1
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Alpuche-Lazcano SP, Scarborough RJ, Gatignol A. MicroRNAs and long non-coding RNAs during transcriptional regulation and latency of HIV and HTLV. Retrovirology 2024; 21:5. [PMID: 38424561 PMCID: PMC10905857 DOI: 10.1186/s12977-024-00637-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2023] [Accepted: 02/21/2024] [Indexed: 03/02/2024] Open
Abstract
Human immunodeficiency virus (HIV) and human T cell leukemia virus (HTLV) have replicative and latent stages of infection. The status of the viruses is dependent on the cells that harbour them and on different events that change the transcriptional and post-transcriptional events. Non-coding (nc)RNAs are key factors in the regulation of retrovirus replication cycles. Notably, micro (mi)RNAs and long non-coding (lnc)RNAs are important regulators that can induce switches between active transcription-replication and latency of retroviruses and have important impacts on their pathogenesis. Here, we review the functions of miRNAs and lncRNAs in the context of HIV and HTLV. We describe how specific miRNAs and lncRNAs are involved in the regulation of the viruses' transcription, post-transcriptional regulation and latency. We further discuss treatment strategies using ncRNAs for HIV and HTLV long remission, reactivation or possible cure.
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Affiliation(s)
- Sergio P Alpuche-Lazcano
- Virus-Cell Interactions Laboratory, Lady Davis Institute for Medical Research, 3999, Côte Ste Catherine St., Montréal, QC, H3T 1E2, Canada
- Department of Medicine, Division of Experimental Medicine, McGill University, Montréal, QC, H4A 3J1, Canada
- National Research Council Canada, Montréal, QC, H4P 2R2, Canada
| | - Robert J Scarborough
- Virus-Cell Interactions Laboratory, Lady Davis Institute for Medical Research, 3999, Côte Ste Catherine St., Montréal, QC, H3T 1E2, Canada
- Department of Microbiology and Immunology, McGill University, Montréal, QC, H3A 2B4, Canada
| | - Anne Gatignol
- Virus-Cell Interactions Laboratory, Lady Davis Institute for Medical Research, 3999, Côte Ste Catherine St., Montréal, QC, H3T 1E2, Canada.
- Department of Medicine, Division of Experimental Medicine, McGill University, Montréal, QC, H4A 3J1, Canada.
- Department of Medicine, Division of Infectious Diseases, McGill University, Montréal, QC, H4A 3J1, Canada.
- Department of Microbiology and Immunology, McGill University, Montréal, QC, H3A 2B4, Canada.
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2
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Kawano K, Hashikura Y, Umekita K. Purification Method of Extracellular Vesicles Derived from Human T-Cell Leukemia Virus Type 1-Infected Cells without Virions. Viruses 2024; 16:249. [PMID: 38400025 PMCID: PMC10892183 DOI: 10.3390/v16020249] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Revised: 01/19/2024] [Accepted: 02/01/2024] [Indexed: 02/25/2024] Open
Abstract
To mediate intercellular communication, cells produce extracellular vesicles (EVs). These EVs transport many biomolecules such as proteins, nucleic acids, and lipids between cells and regulate pathophysiological actions in the recipient cell. However, EVs and virus particles produced from virus-infected cells are of similar size and specific gravity; therefore, the separation and purification of these two particles is often controversial. When analyzing the physiological functions of EVs from virus-infected cells, the presence or absence of virus particle contamination must always be verified. The human T-cell leukemia virus type 1 (HTLV-1)-infected cell line, MT-2, produces EVs and virus particles. Here, we validated a method for purifying EVs from MT-2 cell culture supernatants while avoiding HTLV-1 viral particle contamination. EV fractions were collected using a combination of immunoprecipitation with Tim-4, which binds to phosphatidylserine, and polymer precipitation. The HTLV-1 viral envelope protein, gp46, was not detected in the EV fraction. Proteomic analysis revealed that EV-constituted proteins were predominant in this EV fraction. Furthermore, the EVs were found to contain the HTLV-1 viral genome. The proposed method can purify EVs while avoiding virus particle contamination and is expected to contribute to future research on EVs derived from HTLV-1-infected cells.
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Affiliation(s)
- Katsumi Kawano
- Division of Respirology, Rheumatology, Infectious Diseases and Neurology, Department of Internal Medicine, University of Miyazaki, Kihara 5200, Kiyotake, Miyazaki 889-1692, Japan;
- Clinical Laboratory, University of Miyazaki of Hospital, Kihara 5200, Kiyotake, Miyazaki 889-1692, Japan;
| | - Yuki Hashikura
- Clinical Laboratory, University of Miyazaki of Hospital, Kihara 5200, Kiyotake, Miyazaki 889-1692, Japan;
| | - Kunihiko Umekita
- Division of Respirology, Rheumatology, Infectious Diseases and Neurology, Department of Internal Medicine, University of Miyazaki, Kihara 5200, Kiyotake, Miyazaki 889-1692, Japan;
- Clinical Laboratory, University of Miyazaki of Hospital, Kihara 5200, Kiyotake, Miyazaki 889-1692, Japan;
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3
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Rehman SU, Ullah N, Zhang Z, Zhen Y, Din AU, Cui H, Wang M. Recent insights into the functions and mechanisms of antisense RNA: emerging applications in cancer therapy and precision medicine. Front Chem 2024; 11:1335330. [PMID: 38274897 PMCID: PMC10809404 DOI: 10.3389/fchem.2023.1335330] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2023] [Accepted: 12/19/2023] [Indexed: 01/27/2024] Open
Abstract
The antisense RNA molecule is a unique DNA transcript consisting of 19-23 nucleotides, characterized by its complementary nature to mRNA. These antisense RNAs play a crucial role in regulating gene expression at various stages, including replication, transcription, and translation. Additionally, artificial antisense RNAs have demonstrated their ability to effectively modulate gene expression in host cells. Consequently, there has been a substantial increase in research dedicated to investigating the roles of antisense RNAs. These molecules have been found to be influential in various cellular processes, such as X-chromosome inactivation and imprinted silencing in healthy cells. However, it is important to recognize that in cancer cells; aberrantly expressed antisense RNAs can trigger the epigenetic silencing of tumor suppressor genes. Moreover, the presence of deletion-induced aberrant antisense RNAs can lead to the development of diseases through epigenetic silencing. One area of drug development worth mentioning is antisense oligonucleotides (ASOs), and a prime example of an oncogenic trans-acting long noncoding RNA (lncRNA) is HOTAIR (HOX transcript antisense RNA). NATs (noncoding antisense transcripts) are dysregulated in many cancers, and researchers are just beginning to unravel their roles as crucial regulators of cancer's hallmarks, as well as their potential for cancer therapy. In this review, we summarize the emerging roles and mechanisms of antisense RNA and explore their application in cancer therapy.
