. p30II mutant provirus, impaired for p30II production, exhibited increased multinucleation and the accumulation of cytoplasmic tubulin aggregates following nocodozole-treatment. These findings allude to a mechanism whereby NF-κB-signaling regulates tubulin dynamics and mitotic instability through the modulation of p65RelA-Stathmin/Op-18 interactions, and support the notion that p30II enhances the survival of Tax-expressing HTLV-1-transformed cells.
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Zhou W, Lozano-Torres JL, Blilou I, Zhang X, Zhai Q, Smant G, Li C, Scheres B. A Jasmonate Signaling Network Activates Root Stem Cells and Promotes Regeneration. Cell 2019; 177:942-956.e14. [PMID: 30955889 DOI: 10.1016/j.cell.2019.03.006] [Citation(s) in RCA: 166] [Impact Index Per Article: 33.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Revised: 01/08/2019] [Accepted: 03/04/2019] [Indexed: 12/22/2022]
Abstract
Plants are sessile and have to cope with environmentally induced damage through modification of growth and defense pathways. How tissue regeneration is triggered in such responses and whether this involves stem cell activation is an open question. The stress hormone jasmonate (JA) plays well-established roles in wounding and defense responses. JA also affects growth, which is hitherto interpreted as a trade-off between growth and defense. Here, we describe a molecular network triggered by wound-induced JA that promotes stem cell activation and regeneration. JA regulates organizer cell activity in the root stem cell niche through the RBR-SCR network and stress response protein ERF115. Moreover, JA-induced ERF109 transcription stimulates CYCD6;1 expression, functions upstream of ERF115, and promotes regeneration. Soil penetration and response to nematode herbivory induce and require this JA-mediated regeneration response. Therefore, the JA tissue damage response pathway induces stem cell activation and regeneration and activates growth after environmental stress.
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Affiliation(s)
- Wenkun Zhou
- Laboratory of Plant Developmental Biology, Wageningen University and Research, 6708 PB Wageningen, the Netherlands; State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Jose L Lozano-Torres
- Laboratory of Nematology, Wageningen University and Research, 6708 PB Wageningen, the Netherlands
| | - Ikram Blilou
- Laboratory of Plant Developmental Biology, Wageningen University and Research, 6708 PB Wageningen, the Netherlands; KAUST, Thuwall 23955, Saudi Arabia
| | - Xiaoyue Zhang
- State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Qingzhe Zhai
- State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Geert Smant
- Laboratory of Nematology, Wageningen University and Research, 6708 PB Wageningen, the Netherlands
| | - Chuanyou Li
- State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, 100049 Beijing, China
| | - Ben Scheres
- Laboratory of Plant Developmental Biology, Wageningen University and Research, 6708 PB Wageningen, the Netherlands; Rijk Zwaan R&D, 4793 RS Fijnaart, the Netherlands.
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Liu H, Wang J, Liu Y, Hu L, Zhang C, Xing B, Du X. Human U3 protein14a is a novel type ubiquitin ligase that binds RB and promotes RB degradation depending on a leucine-rich region. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2018; 1865:1611-1620. [DOI: 10.1016/j.bbamcr.2018.08.016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Revised: 08/22/2018] [Accepted: 08/23/2018] [Indexed: 11/16/2022]
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11
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Harhaj EW, Giam CZ. NF-κB signaling mechanisms in HTLV-1-induced adult T-cell leukemia/lymphoma. FEBS J 2018; 285:3324-3336. [PMID: 29722927 DOI: 10.1111/febs.14492] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Revised: 04/12/2018] [Accepted: 04/26/2018] [Indexed: 12/27/2022]
Abstract
The human T-cell leukemia virus type 1 (HTLV-1) is a complex deltaretrovirus linked to adult T-cell leukemia/lymphoma (ATLL), a fatal CD4 + malignancy in 3-5% of infected individuals. The HTLV-1 Tax regulatory protein plays indispensable roles in regulating viral gene expression and activating cellular signaling pathways that drive the proliferation and clonal expansion of T cells bearing HTLV-1 proviral integrations. Tax is a potent activator of NF-κB, a key signaling pathway that is essential for the survival and proliferation of HTLV-1-infected T cells. However, constitutive NF-κB activation by Tax also triggers a senescence response, suggesting the possibility that only T cells capable of overcoming NF-κB-induced senescence can selectively undergo clonal expansion after HTLV-1 infection. Tax expression is often silenced in the majority of ATLL due to genetic alterations in the tax gene or DNA hypermethylation of the 5'-LTR. Despite the loss of Tax, NF-κB activation remains persistently activated in ATLL due to somatic mutations in genes in the T/B-cell receptor (T/BCR) and NF-κB signaling pathways. In this review, we focus on the key events driving Tax-dependent and -independent mechanisms of NF-κB activation during the multistep process leading to ATLL.
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Affiliation(s)
- Edward William Harhaj
- Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Chou-Zen Giam
- Department of Microbiology and Immunology, Uniformed Services University, Bethesda, MD, USA
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12
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Permatasari HK, Nakahata S, Ichikawa T, Morishita K. BCL11B is frequently downregulated in HTLV-1-infected T-cells through Tax-mediated proteasomal degradation. Biochem Biophys Res Commun 2017; 490:1086-1092. [PMID: 28669733 DOI: 10.1016/j.bbrc.2017.06.172] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Accepted: 06/28/2017] [Indexed: 01/01/2023]
Abstract
Human T-cell leukemia virus type 1 (HTLV-1) is a causative agent of adult T-cell leukemia-lymphoma (ATLL). The HTLV-1-encoded protein Tax plays important roles in the proliferation of HTLV-1-infected T-cells by affecting cellular proteins. In this study, we showed that Tax transcriptionally and post-transcriptionally downregulates the expression of the tumor suppressor gene B-cell leukemia/lymphoma 11B (BCL11B), which encodes a lymphoid-related transcription factor. BCL11B expression was downregulated in HTLV-1-infected T-cell lines at the mRNA and protein levels, and forced expression of BCL11B suppressed the proliferation of these cells. The proteasomal inhibitor MG132 increased BCL11B expression in HTLV-1-infected cell lines, and colocalization of Tax with BCL11B was detected in the cytoplasm of HTLV-1-infected T-cells following MG132 treatment. shRNA knock-down of Tax expression also increased the expression of BCL11B in HTLV-1-infected cells. Moreover, we found that Tax physically binds to BCL11B protein and induces the polyubiquitination of BCL11B and proteasome-dependent degradation of BCL11B. Thus, inactivation of BCL11B by Tax protein may play an important role in the Tax-mediated leukemogenesis.
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Affiliation(s)
- Happy Kurnia Permatasari
- Division of Tumor and Cellular Biochemistry, Department of Medical Sciences, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki 889-1692, Japan
| | - Shingo Nakahata
- Division of Tumor and Cellular Biochemistry, Department of Medical Sciences, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki 889-1692, Japan
| | - Tomonaga Ichikawa
- Division of Tumor and Cellular Biochemistry, Department of Medical Sciences, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki 889-1692, Japan
| | - Kazuhiro Morishita
- Division of Tumor and Cellular Biochemistry, Department of Medical Sciences, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki 889-1692, Japan.
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Chan CP, Kok KH, Jin DY. Human T-Cell Leukemia Virus Type 1 Infection and Adult T-Cell Leukemia. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1018:147-166. [PMID: 29052136 DOI: 10.1007/978-981-10-5765-6_9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Human T-cell leukemia virus type 1 (HTLV-1) is the first retrovirus discovered to cause adult T-cell leukemia (ATL), a highly aggressive blood cancer. HTLV-1 research in the past 35 years has been most revealing in the mechanisms of viral oncogenesis. HTLV-1 establishes a lifelong persistent infection in CD4+ T lymphocytes. The infection outcome is governed by host immunity. ATL develops in 2-5% of infected individuals 30-50 years after initial exposure. HTLV-1 encodes two oncoproteins Tax and HBZ, which are required for initiation of cellular transformation and maintenance of cell proliferation, respectively. HTLV-1 oncogenesis is driven by a clonal selection and expansion process during which both host and viral factors cooperate to impair genome stability, immune surveillance, and other mechanisms of tumor suppression. A better understanding of HTLV-1 biology and leukemogenesis will reveal new strategies and modalities for ATL prevention and treatment.
