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Su R, Kang X, Niu Y, Zhao T, Wang H. PCBP1 interacts with the HTLV-1 Tax oncoprotein to potentiate NF-κB activation. Front Immunol 2024; 15:1375168. [PMID: 38690287 PMCID: PMC11058652 DOI: 10.3389/fimmu.2024.1375168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Accepted: 03/25/2024] [Indexed: 05/02/2024] Open
Abstract
Human T-cell leukemia virus type 1 (HTLV-1) is the etiological agent of adult T-cell leukemia/lymphoma. The HTLV-1 Tax constitutively activates nuclear factor-κB (NF-κB) to promote the survival and transformation of HTLV-1-infected T cells. Despite extensive study of Tax, how Tax interacts with host factors to regulate NF-κB activation and HTLV-1-driven cell proliferation is not entirely clear. Here, we showed that overexpression of Poly (rC)-binding protein 1 (PCBP1) promoted Tax-mediated IκB kinase (IKK)-NF-κB signaling activation, whereas knockdown of PCBP1 attenuated Tax-dependent IKK-NF-κB activation. However, Tax activation of HTLV-1 long terminal repeat was unaffected by PCBP1. Furthermore, depletion of PCBP1 led to apoptosis and reduced proliferation of HTLV-1-transformed cells. Mechanistically, PCBP1 interacted and co-localized with Tax in the cytoplasm, and PCBP1 KH3 domain was indispensable for the interaction between PCBP1 and Tax. Moreover, PCBP1 facilitated the assembly of Tax/IKK complex. Collectively, our results demonstrated that PCBP1 may exert an essential effect in Tax/IKK complex combination and subsequent NF-κB activation, which provides a novel insight into the pathogenetic mechanisms of HTLV-1.
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Affiliation(s)
- Rui Su
- Department of Immunology, School of Basic Medical Sciences, Xinxiang Medical University, Xinxiang, China
- Henan Key Laboratory of Immunology and Targeted Drug, Xinxiang Medical University, Xinxiang, China
| | - Xue Kang
- Department of Immunology, School of Basic Medical Sciences, Xinxiang Medical University, Xinxiang, China
- Henan Key Laboratory of Immunology and Targeted Drug, Xinxiang Medical University, Xinxiang, China
| | - Yifan Niu
- Department of Immunology, School of Basic Medical Sciences, Xinxiang Medical University, Xinxiang, China
- Henan Key Laboratory of Immunology and Targeted Drug, Xinxiang Medical University, Xinxiang, China
| | - Tiesuo Zhao
- Department of Immunology, School of Basic Medical Sciences, Xinxiang Medical University, Xinxiang, China
- Xinxiang Engineering Technology Research Center of Immune Checkpoint Drug for Liver-Intestinal Tumors, Xinxiang Medical University, Xinxiang, China
| | - Hui Wang
- Henan Key Laboratory of Immunology and Targeted Drug, Xinxiang Medical University, Xinxiang, China
- Henan Collaborative Innovation Center of Molecular Diagnosis and Laboratory Medicine, School of Medical Technology, Xinxiang Medical University, Xinxiang, China
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Bhattarai K, Holcik M. Diverse roles of heterogeneous nuclear ribonucleoproteins in viral life cycle. FRONTIERS IN VIROLOGY 2022. [DOI: 10.3389/fviro.2022.1044652] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Understanding the host-virus interactions helps to decipher the viral replication strategies and pathogenesis. Viruses have limited genetic content and rely significantly on their host cell to establish a successful infection. Viruses depend on the host for a broad spectrum of cellular RNA-binding proteins (RBPs) throughout their life cycle. One of the major RBP families is the heterogeneous nuclear ribonucleoproteins (hnRNPs) family. hnRNPs are typically localized in the nucleus, where they are forming complexes with pre-mRNAs and contribute to many aspects of nucleic acid metabolism. hnRNPs contain RNA binding motifs and frequently function as RNA chaperones involved in pre-mRNA processing, RNA splicing, and export. Many hnRNPs shuttle between the nucleus and the cytoplasm and influence cytoplasmic processes such as mRNA stability, localization, and translation. The interactions between the hnRNPs and viral components are well-known. They are critical for processing viral nucleic acids and proteins and, therefore, impact the success of the viral infection. This review discusses the molecular mechanisms by which hnRNPs interact with and regulate each stage of the viral life cycle, such as replication, splicing, translation, and assembly of virus progeny. In addition, we expand on the role of hnRNPs in the antiviral response and as potential targets for antiviral drug research and development.