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Affiliation(s)
- Shahab Ur Rehman
- College of Animals Science and Technology Yangzhou University, Yangzhou, China
| | - Numan Ullah
- College of Animals Science and Technology Yangzhou University, Yangzhou, China
| | - Zhenbin Zhang
- College of Animals Science and Technology Yangzhou University, Yangzhou, China
| | - Yongkang Zhen
- College of Animals Nutrition Yangzhou University, Yangzhou, China
| | - Aziz-Ud Din
- Department of Human Genetics, Hazara University Mansehra, Mansehra, Pakistan
| | - Hengmi Cui
- College of Animals Science and Technology Yangzhou University, Yangzhou, China
- Institute of Epigenetics and Epigenomics Yangzhou University, College of Animal Nutrition Yangzhou University, Yangzhou, China
| | - Mengzhi Wang
- College of Animals Science and Technology Yangzhou University, Yangzhou, China
- College of Animals Nutrition Yangzhou University, Yangzhou, China
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4
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Li H, Zou F, Zhang J, Zhu S, Chu K, Zhang X, Zhao T. YAP suppresses human T-cell leukemia virus type 1 transcription. J Med Virol 2023; 95:e29065. [PMID: 37661566 DOI: 10.1002/jmv.29065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Revised: 08/11/2023] [Accepted: 08/17/2023] [Indexed: 09/05/2023]
Abstract
Human T-cell leukemia virus type 1 (HTLV-1) is an oncogenic retrovirus that causes adult T-cell leukemia/lymphoma (ATL). HTLV-1 encodes Tax protein that activates transcription from viral long terminal repeats (LTR). Multiple cofactors are involved in the regulation of HTLV-1 transcription via association with Tax. Yes-associated protein (YAP), which is the key effector of Hippo pathway, is elevated and activated in ATL cells. In this study, we reported that YAP protein suppressed Tax activation of HTLV-1 5' LTR but not 3' LTR. The activation of the 5' LTR by Tax was potentiated when YAP was depleted. Moreover, overexpression of YAP repressed HTLV-1 plus-strand viral gene expression and virion production, whereas compromising YAP by RNA inference augmented the expression of HTLV-1 protein. As mechanisms of YAP-mediated viral transcription inhibition, we found that YAP interacted with Tax, and prevented the association between Tax and p300. It finally led to the inhibition of recruitment of Tax to the Tax-responsive element in the 5' LTR of HTLV-1. Taken together, our results demonstrate the negative regulatory function of YAP in Tax activation of HTLV-1 transcription. It may achieve sufficient transcriptional repression to maintain persistent infection and long-term latency of HTLV-1 in the host cells.
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Affiliation(s)
- Hengbo Li
- School of Medicine, Hangzhou City University, Hangzhou, China
- College of Life Sciences, Zhejiang Normal University, Jinhua, China
| | - Feng Zou
- College of Life Sciences, Zhejiang Normal University, Jinhua, China
| | - Jie Zhang
- School of Medicine, Hangzhou City University, Hangzhou, China
| | - Shengyu Zhu
- School of Medicine, Hangzhou City University, Hangzhou, China
| | - Kaifei Chu
- School of Medicine, Hangzhou City University, Hangzhou, China
- College of Life Sciences, Zhejiang Normal University, Jinhua, China
| | - Xu Zhang
- School of Medicine, Hangzhou City University, Hangzhou, China
- College of Life Sciences, Zhejiang Normal University, Jinhua, China
| | - Tiejun Zhao
- School of Medicine, Hangzhou City University, Hangzhou, China
- College of Life Sciences, Zhejiang Normal University, Jinhua, China
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5
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Toyoda K, Yasunaga JI, Shichijo T, Arima Y, Tsujita K, Tanaka A, Salah T, Zhang W, Hussein O, Sonoda M, Watanabe M, Kurita D, Nakashima K, Yamada K, Miyoshi H, Ohshima K, Matsuoka M. HTLV-1 bZIP Factor-Induced Reprogramming of Lactate Metabolism and Epigenetic Status Promote Leukemic Cell Expansion. Blood Cancer Discov 2023; 4:374-393. [PMID: 37162520 PMCID: PMC10473166 DOI: 10.1158/2643-3230.bcd-22-0139] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 03/17/2023] [Accepted: 04/26/2023] [Indexed: 05/11/2023] Open
Abstract
Acceleration of glycolysis is a common trait of cancer. A key metabolite, lactate, is typically secreted from cancer cells because its accumulation is toxic. Here, we report that a viral oncogene, HTLV-1 bZIP factor (HBZ), bimodally upregulates TAp73 to promote lactate excretion from adult T-cell leukemia-lymphoma (ATL) cells. HBZ protein binds to EZH2 and reduces its occupancy of the TAp73 promoter. Meanwhile, HBZ RNA activates TAp73 transcription via the BATF3-IRF4 machinery. TAp73 upregulates the lactate transporters MCT1 and MCT4. Inactivation of TAp73 leads to intracellular accumulation of lactate, inducing cell death in ATL cells. Furthermore, TAp73 knockout diminishes the development of inflammation in HBZ-transgenic mice. An MCT1/4 inhibitor, syrosingopine, decreases the growth of ATL cells in vitro and in vivo. MCT1/4 expression is positively correlated with TAp73 in many cancers, and MCT1/4 upregulation is associated with dismal prognosis. Activation of the TAp73-MCT1/4 pathway could be a common mechanism contributing to cancer metabolism. SIGNIFICANCE An antisense gene encoded in HTLV-1, HBZ, reprograms lactate metabolism and epigenetic modification by inducing TAp73 in virus-positive leukemic cells. A positive correlation between TAp73 and its target genes is also observed in many other cancer cells, suggesting that this is a common mechanism for cellular oncogenesis. This article is featured in Selected Articles from This Issue, p. 337.
