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Moniruzzaman M, Erazo Garcia MP, Farzad R, Ha AD, Jivaji A, Karki S, Sheyn U, Stanton J, Minch B, Stephens D, Hancks DC, Rodrigues RAL, Abrahao JS, Vardi A, Aylward FO. Virologs, viral mimicry, and virocell metabolism: the expanding scale of cellular functions encoded in the complex genomes of giant viruses. FEMS Microbiol Rev 2023; 47:fuad053. [PMID: 37740576 PMCID: PMC10583209 DOI: 10.1093/femsre/fuad053] [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: 05/19/2023] [Revised: 08/29/2023] [Accepted: 09/21/2023] [Indexed: 09/24/2023] Open
Abstract
The phylum Nucleocytoviricota includes the largest and most complex viruses known. These "giant viruses" have a long evolutionary history that dates back to the early diversification of eukaryotes, and over time they have evolved elaborate strategies for manipulating the physiology of their hosts during infection. One of the most captivating of these mechanisms involves the use of genes acquired from the host-referred to here as viral homologs or "virologs"-as a means of promoting viral propagation. The best-known examples of these are involved in mimicry, in which viral machinery "imitates" immunomodulatory elements in the vertebrate defense system. But recent findings have highlighted a vast and rapidly expanding array of other virologs that include many genes not typically found in viruses, such as those involved in translation, central carbon metabolism, cytoskeletal structure, nutrient transport, vesicular trafficking, and light harvesting. Unraveling the roles of virologs during infection as well as the evolutionary pathways through which complex functional repertoires are acquired by viruses are important frontiers at the forefront of giant virus research.
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Affiliation(s)
- Mohammad Moniruzzaman
- Rosenstiel School of Marine Atmospheric, and Earth Science, University of Miami, Coral Gables, FL 33149, United States
| | - Maria Paula Erazo Garcia
- Department of Biological Sciences, Virginia Tech, 926 West Campus Drive, Blacksburg, VA 24061, United States
| | - Roxanna Farzad
- Department of Biological Sciences, Virginia Tech, 926 West Campus Drive, Blacksburg, VA 24061, United States
| | - Anh D Ha
- Department of Biological Sciences, Virginia Tech, 926 West Campus Drive, Blacksburg, VA 24061, United States
| | - Abdeali Jivaji
- Department of Biological Sciences, Virginia Tech, 926 West Campus Drive, Blacksburg, VA 24061, United States
| | - Sangita Karki
- Department of Biological Sciences, Virginia Tech, 926 West Campus Drive, Blacksburg, VA 24061, United States
| | - Uri Sheyn
- Department of Biological Sciences, Virginia Tech, 926 West Campus Drive, Blacksburg, VA 24061, United States
| | - Joshua Stanton
- Department of Biological Sciences, Virginia Tech, 926 West Campus Drive, Blacksburg, VA 24061, United States
| | - Benjamin Minch
- Rosenstiel School of Marine Atmospheric, and Earth Science, University of Miami, Coral Gables, FL 33149, United States
| | - Danae Stephens
- Rosenstiel School of Marine Atmospheric, and Earth Science, University of Miami, Coral Gables, FL 33149, United States
| | - Dustin C Hancks
- Department of Immunology, University of Texas Southwestern Medical Center, 6000 Harry Hines Blvd, Dallas, TX, United States
| | - Rodrigo A L Rodrigues
- Laboratório de Vírus, Departamento de Microbiologia, Universidade Federal de Minas Gerais, Belo Horizonte 31270-901, MG, Brazil
| | - Jonatas S Abrahao
- Laboratório de Vírus, Departamento de Microbiologia, Universidade Federal de Minas Gerais, Belo Horizonte 31270-901, MG, Brazil
| | - Assaf Vardi
- Department of Plant and Environmental Sciences, Weizmann Institute of Science, 7610001 Rehovot, Israel
| | - Frank O Aylward
- Department of Biological Sciences, Virginia Tech, 926 West Campus Drive, Blacksburg, VA 24061, United States
- Center for Emerging, Zoonotic, and Arthropod-Borne Infectious Disease, Virginia Tech, Blacksburg, VA 24061, United States
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Fan Y, Sanyal S, Bruzzone R. Breaking Bad: How Viruses Subvert the Cell Cycle. Front Cell Infect Microbiol 2018; 8:396. [PMID: 30510918 PMCID: PMC6252338 DOI: 10.3389/fcimb.2018.00396] [Citation(s) in RCA: 88] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Accepted: 10/22/2018] [Indexed: 01/10/2023] Open
Abstract
Interactions between the host and viruses during the course of their co-evolution have not only shaped cellular function and the immune system, but also the counter measures employed by viruses. Relatively small genomes and high replication rates allow viruses to accumulate mutations and continuously present the host with new challenges. It is therefore, no surprise that they either escape detection or modulate host physiology, often by redirecting normal cellular pathways to their own advantage. Viruses utilize a diverse array of strategies and molecular targets to subvert host cellular processes, while evading detection. These include cell-cycle regulation, major histocompatibility complex-restricted antigen presentation, intracellular protein transport, apoptosis, cytokine-mediated signaling, and humoral immune responses. Moreover, viruses routinely manipulate the host cell cycle to create a favorable environment for replication, largely by deregulating cell cycle checkpoints. This review focuses on our current understanding of the molecular aspects of cell cycle regulation that are often targeted by viruses. Further study of their interactions should provide fundamental insights into cell cycle regulation and improve our ability to exploit these viruses.
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Affiliation(s)
- Ying Fan
- HKU-Pasteur Research Pole, LKS Faculty of Medicine, School of Public Health, The University of Hong Kong, Hong Kong, Hong Kong.,MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Sumana Sanyal
- HKU-Pasteur Research Pole, LKS Faculty of Medicine, School of Public Health, The University of Hong Kong, Hong Kong, Hong Kong.,LKS Faculty of Medicine, School of Biomedical Sciences, The University of Hong Kong, Hong Kong, Hong Kong
| | - Roberto Bruzzone
- HKU-Pasteur Research Pole, LKS Faculty of Medicine, School of Public Health, The University of Hong Kong, Hong Kong, Hong Kong.,Department of Cell Biology and Infection, Institut Pasteur, Paris, France
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Abstract
Cancer is ubiquitous in wildlife, affecting animals from bivalves to pachyderms and cetaceans. Reports of increasing frequency demonstrate that neoplasia is associated with substantial mortality in wildlife species. Anthropogenic activities and global weather changes are shaping new geographical limitations for many species, and alterations in living niches are associated with visible examples of genetic bottlenecks, toxin exposures, oncogenic pathogens, stress and immunosuppression, which can all contribute to cancers in wild species. Nations that devote resources to monitoring the health of wildlife often do so for human-centric reasons, including for the prediction of the potential for zoonotic disease, shared contaminants, chemicals and medications, and for observing the effect of exposure from crowding and loss of habitat. Given the increasing human footprint on land and in the sea, wildlife conservation should also become a more important motivating factor. Greater attention to the patterns of the emergence of wildlife cancer is imperative because growing numbers of species are existing at the interface between humans and the environment, making wildlife sentinels for both animal and human health. Therefore, monitoring wildlife cancers could offer interesting and novel insights into potentially unique non-age-related mechanisms of carcinogenesis across species.