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Affiliation(s)
- Chi-Ping Chan
- School of Biomedical Sciences, The University of Hong Kong, 21 Sassoon Road, Pokfulam, Hong Kong
| | - Kin-Hang Kok
- Department of Microbiology, The University of Hong Kong, 145 Pokfulam Road, Pokfulam, Hong Kong
| | - Dong-Yan Jin
- School of Biomedical Sciences, The University of Hong Kong, 21 Sassoon Road, Pokfulam, Hong Kong.
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HTLV-1 bZIP factor protein targets the Rb/E2F-1 pathway to promote proliferation and apoptosis of primary CD4(+) T cells. Oncogene 2016; 35:4509-17. [PMID: 26804169 DOI: 10.1038/onc.2015.510] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2015] [Revised: 11/18/2015] [Accepted: 12/04/2015] [Indexed: 12/13/2022]
Abstract
Human T-cell leukemia virus type 1 (HTLV-1) is an oncogenic retrovirus that induces a fatal T-cell malignancy, adult T-cell leukemia (ATL). Among several regulatory/accessory genes in HTLV-1, HTLV-1 bZIP factor (HBZ) is the only viral gene constitutively expressed in infected cells. Our previous study showed that HBZ functions in two different molecular forms, HBZ protein and HBZ RNA. In this study, we show that HBZ protein targets retinoblastoma protein (Rb), which is a critical tumor suppressor in many types of cancers. HBZ protein interacts with the Rb/E2F-1 complex and activates the transcription of E2F-target genes associated with cell cycle progression and apoptosis. Mouse primary CD4(+) T cells transduced with HBZ show accelerated G1/S transition and apoptosis, and importantly, T cells from HBZ transgenic (HBZ-Tg) mice also demonstrate enhanced cell proliferation and apoptosis. To evaluate the functions of HBZ protein alone in vivo, we generated a new transgenic mouse strain that expresses HBZ mRNA altered by silent mutations but encoding intact protein. In these mice, the numbers of effector/memory and Foxp3(+) T cells were increased, and genes associated with proliferation and apoptosis were upregulated. This study shows that HBZ protein promotes cell proliferation and apoptosis in primary CD4(+) T cells through activation of the Rb/E2F pathway, and that HBZ protein also confers onto CD4(+) T-cell immunophenotype similar to those of ATL cells, suggesting that HBZ protein has important roles in dysregulation of CD4(+) T cells infected with HTLV-1.
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Minarovits J, Demcsák A, Banati F, Niller HH. Epigenetic Dysregulation in Virus-Associated Neoplasms. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 879:71-90. [DOI: 10.1007/978-3-319-24738-0_4] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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16
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Wang Y, Zheng Z, Zhang J, Wang Y, Kong R, Liu J, Zhang Y, Deng H, Du X, Ke Y. A Novel Retinoblastoma Protein (RB) E3 Ubiquitin Ligase (NRBE3) Promotes RB Degradation and Is Transcriptionally Regulated by E2F1 Transcription Factor. J Biol Chem 2015; 290:28200-28213. [PMID: 26442585 DOI: 10.1074/jbc.m115.655597] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Indexed: 12/25/2022] Open
Abstract
Retinoblastoma protein (RB) plays critical roles in tumor suppression and is degraded through the proteasomal pathway. However, E3 ubiquitin ligases responsible for proteasome-mediated degradation of RB are largely unknown. Here we characterize a novel RB E3 ubiquitin ligase (NRBE3) that binds RB and promotes RB degradation. NRBE3 contains an LXCXE motif and bound RB in vitro. NRBE3 interacted with RB in cells when proteasome activity was inhibited. NRBE3 promoted RB ubiquitination and degradation via the ubiquitin-proteasome pathway. Importantly, purified NRBE3 ubiquitinated recombinant RB in vitro, and a U-box was identified as essential for its E3 activity. Surprisingly, NRBE3 was transcriptionally activated by E2F1/DP1. Consequently, NRBE3 affected the cell cycle by promoting G1/S transition. Moreover, NRBE3 was up-regulated in breast cancer tissues. Taken together, we identified NRBE3 as a novel ubiquitin E3 ligase for RB that might play a role as a potential oncoprotein in human cancers.
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Affiliation(s)
- Yingshuang Wang
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education); Genetics Laboratory, Peking University School of Oncology, Beijing Cancer Hospital and Institute, Beijing 100142, China
| | - Zongfang Zheng
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education); Genetics Laboratory, Peking University School of Oncology, Beijing Cancer Hospital and Institute, Beijing 100142, China
| | - Jingyi Zhang
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education)
| | - You Wang
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education); Genetics Laboratory, Peking University School of Oncology, Beijing Cancer Hospital and Institute, Beijing 100142, China
| | - Ruirui Kong
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education); Genetics Laboratory, Peking University School of Oncology, Beijing Cancer Hospital and Institute, Beijing 100142, China
| | - Jiangying Liu
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education); Genetics Laboratory, Peking University School of Oncology, Beijing Cancer Hospital and Institute, Beijing 100142, China
| | - Ying Zhang
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education); Genetics Laboratory, Peking University School of Oncology, Beijing Cancer Hospital and Institute, Beijing 100142, China
| | - Hongkui Deng
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education); Department of Cell Biology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, China
| | - Xiaojuan Du
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education); Department of Cell Biology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, China.
| | - Yang Ke
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education); Genetics Laboratory, Peking University School of Oncology, Beijing Cancer Hospital and Institute, Beijing 100142, China
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17
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Nicot C. HTLV-I Tax-Mediated Inactivation of Cell Cycle Checkpoints and DNA Repair Pathways Contribute to Cellular Transformation: "A Random Mutagenesis Model". ACTA ACUST UNITED AC 2015; 2. [PMID: 26835512 DOI: 10.13188/2377-9292.1000009] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
To achieve cellular transformation, most oncogenic retroviruses use transduction by proto-oncogene capture or insertional mutagenesis, whereby provirus integration disrupts expression of tumor suppressors or proto-oncogenes. In contrast, the Human T-cell leukemia virus type 1 (HTLV-I) has been classified in a separate class referred to as "transactivating retroviruses". Current views suggest that the viral encoded Tax protein transactivates expression of cellular genes leading to deregulated growth and transformation. However, if Tax-mediated transactivation was indeed sufficient for cellular transformation, a fairly high frequency of infected cells would eventually become transformed. In contrast, the frequency of transformation by HTLV-I is very low, likely less than 5%. This review will discuss the current understanding and recent discoveries highlighting critical functions of Tax in cellular transformation. HTLV-I Tax carries out essential functions in order to override cell cycle checkpoints and deregulate cellular division. In addition, Tax expression is associated with increased DNA damage and genome instability. Since Tax can inhibit multiple DNA repair pathways and stimulate unfaithful DNA repair or bypass checkpoints, these processes allow accumulation of genetic mutations in the host genome. Given this, a "Random Mutagenesis" transformation model seems more suitable to characterize the oncogenic activities of HTLV-I.
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Affiliation(s)
- Christophe Nicot
- Department of Pathology and Laboratory Medicine, Center for Viral Oncology, University of Kansas Medical Center, USA
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Tumor Suppressor Inactivation in the Pathogenesis of Adult T-Cell Leukemia. JOURNAL OF ONCOLOGY 2015; 2015:183590. [PMID: 26170835 PMCID: PMC4478360 DOI: 10.1155/2015/183590] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/14/2015] [Accepted: 05/24/2015] [Indexed: 12/12/2022]
Abstract
Tumor suppressor functions are essential to control cellular proliferation, to activate the apoptosis or senescence pathway to eliminate unwanted cells, to link DNA damage signals to cell cycle arrest checkpoints, to activate appropriate DNA repair pathways, and to prevent the loss of adhesion to inhibit initiation of metastases. Therefore, tumor suppressor genes are indispensable to maintaining genetic and genomic integrity. Consequently, inactivation of tumor suppressors by somatic mutations or epigenetic mechanisms is frequently associated with tumor initiation and development. In contrast, reactivation of tumor suppressor functions can effectively reverse the transformed phenotype and lead to cell cycle arrest or death of cancerous cells and be used as a therapeutic strategy. Adult T-cell leukemia/lymphoma (ATLL) is an aggressive lymphoproliferative disease associated with infection of CD4 T cells by the Human T-cell Leukemia Virus Type 1 (HTLV-I). HTLV-I-associated T-cell transformation is the result of a multistep oncogenic process in which the virus initially induces chronic T-cell proliferation and alters cellular pathways resulting in the accumulation of genetic defects and the deregulated growth of virally infected cells. This review will focus on the current knowledge of the genetic and epigenetic mechanisms regulating the inactivation of tumor suppressors in the pathogenesis of HTLV-I.