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Optimization of Bifunctional Antisense Oligonucleotides for Regulation of Mutually Exclusive Alternative Splicing of PKM Gene. Molecules 2022; 27:molecules27175682. [PMID: 36080449 PMCID: PMC9457596 DOI: 10.3390/molecules27175682] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Revised: 08/31/2022] [Accepted: 09/01/2022] [Indexed: 11/23/2022] Open
Abstract
Oligonucleotide tools, as modulators of alternative splicing, have been extensively studied, giving a rise to new therapeutic approaches. In this article, we report detailed research on the optimization of bifunctional antisense oligonucleotides (BASOs), which are targeted towards interactions with hnRNP A1 protein. We performed a binding screening assay, Kd determination, and UV melting experiments to select sequences that can be used as a high potency binding platform for hnRNP A1. Newly designed BASOs were applied to regulate the mutually exclusive alternative splicing of the PKM gene. Our studies demonstrate that at least three repetitions of regulatory sequence are necessary to increase expression of the PKM1 isoform. On the other hand, PKM2 expression can be inhibited by a lower number of regulatory sequences. Importantly, a novel branched type of BASOs was developed, which significantly increased the efficiency of splicing modulation. Herein, we provide new insights into BASOs design and show, for the first time, the possibility to regulate mutually exclusive alternative splicing via BASOs.
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Wan Q, Song D, Li H, He ML. Stress proteins: the biological functions in virus infection, present and challenges for target-based antiviral drug development. Signal Transduct Target Ther 2020; 5:125. [PMID: 32661235 PMCID: PMC7356129 DOI: 10.1038/s41392-020-00233-4] [Citation(s) in RCA: 68] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Revised: 05/26/2020] [Accepted: 06/13/2020] [Indexed: 02/06/2023] Open
Abstract
Stress proteins (SPs) including heat-shock proteins (HSPs), RNA chaperones, and ER associated stress proteins are molecular chaperones essential for cellular homeostasis. The major functions of HSPs include chaperoning misfolded or unfolded polypeptides, protecting cells from toxic stress, and presenting immune and inflammatory cytokines. Regarded as a double-edged sword, HSPs also cooperate with numerous viruses and cancer cells to promote their survival. RNA chaperones are a group of heterogeneous nuclear ribonucleoproteins (hnRNPs), which are essential factors for manipulating both the functions and metabolisms of pre-mRNAs/hnRNAs transcribed by RNA polymerase II. hnRNPs involve in a large number of cellular processes, including chromatin remodelling, transcription regulation, RNP assembly and stabilization, RNA export, virus replication, histone-like nucleoid structuring, and even intracellular immunity. Dysregulation of stress proteins is associated with many human diseases including human cancer, cardiovascular diseases, neurodegenerative diseases (e.g., Parkinson’s diseases, Alzheimer disease), stroke and infectious diseases. In this review, we summarized the biologic function of stress proteins, and current progress on their mechanisms related to virus reproduction and diseases caused by virus infections. As SPs also attract a great interest as potential antiviral targets (e.g., COVID-19), we also discuss the present progress and challenges in this area of HSP-based drug development, as well as with compounds already under clinical evaluation.
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Affiliation(s)
- Qianya Wan
- Department of Biomedical Sciences, City University of Hong Kong, Kowloon, Hong Kong, China
| | - Dan Song
- Department of Biomedical Sciences, City University of Hong Kong, Kowloon, Hong Kong, China
| | - Huangcan Li
- Department of Biomedical Sciences, City University of Hong Kong, Kowloon, Hong Kong, China
| | - Ming-Liang He
- Department of Biomedical Sciences, City University of Hong Kong, Kowloon, Hong Kong, China. .,CityU Shenzhen Research Institute, Shenzhen, China.
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D'Agostino DM, Cavallari I, Romanelli MG, Ciminale V. Post-transcriptional Regulation of HTLV Gene Expression: Rex to the Rescue. Front Microbiol 2019; 10:1958. [PMID: 31507567 PMCID: PMC6714889 DOI: 10.3389/fmicb.2019.01958] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Accepted: 08/08/2019] [Indexed: 11/13/2022] Open
Abstract
Human T-lymphotropic virus type 1 (HTLV-1) and other members of the Deltaretrovirus genus code for a regulatory protein named Rex that binds to the Rex-responsive element present on viral mRNAs. Rex rescues viral mRNAs from complete splicing or degradation and guides them to the cytoplasm for translation. The activity of Rex is essential for expression of viral transcripts coding for the virion components and thus represents a potential target for virus eradication. We present an overview of the functional properties of the HTLV-1 and HTLV-2 Rex proteins (Rex-1 and Rex-2), outline mechanisms controlling Rex function, and discuss similarities and differences in the sequences of Rex coded by HTLV-1, -2, -3, and -4 that may influence their molecular anatomy and functional properties.