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Affiliation(s)
- Patricia A Pesavento
- Department of Pathology, Microbiology, and Immunology, School of Veterinary Medicine, University of California, Davis, CA, USA.
| | - Dalen Agnew
- Veterinary Diagnostic Laboratory, Department of Pathobiology and Diagnostic Investigation, College of Veterinary Medicine, Michigan State University, East Lansing, MI, USA
| | - Michael K Keel
- Department of Pathology, Microbiology, and Immunology, School of Veterinary Medicine, University of California, Davis, CA, USA
| | - Kevin D Woolard
- Department of Pathology, Microbiology, and Immunology, School of Veterinary Medicine, University of California, Davis, CA, USA
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Retroviral cyclin controls cyclin-dependent kinase 8-mediated transcription elongation and reinitiation. J Virol 2015; 89:5450-61. [PMID: 25741012 DOI: 10.1128/jvi.00464-15] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Accepted: 02/24/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Walleye dermal sarcoma virus (WDSV) infection is associated with the seasonal development and regression of walleye dermal sarcoma. Previous work showed that the retroviral cyclin (RV-cyclin), encoded by WDSV, has separable cyclin box and transcription activation domains. It binds to cyclin-dependent kinase 8 (CDK8) and enhances its kinase activity. CDK8 is evolutionarily conserved and is frequently overexpressed in human cancers. It is normally activated by cyclin C and is required for transcription elongation of the serum response genes (immediate early genes [IEGs]) FOS, EGR1, and cJUN. The IEGs drive cell proliferation, and their expression is brief and highly regulated. Here we show that constitutive expression of RV-cyclin in the HCT116 colon cancer cell line significantly increases the level of IEG expression in response to serum stimulation. Quantitative reverse transcription-PCR (RT-PCR) and nuclear run-on assays provide evidence that RV-cyclin does not alter the initiation of IEG transcription but does enhance the overall rate of transcription elongation and maintains transcription reinitiation. RV-cyclin does not increase activating phosphorylation events in the mitogen-activated protein kinase pathway and does not inhibit decay of IEG mRNAs. At the EGR1 gene locus, RV-cyclin increases and maintains RNA polymerase II (Pol II) occupancy after serum stimulation, in conjunction with increased and extended EGR1 gene expression. The RV-cyclin increases CDK8 occupancy at the EGR1 gene locus before and after serum stimulation. Both of RV-cyclin's functional domains, i.e., the cyclin box and the activation domain, are necessary for the overall enhancement of IEG expression. RV-cyclin presents a novel and ancient mechanism of retrovirus-induced oncogenesis. IMPORTANCE The data reported here are important to both virology and cancer biology. The novel mechanism pinpoints CDK8 in the development of walleye dermal sarcoma and sheds light on CDK8's role in many human cancers. CDK8 controls expression from highly regulated genes, including the interferon-stimulated genes. Its function is likely the target of many viral interferon-resistance mechanisms. CDK8 also controls cellular responses to metabolic stimuli, stress, and hypoxia, in addition to the serum response. The retroviral cyclin (RV-cyclin) represents a highly selected probe of CDK8 function. RV-cyclin does not control CDK8 specificity but instead enhances CDK8's effects on regulated genes, an important distinction for its use to delineate natural CDK8 targets. The outcomes of this research are applicable to investigations of normal and abnormal CDK8 functions. The mechanisms defined here will contribute directly to the dermal sarcoma model in fish and clarify an important path for oncogenesis and innate resistance to viruses.
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Chong AY, Kojima KK, Jurka J, Ray DA, Smit AFA, Isberg SR, Gongora J. Evolution and gene capture in ancient endogenous retroviruses - insights from the crocodilian genomes. Retrovirology 2014; 11:71. [PMID: 25499090 PMCID: PMC4299795 DOI: 10.1186/s12977-014-0071-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Accepted: 08/07/2014] [Indexed: 01/12/2023] Open
Abstract
Background Crocodilians are thought to be hosts to a diverse and divergent complement of endogenous retroviruses (ERVs) but a comprehensive investigation is yet to be performed. The recent sequencing of three crocodilian genomes provides an opportunity for a more detailed and accurate representation of the ERV diversity that is present in these species. Here we investigate the diversity, distribution and evolution of ERVs from the genomes of three key crocodilian species, and outline the key processes driving crocodilian ERV proliferation and evolution. Results ERVs and ERV related sequences make up less than 2% of crocodilian genomes. We recovered and described 45 ERV groups within the three crocodilian genomes, many of which are species specific. We have also revealed a new class of ERV, ERV4, which appears to be common to crocodilians and turtles, and currently has no characterised exogenous counterpart. For the first time, we formally describe the characteristics of this ERV class and its classification relative to other recognised ERV and retroviral classes. This class shares some sequence similarity and sequence characteristics with ERV3, although it is phylogenetically distinct from the other ERV classes. We have also identified two instances of gene capture by crocodilian ERVs, one of which, the capture of a host KIT-ligand mRNA has occurred without the loss of an ERV domain. Conclusions This study indicates that crocodilian ERVs comprise a wide variety of lineages, many of which appear to reflect ancient infections. In particular, ERV4 appears to have a limited host range, with current data suggesting that it is confined to crocodilians and some lineages of turtles. Also of interest are two ERV groups that demonstrate evidence of host gene capture. This study provides a framework to facilitate further studies into non-mammalian vertebrates and highlights the need for further studies into such species. Electronic supplementary material The online version of this article (doi:10.1186/s12977-014-0071-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Amanda Y Chong
- Faculty of Veterinary Science, University of Sydney, Sydney, NSW, 2006, Australia.
| | - Kenji K Kojima
- Genetic Information Research Institute, Los Altos, CA, 94022, USA.
| | - Jerzy Jurka
- Genetic Information Research Institute, Los Altos, CA, 94022, USA.
| | - David A Ray
- Department of Biochemistry, Molecular Biology, Plant Pathology and Entomology, Mississippi State University, Starkville, Mississippi State, 39762, USA. .,Institute for Genomics, Biocomputing and Biotechnology, Mississippi State University, Starkville, Mississippi State, 39762, USA. .,Current Address: Department of Biological Sciences, Texas Tech University, Lubbock, TX, 79409, USA.
| | - Arian F A Smit
- Institute for Systems Biology, Seattle, WA, 98109-5234, USA.
| | - Sally R Isberg
- Faculty of Veterinary Science, University of Sydney, Sydney, NSW, 2006, Australia. .,Centre for Crocodile Research, Noonamah, NT, 0837, Australia.
| | - Jaime Gongora
- Faculty of Veterinary Science, University of Sydney, Sydney, NSW, 2006, Australia.
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Coffee LL, Casey JW, Bowser PR. Pathology of Tumors in Fish Associated With Retroviruses. Vet Pathol 2013; 50:390-403. [PMID: 23456970 DOI: 10.1177/0300985813480529] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Thirteen proliferative diseases in fish have been associated in the literature with 1 or more retroviruses. Typically, these occur as seasonal epizootics affecting farmed and wild fish, and most lesions resolve spontaneously. Spontaneous resolution and lifelong resistance to reinfection are 2 features of some piscine retrovirus–induced tumors that have stimulated research interest in this field. The purpose of this review is to present the reader with the epidemiological and morphological features of proliferative diseases in fish that have been associated with retroviruses by 1 or more of the following methods: detection of C-type retrovirus-like particles or reverse transcriptase activity in tumor tissues; successful tumor transmission trials using well-characterized, tumor-derived, cell-free inocula; or molecular characterization of the virus from spontaneous and experimentally induced tumors. Two of the diseases included in this review, European smelt spawning papillomatosis and bicolor damselfish neurofibromatosis, at one time were attributed to a retroviral etiology, but both are now believed to involve additional viral agents based on more recent investigations. We include the latter 2 entities to update the reader about these developments.
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Affiliation(s)
- L. L. Coffee
- Aquatic Animal Health Program, Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA
| | - J. W. Casey
- Aquatic Animal Health Program, Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA
| | - P. R. Bowser
- Aquatic Animal Health Program, Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA
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Xu K, Zhang TT, Wang L, Zhang CF, Zhang L, Ma LX, Xin Y, Ren CH, Zhang ZQ, Yan Q, Martineau D, Zhang ZY. Walleye dermal sarcoma virus: expression of a full-length clone or the rv-cyclin (orf a) gene is cytopathic to the host and human tumor cells. Mol Biol Rep 2012; 40:1451-61. [PMID: 23100064 DOI: 10.1007/s11033-012-2188-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Accepted: 10/09/2012] [Indexed: 12/22/2022]
Abstract
Walleye dermal sarcoma virus (WDSV) is etiologically associated with a skin tumor, walleye dermal sarcoma (WDS), which develops in the fall and regresses in the spring. WDSV genome contains, in addition to gag, pol and env, three open reading frames (orfs) designated orf a (rv-cyclin), orf b and orf c. Unintegrated linear WDSV provirus DNA isolated from infected tumor cells was used to construct a full-length WDSV provirus clone pWDSV, while orf a was cloned into pSVK3 to construct the expression vector porfA. Stable co-transfection of a walleye cell line (W12) with pWDSV and pcDNA3 generated fewer and smaller G418-resistant colonies compared to the control. By Northern blot analysis, several small transcripts (2.8, 1.8, 1.2, and 0.8 kb) were detected using a WDSV LTR-specific probe. By RT-PCR and Southern blot analysis, three cDNAs (2.4, 1.6 and 0.8 kb) were identified, including both orf a and orf b messenger. Furthermore stable co-transfection of both a human lung adenocarcinoma cell line (SPC-A-1) and a cervical cancer cell line (HeLa) with pcDNA3 and ether porfA or pWDSV also generated fewer and smaller G418-resistant colonies. We conclude that expression of the full-length WDSV clone or the orf a gene inhibits the host fish and human tumor cell growth, and Orf A protein maybe a potential factor which contributes to the seasonal tumor development and regression. This is the first fish provirus clone that has been expressed in cell culture system, which will provide a new in vitro model for tumor research and oncotherapy study.