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Affiliation(s)
- Kosuke Toyoda
- Department of Hematology, Rheumatology, and Infectious Disease, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Jun-ichirou Yasunaga
- Department of Hematology, Rheumatology, and Infectious Disease, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Takafumi Shichijo
- Department of Hematology, Rheumatology, and Infectious Disease, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Yuichiro Arima
- Department of Cardiovascular Medicine, Graduate School of Medical Sciences, Kumamoto University, Kumamoto, Japan
- International Research Center for Medical Sciences (IRCMS), Kumamoto University, Kumamoto, Japan
| | - Kenichi Tsujita
- Department of Cardiovascular Medicine, Graduate School of Medical Sciences, Kumamoto University, Kumamoto, Japan
- Center for Metabolic Regulation of Healthy Aging (CMHA), Kumamoto University, Kumamoto, Japan
| | - Azusa Tanaka
- Department of Human Genetics, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Tarig Salah
- Department of Hematology, Rheumatology, and Infectious Disease, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Wenyi Zhang
- Department of Hematology, Rheumatology, and Infectious Disease, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Osama Hussein
- Department of Hematology, Rheumatology, and Infectious Disease, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Miyu Sonoda
- Department of Hematology, Rheumatology, and Infectious Disease, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Miho Watanabe
- Department of Hematology, Rheumatology, and Infectious Disease, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Daisuke Kurita
- Department of Hematology, Rheumatology, and Infectious Disease, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Kazutaka Nakashima
- Department of Pathology, Kurume University School of Medicine, Fukuoka, Japan
| | - Kyohei Yamada
- Department of Pathology, Kurume University School of Medicine, Fukuoka, Japan
| | - Hiroaki Miyoshi
- Department of Pathology, Kurume University School of Medicine, Fukuoka, Japan
| | - Koichi Ohshima
- Department of Pathology, Kurume University School of Medicine, Fukuoka, Japan
| | - Masao Matsuoka
- Department of Hematology, Rheumatology, and Infectious Disease, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
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6
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Romerio F. Origin and functional role of antisense transcription in endogenous and exogenous retroviruses. Retrovirology 2023; 20:6. [PMID: 37194028 DOI: 10.1186/s12977-023-00622-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Accepted: 04/30/2023] [Indexed: 05/18/2023] Open
Abstract
Most proteins expressed by endogenous and exogenous retroviruses are encoded in the sense (positive) strand of the genome and are under the control of regulatory elements within the 5' long terminal repeat (LTR). A number of retroviral genomes also encode genes in the antisense (negative) strand and their expression is under the control of negative sense promoters within the 3' LTR. In the case of the Human T-cell Lymphotropic Virus 1 (HTLV-1), the antisense protein HBZ has been shown to play a critical role in the virus lifecycle and in the pathogenic process, while the function of the Human Immunodeficiency Virus 1 (HIV-1) antisense protein ASP remains unknown. However, the expression of 3' LTR-driven antisense transcripts is not always demonstrably associated with the presence of an antisense open reading frame encoding a viral protein. Moreover, even in the case of retroviruses that do express an antisense protein, such as HTLV-1 and the pandemic strains of HIV-1, the 3' LTR-driven antisense transcript shows both protein-coding and noncoding activities. Indeed, the ability to express antisense transcripts appears to be phylogenetically more widespread among endogenous and exogenous retroviruses than the presence of a functional antisense open reading frame within these transcripts. This suggests that retroviral antisense transcripts may have originated as noncoding molecules with regulatory activity that in some cases later acquired protein-coding function. Here, we will review examples of endogenous and exogenous retroviral antisense transcripts, and the ways through which they benefit viral persistence in the host.