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Affiliation(s)
| | | | - Maria Grazia Romanelli
- Section of Biology and Genetics, Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Vincenzo Ciminale
- Istituto Oncologico Veneto IOV - IRCCS, Padua, Italy.,Department of Surgery, Oncology and Gastroenterology, University of Padova, Padua, Italy
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Nakano K, Watanabe T. HTLV-1 Rex Tunes the Cellular Environment Favorable for Viral Replication. Viruses 2016; 8:58. [PMID: 26927155 PMCID: PMC4810248 DOI: 10.3390/v8030058] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Revised: 02/09/2016] [Accepted: 02/09/2016] [Indexed: 12/18/2022] Open
Abstract
Human T-cell leukemia virus type-1 (HTLV-1) Rex is a viral RNA binding protein. The most important and well-known function of Rex is stabilizing and exporting viral mRNAs from the nucleus, particularly for unspliced/partially-spliced mRNAs encoding the structural proteins essential for viral replication. Without Rex, these unspliced viral mRNAs would otherwise be completely spliced. Therefore, Rex is vital for the translation of structural proteins and the stabilization of viral genomic RNA and, thus, for viral replication. Rex schedules the period of extensive viral replication and suppression to enter latency. Although the importance of Rex in the viral life-cycle is well understood, the underlying molecular mechanism of how Rex achieves its function has not been clarified. For example, how does Rex protect unspliced/partially-spliced viral mRNAs from the host cellular splicing machinery? How does Rex protect viral mRNAs, antigenic to eukaryotic cells, from cellular mRNA surveillance mechanisms? Here we will discuss these mechanisms, which explain the function of Rex as an organizer of HTLV-1 expression based on previously and recently discovered aspects of Rex. We also focus on the potential influence of Rex on the homeostasis of the infected cell and how it can exert its function.
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Affiliation(s)
- Kazumi Nakano
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, 4-6-1, Shirokanedai, Minatoku, Tokyo 108-8639, Japan.
| | - Toshiki Watanabe
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, 4-6-1, Shirokanedai, Minatoku, Tokyo 108-8639, Japan.
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Nakano K, Watanabe T. HTLV-1 Rex: the courier of viral messages making use of the host vehicle. Front Microbiol 2012; 3:330. [PMID: 22973269 PMCID: PMC3434621 DOI: 10.3389/fmicb.2012.00330] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Accepted: 08/24/2012] [Indexed: 01/25/2023] Open
Abstract
The human T-cell leukemia virus type 1 (HTLV-1) is a retrovirus causing an aggressive T-cell malignancy, adult T-cell leukemia (ATL). Although HTLV-1 has a compact RNA genome, it has evolved elaborate mechanisms to maximize its coding potential. The structural proteins Gag, Pro, and Pol are encoded in the unspliced form of viral mRNA, whereas the Env protein is encoded in singly spliced viral mRNA. Regulatory and accessory proteins, such as Tax, Rex, p30II, p12, and p13, are translated only from fully spliced mRNA. For effective viral replication, translation from all forms of HTLV-1 transcripts has to be achieved in concert, although unspliced mRNA are extremely unstable in mammalian cells. It has been well recognized that HTLV-1 Rex enhances the stability of unspliced and singly spliced HTLV-1 mRNA by promoting nuclear export and thereby removing them from the splicing site. Rex specifically binds to the highly structured Rex responsive element (RxRE) located at the 3' end of all HTLV-1 mRNA. Rex then binds to the cellular nuclear exporter, CRM1, via its nuclear export signal domain and the Rex-viral transcript complex is selectively exported from the nucleus to the cytoplasm for effective translation of the viral proteins. Yet, the mechanisms by which Rex inhibits the cellular splicing machinery and utilizes the cellular pathways beneficial to viral survival in the host cell have not been fully explored. Furthermore, physiological impacts of Rex against homeostasis of the host cell via interactions with numerous cellular proteins have been largely left uninvestigated. In this review, we focus on the biological importance of HTLV-1 Rex in the HTLV-1 life cycle by following the historical path in the literature concerning this viral post-transcriptional regulator from its discovery to this day. In addition, for future studies, we discuss recently discovered aspects of HTLV-1 Rex as a post-transcriptional regulator and its use in host cellular pathways.