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Affiliation(s)
- Kun Xu
- College of Animal Science and Technology, Northwest A&F University, No. 22 Xinong Road, Yangling, 712100, Shaan'xi, People's Republic of China
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Abstract
Alterations in the functional levels of cyclin-dependent kinase-8 (CDK8) or its partner, cyclin C, have been clearly associated with cancers, including colon cancer, melanoma, and osteosarcoma. Walleye dermal sarcoma virus encodes a retroviral cyclin (RV-cyclin) that localizes to interchromatin granule clusters and binds CDK8. It also binds to the Aα subunit (PR65) of protein phosphatase 2A (PP2A). Binding to the Aα subunit excludes the regulatory B subunit, but not the catalytic C subunit, in a manner similar to that of T antigens of the small DNA tumor viruses. The expression of the RV-cyclin enhances the activity of immune affinity-purified CDK8 in vitro for RNA polymerase II carboxy-terminal domain (CTD) and histone H3 substrates. PP2A also enhances CDK8 kinase activity in vitro for the CTD but not for histone H3. The PP2A enhancement of CDK8 is independent of RV-cyclin expression and likely plays a role in the normal regulation of CDK8. The manipulation of endogenous PP2A activity by inhibition, amendment, or depletion confirmed its role in CDK8 activation by triggering CDK8 autophosphorylation. Although RV-cyclin and PP2A both enhance CDK8 activity, their actions are uncoupled and additive in kinase reactions. PP2A may be recruited to CDK8 in the Mediator complex by a specific PP2A B subunit or additionally by the RV-cyclin in infected cells, but the RV-cyclin appears to activate CDK8 directly and in a manner independent of its physical association with PP2A.
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Paul TA, Rovnak J, Quackenbush SL, Whitlock K, Zhan H, Gong Z, Spitsbergen J, Bowser PR, Casey JW. Transgenic expression of walleye dermal sarcoma virus rv-cyclin (orfA) in zebrafish does not result in tissue proliferation. MARINE BIOTECHNOLOGY (NEW YORK, N.Y.) 2011; 13:142-150. [PMID: 20349325 PMCID: PMC3364296 DOI: 10.1007/s10126-010-9274-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2009] [Accepted: 01/19/2010] [Indexed: 05/29/2023]
Abstract
Walleye dermal sarcoma (WDS) is a benign tumor of walleye fish that develops and completely regresses seasonally. The retrovirus associated with this disease, walleye dermal sarcoma virus, encodes three accessory genes, two of which, rv-cyclin (orfA) and orfb, are thought to play a role in tumor development. In this study, we attempted to recapitulate WDS development by expressing rv-cyclin in chimeric and stable transgenic zebrafish. Six stable transgenic lines expressing rv-cyclin from the constitutive CMVtk promoter were generated. Immunohistochemistry and quantitative reverse transcriptase polymerase chain reaction demonstrate that rv-cyclin is widely expressed in different tissues in these fish. These lines were viable and histologically normal for up to 2 years. No increase in tumors or tissue proliferation was observed following N-ethyl N-nitrosourea exposure or following tail wounding and subsequent tissue regeneration compared to controls. These data indicate that rv-cyclin is not independently sufficient for tumor induction in zebrafish.
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Affiliation(s)
- Thomas A. Paul
- Department of Microbiology and Immunology, Cornell University, Ithaca, NY, USA
| | - Joel Rovnak
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO, USA
| | - Sandra L. Quackenbush
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO, USA
| | - Kathleen Whitlock
- Centro de Genómica de la Célula, Centro de Neurociencia, Universidad de Valparaíso, Valparaíso, Chile
| | - Huiqing Zhan
- Department of Biological Sciences, National University of Singapore, Singapore, Singapore
| | - Zhiyuan Gong
- Department of Biological Sciences, National University of Singapore, Singapore, Singapore
| | - Jan Spitsbergen
- Department of Microbiology and Marine and Freshwater Biomedical Sciences Center, Oregon State University, Corvallis, OR, USA
| | - Paul R. Bowser
- Department of Microbiology and Immunology, Cornell University, Ithaca, NY, USA
| | - James W. Casey
- Department of Microbiology and Immunology, Cornell University, Ithaca, NY, USA
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Brewster CD, Birkenheuer CH, Vogt MB, Quackenbush SL, Rovnak J. The retroviral cyclin of walleye dermal sarcoma virus binds cyclin-dependent kinases 3 and 8. Virology 2010; 409:299-307. [PMID: 21067790 DOI: 10.1016/j.virol.2010.10.022] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2010] [Revised: 09/13/2010] [Accepted: 10/14/2010] [Indexed: 12/20/2022]
Abstract
Walleye dermal sarcoma virus encodes a retroviral cyclin (rv-cyclin) with a cyclin box fold and transcription activation domain (AD). Co-immune precipitation (co-IP) identified an association of rv-cyclin with cyclin-dependent kinase 8 (cdk8). Cdk8 is dependent upon cyclin C and regulates transcription with the Mediator complex, a co-activator of transcription. Mutation of cyclin residues, required for cdk binding, disrupts rv-cyclin-cdk8 co-IP. Mutation or removal of the AD has no effect on cdk8 interaction. Direct rv-cyclin-cdk8 binding is demonstrated by pulldown of active cdk8 and by GST-rv-cyclin binding to recombinant cdk8. Cdk3 is also activated by cyclin C and phosphorylates retinoblastoma protein to initiate entry into the cell division cycle. Co-IP and pulldowns demonstrate direct rv-cyclin binding to cdk3 as well. The rv-cyclin functions as a structural ortholog of cyclin C in spite of its limited amino acid sequence identity with C cyclins or with any known cyclins.
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Affiliation(s)
- Connie D Brewster
- Department of Microbiology, Immunology, and Pathology, 1619 Campus Delivery, Colorado State University, Fort Collins, CO 80523, USA.
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12
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Zhan H, Spitsbergen J, Qing W, Wu YL, Paul TA, Casey JW, Gong Z. Transgenic expression of walleye dermal sarcoma virus rv-cyclin gene in zebrafish and its suppressive effect on liver tumor development after carcinogen treatment. MARINE BIOTECHNOLOGY (NEW YORK, N.Y.) 2010; 12:640-9. [PMID: 20052603 PMCID: PMC4154541 DOI: 10.1007/s10126-009-9251-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2009] [Accepted: 11/23/2009] [Indexed: 05/14/2023]
Abstract
A retrovirus homologue gene of cellular cyclin D₁, walleye dermal sarcoma virus rv-cyclin gene (orf A or rv-cyclin), was expressed in the livers of zebrafish under the control of liver fatty acid-binding protein (lfabp) promoter. To prevent possible fatality caused by overexpression of the oncogene, the GAL4/upstream activation sequence (GAL4/UAS) system was used to maintain the transgenic lines. Thus, both GAL4-activator [Tg(lfabp:GAL4)] and UAS-effector [Tg(UAS:rvcyclin)] lines were generated, and the rv-cyclin gene was activated in the liver after crossing these two lines. Since no obvious neoplasia phenotypes were observed in the double-transgenic line, cancer susceptibility of the transgenic fish expressing rv-cyclin was tested by carcinogen treatment. Unexpectedly, transgenic fish expressing rv-cyclin gene (rvcyclin+) were more resistant to the carcinogen than siblings not expressing this gene (rvcyclin-). Lower incidences of multiple and malignant liver tumors were observed in rvcyclin+ than in rvcyclin- fish, and the liver tumors in the rvcyclin+ group appeared later and were less malignant. These results suggest that expression of rv-cyclin protects the fish liver from carcinogen damage and delays onset of malignancy. These findings indicate that transgenic fish models are powerful systems for investigating mechanisms of inhibition and regression of liver tumors.