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Modulation of DNA damage and repair pathways by human tumour viruses. Viruses 2015; 7:2542-91. [PMID: 26008701 PMCID: PMC4452920 DOI: 10.3390/v7052542] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Accepted: 05/12/2015] [Indexed: 02/07/2023] Open
Abstract
With between 10% and 15% of human cancers attributable to viral infection, there is great interest, from both a scientific and clinical viewpoint, as to how these pathogens modulate host cell functions. Seven human tumour viruses have been identified as being involved in the development of specific malignancies. It has long been known that the introduction of chromosomal aberrations is a common feature of viral infections. Intensive research over the past two decades has subsequently revealed that viruses specifically interact with cellular mechanisms responsible for the recognition and repair of DNA lesions, collectively known as the DNA damage response (DDR). These interactions can involve activation and deactivation of individual DDR pathways as well as the recruitment of specific proteins to sites of viral replication. Since the DDR has evolved to protect the genome from the accumulation of deleterious mutations, deregulation is inevitably associated with an increased risk of tumour formation. This review summarises the current literature regarding the complex relationship between known human tumour viruses and the DDR and aims to shed light on how these interactions can contribute to genomic instability and ultimately the development of human cancers.
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Regulation of HTLV-1 tax stability, cellular trafficking and NF-κB activation by the ubiquitin-proteasome pathway. Viruses 2014; 6:3925-43. [PMID: 25341660 PMCID: PMC4213571 DOI: 10.3390/v6103925] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2014] [Revised: 10/15/2014] [Accepted: 10/21/2014] [Indexed: 12/22/2022] Open
Abstract
Human T-cell leukemia virus type 1 (HTLV-1) is a complex retrovirus that infects CD4+ T cells and causes adult T-cell leukemia/lymphoma (ATLL) in 3%–5% of infected individuals after a long latent period. HTLV-1 Tax is a trans-activating protein that regulates viral gene expression and also modulates cellular signaling pathways to enhance T-cell proliferation and cell survival. The Tax oncoprotein promotes T-cell transformation, in part via constitutive activation of the NF-κB transcription factor; however, the underlying mechanisms remain unknown. Ubiquitination is a type of post-translational modification that occurs in a three-step enzymatic cascade mediated by E1, E2 and E3 enzymes and regulates protein stability as well as signal transduction, protein trafficking and the DNA damage response. Emerging studies indicate that Tax hijacks the ubiquitin machinery to activate ubiquitin-dependent kinases and downstream NF-κB signaling. Tax interacts with the E2 conjugating enzyme Ubc13 and is conjugated on C-terminal lysine residues with lysine 63-linked polyubiquitin chains. Tax K63-linked polyubiquitination may serve as a platform for signaling complexes since this modification is critical for interactions with NEMO and IKK. In addition to NF-κB signaling, mono- and polyubiquitination of Tax also regulate its subcellular trafficking and stability. Here, we review recent advances in the diverse roles of ubiquitin in Tax function and how Tax usurps the ubiquitin-proteasome pathway to promote oncogenesis.
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21
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Chen H, Zhao Y, Li H, Zhang D, Huang Y, Shen Q, Van Duyne R, Kashanchi F, Zeng C, Liu S. Break CDK2/Cyclin E1 interface allosterically with small peptides. PLoS One 2014; 9:e109154. [PMID: 25290691 PMCID: PMC4188581 DOI: 10.1371/journal.pone.0109154] [Citation(s) in RCA: 17] [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: 03/31/2014] [Accepted: 09/03/2014] [Indexed: 02/07/2023] Open
Abstract
Most inhibitors of Cyclin-dependent kinase 2 (CDK2) target its ATP-binding pocket. It is difficult, however, to use this pocket to design very specific inhibitors because this catalytic pocket is highly conserved in the protein family of CDKs. Here we report some short peptides targeting a noncatalytic pocket near the interface of the CDK2/Cyclin complex. Docking and molecular dynamics simulations were used to select the peptides, and detailed dynamical network analysis revealed that these peptides weaken the complex formation via allosteric interactions. Our experiments showed that upon binding to the noncatalytic pocket, these peptides break the CDK2/Cyclin complex partially and diminish its kinase activity in vitro. The binding affinity of these peptides measured by Surface Plasmon Resonance can reach as low as 0.5 µM.
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Affiliation(s)
- Hao Chen
- Department of Physics, The George Washington University, Washington, D. C., United States of America
| | - Yunjie Zhao
- Department of Physics, The George Washington University, Washington, D. C., United States of America
| | - Haotian Li
- Department of Physics, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Dongyan Zhang
- Department of Physics, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Yanzhao Huang
- Department of Physics, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Qi Shen
- BNLMS, Center for Quantitative Biology, Peking University, Beijing, China
| | - Rachel Van Duyne
- George Mason University, National Center for Biodefense & Infectious Diseases, Manassas, Virginia, United States of America
- The George Washington University Medical Center, Department of Microbiology, Immunology, and Tropical Medicine, Washington, D. C., United States of America
| | - Fatah Kashanchi
- George Mason University, National Center for Biodefense & Infectious Diseases, Manassas, Virginia, United States of America
| | - Chen Zeng
- Department of Physics, Huazhong University of Science and Technology, Wuhan, Hubei, China
- Department of Physics, The George Washington University, Washington, D. C., United States of America
| | - Shiyong Liu
- Department of Physics, Huazhong University of Science and Technology, Wuhan, Hubei, China
- * E-mail:
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22
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Ben-Nissan G, Sharon M. Regulating the 20S proteasome ubiquitin-independent degradation pathway. Biomolecules 2014; 4:862-84. [PMID: 25250704 PMCID: PMC4192676 DOI: 10.3390/biom4030862] [Citation(s) in RCA: 242] [Impact Index Per Article: 24.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2014] [Revised: 08/27/2014] [Accepted: 09/05/2014] [Indexed: 02/07/2023] Open
Abstract
For many years, the ubiquitin-26S proteasome degradation pathway was considered the primary route for proteasomal degradation. However, it is now becoming clear that proteins can also be targeted for degradation by the core 20S proteasome itself. Degradation by the 20S proteasome does not require ubiquitin tagging or the presence of the 19S regulatory particle; rather, it relies on the inherent structural disorder of the protein being degraded. Thus, proteins that contain unstructured regions due to oxidation, mutation, or aging, as well as naturally, intrinsically unfolded proteins, are susceptible to 20S degradation. Unlike the extensive knowledge acquired over the years concerning degradation by the 26S proteasome, relatively little is known about the means by which 20S-mediated proteolysis is controlled. Here, we describe our current understanding of the regulatory mechanisms that coordinate 20S proteasome-mediated degradation, and highlight the gaps in knowledge that remain to be bridged.
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Affiliation(s)
- Gili Ben-Nissan
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 7610001, Israel.
| | - Michal Sharon
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 7610001, Israel.
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23
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The interaction of nonstructural protein 9 with retinoblastoma protein benefits the replication of genotype 2 porcine reproductive and respiratory syndrome virus in vitro. Virology 2014; 464-465:432-440. [PMID: 25146601 PMCID: PMC7112046 DOI: 10.1016/j.virol.2014.07.036] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Revised: 07/18/2014] [Accepted: 07/21/2014] [Indexed: 11/23/2022]
Abstract
The nonstructural protein 9 (Nsp9) of porcine reproductive and respiratory syndrome virus (PRRSV) is a RNA-dependent RNA polymerase (RdRp) that plays a vital role in viral replication. This study first demonstrated that the Nsp9 of genotype 2 PRRSV interacted with cellular retinoblastoma protein (pRb), and Nsp9 co-localized with pRb in the cytoplasm of PRRSV-infected MARC-145 cells and pulmonary alveolar macrophages (PAMs). Next, the overexpression of truncated pRb was shown to inhibit the PRRSV replication and silencing the pRb gene could facilitate the PRRSV replication in MARC-145 cells. Finally, the pRb level was confirmed to be down-regulated in PRRSV-infected MARC-145 cells, and Nsp9 was shown to promote the pRb degradation by proteasome pathway. These findings indicate that the interaction of Nsp 9 with pRb benefits the replication of genotype 2 PRRSV in vitro, helping to understand the roles of Nsp9 in the replication and pathogenesis of PRRSV. The Nsp9 of genotype 2 PRRSV interacted with retinoblastoma protein (pRb). The pRb level was down-regulated in PRRSV-infected MARC-145 cells. The Nsp9 of genotype 2 PRRSV promoted the pRb degradation by proteasome pathway. The interaction of Nsp 9 with pRb benefits the genotype 2 PRRSV replication in vitro.