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Affiliation(s)
- Kazumi Nakano
- Laboratory of Tumor Cell Biology, Department of Medical Genome Sciences, Graduate School of Frontier Sciences, The University of Tokyo Tokyo, Japan
| | - Toshiki Watanabe
- Laboratory of Tumor Cell Biology, Department of Medical Genome Sciences, Graduate School of Frontier Sciences, The University of Tokyo Tokyo, Japan
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8
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Abstract
Persistent infection with cancer risk-related viruses leads to molecular, cellular and immune response changes in host organisms that in some cases direct cellular transformation. Alternative splicing is a conserved cellular process that increases the coding complexity of genomes at the pre-mRNA processing stage. Human and other animal tumour viruses use alternative splicing as a process to maximize their transcriptomes and proteomes. Medical therapeutics to clear persistent viral infections are still limited. However, specific lessons learned in some viruses [e.g. HIV and HCV (hepatitis C virus)] suggest that drug-directed inhibition of alternative splicing could be useful for this purpose. The present review describes the basic mechanisms of constitutive and alternative splicing in a cellular context and known splicing patterns and the mechanisms by which these might be achieved for the major human infective tumour viruses. The roles of splicing-related proteins expressed by these viruses in cellular and viral gene regulation are explored. Moreover, we discuss some currently available drugs targeting SR (serine/arginine-rich) proteins that are the main regulators of constitutive and alternative splicing, and their potential use in treatment for so-called persistent viral infections.
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9
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Castilla V, Scolaro LA. Involvement of heterogeneous nuclear ribonucleoproteins in viral multiplication. Future Virol 2012. [DOI: 10.2217/fvl.12.48] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The study of virus–host interactions is a major goal in molecular virology and provides new effective targets for antiviral therapies. Heterogeneous nuclear ribonucleoproteins (hnRNPs) constitute a group of cellular RNA-binding proteins localized predominantly within the nucleus, which participate in gene transcription and subsequent RNA post-transcriptional modifications. The interaction between hnRNPs and viral components was extensively demonstrated, as well as the ability of virus infections to alter the intracellular localization or the level of expression of different hnRNPs. The involvement of these proteins in the replication of numerous viruses including members from the Retroviridae, Flaviviridae, Coronaviridae, Arenaviridae, Rhabdoviridae, Papillomaviridae, Orthomyxoviridae, Picornaviridae, Togaviridae and Herpesviridae families, has been reported. In order to gain an increased understanding of the interactions between virus and cell that result in the productive infection of the latter, in this review we discuss the main findings about the role of hnRNPs in different steps of viral replication, such as RNA synthesis, translation, RNA processing and egress of newly assembled progeny virus.
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Affiliation(s)
- Viviana Castilla
- Laboratorio de Virología, Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Luis A Scolaro
- Laboratorio de Virología, Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
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Comparison of the Genetic Organization, Expression Strategies and Oncogenic Potential of HTLV-1 and HTLV-2. LEUKEMIA RESEARCH AND TREATMENT 2011; 2012:876153. [PMID: 23213551 PMCID: PMC3504254 DOI: 10.1155/2012/876153] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/09/2011] [Accepted: 09/24/2011] [Indexed: 11/30/2022]
Abstract
Human T cell leukemia virus types 1 and 2 (HTLV-1 and HTLV-2) are genetically related complex retroviruses that are capable of immortalizing human T-cells in vitro and establish life-long persistent infections in vivo. In spite of these apparent similarities, HTLV-1 and HTLV-2 exhibit a significantly different pathogenic potential. HTLV-1 is recognized as the causative agent of adult T-cell leukemia/lymphoma (ATLL) and tropical spastic paraparesis/HTLV-1-associated myelopathy (TSP/HAM). In contrast, HTLV-2 has not been causally linked to human malignancy, although it may increase the risk of developing inflammatory neuropathies and infectious diseases. The present paper is focused on the studies aimed at defining the viral genetic determinants of the pathobiology of HTLV-1 and HTLV-2 through a comparison of the expression strategies and functional properties of the different gene products of the two viruses.
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11
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Sha Y, Marshall HE. S-nitrosylation in the regulation of gene transcription. Biochim Biophys Acta Gen Subj 2011; 1820:701-11. [PMID: 21640163 DOI: 10.1016/j.bbagen.2011.05.008] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2011] [Accepted: 05/14/2011] [Indexed: 12/30/2022]
Abstract
BACKGROUND Post-translational modification of proteins by S-nitrosylation serves as a major mode of signaling in mammalian cells and a growing body of evidence has shown that transcription factors and their activating pathways are primary targets. S-nitrosylation directly modifies a number of transcription factors, including NF-κB, HIF-1, and AP-1. In addition, S-nitrosylation can indirectly regulate gene transcription by modulating other cell signaling pathways, in particular JNK kinase and ras. SCOPE OF REVIEW The evolution of S-nitrosylation as a signaling mechanism in the regulation of gene transcription, physiological advantages of protein S-nitrosylation in the control of gene transcription, and discussion of the many transcriptional proteins modulated by S-nitrosylation is summarized. MAJOR CONCLUSIONS S-nitrosylation plays a crucial role in the control of mammalian gene transcription with numerous transcription factors regulated by this modification. Many of these proteins serve as immunomodulators, and inducible nitric oxide synthase (iNOS) is regarded as a principal mediatiator of NO-dependent S-nitrosylation. However, additional targets within the nucleus (e.g. histone deacetylases) and alternative mechanisms of S-nitrosylation (e.g. GAPDH-mediated trans-nitrosylation) are thought to play a role in NOS-dependent transcriptional regulation. GENERAL SIGNIFICANCE Derangement of SNO-regulated gene transcription is an important factor in a variety of pathological conditions including neoplasia and sepsis. A better understanding of protein S-nitrosylation as it relates to gene transcription and the physiological mechanisms behind this process is likely to lead to novel therapies for these disorders. This article is part of a Special Issue entitled Regulation of Cellular Processes by S-nitrosylation.