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MESH Headings
- Adenoma, Liver Cell/genetics
- Adenoma, Liver Cell/metabolism
- Adenoma, Liver Cell/pathology
- Animals
- Animals, Genetically Modified/genetics
- Animals, Genetically Modified/metabolism
- Carcinoma, Hepatocellular/genetics
- Carcinoma, Hepatocellular/metabolism
- Carcinoma, Hepatocellular/pathology
- Cholangiocarcinoma/genetics
- Cholangiocarcinoma/metabolism
- Cholangiocarcinoma/pathology
- Epsilonretrovirus/genetics
- Gene Expression Regulation, Neoplastic
- Genes, Tumor Suppressor
- Genes, Viral
- Liver/metabolism
- Liver Neoplasms, Experimental/genetics
- Liver Neoplasms, Experimental/metabolism
- Liver Neoplasms, Experimental/pathology
- Viral Proteins/genetics
- Viral Proteins/metabolism
- Zebrafish/genetics
- Zebrafish/metabolism
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Affiliation(s)
- Huiqing Zhan
- Department of Biological Sciences, National University of Singapore, Singapore
| | - Jan Spitsbergen
- Marine and Freshwater Biomedical Sciences Center, Oregon State University, Corvallis, Oregon, USA
| | - Wei Qing
- Department of Biological Sciences, National University of Singapore, Singapore
| | - Yi Lian Wu
- Department of Biological Sciences, National University of Singapore, Singapore
| | - Thomas A. Paul
- Department of Microbiology and Immunology, Cornell University, Ithaca, New York, USA
| | - James W. Casey
- Department of Microbiology and Immunology, Cornell University, Ithaca, New York, USA
| | - Zhiyuan Gong
- Department of Biological Sciences, National University of Singapore, Singapore
- Corresponding author. Dr. Zhiyuan Gong, Department of Biological Sciences, National University of Singapore, Singapore, 117543, Tel.: +65 65162860, Fax: +65 67792486,
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Walleye dermal sarcoma virus: molecular biology and oncogenesis. Viruses 2010; 2:1984-1999. [PMID: 21994717 PMCID: PMC3185748 DOI: 10.3390/v2091984] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2010] [Revised: 08/05/2010] [Accepted: 09/02/2010] [Indexed: 12/21/2022] Open
Abstract
Retroviruses have been detected in most vertebrate species and are etiologic agents of a variety of neoplastic diseases. The study of retroviruses has been instrumental in uncovering the molecular mechanisms responsible for oncogenesis. Retroviruses have been isolated from three neoplastic diseases in fish, two of which affect the dermis and regress naturally coincident with spawning. This feature provides a unique model to study mechanisms of tumor development and regression. Three complex retroviruses, isolated from walleye (Sander vitreus) with dermal sarcoma and epidermal hyperplasia, are the members of the newest retroviral genus, Epsilonretrovirus. Three accessory proteins, encoded by walleye dermal sarcoma virus (WDSV), function in the regulation of host and viral gene expression and cell cycle, alter cell-signaling pathways to promote cell proliferation and block apoptosis, and, finally, induce apoptosis through dissipation of the mitochondrial membrane potential.
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Robert J. Comparative study of tumorigenesis and tumor immunity in invertebrates and nonmammalian vertebrates. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2010; 34:915-25. [PMID: 20553753 PMCID: PMC2900388 DOI: 10.1016/j.dci.2010.05.011] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2010] [Revised: 05/19/2010] [Accepted: 05/20/2010] [Indexed: 05/29/2023]
Abstract
Despite intense study in mammals, the different roles played by the immune system in detecting (immunosurveillance), controlling and remodeling (immunoediting) neoplasia, and perhaps in metastasis are not fully understood. In this review, I will present evidence of neoplasia and invasive malignancy, as well as tumor immunity in invertebrates and nonmammalian vertebrates. I will also present a comparative and evolutionary view of the complex interactions between neoplasia and the host immune system. Overall, I wish to go beyond the too simplistic dichotomy between invertebrates with innate immunity that are only affected with benign neoplasia and vertebrates with adaptive immunity that are affected by metastatic malignancies or cancer.
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Affiliation(s)
- Jacques Robert
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY 14642, United States. jacques
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15
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Evolution of teleost fish retroviruses: characterization of new retroviruses with cellular genes. J Virol 2009; 83:10152-62. [PMID: 19625413 DOI: 10.1128/jvi.02546-08] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The interactions between retroviruses and their hosts can be of a beneficial or detrimental nature. Some endogenous retroviruses are involved in development, while others cause disease. The Genome Parsing Suite (GPS) is a software tool to track and trace all Retroid agents in any sequenced genome (M. A. McClure et al., Genomics 85:512-523, 2005). Using the GPS, the retroviral content was assessed in four model teleost fish. Eleven new species of fish retroviruses are identified and characterized. The reverse transcriptase protein sequences were used to reconstruct a fish retrovirus phylogeny, thereby, significantly expanding the epsilon-retrovirus family. Most of these novel retroviruses encode additional genes, some of which are homologous to cellular genes that would confer viral advantage. Although the fish divergence is much more ancient, retroviruses began infecting fish genomes approximately 4 million years ago.
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16
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Quackenbush SL, Linton A, Brewster CD, Rovnak J. Walleye dermal sarcoma virus rv-cyclin inhibits NF-kappaB-dependent transcription. Virology 2009; 386:55-60. [PMID: 19176230 DOI: 10.1016/j.virol.2008.12.026] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2008] [Revised: 09/02/2008] [Accepted: 12/17/2008] [Indexed: 12/23/2022]
Abstract
The retroviral cyclin protein (rv-cyclin) of walleye dermal sarcoma virus contains two known functional domains, a cyclin box motif and a carboxy terminal transcription activation domain (AD). The AD contacts TATA-binding protein-associated factor 9 (TAF9), and this action is necessary for both positive and negative regulation of transcription from host and viral promoters. Negative regulation occurs via interference with TAF9 binding by transcriptional activators. Transcription factors that share a functional TAF9-binding motif include NF-kappaB. Rv-cyclin down regulates NF-kappaB-dependent transcription, whether induced by TNFalpha or by direct phosphorylation of IkappaB by expressed MEKK1. In rv-cyclin-expressing cells, NF-kappaB p65 is phosphorylated and translocated to the nucleus, where it forms heterodimers with p50 and binds NF-kappaB response elements. Furthermore, interference with NF-kappaB is dependent upon an intact TAF9-binding motif in rv-cyclin. The outcome of this NF-kappaB down regulation is likely to be important in the control of virus replication and tumorigenesis.
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Affiliation(s)
- Sandra L Quackenbush
- Department of Microbiology, Immunology and Pathology, Campus Delivery 1619, Colorado State University, Fort Collins, CO 80523, USA.
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17
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Daniels CC, Rovnak J, Quackenbush SL. Walleye dermal sarcoma virus Orf B functions through receptor for activated C kinase (RACK1) and protein kinase C. Virology 2008; 375:550-60. [PMID: 18343476 PMCID: PMC2453751 DOI: 10.1016/j.virol.2008.01.034] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2007] [Revised: 01/18/2008] [Accepted: 01/25/2008] [Indexed: 01/02/2023]
Abstract
Walleye dermal sarcoma virus is a complex retrovirus that is associated with walleye dermal sarcomas that are seasonal in nature. Fall developing tumors contain low levels of spliced accessory gene transcripts A and B, suggesting a role for the encoded proteins, Orf A and Orf B, in oncogenesis. In explanted tumor cells the 35 kDa Orf B accessory protein is localized to the cell periphery in structures similar to focal adhesions and along actin stress fibers. Similar localization was observed in mammalian cells. The cellular protein, receptor for activated C kinase 1 (RACK1), bound Orf B in yeast two-hybrid assays and in cell culture. Sequence analysis of walleye RACK1 demonstrated high conservation to other known RACK1 sequences. RACK1 binds to activated protein kinase C (PKC). Orf B associates with PKCalpha, which is constitutively activated and localized at the membrane. Activated PKC promoted cell survival, proliferation, and increased cell viability in Orf B-expressing cells.