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Affiliation(s)
- Fabio Romerio
- Department of Molecular and Comparative Pathobiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
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7
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Kulkarni V, Jayakumar S, Mohan M, Kulkarni S. Aid or Antagonize: Nuclear Long Noncoding RNAs Regulate Host Responses and Outcomes of Viral Infections. Cells 2023; 12:987. [PMID: 37048060 PMCID: PMC10093752 DOI: 10.3390/cells12070987] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Revised: 03/12/2023] [Accepted: 03/15/2023] [Indexed: 04/14/2023] Open
Abstract
Long noncoding RNAs (lncRNAs) are transcripts measuring >200 bp in length and devoid of protein-coding potential. LncRNAs exceed the number of protein-coding mRNAs and regulate cellular, developmental, and immune pathways through diverse molecular mechanisms. In recent years, lncRNAs have emerged as epigenetic regulators with prominent roles in health and disease. Many lncRNAs, either host or virus-encoded, have been implicated in critical cellular defense processes, such as cytokine and antiviral gene expression, the regulation of cell signaling pathways, and the activation of transcription factors. In addition, cellular and viral lncRNAs regulate virus gene expression. Viral infections and associated immune responses alter the expression of host lncRNAs regulating immune responses, host metabolism, and viral replication. The influence of lncRNAs on the pathogenesis and outcomes of viral infections is being widely explored because virus-induced lncRNAs can serve as diagnostic and therapeutic targets. Future studies should focus on thoroughly characterizing lncRNA expressions in virus-infected primary cells, investigating their role in disease prognosis, and developing biologically relevant animal or organoid models to determine their suitability for specific therapeutic targeting. Many cellular and viral lncRNAs localize in the nucleus and epigenetically modulate viral transcription, latency, and host responses to infection. In this review, we provide an overview of the role of nuclear lncRNAs in the pathogenesis and outcomes of viral infections, such as the Influenza A virus, Sendai Virus, Respiratory Syncytial Virus, Hepatitis C virus, Human Immunodeficiency Virus, and Herpes Simplex Virus. We also address significant advances and barriers in characterizing lncRNA function and explore the potential of lncRNAs as therapeutic targets.
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Affiliation(s)
- Viraj Kulkarni
- Disease Intervention and Prevention Program, Texas Biomedical Research Institute, San Antonio, TX 78227, USA;
| | - Sahana Jayakumar
- Host-Pathogen Interaction Program, Texas Biomedical Research Institute, San Antonio, TX 78227, USA; (S.J.); (M.M.)
| | - Mahesh Mohan
- Host-Pathogen Interaction Program, Texas Biomedical Research Institute, San Antonio, TX 78227, USA; (S.J.); (M.M.)
| | - Smita Kulkarni
- Host-Pathogen Interaction Program, Texas Biomedical Research Institute, San Antonio, TX 78227, USA; (S.J.); (M.M.)
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8
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Zuo X, Zhou R, Yang S, Ma G. HTLV-1 persistent infection and ATLL oncogenesis. J Med Virol 2023; 95:e28424. [PMID: 36546414 DOI: 10.1002/jmv.28424] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 12/08/2022] [Accepted: 12/16/2022] [Indexed: 12/24/2022]
Abstract
Human T-cell leukemia virus type 1 (HTLV-1) is an oncogenic retrovirus; whereas HTLV-1 mainly persists in the infected host cell as a provirus, it also causes a malignancy called adult T-cell leukemia/lymphoma (ATLL) in about 5% of infection. HTLV-1 replication is in most cases silent in vivo and viral de novo infection rarely occurs; HTLV-1 rather relies on clonal proliferation of infected T cells for viral propagation as it multiplies the number of the provirus copies. It is mechanistically elusive how leukemic clones emerge during the course of HTLV-1 infection in vivo and eventually cause the onset of ATLL. This review summarizes our current understanding of HTLV-1 persistence and oncogenesis, with the incorporation of recent cutting-edge discoveries obtained by high-throughput sequencing.
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Affiliation(s)
- Xiaorui Zuo
- Institute of Pharmaceutical Science, China Pharmaceutical University, Nanjing, China.,State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing, China
| | - Ruoning Zhou
- Institute of Pharmaceutical Science, China Pharmaceutical University, Nanjing, China.,State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing, China
| | - Sikai Yang
- Institute of Pharmaceutical Science, China Pharmaceutical University, Nanjing, China.,State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing, China
| | - Guangyong Ma
- Institute of Pharmaceutical Science, China Pharmaceutical University, Nanjing, China.,State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing, China
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9
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Shah R, Gallardo CM, Jung YH, Clock B, Dixon JR, McFadden WM, Majumder K, Pintel DJ, Corces VG, Torbett BE, Tedbury PR, Sarafianos SG. Activation of HIV-1 proviruses increases downstream chromatin accessibility. iScience 2022; 25:105490. [PMID: 36505924 PMCID: PMC9732416 DOI: 10.1016/j.isci.2022.105490] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Revised: 09/15/2022] [Accepted: 10/31/2022] [Indexed: 11/09/2022] Open
Abstract
It is unclear how the activation of HIV-1 transcription affects chromatin structure. We interrogated chromatin organization both genome-wide and nearby HIV-1 integration sites using Hi-C and ATAC-seq. In conjunction, we analyzed the transcription of the HIV-1 genome and neighboring genes. We found that long-range chromatin contacts did not differ significantly between uninfected cells and those harboring an integrated HIV-1 genome, whether the HIV-1 genome was actively transcribed or inactive. Instead, the activation of HIV-1 transcription changes chromatin accessibility immediately downstream of the provirus, demonstrating that HIV-1 can alter local cellular chromatin structure. Finally, we examined HIV-1 and neighboring host gene transcripts with long-read sequencing and found populations of chimeric RNAs both virus-to-host and host-to-virus. Thus, multiomics profiling revealed that the activation of HIV-1 transcription led to local changes in chromatin organization and altered the expression of neighboring host genes.