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Jaworski E, Narayanan A, Van Duyne R, Shabbeer-Meyering S, Iordanskiy S, Saifuddin M, Das R, Afonso PV, Sampey GC, Chung M, Popratiloff A, Shrestha B, Sehgal M, Jain P, Vertes A, Mahieux R, Kashanchi F. Human T-lymphotropic virus type 1-infected cells secrete exosomes that contain Tax protein. J Biol Chem 2014; 289:22284-305. [PMID: 24939845 DOI: 10.1074/jbc.m114.549659] [Citation(s) in RCA: 112] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Human T-lymphotropic virus type 1 (HTLV-1) is the causative agent of adult T-cell leukemia and HTLV-1-associated myelopathy/tropical spastic paraparesis. The HTLV-1 transactivator protein Tax controls many critical cellular pathways, including host cell DNA damage response mechanisms, cell cycle progression, and apoptosis. Extracellular vesicles called exosomes play critical roles during pathogenic viral infections as delivery vehicles for host and viral components, including proteins, mRNA, and microRNA. We hypothesized that exosomes derived from HTLV-1-infected cells contain unique host and viral proteins that may contribute to HTLV-1-induced pathogenesis. We found exosomes derived from infected cells to contain Tax protein and proinflammatory mediators as well as viral mRNA transcripts, including Tax, HBZ, and Env. Furthermore, we observed that exosomes released from HTLV-1-infected Tax-expressing cells contributed to enhanced survival of exosome-recipient cells when treated with Fas antibody. This survival was cFLIP-dependent, with Tax showing induction of NF-κB in exosome-recipient cells. Finally, IL-2-dependent CTLL-2 cells that received Tax-containing exosomes were protected from apoptosis through activation of AKT. Similar experiments with primary cultures showed protection and survival of peripheral blood mononuclear cells even in the absence of phytohemagglutinin/IL-2. Surviving cells contained more phosphorylated Rb, consistent with the role of Tax in regulation of the cell cycle. Collectively, these results suggest that exosomes may play an important role in extracellular delivery of functional HTLV-1 proteins and mRNA to recipient cells.
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Affiliation(s)
- Elizabeth Jaworski
- From the School of Systems Biology, National Center for Biodefense and Infectious Diseases, George Mason University, Manassas, Virginia 20110
| | - Aarthi Narayanan
- From the School of Systems Biology, National Center for Biodefense and Infectious Diseases, George Mason University, Manassas, Virginia 20110
| | - Rachel Van Duyne
- From the School of Systems Biology, National Center for Biodefense and Infectious Diseases, George Mason University, Manassas, Virginia 20110, the Department of Microbiology, Immunology, and Tropical Medicine and
| | - Shabana Shabbeer-Meyering
- From the School of Systems Biology, National Center for Biodefense and Infectious Diseases, George Mason University, Manassas, Virginia 20110
| | - Sergey Iordanskiy
- From the School of Systems Biology, National Center for Biodefense and Infectious Diseases, George Mason University, Manassas, Virginia 20110, the Department of Microbiology, Immunology, and Tropical Medicine and
| | - Mohammed Saifuddin
- From the School of Systems Biology, National Center for Biodefense and Infectious Diseases, George Mason University, Manassas, Virginia 20110
| | - Ravi Das
- From the School of Systems Biology, National Center for Biodefense and Infectious Diseases, George Mason University, Manassas, Virginia 20110
| | - Philippe V Afonso
- the Unité d'Epidémiologie et Physiopathologie des Virus Oncogènes, Département de Virologie, Institut Pasteur, F-75015 Paris, France, CNRS, UMR3569, F-75015 Paris, France, and
| | - Gavin C Sampey
- From the School of Systems Biology, National Center for Biodefense and Infectious Diseases, George Mason University, Manassas, Virginia 20110
| | - Myung Chung
- From the School of Systems Biology, National Center for Biodefense and Infectious Diseases, George Mason University, Manassas, Virginia 20110
| | - Anastas Popratiloff
- the Department of Chemistry, George Washington University, Washington, D. C. 20037
| | - Bindesh Shrestha
- Center for Microscopy and Image Analysis, George Washington University Medical Center, Washington, D. C. 20037
| | - Mohit Sehgal
- the Department of Microbiology and Immunology, Drexel Institute for Biotechnology and Virology Research, Drexel University College of Medicine, Doylestown, Pennsylvania 18902
| | - Pooja Jain
- the Department of Microbiology and Immunology, Drexel Institute for Biotechnology and Virology Research, Drexel University College of Medicine, Doylestown, Pennsylvania 18902
| | - Akos Vertes
- Center for Microscopy and Image Analysis, George Washington University Medical Center, Washington, D. C. 20037
| | - Renaud Mahieux
- the Equipe Oncogenèse Rétrovirale, Equipe labelisée "Ligue Nationale Contre le Cancer," International Center for Research in Infectiology, INSERM U1111-CNRS UMR5308, Ecole Normale Supérieure de Lyon, Université Lyon 1, Lyon 69364 Cedex 07, France
| | - Fatah Kashanchi
- From the School of Systems Biology, National Center for Biodefense and Infectious Diseases, George Mason University, Manassas, Virginia 20110,
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25
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Zane L, Jeang KT. HTLV-1 and leukemogenesis: virus-cell interactions in the development of adult T-cell leukemia. Recent Results Cancer Res 2014; 193:191-210. [PMID: 24008300 DOI: 10.1007/978-3-642-38965-8_11] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Human T-cell lymphotropic virus type 1 (HTLV-1) was originally discovered in the early 1980s. It is the first retrovirus to be unambiguously linked causally to a human cancer. HTLV-1 currently infects approximately 20 million people worldwide. In this chapter, we review progress made over the last 30 years in our understanding of HTLV-1 infection, replication, gene expression, and cellular transformation.
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Affiliation(s)
- Linda Zane
- Molecular Virology Section, Laboratory of Molecular Microbiology, The National Institutes of Allergy and Infectious Diseases, The National Institutes of Health, Bethesda, MD, 20892-0460, USA
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Abstract
To replicate their genomes in cells and generate new progeny, viruses typically require factors provided by the cells that they have infected. Subversion of the cellular machinery that controls replication of the infected host cell is a common activity of many viruses. Viruses employ different strategies to deregulate cell cycle checkpoint controls and modulate cell proliferation pathways. A number of DNA and RNA viruses encode proteins that target critical cell cycle regulators to achieve cellular conditions that are beneficial for viral replication. Many DNA viruses induce quiescent cells to enter the cell cycle; this is thought to increase pools of deoxynucleotides and thus, facilitate viral replication. In contrast, some viruses can arrest cells in a particular phase of the cell cycle that is favorable for replication of the specific virus. Cell cycle arrest may inhibit early cell death of infected cells, allow the cells to evade immune defenses, or help promote virus assembly. Although beneficial for the viral life cycle, virus-mediated alterations in normal cell cycle control mechanisms could have detrimental effects on cellular physiology and may ultimately contribute to pathologies associated with the viral infection, including cell transformation and cancer progression and maintenance. In this chapter, we summarize various strategies employed by DNA and RNA viruses to modulate the replication cycle of the virus-infected cell. When known, we describe how these virus-associated effects influence replication of the virus and contribute to diseases associated with infection by that specific virus.