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Affiliation(s)
- Candelaria C. Daniels
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO 80523
| | - Joel Rovnak
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO 80523
| | - Sandra L. Quackenbush
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO 80523
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18
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Rovnak J, Casey RN, Brewster CD, Casey JW, Quackenbush SL. Establishment of productively infected walleye dermal sarcoma explant cells. J Gen Virol 2007; 88:2583-2589. [PMID: 17698670 PMCID: PMC3364294 DOI: 10.1099/vir.0.82967-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Walleye dermal sarcoma virus (WDSV) is a complex retrovirus associated with dermal sarcomas in walleye fish. Virus expression is tightly regulated and limited to accessory gene transcripts throughout tumour development. During tumour regression, this regulation is lost and the replication of virus is greatly enhanced. Cultured walleye fibroblasts infected in vitro do not produce significant quantities of infectious virus. Tissue culture cells established by explantation of tumour cells were found to harbour WDSV provirus and to express accessory and structural proteins. The sequence of the provirus showed little variation from a previous WDSV isolate. Retroviral particles were isolated from supernatants from these cells and were able to transfer infection to uninfected walleye fibroblasts. In addition to the virus present in supernatants, much of the virus was cell associated and liberated only by sonication. This virus was found at internal cellular membranes, including mitochondria, and was infectious.
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Affiliation(s)
- Joel Rovnak
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO, USA
| | - Rufina N. Casey
- Department Microbiology and Immunology, Cornell University, Ithaca, NY, USA
| | - Connie D. Brewster
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO, USA
| | - James W. Casey
- Department Microbiology and Immunology, Cornell University, Ithaca, NY, USA
| | - Sandra L. Quackenbush
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO, USA
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19
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Abstract
Walleye dermal sarcoma virus (WDSV) is a complex retrovirus associated with dermal sarcomas in walleye fish. A WDSV accessory gene encodes a cyclin homolog or retroviral cyclin (rv-cyclin). WDSV rv-cyclin was found to be associated with transcription complexes and to affect transcription in a cell-type and promoter-dependent manner. It inhibited the WDSV promoter in walleye fibroblasts and activated transcription from GAL4 promoters when fused to the GAL4 DNA binding domain, and an activation domain (AD) has been localized to 30 amino acids in the carboxyl region. rv-cyclin can block the pulldown of transcription coactivators by the AD of VP16, and the isolated rv-cyclin AD interferes specifically with the interaction between the carboxyl halves of the VP16 AD, VP16C, and TATA-binding protein-associated factor 9 (TAF9). The carboxyl region and isolated AD can bind TAF9 directly in assays of protein-protein interaction in vitro. Furthermore, rv-cyclin and the isolated rv-cyclin AD interfere specifically with the function of VP16C in transcription assays. A previously identified motif within the VP16C sequence mediates TAF9 binding, and this motif is present in the activation domains of a variety of TAF9-binding transcriptional activators. A similar motif is present in the rv-cyclin AD, and point mutations within this motif affect rv-cyclin function and protein-protein interactions. The results support a model of transcription regulation by direct interaction with TAF9.
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Affiliation(s)
- Joel Rovnak
- Department of Microbiology, Immunology, and Pathology, Campus Delivery 1619, Colorado State University, Fort Collins, CO 80523, USA.
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20
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Rovnak J, Hronek BW, Ryan SO, Cai S, Quackenbush SL. An activation domain within the walleye dermal sarcoma virus retroviral cyclin protein is essential for inhibition of the viral promoter. Virology 2005; 342:240-51. [PMID: 16150476 PMCID: PMC3364292 DOI: 10.1016/j.virol.2005.08.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2005] [Revised: 07/01/2005] [Accepted: 08/09/2005] [Indexed: 12/21/2022]
Abstract
Walleye dermal sarcoma virus (WDSV) is a complex retrovirus associated with seasonal dermal sarcomas. Developing tumors have low levels of accessory gene transcripts, A1 and B, and regressing tumors have high levels of full-length and spliced transcripts. Transcript A1 encodes a retroviral cyclin (rv-cyclin) with limited homology to host cyclins. The rv-cyclin is physically linked to components of the transcriptional co-activator complex, Mediator, and regulates transcription. In walleye fibroblasts, it inhibits the WDSV promoter independently of cis-acting DNA sequences. The rv-cyclin activates transcription from GAL4 promoters when fused to the GAL4 DNA binding domain. A 30 a.a. activation domain in the carboxy region can be inactivated by single point mutations, and these mutations diminish the ability of the rv-cyclin to inhibit the WDSV promoter. When fused to glutathione S-transferase, the rv-cyclin, its carboxy region, and the activation domain pull down components of transcription complexes from nuclear extracts, and pull down is lost by mutation of the activation domain.
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Affiliation(s)
- Joel Rovnak
- Department of Molecular Biosciences, University of Kansas, Lawrence, KS 66045, USA
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO 80523, USA
| | - Brett W. Hronek
- Department of Molecular Biosciences, University of Kansas, Lawrence, KS 66045, USA
| | - Sean O. Ryan
- Department of Molecular Biosciences, University of Kansas, Lawrence, KS 66045, USA
| | - Sumin Cai
- Department of Molecular Biosciences, University of Kansas, Lawrence, KS 66045, USA
| | - Sandra L. Quackenbush
- Department of Molecular Biosciences, University of Kansas, Lawrence, KS 66045, USA
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO 80523, USA
- Corresponding author. Department of Microbiology, Immunology, and Pathology, Campus Delivery 1619, Colorado State University, Fort Collins, CO 80523, USA. Fax: +1 970 491 0603. (S.L. Quackenbush)
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21
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Boya P, Pauleau AL, Poncet D, Gonzalez-Polo RA, Zamzami N, Kroemer G. Viral proteins targeting mitochondria: controlling cell death. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2005; 1659:178-89. [PMID: 15576050 DOI: 10.1016/j.bbabio.2004.08.007] [Citation(s) in RCA: 137] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Received: 06/03/2004] [Revised: 07/20/2004] [Accepted: 08/16/2004] [Indexed: 01/21/2023]
Abstract
Mitochondrial membrane permeabilization (MMP) is a critical step regulating apoptosis. Viruses have evolved multiple strategies to modulate apoptosis for their own benefit. Thus, many viruses code for proteins that act on mitochondria and control apoptosis of infected cells. Viral proapoptotic proteins translocate to mitochondrial membranes and induce MMP, which is often accompanied by mitochondrial swelling and fragmentation. From a structural point of view, all the viral proapoptotic proteins discovered so far contain amphipathic alpha-helices that are necessary for the proapoptotic effects and seem to have pore-forming properties, as it has been shown for Vpr from human immunodeficiency virus-1 (HIV-1) and HBx from hepatitis B virus (HBV). In contrast, antiapoptotic viral proteins (e.g., M11L from myxoma virus, F1L from vaccinia virus and BHRF1 from Epstein-Barr virus) contain mitochondrial targeting sequences (MTS) in their C-terminus that are homologous to tail-anchoring domains. These domains are similar to those present in many proteins of the Bcl-2 family and are responsible for inserting the protein in the outer mitochondrial membrane leaving the N-terminus of the protein facing the cytosol. The antiapoptotic proteins K7 and K15 from avian encephalomyelitis virus (AEV) and viral mitochondria inhibitor of apoptosis (vMIA) from cytomegalovirus are capable of binding host-specific apoptosis-modulatory proteins such as Bax, Bcl-2, activated caspase 3, CAML, CIDE-B and HAX. In conclusion, viruses modulate apoptosis at the mitochondrial level by multiple different strategies.