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Affiliation(s)
- Raven Shah
- Laboratory of Biochemical Pharmacology, Department of Pediatrics, Emory University School of Medicine, Atlanta, GA 30329, USA
- Children’s Healthcare of Atlanta, Atlanta, GA 30329, USA
| | - Christian M. Gallardo
- Center for Immunity and Immunotherapies, Seattle Children’s Research Institute, Seattle, WA 98101, USA
| | - Yoonhee H. Jung
- Department of Biology, Emory University, Atlanta, GA 30329, USA
| | - Ben Clock
- Salk Institute for Biological Studies, La Jolla, CA 92037, USA
| | - Jesse R. Dixon
- Salk Institute for Biological Studies, La Jolla, CA 92037, USA
| | - William M. McFadden
- Laboratory of Biochemical Pharmacology, Department of Pediatrics, Emory University School of Medicine, Atlanta, GA 30329, USA
- Children’s Healthcare of Atlanta, Atlanta, GA 30329, USA
| | - Kinjal Majumder
- Institute for Molecular Virology and McArdle Laboratory for Cancer Research, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - David J. Pintel
- Department of Molecular Microbiology and Immunology, Christopher S. Bond Life Sciences Center, University of Missouri School of Medicine, Columbia, MO 65211, USA
| | | | - Bruce E. Torbett
- Center for Immunity and Immunotherapies, Seattle Children’s Research Institute, Seattle, WA 98101, USA
- Department of Pediatrics, University of Washington School of Medicine, Seattle, WA 98101, USA
| | - Philip R. Tedbury
- Laboratory of Biochemical Pharmacology, Department of Pediatrics, Emory University School of Medicine, Atlanta, GA 30329, USA
- Children’s Healthcare of Atlanta, Atlanta, GA 30329, USA
| | - Stefan G. Sarafianos
- Laboratory of Biochemical Pharmacology, Department of Pediatrics, Emory University School of Medicine, Atlanta, GA 30329, USA
- Children’s Healthcare of Atlanta, Atlanta, GA 30329, USA
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10
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Liu Z, Larocque É, Xie Y, Xiao Y, Lemay G, Peloponese JM, Mesnard JM, Rassart É, Lin R, Zhou S, Zeng Y, Gao H, Cen S, Barbeau B. A newly identified interaction between nucleolar NPM1/B23 and the HTLV-I basic leucine zipper factor in HTLV-1 infected cells. Front Microbiol 2022; 13:988944. [PMID: 36532440 PMCID: PMC9753777 DOI: 10.3389/fmicb.2022.988944] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Accepted: 11/08/2022] [Indexed: 08/05/2023] Open
Abstract
Human T-cell leukemia virus type 1 is the causative agent of HTLV-1-associated myelopathy/tropical spastic paraparesis and adult T-cell leukemia-lymphoma (ATL). The HTLV-1 basic leucine zipper factor (HBZ) has been associated to the cancer-inducing properties of this virus, although the exact mechanism is unknown. In this study, we identified nucleophosmin (NPM1/B23) as a new interaction partner of HBZ. We show that sHBZ and the less abundant uHBZ isoform interact with nucleolar NPM1/B23 in infected cells and HTLV-1 positive patient cells, unlike equivalent antisense proteins of related non-leukemogenic HTLV-2, -3 and-4 viruses. We further demonstrate that sHBZ association to NPM1/B23 is sensitive to RNase. Interestingly, sHBZ was shown to interact with its own RNA. Through siRNA and overexpression experiments, we further provide evidence that NPM1/B23 acts negatively on viral gene expression with potential impact on cell transformation. Our results hence provide a new insight over HBZ-binding partners in relation to cellular localization and potential function on cell proliferation and should lead to a better understanding of the link between HBZ and ATL development.
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Affiliation(s)
- Zhenlong Liu
- Département de chimie, Université du Québec à Montréal, Montréal, QC, Canada
- Centre d’excellence en recherche sur les maladies orphelines-Fondation Courtois, Université du Québec à Montréal, Montréal, QC, Canada
- Lady Davis Institute, Jewish General Hospital & Department of Medicine, McGill University, Montreal, QC, Canada
| | - Émilie Larocque
- Centre d’excellence en recherche sur les maladies orphelines-Fondation Courtois, Université du Québec à Montréal, Montréal, QC, Canada
- Département de microbiologie et immunologie, Université de Montréal, Montréal, QC, Canada
| | - Yongli Xie
- Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences, Beijing, China
| | - Yong Xiao
- Département de chimie, Université du Québec à Montréal, Montréal, QC, Canada
- Centre d’excellence en recherche sur les maladies orphelines-Fondation Courtois, Université du Québec à Montréal, Montréal, QC, Canada
| | - Guy Lemay
- Département de microbiologie et immunologie, Université de Montréal, Montréal, QC, Canada
| | - Jean-Marie Peloponese
- Institut de Recherche en Infectiologie de Montpellier (IRIM), CNRS, Université Montpellier, Montpellier, France
| | - Jean-Michel Mesnard
- Institut de Recherche en Infectiologie de Montpellier (IRIM), CNRS, Université Montpellier, Montpellier, France
| | - Éric Rassart
- Centre d’excellence en recherche sur les maladies orphelines-Fondation Courtois, Université du Québec à Montréal, Montréal, QC, Canada
- Département des sciences biologiques, Université du Québec à Montréal, Montréal, QC, Canada
| | - Rongtuan Lin
- Lady Davis Institute, Jewish General Hospital & Department of Medicine, McGill University, Montreal, QC, Canada
| | - Shuang Zhou
- Neurosurgery Department, 2nd Affiliated Hospital of Fujian Medical University, Quanzhou, Fujian, China
| | - Yiming Zeng
- Neurosurgery Department, 2nd Affiliated Hospital of Fujian Medical University, Quanzhou, Fujian, China