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Affiliation(s)
- Eishi Noguchi
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, Pennsylvania USA
| | - Mariana C. Gadaleta
- Dept of Biochemistry & Molecular Biology, Drexel University College of Medicine, Philadelphia, USA
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Niller HH, Banati F, Nagy K, Buzas K, Minarovits J. Update on microbe-induced epigenetic changes: bacterial effectors and viral oncoproteins as epigenetic dysregulators. Future Virol 2013. [DOI: 10.2217/fvl.13.97] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Pathoepigenetics is a new discipline describing how disturbances in epigenetic regulation alter the epigenotype and gene-expression pattern of human, animal or plant cells. Such ‘epigenetic reprogramming’ may play an important role in the initiation and progression of a wide variety of diseases. Infectious diseases also belong to this category: recent data demonstrated that microbial pathogens, including bacteria and viruses, are capable of dysregulating the epigenetic machinery of their host cell. The resulting heritable changes in host cell gene expression may favor the colonization, growth or spread of infectious pathogens. It may also facilitate the establishment of latency and malignant cell transformation. In this article, we review how bacterial epigenetic effectors and inflammatory processes elicited by bacteria alter the host cell epigenotype, and describe how oncoproteins encoded by human tumor viruses act as epigenetic dysregulators to alter the phenotype and behavior of host cells.
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Affiliation(s)
- Hans Helmut Niller
- Institute for Medical Microbiology & Hygiene, University of Regensburg, Franz-Josef-Strauss Allee 11, Regensburg D93053, Germany
| | - Ferenc Banati
- RT-Europe Nonprofit Research Center, H-9200 Mosonmagyarovar, Pozsonyi út 88, Hungary
| | - Katalin Nagy
- University of Szeged, Faculty of Dentistry, Department of Oral Surgery, H-6720 Szeged, Tisza Lajos Krt. 64, Hungary
| | - Krisztina Buzas
- University of Szeged, Faculty of Dentistry, Department of Oral Biology & Experimental Dental Research, H-6720 Szeged, Tisza Lajos Krt. 64, Hungary
| | - Janos Minarovits
- University of Szeged, Faculty of Dentistry, Department of Oral Biology & Experimental Dental Research, H-6720 Szeged, Tisza Lajos Krt. 64, Hungary
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Sampey GC, Van Duyne R, Currer R, Das R, Narayanan A, Kashanchi F. Complex role of microRNAs in HTLV-1 infections. Front Genet 2012; 3:295. [PMID: 23251140 PMCID: PMC3523292 DOI: 10.3389/fgene.2012.00295] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2012] [Accepted: 11/29/2012] [Indexed: 12/15/2022] Open
Abstract
Human T-lymphotropic virus 1 (HTLV-1) was the first human retrovirus to be discovered and is the causative agent of adult T-cell leukemia/lymphoma (ATL) and the neurodegenerative disease HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). The importance of microRNA (miRNA) in the replicative cycle of several other viruses, as well as in the progression of associated pathologies, has been well established in the past decade. Moreover, involvement of miRNA alteration in the HTLV-1 life cycle, and in the progression of its related oncogenic and neurodegenerative diseases, has recently come to light. Several HTLV-1 derived proteins alter transcription factor functionalities, interact with chromatin remodelers, or manipulate components of the RNA interference (RNAi) machinery, thereby establishing various routes by which miRNA expression can be up- or down-regulated in the host cell. Furthermore, the mechanism of action through which dysregulation of host miRNAs affects HTLV-1 infected cells can vary substantially and include mRNA silencing via the RNA-induced silencing complex (RISC), transcriptional gene silencing, inhibition of RNAi components, and chromatin remodeling. These miRNA-induced changes can lead to increased cell survival, invasiveness, proliferation, and differentiation, as well as allow for viral latency. While many recent studies have successfully implicated miRNAs in the life cycle and pathogenesis of HTLV-1 infections, there are still significant outstanding questions to be addressed. Here we will review recent discoveries elucidating HTLV-1 mediated manipulation of host cell miRNA profiles and examine the impact on pathogenesis, as well as explore future lines of inquiry that could increase understanding in this field of study.
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Affiliation(s)
- Gavin C Sampey
- National Center for Biodefense and Infectious Diseases, School of Systems Biology, George Mason University Manassas, VA, USA
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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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HTLV-I tax increases genetic instability by inducing DNA double strand breaks during DNA replication and switching repair to NHEJ. PLoS One 2012; 7:e42226. [PMID: 22916124 PMCID: PMC3423393 DOI: 10.1371/journal.pone.0042226] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2012] [Accepted: 07/02/2012] [Indexed: 01/23/2023] Open
Abstract
BACKGROUND Appropriate responses to damaged DNA are indispensible for preserving genome stability and preventing cancer. Tumor viruses often target DNA repair machinery to achieve transformation. The Human T-cell leukemia virus type I (HTLV-I) is the only known transforming human retrovirus and the etiological agent of Adult T-cell Leukemia (ATLL). Although HTLV-I-transformed leukemic cells have numerous genetic lesions, the precise role of the viral tax gene in this process is not fully understood. RESULTS Our results show a novel function of HTLV-I oncoprotein Tax as an inducer of genomic DNA double strand breaks (DDSB) during DNA replication. We also found that Tax acts as a potent inhibitor of homologous recombination (HR) DNA repair through the activation of the NF-kB pathway. These results were confirmed using HTLV-I molecular clones expressing Tax at physiological levels in a natural context. We further found that HTLV-I- and Tax-transformed cells are not more susceptible to DNA damaging agents and repair DNA lesions at a rate similar to that of normal cells. Finally, we demonstrated that during S phase, Tax-associated DDSB are preferentially repaired using the error-prone non-homologous end joining (NHEJ) pathway. CONCLUSIONS This study provides new insights in Tax effects on DNA repair and genome instability. Although it may not be self sufficient, the creation of DNA breaks and subsequent abnormal use of the non-conservative NHEJ DNA repair during the S phase in HTLV-I-infected Tax-expressing cells may cooperate with other factors to increase genetic and genome instability and favor transformation.
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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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Localization and sub-cellular shuttling of HTLV-1 tax with the miRNA machinery. PLoS One 2012; 7:e40662. [PMID: 22808228 PMCID: PMC3393700 DOI: 10.1371/journal.pone.0040662] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2012] [Accepted: 06/11/2012] [Indexed: 12/18/2022] Open
Abstract
The innate ability of the human cell to silence endogenous retroviruses through RNA sequences encoding microRNAs, suggests that the cellular RNAi machinery is a major means by which the host mounts a defense response against present day retroviruses. Indeed, cellular miRNAs target and hybridize to specific sequences of both HTLV-1 and HIV-1 viral transcripts. However, much like the variety of host immune responses to retroviral infection, the virus itself contains mechanisms that assist in the evasion of viral inhibition through control of the cellular RNAi pathway. Retroviruses can hijack both the enzymatic and catalytic components of the RNAi pathway, in some cases to produce novel viral miRNAs that can either assist in active viral infection or promote a latent state. Here, we show that HTLV-1 Tax contributes to the dysregulation of the RNAi pathway by altering the expression of key components of this pathway. A survey of uninfected and HTLV-1 infected cells revealed that Drosha protein is present at lower levels in all HTLV-1 infected cell lines and in infected primary cells, while other components such as DGCR8 were not dramatically altered. We show colocalization of Tax and Drosha in the nucleus in vitro as well as coimmunoprecipitation in the presence of proteasome inhibitors, indicating that Tax interacts with Drosha and may target it to specific areas of the cell, namely, the proteasome. In the presence of Tax we observed a prevention of primary miRNA cleavage by Drosha. Finally, the changes in cellular miRNA expression in HTLV-1 infected cells can be mimicked by the add back of Drosha or the addition of antagomiRs against the cellular miRNAs which are downregulated by the virus.