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Affiliation(s)
- Patricia Boya
- Centre National de la Recherche Scientifique, UMR 8125, Institut Gustave Roussy, Pavillon de Recherche 1, 39 rue Camille-Desmoulins, F-94805 Villejuif, France
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22
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Schang LM. Effects of pharmacological cyclin-dependent kinase inhibitors on viral transcription and replication. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2004; 1697:197-209. [PMID: 15023361 DOI: 10.1016/j.bbapap.2003.11.024] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2003] [Accepted: 11/12/2003] [Indexed: 10/26/2022]
Abstract
Cyclin-dependent kinases (CDKs) are required for replication of adeno-, papilloma- and other viruses that replicate only in dividing cells. Surprisingly, CDKs are also required for replication of HIV-1, HSV-1, and other viruses that can replicate in non-dividing cells. Since two low-molecular weight pharmacological CDK inhibitors (PCIs), flavopiridol (Flavo) and roscovitine (Rosco), appear to be non-toxic in human clinical trials against cancer, these drugs have been proposed as potential antiviral drugs. Rosco preferentially inhibits CDKs involved in cell cycle regulation (CDK1, 2, and 7) or neuronal functions (CDK5), whereas Flavo preferentially inhibits CDKs involved in cell cycle (CDK1, 2, 4, 7) or transcription (CDK7, and 9). As potential antivirals, PCIs display several advantages: (i) they are active against many different viruses, including drug-resistant strains of HIV-1 and HSV-1; (ii) PCI-resistant mutants of HIV-1 or HSV-1 have not been identified; and (iii) the antiviral effects of PCIs and conventional antivirals appear to be additive (as expected from drugs that target independent pathways). Moreover, PCIs target both the etiological agents (i.e., the virus) and the pathogenic mechanisms (i.e., unrestricted cell division) of the many diseases that include both a CDK-requiring virus and unrestricted cell division (e.g., Kaposi's sarcoma, cervical carcinoma, HIV-associated nephropathy-HIVAN). This is nicely illustrated in a recent study which demonstrated the efficacy of Flavo in a mouse model of HIVAN. Herein, we will review the involvement of CDKs in viral replication and the antiviral properties of the most extensively characterized PCIs, with special emphasis on the mechanisms of inhibition of viral transcription.
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Affiliation(s)
- Luis M Schang
- Department of Biochemistry and Department of Medical Microbiology and Immunology, Signal Transduction Research Group, Molecular Mechanisms of Growth Control Research Group, University of Alberta, Canada.
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23
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Affiliation(s)
- Donald Holzschu
- Department of Biological Sciences, Ohio University, Athens, Ohio 45701, USA.
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24
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Kambol R, Kabat P, Tristem M. Complete nucleotide sequence of an endogenous retrovirus from the amphibian, Xenopus laevis. Virology 2003; 311:1-6. [PMID: 12832197 DOI: 10.1016/s0042-6822(03)00263-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
We report the first full-length sequence of an endogenous amphibian retrovirus derived from the African clawed toad Xenopus laevis. The virus, termed Xen1, has one of the largest endogenous retroviral genomes described to date of over 10 kb in length and it also has a relatively complex genomic organisation consisting of LTR-orf1, orf2, gag, pol, env-LTR. Orfs 1 and 2 are novel, duplicated genes of unknown function. Phylogenetic analysis indicates that Xen1 is most closely related to the epsilon -retroviruses WDSV and WEHV types 1 and 2, which are large, complex exogenous retroviruses present within Walleye fish.
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Affiliation(s)
- Roziah Kambol
- Department of Biological Sciences, Imperial College, Silwood Park, Buckhurst Road, SL5 7PY, Ascot, Berkshire, UK
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25
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Abstract
The retroviral capacity for integration into the host genome can give rise to endogenous retroviruses (ERVs): retroviral sequences that are transmitted vertically as part of the host germ line, within which they may continue to replicate and evolve. ERVs represent both a unique archive of ancient viral sequence information and a dynamic component of host genomes. As such they hold great potential as informative markers for studies of both virus evolution and host genome evolution. Numerous novel ERVs have been described in recent years, particularly as genome sequencing projects have advanced. This review discusses the evolution of ERV lineages, considering the processes by which ERV distribution and diversity is generated. The diversity of ERVs isolated so far is summarised in terms of both their distribution across host taxa, and their relationships to recognised retroviral genera. Finally the relevance of ERVs to studies of genome evolution, host disease and viral ecology is considered, and recent findings discussed.
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Affiliation(s)
- Robert Gifford
- Department of Biological Sciences, Imperial College, Silwood Park, Buckhurst Road, Ascot Berkshire, SL5 7PY, UK
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26
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Nudson WA, Rovnak J, Buechner M, Quackenbush SL. Walleye dermal sarcoma virus Orf C is targeted to the mitochondria. J Gen Virol 2003; 84:375-381. [PMID: 12560570 DOI: 10.1099/vir.0.18570-0] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Walleye dermal sarcomas are associated with the presence of a complex retrovirus, walleye dermal sarcoma virus (WDSV). These sarcomas develop and regress seasonally in naturally infected fish. In addition to gag, pol and env, WDSV contains three open reading frames (ORFs), designated orf a, orf b and orf c. orf c is located between the 5' long terminal repeat and gag. Developing tumours contain low levels of orf a and orf b transcripts, whereas regressing tumours contain high levels of genomic transcripts and virus particles. Orf C protein is encoded by the full-length, genomic transcript and can be detected in tumour extracts with anti-Orf C-specific antisera. To determine the subcellular location of WDSV Orf C, cultured cells were transfected with an expression vector encoding haemagglutinin-tagged Orf C and examined by immunofluorescence. Orf C was observed throughout the cytoplasm and accumulated in cytoplasmic organelles. Dual-antibody staining for Orf C and mitochondrial cytochrome c demonstrated colocalization of Orf C with mitochondria and loss of the normal distribution of mitochondria in the cytoplasm. Cells transiently expressing Orf C exhibited apoptotic morphology and increased levels of surface phosphatidylserine and were unable to retain MitoTracker Orange, a dye that accumulates in active mitochondria. These results imply a functional role for WDSV Orf C in an alteration of mitochondrial function that results in apoptosis contributing to tumour regression.
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Affiliation(s)
- Wade A Nudson
- Department of Molecular Biosciences, University of Kansas, 7047 Haworth Hall, 1200 Sunnyside Avenue, Lawrence, KS 66045-7534, USA
| | - Joel Rovnak
- Department of Molecular Biosciences, University of Kansas, 7047 Haworth Hall, 1200 Sunnyside Avenue, Lawrence, KS 66045-7534, USA
| | - Matthew Buechner
- Department of Molecular Biosciences, University of Kansas, 7047 Haworth Hall, 1200 Sunnyside Avenue, Lawrence, KS 66045-7534, USA
| | - Sandra L Quackenbush
- Department of Molecular Biosciences, University of Kansas, 7047 Haworth Hall, 1200 Sunnyside Avenue, Lawrence, KS 66045-7534, USA
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27
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Rovnak J, Quackenbush SL. Walleye dermal sarcoma virus cyclin interacts with components of the mediator complex and the RNA polymerase II holoenzyme. J Virol 2002; 76:8031-9. [PMID: 12134008 PMCID: PMC155167 DOI: 10.1128/jvi.76.16.8031-8039.2002] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Walleye dermal sarcoma virus (WDSV) encodes an accessory protein, OrfA, with sequence homology to cyclins (retrovirus cyclin). In cells transfected with an expression construct, OrfA was localized to the nucleus and was concentrated in interchromatin granule clusters (IGCs), sites where splicing factors are concentrated. Other proteins identified in IGCs include transcription factors, the large subunit of RNA polymerase II (Pol II), and cyclin-dependent kinase 8 (cdk8). cdk8 is the kinase partner of cyclin C and a component of the mediator complex, associated with the Pol II holoenzyme. cdk8 and cyclin C can regulate transcription via phosphorylation of cyclin H and the carboxy-terminal domain of Pol II. OrfA in transfected HeLa cells was found to colocalize and copurify with hyperphosphorylated forms of Pol II (Pol IIO) in IGCs, and OrfA was coimmunoprecipitated from lysates of transfected cells with an antibody against Pol IIO. Likewise, Pol IIO could be coprecipitated with an antibody against OrfA. A survey with antibodies against several different cdks resulted in coimmunoprecipitation of OrfA with anti-cdk8, and antiserum against OrfA was able to coprecipitate cdk8 from lysates of cells that express OrfA. Coprecipitation of OrfA with anti-cyclin C demonstrated that it was included in complexes with OrfA and cdk8. OrfA has sequence and structural similarities to cyclin C, and, functionally, OrfA appears to have the capacity to both enhance and inhibit the activity of promoters in a cell-specific manner, similar to functions of the mediator complex. These data suggest that WDSV OrfA functions through its interactions with these large, transcription complexes. Further investigations will clarify the role of the retrovirus cyclin in control of virus expression and transformation.