| | - Hongzhi Gao
- Neurosurgery Department, 2nd Affiliated Hospital of Fujian Medical University, Quanzhou, Fujian, China
| | - Shan Cen
- Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences, Beijing, China
| | - Benoit Barbeau
- Département de chimie, Université du Québec à Montréal, Montréal, QC, Canada
- Centre d’excellence en recherche sur les maladies orphelines-Fondation Courtois, Université du Québec à Montréal, Montréal, QC, Canada
- Département de microbiologie et immunologie, Université de Montréal, Montréal, QC, Canada
- Département des sciences biologiques, Université du Québec à Montréal, Montréal, QC, Canada
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11
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Accolla RS. The Road to HTLV-1-Induced Leukemia by Following the Subcellular Localization of HTLV-1-Encoded HBZ Protein. Front Immunol 2022; 13:940131. [PMID: 35812456 PMCID: PMC9259882 DOI: 10.3389/fimmu.2022.940131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Accepted: 06/01/2022] [Indexed: 11/13/2022] Open
Abstract
Human T cell leukemia virus-1 (HTLV-1) is the causative agent of a severe cancer of the lymphoid lineage that develops in 3-5% of infected individuals after many years. HTLV-1 infection may also induce a serious inflammatory pathology of the nervous system designated HTLV-associated myelopathy/tropical spastic paraparesis (HAM/TSP). Two virus-encoded proteins, the viral transactivator Tax-1 and the HTLV-1 basic leucine-zipper factor HBZ, are strongly involved in the oncogenic process. Tax-1 is involved in initial phases of the oncogenic process. Conversely, HBZ seems to be involved in maintenance of the neoplastic state as witnessed by the generation of leukemic/lymphomatous phenotype in HBZ transgenic mice and the persistent expression of HBZ in all phases of the oncogenic process. Nevertheless, the intimate molecular and cellular mechanism mediated by the two viral proteins, particularly HBZ, in oncogenesis still remain elusive. An important step toward the complete comprehension of HBZ-associated oncogenicity is the clarification of the anatomical correlates of HBZ during the various phases of HTLV-1 infection to development of HTLV-1-associated inflammatory pathology and ultimately to the establishment of leukemia. In this review, I will summarize recent studies that have established for the first time a temporal and unidirectional expression of HBZ, beginning with an exclusive cytoplasmic localization in infected asymptomatic individuals and in HAM/TSP patients and ending to a progressive cytoplasmic-to-nuclear transition in leukemic cells. These results are framed within the present knowledge of HTLV-1 infection and the future lines of research that may shed new light on the complex mechanism of HTLV-1- mediated oncogenesis.
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12
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HIV UTR, LTR, and Epigenetic Immunity. Viruses 2022; 14:v14051084. [PMID: 35632825 PMCID: PMC9146425 DOI: 10.3390/v14051084] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Revised: 05/05/2022] [Accepted: 05/13/2022] [Indexed: 02/06/2023] Open
Abstract
The duel between humans and viruses is unending. In this review, we examine the HIV RNA in the form of un-translated terminal region (UTR), the viral DNA in the form of long terminal repeat (LTR), and the immunity of human DNA in a format of epigenetic regulation. We explore the ways in which the human immune responses to invading pathogenic viral nucleic acids can inhibit HIV infection, exemplified by a chromatin vaccine (cVaccine) to elicit the immunity of our genome—epigenetic immunity towards a cure.
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13
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Estevez M, Li R, Paul B, Daneshvar K, Mullen AC, Romerio F, Addepalli B. Identification and mapping of post-transcriptional modifications on the HIV-1 antisense transcript Ast in human cells. RNA (NEW YORK, N.Y.) 2022; 28:697-710. [PMID: 35168996 PMCID: PMC9014878 DOI: 10.1261/rna.079043.121] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Accepted: 01/29/2022] [Indexed: 05/03/2023]
Abstract
The human immunodeficiency virus type 1 (HIV-1) encodes multiple RNA molecules. Transcripts that originate from the proviral 5' long terminal repeat (LTR) function as messenger RNAs for the expression of 16 different mature viral proteins. In addition, HIV-1 expresses an antisense transcript (Ast) from the 3'LTR, which has both protein-coding and noncoding properties. While the mechanisms that regulate the coding and noncoding activities of Ast remain unknown, post-transcriptional modifications are known to influence RNA stability, interaction with protein partners, and translation capacity. Here, we report the nucleoside modification profile of Ast obtained through liquid chromatography coupled with mass spectrometry (LC-MS) analysis. The epitranscriptome includes a limited set of modified nucleosides but predominantly ribose methylations. A number of these modifications were mapped to specific positions of the sequence through RNA modification mapping procedures. The presence of modifications on Ast is consistent with the RNA-modifying enzymes interacting with Ast The identification and mapping of Ast post-transcriptional modifications is expected to elucidate the mechanisms through which this versatile molecule can carry out diverse activities in different cell compartments. Manipulation of post-transcriptional modifications on the Ast RNA may have therapeutic implications.