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Hasui K, Wang J, Tanaka Y, Izumo S, Eizuru Y, Matsuyama T. Development of ultra-super sensitive immunohistochemistry and its application to the etiological study of adult T-cell leukemia/lymphoma. Acta Histochem Cytochem 2012; 45:83-106. [PMID: 22685351 PMCID: PMC3365307 DOI: 10.1267/ahc.11034] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2011] [Accepted: 02/14/2012] [Indexed: 01/20/2023] Open
Abstract
Antigen retrieval (AR) and ultra-super sensitive immunohistochemistry (ultra-IHC) have been established for application to archival human pathology specimens. The original ultra-IHC was the ImmunoMax method or the catalyzed signal amplification system (ImmunoMax/CSA method), comprising the streptavidin-biotin complex (sABC) method and catalyzed reporter deposition (CARD) reaction with visualization of its deposition. By introducing procedures to diminish non-specific staining in the original ultra-IHC method, we developed the modified ImmunoMax/CSA method with AR heating sections in an AR solution (heating-AR). The heating-AR and modified ImmunoMax/CSA method visualized expression of the predominantly simple present form of HTLV-1 proviral DNA pX region p40Tax protein (Tax) in adult T-cell leukemia/lymphoma (ATLL) cells in archival pathology specimens in approximately 75% of cases. The simple present form of Tax detected exhibited a close relation with ATLL cell proliferation. We also established a new simplified CSA (nsCSA) system by replacing the sABC method with the secondary antibody- and horse radish peroxidase-labeled polymer reagent method, introducing the pretreatments blocking non-specific binding of secondary antibody reagent, and diminishing the diffusion of deposition in the CARD reaction. Combined with AR treating sections with proteinase K solution (enzymatic-AR), the nsCSA system visualized granular immunostaining of the complex present form of Tax in a small number of ATLL cells in most cases, presenting the possibility of etiological pathological diagnosis of ATLL and suggesting that the complex present form of Tax-positive ATLL cells were young cells derived from ATLL stem cells. The heating-AR and ultra-IHC detected physiological expression of the p53 protein and its probable phosphorylation by Tax in peripheral blood mononuclear cells of peripheral blood tissue specimens from HTLV-1 carriers, as well as physiological and pathological expression of the molecules involved with G1 phase progression and G1–S phase transition (E2F-1, E2F-4, DP-1, and cyclin E) in ATLL and peripheral T-cell lymphoma cells. The ultra-IHC with AR is useful for etiological pathological diagnosis of ATLL since HTLV-1 pathogenicity depends on that of Tax, and can be a useful tool for studies translating advanced molecular biology and pathology to human pathology.
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Affiliation(s)
- Kazuhisa Hasui
- Division of Immunology, Department of Infection and Immunity, Institute Research Center (Health Research Course), Kagoshima University Graduate School of Medical and Dental Sciences
- Division of Immunology, Department of Infection and Immunity, Institute Research Center (Health Research Course), Kagoshima University Graduate School of Medical and Dental Sciences
| | - Jia Wang
- Division of Immunology, Department of Infection and Immunity, Institute Research Center (Health Research Course), Kagoshima University Graduate School of Medical and Dental Sciences
- INAMORI Frontier Research Center, Kyushu University
- Division of Immunology, Department of Infection and Immunity, Institute Research Center (Health Research Course), Kagoshima University Graduate School of Medical and Dental Sciences
- INAMORI Frontier Research Center, Kyushu University
| | - Yuetsu Tanaka
- Department of Immunology, Graduate School of Medicine, University of the Ryukyus
- Department of Immunology, Graduate School of Medicine, University of the Ryukyus
| | - Shuji Izumo
- Chronic Viral Diseases Div. of Molecular Pathology, Center for Chronic Viral Diseases (Infection and Immunity), Institute Research Center (Health Research Course), Kagoshima University Graduate School of Medical and Dental Sciences
- Chronic Viral Diseases Div. of Molecular Pathology, Center for Chronic Viral Diseases (Infection and Immunity), Institute Research Center (Health Research Course), Kagoshima University Graduate School of Medical and Dental Sciences
| | - Yoshito Eizuru
- Chronic Viral Diseases Div. of Persistent & Oncogenic Viruses, Center for Chronic Viral Diseases (Infection and Immunity), Institute Research Center (Health Research Course), Kagoshima University Graduate School of Medical and Dental Sciences
- Chronic Viral Diseases Div. of Persistent & Oncogenic Viruses, Center for Chronic Viral Diseases (Infection and Immunity), Institute Research Center (Health Research Course), Kagoshima University Graduate School of Medical and Dental Sciences
| | - Takami Matsuyama
- Division of Immunology, Department of Infection and Immunity, Institute Research Center (Health Research Course), Kagoshima University Graduate School of Medical and Dental Sciences
- Division of Immunology, Department of Infection and Immunity, Institute Research Center (Health Research Course), Kagoshima University Graduate School of Medical and Dental Sciences
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Cotranscriptional Chromatin Remodeling by Small RNA Species: An HTLV-1 Perspective. LEUKEMIA RESEARCH AND TREATMENT 2012; 2012:984754. [PMID: 23213554 PMCID: PMC3504244 DOI: 10.1155/2012/984754] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/23/2011] [Revised: 10/28/2011] [Accepted: 11/03/2011] [Indexed: 12/22/2022]
Abstract
Cell type specificity of human T cell leukemia virus 1 has been proposed as a possible reason for differential viral outcome in primary target cells versus secondary. Through chromatin remodeling, the HTLV-1 transactivator protein Tax interacts with cellular factors at the chromosomally integrated viral promoter to activate downstream genes and control viral transcription. RNA interference is the host innate defense mechanism mediated by short RNA species (siRNA or miRNA) that regulate gene expression. There exists a close collaborative functioning of cellular transcription factors with miRNA in order to regulate the expression of a number of eukaryotic genes including those involved in suppression of cell growth, induction of apoptosis, as well as repressing viral replication and propagation. In addition, it has been suggested that retroviral latency is influenced by chromatin alterations brought about by miRNA. Since Tax requires the assembly of transcriptional cofactors to carry out viral gene expression, there might be a close association between miRNA influencing chromatin alterations and Tax-mediated LTR activation. Herein we explore the possible interplay between HTLV-1 infection and miRNA pathways resulting in chromatin reorganization as one of the mechanisms determining HTLV-1 cell specificity and viral fate in different cell types.
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Chemes LB, Sánchez IE, de Prat-Gay G. Kinetic Recognition of the Retinoblastoma Tumor Suppressor by a Specific Protein Target. J Mol Biol 2011; 412:267-84. [DOI: 10.1016/j.jmb.2011.07.015] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2011] [Revised: 07/04/2011] [Accepted: 07/11/2011] [Indexed: 12/25/2022]
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36
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Construction of a full transcription map of human papillomavirus type 18 during productive viral infection. J Virol 2011; 85:8080-92. [PMID: 21680515 DOI: 10.1128/jvi.00670-11] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Human papillomavirus type 18 (HPV18) is the second most common oncogenic HPV genotype, responsible for ∼15% of cervical cancers worldwide. In this study, we constructed a full HPV18 transcription map using HPV18-infected raft tissues derived from primary human vaginal or foreskin keratinocytes. By using 5' rapid amplification of cDNA ends (RACE), we mapped two HPV18 transcription start sites (TSS) for early transcripts at nucleotide (nt) 55 and nt 102 and the HPV18 late TSS frequently at nt 811, 765, or 829 within the E7 open reading frame (ORF) of the virus genome. HPV18 polyadenylation cleavage sites for early and late transcripts were mapped to nt 4270 and mainly to nt 7299 or 7307, respectively, by using 3' RACE. Although all early transcripts were cleaved exclusively at a single cleavage site, HPV18 late transcripts displayed the heterogeneity of 3' ends, with multiple minor cleavage sites for late RNA polyadenylation. HPV18 splice sites/splice junctions for both early and late transcripts were identified by 5' RACE and primer walking techniques. Five 5' splice sites (donor sites) and six 3' splice sites (acceptor sites) that are highly conserved in other papillomaviruses were identified in the HPV18 genome. HPV18 L1 mRNA translates a L1 protein of 507 amino acids (aa), smaller than the 568 aa residues previously predicted. Collectively, a full HPV18 transcription map constructed from this report will lead us to further understand HPV18 gene expression and virus oncogenesis.
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Ubiquitin-independent proteasomal degradation during oncogenic viral infections. Biochim Biophys Acta Rev Cancer 2011; 1816:147-57. [PMID: 21664948 DOI: 10.1016/j.bbcan.2011.05.005] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Revised: 05/26/2011] [Accepted: 05/27/2011] [Indexed: 02/07/2023]
Abstract
Most eukaryotic proteins destined for imminent destruction are first tagged with a chain of ubiquitin molecules and are subsequently dismantled by the proteasome. Ubiquitin-independent degradation of substrates by the proteasome, however, also occurs. The number of documented proteasome-dependent, ubiquitin-independent degradation events remains relatively small but continues to grow. Proteins involved in oncogenesis and tumor suppression make up the majority of the known cases for this type of protein destruction. Provocatively, viruses with confirmed or suspected oncogenic properties are also prominent participants in the pantheon of ubiquitin-independent proteasomal degradation events. In this review, we identify and describe examples of proteasome-dependent, ubiquitin-independent protein degradation that occur during tumor virus infections, speculate why this type of protein destruction may be preferred during oncogenesis, and argue that this uncommon type of protein turnover represents a prime target for antiviral and anticancer therapeutics.