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Affiliation(s)
- Joel Rovnak
- Department of Molecular Biosciences, The University of Kansas, Lawrence 66045, USA
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28
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Fodor SK, Vogt VM. Walleye dermal sarcoma virus reverse transcriptase is temperature sensitive. J Gen Virol 2002; 83:1361-1365. [PMID: 12029151 DOI: 10.1099/0022-1317-83-6-1361] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Walleye dermal sarcoma virus (WDSV) is a piscine retrovirus that replicates naturally in fish at temperatures near 4 degrees C. The reverse transcriptase (RT) protein from virus particles isolated from walleye tumours was purified and biochemically characterized. Like the RT of the distantly related murine leukaemia virus, WDSV RT sediments as a monomer in the absence of template. It exhibits a K(m) of 22 microM for TTP in an assay with poly(rA) as a template and oligo(dT) as a primer. The enzyme is rapidly inactivated at temperatures greater than 15 degrees C. The ratio of RT activity at 15 degrees C to that at 4 degrees C is similar for WDSV and recombinant human immunodeficiency virus type 1, suggesting that, at least with this template, the fish enzyme is not specially adapted to function more efficiently in the cold.
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Affiliation(s)
- Sharon K Fodor
- Department of Molecular Biology and Genetics, Biotechnology Building, Cornell University, Ithaca, NY 14853, USA1
| | - Volker M Vogt
- Department of Molecular Biology and Genetics, Biotechnology Building, Cornell University, Ithaca, NY 14853, USA1
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29
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Abstract
Three fish retroviruses infecting walleyes constitute the recently recognized genus called epsilonretrovirus. The founding member of this group, walleye dermal sarcoma virus (WDSV), induces benign skin tumors in the infected fish and replicates near 4 degrees C. While the viral genomic sequence is known, biochemical characterization of the virus has been limited to the identification of the mature structural and envelope proteins present in virions. We undertook this study to determine the cleavage sites in the WDSV Pro and Pol proteins and to characterize the viral protease (PR) in vitro. A recombinant PR was expressed in and purified from Escherichia coli as a larger fusion with additional nucleocapsid and reverse transcriptase residues flanking the PR domain. Autocleavage produced a functional, mature PR. Autocleavage as well as cleavage of peptides and of Gag protein by the mature PR occurred at a pH optimum of 7.0, higher than that of other retroviral proteases. Analysis of the cleavage sites identified a glutamine residue in the P2 position of all WDSV sites, both in Gag and in Pol. Amino acid sequence alignments of Gag-Pro-Pol from WDSV, walleye epidermal hyperplasia virus type 1, and walleye epidermal hyperplasia virus type 2 showed the P2 glutamine to be conserved in all cleavage sites in these three viruses. Such conservation is unprecedented in other retroviruses.
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Affiliation(s)
- Sharon K Fodor
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853, USA
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30
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Braunagel SC, Guidry PA, Rosas-Acosta G, Engelking L, Summers MD. Identification of BV/ODV-C42, an Autographa californica nucleopolyhedrovirus orf101-encoded structural protein detected in infected-cell complexes with ODV-EC27 and p78/83. J Virol 2001; 75:12331-8. [PMID: 11711623 PMCID: PMC116129 DOI: 10.1128/jvi.75.24.12331-12338.2001] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
orf101 is a late gene of Autographa californica nucleopolyhedrovirus (AcMNPV). It encodes a protein of 42 kDa which is a component of the nucleocapsid of budded virus (BV) and occlusion-derived virus (ODV). To reflect this viral localization, the product of orf101 was named BV/ODV-C42 (C42). C42 is predominantly detected within the infected-cell nucleus: at 24 h postinfection (p.i.), it is coincident with the virogenic stroma, but by 72 h p.i., the stroma is minimally labeled while C42 is more uniformly located throughout the nucleus. Yeast two-hybrid screens indicate that C42 is capable of directly interacting with the viral proteins p78/83 (1629K) and ODV-EC27 (orf144). These interactions were confirmed using blue native gels and Western blot analyses. At 28 h p.i., C42 and p78/83 are detected in two complexes: one at approximately 180 kDa and a high-molecular-mass complex (500 to 600 kDa) which also contains EC27.
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Affiliation(s)
- S C Braunagel
- Texas Agricultural Experiment Station, Texas A&M University, College Station, Texas 77843-2475, USA
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31
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Rovnak J, Casey JW, Quackenbush SL. Intracellular targeting of walleye dermal sarcoma virus Orf A (rv-cyclin). Virology 2001; 280:31-40. [PMID: 11162816 DOI: 10.1006/viro.2000.0731] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Walleye dermal sarcoma virus (WDSV) induces tumors and allows or possibly directs tumor regression. WDSV encodes a putative cyclin homologue, Orf A, and six variant Orf A transcripts have been identified. Northern analysis indicated that a 3.3-kb transcript, encoding full-length Orf A, is the predominant transcript in developing, but not regressing, tumors. Three Orf A proteins, one full-length and two amino-truncated forms, were expressed in mammalian and piscine cells, and their intracellular locations were determined. The full-length form was nuclear and concentrated in interchromatin granule clusters, defined by colocalization with SC-35. The amino-truncated forms were cytoplasmic. Fusion of amino-terminal portions of Orf A to a heterologous protein demonstrated that residues 1-112 were necessary for nuclear localization. Mutation of aa K80 and/or E110 disrupted nuclear localization, suggesting a mechanism similar to that of cellular A- and D-type cyclins for its nuclear import.
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Affiliation(s)
- J Rovnak
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas 66045, USA
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Lairmore MD, Stanley JR, Weber SA, Holzschu DL. Squamous epithelial proliferation induced by walleye dermal sarcoma retrovirus cyclin in transgenic mice. Proc Natl Acad Sci U S A 2000; 97:6114-9. [PMID: 10811912 PMCID: PMC18567 DOI: 10.1073/pnas.110024497] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Walleye dermal sarcoma (WDS) is a common disease of walleye fish in the United States and Canada. These proliferative lesions are present autumn through winter and regress in the spring. Walleye dermal sarcoma virus (WDSV), a retrovirus distantly related to other members of the family Retroviridae, has been etiologically linked to the development of WDS. We have reported that the D-cyclin homologue [retroviral (rv) cyclin] encoded by WDSV rescues yeast conditionally deficient for cyclin synthesis from growth arrest and that WDSV-cyclin mRNA is present in developing tumors. These data strongly suggest that the rv-cyclin plays a central role in the development of WDS. To test the ability of the WDSV rv-cyclin to induce cell proliferation, we have generated transgenic mice expressing the rv-cyclin in squamous epithelia from the bovine keratin-5 promoter. The transgenic animals were smaller than littermates, had reduced numbers of hair follicles, and transgenic females did not lactate properly. Following injury the transgenic animals developed severe squamous epithelial hyperplasia and dysplasia with ultrastructural characteristics of neoplastic squamous epithelium. Immunocytochemistry studies demonstrated that the hyperplastic epithelium stained positive for cytokeratin and were abnormally differentiated. Furthermore, the rv-cyclin protein was detected in the thickened basal cell layers of the proliferating lesions. These data are the first to indicate that the highly divergent WDSV rv-cyclin is a very potent stimulator of eukaryotic cell proliferation and to demonstrate the potential of a cyclin homologue encoded by a retrovirus to induce hyperplastic skin lesions.
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Affiliation(s)
- M D Lairmore
- Center for Retrovirus Research and Department of Veterinary Biosciences and Molecular Virology, Arthur James Cancer Hospital and Solove Research Institute, Ohio State University, Columbus 43210, USA
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Abstract
Cyclins are regulatory subunits of the cyclin-dependent protein kinases (CDKs). Members of this serine-threonine kinase family regulate the progression of cells through the division cycle. Until some years ago, cyclins were presumed to be encoded exclusively by eukaryotic cells. However, sequencing in 1996 of a simian herpesvirus, the herpesvirus saimiri, uncovered an open reading frame with sequence similarity to cellular cyclins. What at the time was a surprise for virologists and cell biologists alike, has become an accepted occurrence now. Eight different cyclin-encoding viruses have been described to date. One of them is the recently discovered human herpesvirus 8 (KSHV) suspected to cause Kaposi's sarcoma and certain B cell-lymphoproliferations in man. The significance of virus-encoded cyclins in the viral life cycle is currently unclear. However, the link between specific cellular cyclins and cancer suggests that virus-encoded cyclins could be involved in oncogenic events associated with these cyclin-encoding viruses.