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Affiliation(s)
- Mariana Estevez
- Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221, USA
| | - Rui Li
- Department of Molecular and Comparative Pathobiology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
| | - Biplab Paul
- Massachusetts General Hospital, Boston, Massachusetts 02114, USA
| | - Kaveh Daneshvar
- Massachusetts General Hospital, Boston, Massachusetts 02114, USA
| | - Alan C Mullen
- Massachusetts General Hospital, Boston, Massachusetts 02114, USA
| | - Fabio Romerio
- Department of Molecular and Comparative Pathobiology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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14
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Toyoda K, Matsuoka M. Functional and Pathogenic Roles of Retroviral Antisense Transcripts. Front Immunol 2022; 13:875211. [PMID: 35572593 PMCID: PMC9100821 DOI: 10.3389/fimmu.2022.875211] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2022] [Accepted: 04/06/2022] [Indexed: 11/13/2022] Open
Abstract
Exogenous retroviruses such as human immunodeficiency virus type 1 (HIV-1), human T-cell leukemia virus type 1 (HTLV-1) and bovine leukemia virus (BLV) can cause various diseases including immunodeficiency, inflammatory diseases and hematologic malignancies. These retroviruses persistently infect their hosts. Therefore, they need to evade host immune surveillance. One way in which these viruses might avoid immune detection is to utilize functional RNAs, rather than proteins, for certain activities, because RNAs are not recognized by the host immune system. HTLV-1 encodes the HTLV-1 bZIP factor (HBZ) gene in the antisense strand of the provirus. The HBZ protein is constantly expressed in HTLV-1 carriers and patients with adult T-cell leukemia-lymphoma, and it plays critical roles in pathogenesis. However, HBZ not only encodes this protein, but also functions as mRNA. Thus, HBZ gene mRNA is bifunctional. HIV-1 and BLV also encode long non-coding RNAs as antisense transcripts. In this review, we reshape our current understanding of how these antisense transcripts function and how they influence disease pathogenesis.
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15
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Zuo X, Ma G. Antisense protein: a novel HIV-1 gene requiring attention. Future Virol 2022. [DOI: 10.2217/fvl-2022-0008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- Xiaorui Zuo
- Institute of Pharmaceutical Sciences, China Pharmaceutical University, Nanjing, China
| | - Guangyong Ma
- Institute of Pharmaceutical Sciences, China Pharmaceutical University, Nanjing, China
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16
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Miura M, Naito T, Saito M. Current Perspectives in Human T-Cell Leukemia Virus Type 1 Infection and Its Associated Diseases. Front Med (Lausanne) 2022; 9:867478. [PMID: 35463007 PMCID: PMC9024061 DOI: 10.3389/fmed.2022.867478] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Accepted: 03/15/2022] [Indexed: 11/25/2022] Open
Abstract
Human T-cell leukemia virus type 1 (HTLV-1) is a replication-competent human retrovirus associated with two distinct types of diseases: a malignancy of mature CD4+ T cells called adult T-cell leukemia-lymphoma (ATL) and a chronic inflammatory central nervous system disease HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). It was the first human retrovirus ever associated with a human cancer. Although most HTLV-1-infected individuals remain asymptomatic for life, a subpopulation develops ATL or HAM/TSP. Although the factors that cause these different manifestations of HTLV-1 infection are not fully understood, accumulating evidence suggests that the complex virus-host interactions, as well as the host immune response against HTLV-1 infection, appear to regulate the development of HTLV-1-associated diseases. This review outlines and discusses the current understanding, ongoing developments, and future perspectives of HTLV-1 research.
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17
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Lin E, Panfil AR, Sandel G, Jain P. Novel perspectives on antisense transcription in HIV-1, HTLV-1, and HTLV-2. Front Microbiol 2022; 13:1042761. [PMID: 36620051 PMCID: PMC9822710 DOI: 10.3389/fmicb.2022.1042761] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Accepted: 11/24/2022] [Indexed: 12/25/2022] Open
Abstract
The genome of retroviruses contains two promoter elements (called long terminal repeat or LTR) at the 5' and 3' end of their genome. Although the expression of retroviral genes generally depends on the promoter located in the 5' LTR, the 3' LTR also has promoter activity responsible for producing antisense transcripts. These natural antisense transcripts (NATs) are a class of RNA molecules transcribed from the opposite strand of a protein-coding gene. NATs have been identified in many prokaryotic and eukaryotic systems, as well as in human retroviruses such as human immunodeficiency virus type 1 (HIV-1) and HTLV-1/2 (human T-cell leukemia virus type 1/2). The antisense transcripts of HIV-1, HTLV-1, and HTLV-2 have been briefly characterized over the past several years. However, a complete appreciation of the role these transcripts play in the virus lifecycle and the cellular factors which regulate their transcription is still lacking. This review provides an overview of antisense transcription in human retroviruses with a specific focus on the MEF-2 family of transcription factors, the function(s) of the antisense protein products, and the application of antisense transcription models in therapeutics against HIV-1 and HTLV-1 in the context of co-infection.