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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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39
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Abstract
Human T-lymphotropic virus type 1 (HTLV-1) is the causative agent of adult T-cell leukemia/lymphoma (ATL), a malignancy of CD4(+) T cells whose etiology is thought to be associated with the viral trans-activator Tax. We have shown recently that Tax can drastically upregulate the expression of p27(Kip1) and p21(CIP1/WAF1) through protein stabilization and mRNA trans-activation and stabilization, respectively. The Tax-induced surge in p21(CIP1/WAF1) and p27(Kip1) begins in S phase and results in cellular senescence. Importantly, HeLa and SupT1 T cells infected by HTLV-1 also arrest in senescence, thus challenging the notion that HTLV-1 infection causes cell proliferation. Here we use time-lapse microscopy to investigate the effect of Tax on cell cycle progression in two reporter cell lines, HeLa/18x21-EGFP and HeLa-FUCCI, that express enhanced green fluorescent protein (EGFP) under the control of 18 copies of the Tax-responsive 21-bp repeat element and fluorescent ubiquitin cell cycle indicators, respectively. Tax-expressing HeLa cells exhibit elongated or stalled cell cycle phases. Many of them bypass mitosis and become single senescent cells as evidenced by the expression of senescence-associated β-galactosidase. Such cells have twice the normal equivalent of cellular contents and hence are enlarged, with exaggerated nuclei. Interestingly, nocodazole treatment revealed a small variant population of HeLa/18x21-EGFP cells that could progress into mitosis normally with high levels of Tax expression, suggesting that genetic or epigenetic changes that prevent Tax-induced senescence can occur spontaneously at a detectable frequency.
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40
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Zheng ZM. Viral oncogenes, noncoding RNAs, and RNA splicing in human tumor viruses. Int J Biol Sci 2010; 6:730-55. [PMID: 21152115 PMCID: PMC2999850 DOI: 10.7150/ijbs.6.730] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2010] [Accepted: 11/27/2010] [Indexed: 12/13/2022] Open
Abstract
Viral oncogenes are responsible for oncogenesis resulting from persistent virus infection. Although different human tumor viruses express different viral oncogenes and induce different tumors, their oncoproteins often target similar sets of cellular tumor suppressors or signal pathways to immortalize and/or transform infected cells. Expression of the viral E6 and E7 oncogenes in papillomavirus, E1A and E1B oncogenes in adenovirus, large T and small t antigen in polyomavirus, and Tax oncogene in HTLV-1 are regulated by alternative RNA splicing. However, this regulation is only partially understood. DNA tumor viruses also encode noncoding RNAs, including viral microRNAs, that disturb normal cell functions. Among the determined viral microRNA precursors, EBV encodes 25 from two major clusters (BART and BHRF1), KSHV encodes 12 from a latent region, human polyomavirus MCV produce only one microRNA from the late region antisense to early transcripts, but HPVs appears to produce no viral microRNAs.
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Affiliation(s)
- Zhi-Ming Zheng
- Tumor Virus RNA Biology Laboratory, HIV and AIDS Malignancy Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
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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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Zane L, Sibon D, Legras C, Lachuer J, Wierinckx A, Mehlen P, Delfau-Larue MH, Gessain A, Gout O, Pinatel C, Lançon A, Mortreux F, Wattel E. Clonal expansion of HTLV-1 positive CD8+ cells relies on cIAP-2 but not on c-FLIP expression. Virology 2010; 407:341-51. [DOI: 10.1016/j.virol.2010.07.023] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2010] [Revised: 05/11/2010] [Accepted: 07/16/2010] [Indexed: 10/19/2022]
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Chlichlia K, Khazaie K. HTLV-1 Tax: Linking transformation, DNA damage and apoptotic T-cell death. Chem Biol Interact 2010; 188:359-65. [PMID: 20558150 DOI: 10.1016/j.cbi.2010.06.005] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2010] [Revised: 06/01/2010] [Accepted: 06/06/2010] [Indexed: 11/20/2022]
Abstract
The human T-cell leukemia virus type I (HTLV-1) is the causative agent of adult T-cell leukemia (ATL), an aggressive CD4-positive T-cell neoplasia. The HTLV-1 proto-oncogene Tax, a potent transcriptional activator of cellular and viral genes, is thought to play a pivotal role in the transforming properties of the virus by deregulating intracellular signaling pathways. During the course of HTLV-1 infection, the dysregulation of cell-cycle checkpoints and the suppression of DNA damage repair is tightly linked to the activity of the viral oncoprotein Tax. Tax activity is associated with production of reactive oxygen intermediates (ROS), chromosomal instability and DNA damage, apoptotic cell death and cellular transformation. Changes in the intracellular redox status induced by Tax promote DNA damage. Tax-mediated DNA damage is believed to be essential in initiating the transformation process by subjecting infected T cells to genetic changes that eventually promote the neoplastic state. Apoptosis and immune surveillance would then exert the necessary selection pressure for eliminating the majority of virally infected cells, while escape variants acquiring a mutator phenotype would constitute a subpopulation of genetically altered cells prone to neoplasia. While the potency of Tax-activity seems to be a determining factor for the observed effects, the cooperation of Tax with other viral proteins determines the fate and progression of HTLV-1-infected cells through DNA damage, apoptosis, survival and transformation.
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Affiliation(s)
- Katerina Chlichlia
- Department of Molecular Biology and Genetics, Democritus University of Thrace, Alexandroupolis, Greece.
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Low- and high-risk human papillomavirus E7 proteins regulate p130 differently. Virology 2010; 400:233-9. [PMID: 20189212 DOI: 10.1016/j.virol.2010.01.034] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2009] [Revised: 12/17/2009] [Accepted: 01/27/2010] [Indexed: 11/23/2022]
Abstract
The E7 protein of high-risk human papillomaviruses (HR HPVs) targets pRb family members (pRb, p107 and p130) for degradation; low-risk (LR) HPV E7 only targets p130 for degradation. The effect of HR HPV 16 E7 and LR HPV 6 E7 on p130 intracellular localization and half-life was examined. Nuclear/cytoplasmic fractionation and immunofluorescence showed that, in contrast to control and HPV 6 E7-expressing cells, a greater amount of p130 was present in the cytoplasm in the presence of HPV 16 E7. The half-life of p130, relative to control cells, was decreased in the cytoplasm in the presence of HPV 6 E7 or HPV 16 E7, but only decreased by HPV 6 E7 in the nucleus. Inhibition of proteasomal degradation extended the half-life of p130, regardless of intracellular localization. These results suggest that there may be divergent mechanisms by which LR and HR HPV E7 target p130 for degradation.
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Oh KJ, Kalinina A, Bagchi S. Destabilization of Rb by human papillomavirus E7 is cell cycle dependent: E2-25K is involved in the proteolysis. Virology 2009; 396:118-24. [PMID: 19906396 DOI: 10.1016/j.virol.2009.10.018] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2009] [Revised: 09/16/2009] [Accepted: 10/13/2009] [Indexed: 01/12/2023]
Abstract
The HPV oncoprotein E7 promotes proteasomal degradation of the tumor suppressor protein Rb. In this study, we analyzed the regulation of E7-induced Rb proteolysis in HPV-containing Caski cervical cancer cells. We show that the Rb proteolysis is cell cycle dependent; in S phase Rb is stable while in post-mitotic early G1 phase cells and in differentiated cells, Rb is unstable. Similarly, the in vivo Rb/E7 interaction is not detected in S-phase cells, but is readily detected in differentiating Caski cells. The ubiquitinating enzymes involved in Rb proteolysis have not been identified. We find that the E3 ligase MDM2 is not involved in the Rb proteolysis in Caski cells. An in vivo analysis using multiple catalytic site mutant dominant negative E2 enzymes show that the C92A E2-25K most effectively blocks E7-induced Rb proteolysis. Taken together, these results show that E7 induces Rb proteolysis in growth-arrested cells and E2-25K is involved in the proteolysis.