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Affiliation(s)
- S Mittnacht
- Section of Cell and Molecular Biology, Institute of Cancer Research, Chester Beatty Laboratory, London, UK
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Abstract
D-type cyclin homologs have been found in the genomes of herpesviruses associated with neoplasias. They appear to exploit features of G(1) cyclins but extend their properties to allow for deregulation of the cell cycle. Advances in the study of the molecular basis for these novel features as well as the potential role of viral cyclins in tumorigenesis are addressed.
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Affiliation(s)
- H Laman
- Molecular Oncology Laboratory, Imperial Cancer Research Fund, London, WC2A 3PX, UK
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LaPierre LA, Holzschu DL, Bowser PR, Casey JW. Sequence and transcriptional analyses of the fish retroviruses walleye epidermal hyperplasia virus types 1 and 2: evidence for a gene duplication. J Virol 1999; 73:9393-403. [PMID: 10516048 PMCID: PMC112974 DOI: 10.1128/jvi.73.11.9393-9403.1999] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Walleye epidermal hyperplasia virus types 1 and 2 (WEHV1 and WEHV2, respectively) are associated with a hyperproliferative skin lesion on walleyes that appears and regresses seasonally. We have determined the complete nucleotide sequences and transcriptional profiles of these viruses. WEHV1 and WEHV2 are large, complex retroviruses of 12,999 and 13,125 kb in length, respectively, that are closely related to one another and to walleye dermal sarcoma virus (WDSV). These walleye retroviruses contain three open reading frames, orfA, orfB, and orfC, in addition to gag, pol, and env. orfA and orfB are adjacent to one another and located downstream of env. The OrfA proteins were previously identified as cyclin D homologs that may contribute to the induction of cell proliferation leading to epidermal hyperplasia and dermal sarcoma. The sequence analysis of WEHV1 and WEHV2 revealed that the OrfB proteins are distantly related to the OrfA proteins, suggesting that orfB arose by gene duplication. Presuming that the precursor of orfA and orfB was derived from a cellular cyclin, these genes are the first accessory genes of complex retroviruses that can be traced to a cellular origin. WEHV1, WEHV2, and WDSV are the only retroviruses that have an open reading frame, orfC, of considerable size (ca. 130 amino acids) in the leader region preceding gag. While we were unable to predict a function for the OrfC proteins, they are more conserved than OrfA and OrfB, suggesting that they may be biologically important to the viruses. The transcriptional profiles of WEHV1 and WEHV2 were also similar to that of WDSV; Northern blot analyses detected only low levels of the orfA transcripts in developing lesions, whereas abundant levels of genomic, env, orfA, and orfB transcripts were detected in regressing lesions. The splice donors and acceptors of individual transcripts were identified by reverse transcriptase PCR. The similarities of WEHV1, WEHV2, and WDSV suggest that these viruses use similar strategies of viral replication and induce cell proliferation by a similar mechanism.
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Affiliation(s)
- L A LaPierre
- Department of Microbiology, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853, USA
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Zhang Z, Martineau D. Walleye dermal sarcoma virus: OrfA N-terminal end inhibits the activity of a reporter gene directed by eukaryotic promoters and has a negative effect on the growth of fish and mammalian cells. J Virol 1999; 73:8884-9. [PMID: 10482648 PMCID: PMC112915 DOI: 10.1128/jvi.73.10.8884-8889.1999] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Walleye dermal sarcoma virus (WDSV) is a fish retrovirus causing a skin tumor termed walleye dermal sarcoma, which develops and regresses on a seasonal basis. The WDSV genome contains three short open reading frames designated orfA, orfB, and orfC in addition to the viral structural genes, gag, pol, and env. orfA and orfB transcripts are detected in tumors by reverse transcription-PCR. Recently, OrfA, whose amino acid sequence is similar to that of cyclins A and D, has been shown to complement a cyclin-deficient yeast strain. We report that expression of the accessory gene orfA inhibited nonspecifically the activity of a reporter gene directed by various eukaryotic promoters. In addition, stable transfection with the wild-type orfA generated substantially fewer G418-resistant colonies in both fish and mammalian cells than the parent vector. An orfA mutant expressing only the first N-terminal 49 residues of the full-length protein had the same negative effect on the activity of the reporter gene and on the number of stably transfected colonies as the full-length OrfA. Thus, OrfA inhibits cell growth and/or causes cell death, and the first 49 N-terminal residues of this protein are sufficient to cause these negative effects.
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Affiliation(s)
- Z Zhang
- Département de Pathologie et Microbiologie, Faculté de Médecine Vétérinaire, Université de Montréal, Saint-Hyacinthe PQ J2S 7C5, Canada
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Affiliation(s)
- C Boshoff
- Departments of Oncology and Molecular Pathology, University College London, 91 Riding House Street, London, W1P 6BT, UK
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van Dyk LF, Hess JL, Katz JD, Jacoby M, Speck SH, Virgin HW IV. The murine gammaherpesvirus 68 v-cyclin gene is an oncogene that promotes cell cycle progression in primary lymphocytes. J Virol 1999; 73:5110-22. [PMID: 10233974 PMCID: PMC112556 DOI: 10.1128/jvi.73.6.5110-5122.1999] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Several gammaherpesviruses contain open reading frames encoding proteins homologous to mammalian D-type cyclins. In this study, we analyzed the expression and function of the murine gammaherpesvirus 68 (gammaHV68) viral cyclin (v-cyclin). The gammaHV68 v-cyclin gene was expressed in lytically infected fibroblasts as a leaky-late mRNA of approximately 0.9 kb encoding a protein of approximately 25 kDa. To evaluate the effect of the gammaHV68 v-cyclin on cell cycle progression in primary lymphocytes and to determine if the gammaHV68 v-cyclin gene is an oncogene, we generated transgenic mice by using the lck proximal promoter to express the gammaHV68 v-cyclin in early T cells. Expression of the gammaHV68 v-cyclin significantly increased the number of thymocytes in cell culture, as determined by measuring both DNA content and incorporation of 5-bromo-2-deoxyuridine following in vivo pulse-labeling. Expression of the gammaHV68 v-cyclin interfered with normal thymocyte maturation, as shown by increased numbers of CD4(+) CD8(+) double-positive thymocytes and decreased numbers of CD4(+) or CD8(+) single-positive and T-cell-receptor-bright thymocytes and splenocytes in transgenic mice. Despite increased numbers of cycling thymocytes, gammaHV68-v-cyclin-transgenic mice did not have proportionately increased thymocyte numbers, and staining by terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling demonstrated increased apoptosis in the thymi of v-cyclin-transgenic mice. Fifteen of 38 gammaHV68-v-cyclin-transgenic mice developed high-grade lymphoblastic lymphoma between 3 and 12 months of age. We conclude that (i) the gammaHV68 v-cyclin is expressed as a leaky-late gene in lytically infected cells, (ii) expression of the gammaHV68 v-cyclin in thymocytes promotes cell cycle progression and inhibits normal T-cell differentiation, and (iii) the gammaHV68 v-cyclin gene is an oncogene.
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Affiliation(s)
- L F van Dyk
- Center for Immunology, Departments of Pathology and Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA
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Swanton C, Card GL, Mann D, McDonald N, Jones N. Overcoming inhibitions: subversion of CKI function by viral cyclins. Trends Biochem Sci 1999; 24:116-20. [PMID: 10203759 DOI: 10.1016/s0968-0004(99)01354-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
DNA tumour viruses deregulate the mammalian cell cycle to provide a better environment for their replication. Studies of such deregulation have led to the identification of key regulatory steps that normally control the G1-S phase transition of the cell cycle. The balance between the activities of G1-specific cyclin-CDK complexes and their inhibitors is critical. Recent studies suggest that certain herpesviruses disrupt this balance: the viruses encode a cyclin that generates active complexes even in the presence of high inhibitor levels.
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Affiliation(s)
- C Swanton
- Gene Regulation Laboratory, ICRF, PO Box 123, Lincoln's Inn Fields, London, UK WC2A 3PX
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