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Affiliation(s)
- Edward Lin
- Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, PA, United States
| | - Amanda R. Panfil
- Department of Veterinary Biosciences, Center for Retrovirus Research, The Ohio State University, Columbus, OH, United States
| | - Grace Sandel
- Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, PA, United States
| | - Pooja Jain
- Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, PA, United States
- *Correspondence: Pooja Jain,
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18
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Retroviral Antisense Transcripts and Genes: 33 Years after First Predicted, a Silent Retroviral Revolution? Viruses 2021; 13:v13112221. [PMID: 34835027 PMCID: PMC8622228 DOI: 10.3390/v13112221] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Revised: 10/28/2021] [Accepted: 11/02/2021] [Indexed: 12/29/2022] Open
Abstract
Paradigm shifts throughout the history of microbiology have typically been ignored, or met with skepticism and resistance, by the scientific community. This has been especially true in the field of virology, where the discovery of a “contagium vivum fluidum”, or infectious fluid remaining after excluding bacteria by filtration, was initially ignored because it did not coincide with the established view of microorganisms. Subsequent studies on such infectious agents, eventually termed “viruses”, were met with skepticism. However, after an abundance of proof accumulated, viruses were eventually acknowledged as defined microbiological entities. Next, the proposed role of viruses in oncogenesis in animals was disputed, as was the unique mechanism of genome replication by reverse transcription of RNA by the retroviruses. This same pattern of skepticism holds true for the prediction of the existence of retroviral “antisense” transcripts and genes. From the time of their discovery, it was thought that retroviruses encoded proteins on only one strand of proviral DNA. However, in 1988, it was predicted that human immunodeficiency virus type 1 (HIV-1), and other retroviruses, express an antisense protein encoded on the DNA strand opposite that encoding the known viral proteins. Confirmation came quickly with the characterization of the antisense protein, HBZ, of the human T-cell leukemia virus type 1 (HTLV-1), and the finding that both the protein and its antisense mRNA transcript play key roles in viral replication and pathogenesis. However, acceptance of the existence, and potential importance, of a corresponding antisense transcript and protein (ASP) in HIV-1 infection and pathogenesis has lagged, despite gradually accumulating theoretical and experimental evidence. The most striking theoretical evidence is the finding that asp is highly conserved in group M viruses and correlates exclusively with subtypes, or clades, responsible for the AIDS pandemic. This review outlines the history of the major shifts in thought pertaining to the nature and characteristics of viruses, and in particular retroviruses, and details the development of the hypothesis that retroviral antisense transcripts and genes exist. We conclude that there is a need to accelerate studies on ASP, and its transcript(s), with the view that both may be important, and overlooked, targets in anti-HIV therapeutic and vaccine strategies.
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Pietropaolo V, Prezioso C, Moens U. Role of Virus-Induced Host Cell Epigenetic Changes in Cancer. Int J Mol Sci 2021; 22:ijms22158346. [PMID: 34361112 PMCID: PMC8346956 DOI: 10.3390/ijms22158346] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Revised: 07/30/2021] [Accepted: 08/02/2021] [Indexed: 12/12/2022] Open
Abstract
The tumor viruses human T-lymphotropic virus 1 (HTLV-1), hepatitis C virus (HCV), Merkel cell polyomavirus (MCPyV), high-risk human papillomaviruses (HR-HPVs), Epstein-Barr virus (EBV), Kaposi’s sarcoma-associated herpes virus (KSHV) and hepatitis B virus (HBV) account for approximately 15% of all human cancers. Although the oncoproteins of these tumor viruses display no sequence similarity to one another, they use the same mechanisms to convey cancer hallmarks on the infected cell. Perturbed gene expression is one of the underlying mechanisms to induce cancer hallmarks. Epigenetic processes, including DNA methylation, histone modification and chromatin remodeling, microRNA, long noncoding RNA, and circular RNA affect gene expression without introducing changes in the DNA sequence. Increasing evidence demonstrates that oncoviruses cause epigenetic modifications, which play a pivotal role in carcinogenesis. In this review, recent advances in the role of host cell epigenetic changes in virus-induced cancers are summarized.
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Affiliation(s)
- Valeria Pietropaolo
- Department of Public Health and Infectious Diseases, “Sapienza” University, 00185 Rome, Italy;
- Correspondence: (V.P.); (U.M.)
| | - Carla Prezioso
- Department of Public Health and Infectious Diseases, “Sapienza” University, 00185 Rome, Italy;
- IRCSS San Raffaele Roma, Microbiology of Chronic Neuro-Degenerative Pathologies, 00161 Rome, Italy
| | - Ugo Moens
- Molecular Inflammation Research Group, Department of Medical Biology, Faculty of Health Sciences, University of Tromsø—The Arctic University of Norway, 9037 Tromsø, Norway
- Correspondence: (V.P.); (U.M.)
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20
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Schnell AP, Kohrt S, Thoma-Kress AK. Latency Reversing Agents: Kick and Kill of HTLV-1? Int J Mol Sci 2021; 22:ijms22115545. [PMID: 34073995 PMCID: PMC8197370 DOI: 10.3390/ijms22115545] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Revised: 05/19/2021] [Accepted: 05/20/2021] [Indexed: 12/14/2022] Open
Abstract
Human T-cell leukemia virus type 1 (HTLV-1), the cause of adult T-cell leukemia/lymphoma (ATLL), is a retrovirus, which integrates into the host genome and persistently infects CD4+ T-cells. Virus propagation is stimulated by (1) clonal expansion of infected cells and (2) de novo infection. Viral gene expression is induced by the transactivator protein Tax, which recruits host factors like positive transcription elongation factor b (P-TEFb) to the viral promoter. Since HTLV-1 gene expression is repressed in vivo by viral, cellular, and epigenetic mechanisms in late phases of infection, HTLV-1 avoids an efficient CD8+ cytotoxic T-cell (CTL) response directed against the immunodominant viral Tax antigen. Hence, therapeutic strategies using latency reversing agents (LRAs) sought to transiently activate viral gene expression and antigen presentation of Tax to enhance CTL responses towards HTLV-1, and thus, to expose the latent HTLV-1 reservoir to immune destruction. Here, we review strategies that aimed at enhancing Tax expression and Tax-specific CTL responses to interfere with HTLV-1 latency. Further, we provide an overview of LRAs including (1) histone deacetylase inhibitors (HDACi) and (2) activators of P-TEFb, that have mainly been studied in context of human immunodeficiency virus (HIV), but which may also be powerful in the context of HTLV-1.
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