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Affiliation(s)
- Yonggang Sha
- Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Medicine, Duke University Medical Center, Durham, North Carolina, USA
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Denard J, Rundwasser S, Laroudie N, Gonnet F, Naldini L, Radrizzani M, Galy A, Merten OW, Danos O, Svinartchouk F. Quantitative proteomic analysis of lentiviral vectors using 2-DE. Proteomics 2009; 9:3666-76. [DOI: 10.1002/pmic.200800747] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Lévesque K, Halvorsen M, Abrahamyan L, Chatel-Chaix L, Poupon V, Gordon H, DesGroseillers L, Gatignol A, Mouland AJ. Trafficking of HIV-1 RNA is mediated by heterogeneous nuclear ribonucleoprotein A2 expression and impacts on viral assembly. Traffic 2007; 7:1177-93. [PMID: 17004321 DOI: 10.1111/j.1600-0854.2006.00461.x] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Few details are known about how the human immunodeficiency virus type 1 (HIV-1) genomic RNA is trafficked in the cytoplasm. Part of this process is controlled by the activity of heterogeneous nuclear ribonucleoprotein A2 (hnRNP A2). The role of hnRNP A2 during the expression of a bona fide provirus in HeLa cells is investigated in this study. Using immunofluorescence and fluorescence in situ hybridization techniques, we show that knockdown of hnRNP A2 expression in HIV-1-expressing cells results in the rapid accumulation of HIV-1 genomic RNA in a distinct, cytoplasmic space that corresponds to the microtubule-organizing center (MTOC). The RNA exits in the nucleus and accumulates at the MTOC region as a result of hnRNP A2 knockdown even during the expression of a provirus harboring mutations in the hnRNP A2-response element (A2RE), the expression of which results in nuclear retention of genomic RNA. We also demonstrate that hnRNP A2 expression is required for downstream trafficking of genomic RNA from the MTOC in the cytoplasm. Genomic RNA localization at the MTOC that was both the result of hnRNP A2 knockdown and the overexpression of Rab7-interacting lysosomal protein had little effect on pr55Gag synthesis but negatively influenced virus production and infectivity. These data indicate that altered HIV-1 genomic RNA localization modulates viral assembly and that the MTOC serves as a central site to which HIV-1 genomic RNA converges following its exit from the nucleus, with the host protein, hnRNP A2, playing a central role in taking it to and from this site in the cell.
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Affiliation(s)
- Kathy Lévesque
- HIV-1 RNA Trafficking Laboratory, 3755 Côte-Ste-Catherine Road, Montréal, Québec, Canada H3T 1E2
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14
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Baydoun H, Duc-Dodon M, Lebrun S, Gazzolo L, Bex F. Regulation of the human T-cell leukemia virus gene expression depends on the localization of regulatory proteins Tax, Rex and p30II in specific nuclear subdomains. Gene 2007; 386:191-201. [PMID: 17071021 DOI: 10.1016/j.gene.2006.09.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2006] [Revised: 08/31/2006] [Accepted: 09/07/2006] [Indexed: 12/11/2022]
Abstract
The human T-cell leukemia virus HTLV-1 encodes regulatory proteins, Tax, Rex and p30(II), which are involved in the control of viral gene expression at the transcriptional and post-transcriptional levels. Tax localizes in unique nuclear bodies that contain components of the transcription and splicing complexes. In this work, we studied the relative intracellular localizations of Tax, Rex and p30(II). Run-on transcription assays and immunocytochemistry at light and electron microscopy levels indicated that the Tax nuclear bodies included both de novo transcribed RNA and the RNA polymerase II form that is phosphorylated on its carboxy-terminal domain whereas contacts with chromatin were observed at the periphery of these nuclear bodies. Rex first accumulated in nucleolar foci and then spread across the whole nucleus to display a diffuse and punctuate nucleoplasmic distribution. This distribution of Rex was observed in HTLV-1 transformed lymphocytes and in COS cells expressing the HTLV-1 provirus. Rex colocalized with the cellular export factor CRM-1 in the nucleolar foci as well as in the nucleoplasmic foci that did not overlap with Tax nuclear bodies but were found at the boundaries of the Tax bodies. In addition, we demonstrate that p30(II) interacts with Rex and colocalizes with the Rex/CRM-1 complexes in the nucleoli leading to their clearance from the nucleoplasm. Our results suggest that transcripts originating from Tax-induced activation of gene expression at the boundaries of the Tax bodies are transported out of the nucleus by nucleoplasmic Rex/CRM-1 complexes that are first assembled in nucleolar foci. In addition, p30(II) might exert its negative effect on viral RNA transport by preventing the release of the Rex/CRM-1 complexes from sequestration in nucleolar foci. These data support the idea that the transcriptional and post-transcriptional regulation of HTLV-1 gene expression depends on the concentration of select regulatory complexes at specific area of the nucleus.