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Affiliation(s)
- Kwang-Jin Oh
- Center for Molecular Biology of Oral Diseases, University of Illinois at Chicago, Chicago, IL 60612, USA
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Radulescu RT, Poznic M, Pavelic K. Complex formation between metabolic enzymes in tumor cells: unfolding the MDR1-IDE paradigm. Mol Cancer Ther 2009; 8:3171. [PMID: 19825794 DOI: 10.1158/1535-7163.mct-09-0706] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Vassilaki N, Mavromara P. The HCV ARFP/F/core+1 protein: production and functional analysis of an unconventional viral product. IUBMB Life 2009; 61:739-52. [PMID: 19548320 DOI: 10.1002/iub.201] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Hepatitis C virus (HCV) is an enveloped positive-strand RNA virus of the Flaviviridae family. It has a genome of about 9,600 nucleotides encoding a large polyprotein (about 3,000 amino acids) that is processed by cellular and viral proteases into at least 10 structural and nonstructural viral proteins. A novel HCV protein has also been identified by our laboratory and others. This protein--known as ARFP (alternative reading frame protein), F (for frameshift) or core+1 (to indicate the position) protein--is synthesized by an open reading frame overlapping the core gene at nucleotide +1 (core+1 ORF). However, almost 10 years after its discovery, we still know little of the biological role of the ARFP/F/core+1 protein. Abolishing core+1 protein production has no affect on HCV replication in cell culture or uPA-SCID mice, suggesting that core+1 protein is probably not important for the HCV reproductive cycle. However, the detection of specific anti-core+1 antibodies and T-cell responses in HCV-infected patients, as reported by many independent laboratories, provides strong evidence that this protein is produced in vivo. Furthermore, analyses of the HCV sequences isolated from patients with hepatocellular carcinoma and in vitro studies have provided strong preliminary evidence to suggest that core+1 protein plays a role in advanced liver disease and liver cancer. The available in vitro data also suggest that certain core function proteins may depend on production of the core+1 protein. We describe here the discovery of the various forms of the core+1 protein and what is currently known about the mechanisms of their production and their biochemical and functional properties. We also provide a detailed summary of the results of patient-based research.
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Affiliation(s)
- Niki Vassilaki
- Molecular Virology Laboratory, Hellenic Pasteur Institute, Athens, Greece.
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Dimerization and a novel Tax speckled structure localization signal are required for Tax nuclear localization. J Virol 2009; 83:5339-52. [PMID: 19321601 DOI: 10.1128/jvi.00232-09] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The human T-cell leukemia virus type 1 oncoprotein Tax has pleiotropic activities, a subset of which likely leads to immortalization of T cells. Tax is expressed and known to function in both the cell nucleus and the cytoplasm. Tax has defined nuclear localization (NLS) and nuclear export signals that enable shuttling between the two compartments. In this study, we identified a novel region in Tax that targets the protein to discrete nuclear foci that we have previously termed Tax speckled structures (TSS). We demonstrated that the identified region is both necessary and sufficient for directing proteins to TSS. This novel TSS localization signal (TSLS), spanning amino acids 50 to 75, is separable from and adjacent to the NLS of Tax. Coexpression of a Tax NLS mutant and a Tax TSLS mutant rescued the nuclear entry and subnuclear TSS targeting of both proteins, demonstrating that these signals are independent domains. Our analysis also revealed that Tax proteins deficient for dimerization fail to localize to the nucleus. Consequently, when we restored dimerization via induction of a heterologous "dimerizer" domain, nuclear localization was rescued. Thus, we defined additional domains in Tax specific for nuclear localization and subnuclear targeting. Our results reveal a more complex network for regulation of Tax subcellular localization and subsequent function.
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Lodewick J, Lamsoul I, Polania A, Lebrun S, Burny A, Ratner L, Bex F. Acetylation of the human T-cell leukemia virus type 1 Tax oncoprotein by p300 promotes activation of the NF-kappaB pathway. Virology 2009; 386:68-78. [PMID: 19200568 DOI: 10.1016/j.virol.2008.12.043] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2008] [Revised: 10/17/2008] [Accepted: 12/31/2008] [Indexed: 01/28/2023]
Abstract
The oncogenic potential of the HTLV-1 Tax protein involves activation of the NF-kappaB pathway, which depends on Tax phosphorylation, ubiquitination and sumoylation. We demonstrate that the nuclei of Tax-expressing cells, including HTLV-1 transformed T-lymphocytes, contain a pool of Tax molecules acetylated on lysine residue at amino acid position 346 by the transcriptional coactivator p300. Phosphorylation of Tax on serine residues 300/301 was a prerequisite for Tax localization in the nucleus and correlated with its subsequent acetylation by p300, whereas sumoylation, resulting in the formation of Tax nuclear bodies in which p300 was recruited, favored Tax acetylation. Overexpression of p300 markedly increased Tax acetylation and the ability of a wild type HTLV-1 provirus, but not of a mutant provirus carrying an acetylation deficient Tax gene, to activate gene expression from an integrated NF-kappaB-controlled promoter. Thus, Tax acetylation favors NF-kappaB activation and might play an important role in HTLV-1-induced cell transformation.
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Affiliation(s)
- Julie Lodewick
- Institute for Microbiological Research J-M Wiame and Laboratory of Microbiology, Université Libre de Bruxelles, 1, Avenue Emile Gryson, B-1070 Brussels, Belgium
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Alteration of blood-brain barrier integrity by retroviral infection. PLoS Pathog 2008; 4:e1000205. [PMID: 19008946 PMCID: PMC2575404 DOI: 10.1371/journal.ppat.1000205] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2008] [Accepted: 10/15/2008] [Indexed: 01/18/2023] Open
Abstract
The blood–brain barrier (BBB), which forms the interface between the blood and the cerebral parenchyma, has been shown to be disrupted during retroviral-associated neuromyelopathies. Human T Lymphotropic Virus (HTLV-1) Associated Myelopathy/Tropical Spastic Paraparesis (HAM/TSP) is a slowly progressive neurodegenerative disease associated with BBB breakdown. The BBB is composed of three cell types: endothelial cells, pericytes and astrocytes. Although astrocytes have been shown to be infected by HTLV-1, until now, little was known about the susceptibility of BBB endothelial cells to HTLV-1 infection and the impact of such an infection on BBB function. We first demonstrated that human cerebral endothelial cells express the receptors for HTLV-1 (GLUT-1, Neuropilin-1 and heparan sulfate proteoglycans), both in vitro, in a human cerebral endothelial cell line, and ex vivo, on spinal cord autopsy sections from HAM/TSP and non-infected control cases. In situ hybridization revealed HTLV-1 transcripts associated with the vasculature in HAM/TSP. We were able to confirm that the endothelial cells could be productively infected in vitro by HTLV-1 and that blocking of either HSPGs, Neuropilin 1 or Glut1 inhibits this process. The expression of the tight-junction proteins within the HTLV-1 infected endothelial cells was altered. These cells were no longer able to form a functional barrier, since BBB permeability and lymphocyte passage through the monolayer of endothelial cells were increased. This work constitutes the first report of susceptibility of human cerebral endothelial cells to HTLV-1 infection, with implications for HTLV-1 passage through the BBB and subsequent deregulation of the central nervous system homeostasis. We propose that the susceptibility of cerebral endothelial cells to retroviral infection and subsequent BBB dysfunction is an important aspect of HAM/TSP pathogenesis and should be considered in the design of future therapeutics strategies. The blood–brain barrier (BBB) forms the interface between the blood and the central nervous system (CNS). BBB disruption is considered to be a key event in the pathogenesis of retroviral-associated neurological diseases. The present paper deals with the susceptibility of the endothelial cells (i.e., one of the main cellular components of BBB) to retroviral infection, and with the impact of infection in BBB function. This study focuses on the Human T-Lymphotropic Virus (HTLV-1), which infects 20 million people worldwide, and is the etiological agent of a neurodegenerative disease called HTLV-1 Associated Myelopathy/Tropical Spastic Paraparesis (HAM/TSP). We first demonstrated that the cerebral endothelial cells express the receptors for the retrovirus in vitro, and on spinal cord autopsy sections from non-infected and HAM/TSP patients. We found on these latter that vascular-like structures were infected and confirmed in vitro that the endothelial cells could be productively infected by HTLV-1. We demonstrated that such an infection impairs BBB properties in vitro, as well as tight junctions, that are cell adhesion structures. This study is the first to demonstrate the impact of HTLV-1 infection on human BBB integrity; such a susceptibility has to be considered in the design of future therapeutics strategies.
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