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Affiliation(s)
- Hicham Baydoun
- Institute for Microbiological Research J-M Wiame and Laboratory of Microbiology, University of Brussels, Belgium
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15
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Abstract
Adult T-cell leukemia (ATL) is an aggressive hematologic malignancy caused by human T-cell leukemia virus type I (HTLV-1). Tax, encoded by the HTLV-1 pX region, has been recognized by its pleiotropic actions to play a critical role in leukemogenesis. Three highly conserved 21-bp repeat elements located within the long terminal repeat, commonly referred to as Tax-responsive element 1 (TRE-1), are critical to Tax-mediated viral transcriptional activation through complex interaction with cyclic AMP-responsive element binding protein (CREB), CBP/p300 and PCAF. Tax has also been shown to activate transcription from a number of critical cellular genes through the NF-kappaB and serum-responsive factor pathways. Tax transactivation has been attributed to the protein's interaction with transcription factors, chromatin remodeling complexes, cell cycle and repair genes. In this review, we will discuss some of the latest findings on this fascinating viral activator and highlight its regulation of cellular factors including CREB, p300/CBP and their effect on RNA polymerase II and chromatin remodeling, as well as its role in cytoplasmic and nuclear function. We will highlight the possible contribution of each factor, discuss Tax's critical peptide domains and highlight its post-transcriptional modifications. It is quite obvious that, collectively, Tax's effects on a wide variety of cellular targets cooperate in promoting cell proliferation and leukemogenesis. In addition, the post-transcriptional effects of Rex play an important role in virus replication. Understanding these interactions at a molecular level will facilitate the targeted development of drugs to effectively inhibit or treat ATL.
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Affiliation(s)
- Fatah Kashanchi
- Department of Biochemistry and Molecular Biology, The George Washington University School of Medicine, 2300 Eye St, NW, Ross Hall, Washington, DC, USA.
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Kress E, Baydoun HH, Bex F, Gazzolo L, Duc Dodon M. Critical role of hnRNP A1 in HTLV-1 replication in human transformed T lymphocytes. Retrovirology 2005; 2:8. [PMID: 15703079 PMCID: PMC551596 DOI: 10.1186/1742-4690-2-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2004] [Accepted: 02/09/2005] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND In this study, we have examined the role of heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) in viral gene expression in T lymphocytes transformed by HTLV-1. RESULTS We have previously observed that hnRNP A1 (A1) down-modulates the post transcriptional activity of Rex protein of HTLV-1. Here, we tested whether the ectopic expression of a dominant negative mutant (NLS-A1-HA) defective in shuttling activity or knockdown of the hnRNPA1 gene using RNA interference could inhibit Rex-mediated export of viral mRNAs in HTLV-1 producing C91PL T-cells. We show that the expression of NLS-A1-HA does not modify the export of Rex-dependent viral mRNAs. Conversely, inhibiting A1 expression in C91PL cells by RNA interference provoked an increase in the Rex-dependent export of unspliced and singly spliced mRNAs. Surprisingly, we also observed a significant increase in proviral transcription and an accumulation of unspliced mRNAs, suggesting that the splicing process was affected. Finally, A1 knockdown in C91PL cells increased viral production by these cells. Thus, hnRNP A1 is implicated in the modulation of the level of HTLV-1 gene expression in T cells transformed by this human retrovirus. CONCLUSIONS These observations provide an insight into a new cellular control of HTLV-1 replication and suggest that hnRNP A1 is likely part of the regulatory mechanisms of the life cycle of this human retrovirus in T cells.
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Affiliation(s)
- Elsa Kress
- Virologie Humaine INSERM-U412, Ecole Normale Supérieure de Lyon, IFR 128 Biosciences Lyon-Gerland, 46 allée d'ltalie 69364 Lyon Cedex 07, France
| | - Hicham Hachem Baydoun
- Laboratory of Microbiology, University of Brussels, 1 Avenue E. Gryson, 1070 Brussels, Belgium
| | - Françoise Bex
- Laboratory of Microbiology, University of Brussels, 1 Avenue E. Gryson, 1070 Brussels, Belgium
| | - Louis Gazzolo
- Virologie Humaine INSERM-U412, Ecole Normale Supérieure de Lyon, IFR 128 Biosciences Lyon-Gerland, 46 allée d'ltalie 69364 Lyon Cedex 07, France
| | - Madeleine Duc Dodon
- Virologie Humaine INSERM-U412, Ecole Normale Supérieure de Lyon, IFR 128 Biosciences Lyon-Gerland, 46 allée d'ltalie 69364 Lyon Cedex 07, France
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Younis I, Green PL. The human T-cell leukemia virus Rex protein. FRONTIERS IN BIOSCIENCE : A JOURNAL AND VIRTUAL LIBRARY 2005; 10:431-45. [PMID: 15574380 PMCID: PMC2659543 DOI: 10.2741/1539] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
A critical step in the life cycle of complex retroviruses, including HTLV-1 and HTLV-2 is the ability of these viruses to adopt a mechanism by which the genome-length unspliced mRNA as well as the partially spliced mRNAs are exported from the nucleus instead of being subjected to splicing or degradation. In HTLV, this is accomplished through the expression of the viral Rex, which recognizes a specific response element on the incompletely spliced mRNAs, stabilizes them, inhibits their splicing, and utilizes the CRM1-dependent cellular pathway for transporting them from the nucleus to the cytoplasm. Rex itself is regulated by phosphorylation, which implies that proper activation of the protein in response to certain cellular cues is an important tool for the virus to ensure that specific viral gene expression is allowed only when the host cell can provide the best conditions for virion production. Having such a critical role in HTLV life cycle, Rex is indispensable for efficient viral replication, infection and spread. Indeed, Rex is considered to regulate the switch between the latent and productive phases of the HTLV life cycle. Without a functional Rex, the virus would still produce regulatory and some accessory gene products; however, structural and enzymatic post-transcriptional gene expression would be severely repressed, essentially leading to non-productive viral replication. More detailed understanding of the exact molecular mechanism of action of Rex will thus allow for better design of therapeutic drugs against Rex function and ultimately HTLV replication. Herein we summarize the progress made towards understanding Rex function and its role in the HTLV life cycle.
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Affiliation(s)
- Ihab Younis
- Department of Veterinary Biosciences, The Ohio State University, Columbus, OH 43210
- Center for Retrovirus Research, The Ohio State University, Columbus, OH 43210
- Molecular, Cellular and Developmental Biology Graduate Program, The Ohio State University, Columbus, OH 43210
| | - Patrick L. Green
- Department of Veterinary Biosciences, The Ohio State University, Columbus, OH 43210
- Department of Molecular Virology, Immunology, and Medical Genetics, The Ohio State University, Columbus, OH 43210
- Center for Retrovirus Research, The Ohio State University, Columbus, OH 43210
- Comprehensive Cancer Center, The Ohio State University, Columbus, OH 43210
- Molecular, Cellular and Developmental Biology Graduate Program, The Ohio State University, Columbus, OH 43210
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Bériault V, Clément JF, Lévesque K, Lebel C, Yong X, Chabot B, Cohen EA, Cochrane AW, Rigby WFC, Mouland AJ. A late role for the association of hnRNP A2 with the HIV-1 hnRNP A2 response elements in genomic RNA, Gag, and Vpr localization. J Biol Chem 2004; 279:44141-53. [PMID: 15294897 DOI: 10.1074/jbc.m404691200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Two cis-acting RNA trafficking sequences (heterogenous ribonucleoprotein A2 (hnRNP A2)-response elements 1 and 2 or A2RE-1 and A2RE-2) have been identified in HIV-1 vpr and gag mRNAs and were found to confer cytoplasmic RNA trafficking in a murine oligodendrocyte assay. Their activities were assessed during HIV-1 proviral gene expression in COS7 cells. Single point mutations that were shown to severely block RNA trafficking were introduced into each of the A2REs. In both cases, this resulted in a marked decrease in hnRNP A2 binding to HIV-1 genomic RNA in whole cell extracts and hnRNP A2-containing polysomes. This also resulted in an accumulation of HIV-1 genomic RNA in the nucleus and a significant reduction in genomic RNA encapsidation levels. Immunofluorescence analyses revealed altered expression patterns for pr55Gag and particularly that for Vpr. Vpr localization became almost completely nuclear and this was reflected in a significant reduction in virion-associated Vpr levels. These effects coincided with late steps of the viral replication cycle and were not seen at early time points post-transfection. Transcription, splicing, steady state RNA levels, and pr55Gag processing were not affected. On the other hand, viral replication was markedly compromised in A2RE-2 mutant viruses and this correlated with lowered genomic RNA encapsidation levels. These data reveal new insights into the virus-host interactions between hnRNP A2 and the HIV-1 A2REs and their influence on the patterns of HIV-1 gene expression and viral assembly.
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Affiliation(s)
- Véronique Bériault
- HIV-1 RNA Trafficking Laboratory, Lady Davis Institute for Medical Research-Sir Mortimer B. Davis Jewish General Hospital, Room 323A, 3755 Côte-Ste-Catherine Road, Montréal, Québec H3T 1E2, Canada
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19
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Marchand V, Méreau A, Jacquenet S, Thomas D, Mougin A, Gattoni R, Stévenin J, Branlant C. A Janus splicing regulatory element modulates HIV-1 tat and rev mRNA production by coordination of hnRNP A1 cooperative binding. J Mol Biol 2002; 323:629-52. [PMID: 12419255 DOI: 10.1016/s0022-2836(02)00967-1] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Retroviral protein production depends upon alternative splicing of the viral transcript. The HIV-1 acceptor site A7 is required for tat and rev mRNA production. Production of the Tat transcriptional activator is highly controlled because of its apoptotic properties. Two silencer elements (ESS3 and ISS) and two enhancer elements (ESE2 and ESE3/(GAA)3) were previously identified at site A7. hnRNP A1 binds ISS and ESS3 and is involved in the inhibitory process, ASF/SF2 activates site A7 utilisation. Here, by using chemical and enzymatic probes we established the 2D structure of the HIV-1(BRU) RNA region containing site A7 and identified the RNA segments protected in nuclear extract and by purified hnRNP A1. ISS, ESE3/(GAA)3 and ESS3 are located in three distinct stem-loop structures (SLS1, 2 and 3). As expected, hnRNP A1 binds sites 1, 2 and 3 of ISS and ESS3b, and oligomerises on the polypurine sequence upstream of ESS3b. In addition, we discovered an unidentified hnRNP A1 binding site (AUAGAA), that overlaps ESE3/(GAA)3. On the basis of competition experiments, hnRNP A1 has a stronger affinity for this site than for ESS3b. By insertion of (GAA)3 alone or preceded by the AUA trinucleotide in a foreign context, the AUAGAA sequence was found to modulate strongly the (GAA)3 splicing enhancer activity. Cross-linking experiments on these heterologous RNAs and the SLS2-SLS3 HIV-1 RNA region, in nuclear extract and with recombinant proteins, showed that binding of hnRNP A1 to AUA(GAA)3 strongly competes the association of ASF/SF2 with (GAA)3. In addition, disruption of AUA(GAA)3 demonstrated a key role of this sequence in hnRNP A1 cooperative binding to the ISS and ESS3b inhibitors and hnRNP A1 oligomerisation on the polypurine sequence. Thus, depending on the cellular context ([ASF/SF2]/[hnRNP A1] ratio), AUA(GAA)3 will activate or repress site A7 utilisation and can thus be considered as a Janus splicing regulator.
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MESH Headings
- Alternative Splicing
- Base Sequence
- Binding Sites
- Electrophoretic Mobility Shift Assay
- Gene Expression Regulation, Viral
- Gene Products, rev/genetics
- Gene Products, tat/genetics
- HIV-1/genetics
- HeLa Cells
- Heterogeneous Nuclear Ribonucleoprotein A1
- Heterogeneous-Nuclear Ribonucleoprotein Group A-B/metabolism
- Humans
- Molecular Sequence Data
- Mutagenesis, Site-Directed
- Nucleic Acid Conformation
- Protein Binding
- RNA, Messenger/biosynthesis
- RNA, Messenger/chemistry
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Viral/biosynthesis
- RNA, Viral/chemistry
- RNA, Viral/genetics
- RNA, Viral/metabolism
- Silencer Elements, Transcriptional/genetics
- Transcription, Genetic
- rev Gene Products, Human Immunodeficiency Virus
- tat Gene Products, Human Immunodeficiency Virus
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Affiliation(s)
- Virginie Marchand
- Laboratoire de Maturation des ARN et Enzymologie Moléculaire, UMR 7567 UHP-CNRS, Université Henri Poincaré Nancy 1, Boulevard des Aiguillettes, BP239, 54506 Cedex, Vandoeuvre-lès-Nancy, France
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