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Moens U, Passerini S, Falquet M, Sveinbjørnsson B, Pietropaolo V. Phosphorylation of Human Polyomavirus Large and Small T Antigens: An Ignored Research Field. Viruses 2023; 15:2235. [PMID: 38005912 PMCID: PMC10674619 DOI: 10.3390/v15112235] [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: 10/17/2023] [Revised: 11/02/2023] [Accepted: 11/07/2023] [Indexed: 11/26/2023] Open
Abstract
Protein phosphorylation and dephosphorylation are the most common post-translational modifications mediated by protein kinases and protein phosphatases, respectively. These reversible processes can modulate the function of the target protein, such as its activity, subcellular localization, stability, and interaction with other proteins. Phosphorylation of viral proteins plays an important role in the life cycle of a virus. In this review, we highlight biological implications of the phosphorylation of the monkey polyomavirus SV40 large T and small t antigens, summarize our current knowledge of the phosphorylation of these proteins of human polyomaviruses, and conclude with gaps in the knowledge and a proposal for future research directions.
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Affiliation(s)
- Ugo Moens
- Department of Medical Biology, Faculty of Health Sciences, University of Tromsø—The Arctic University of Norway, 9037 Tromsø, Norway; (M.F.); (B.S.)
| | - Sara Passerini
- Department of Public Health and Infectious Diseases, “Sapienza” University of Rome, 00185 Rome, Italy;
| | - Mar Falquet
- Department of Medical Biology, Faculty of Health Sciences, University of Tromsø—The Arctic University of Norway, 9037 Tromsø, Norway; (M.F.); (B.S.)
| | - Baldur Sveinbjørnsson
- Department of Medical Biology, Faculty of Health Sciences, University of Tromsø—The Arctic University of Norway, 9037 Tromsø, Norway; (M.F.); (B.S.)
| | - Valeria Pietropaolo
- Department of Public Health and Infectious Diseases, “Sapienza” University of Rome, 00185 Rome, Italy;
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2
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Idrees S, Paudel KR, Sadaf T, Hansbro PM. How different viruses perturb host cellular machinery via short linear motifs. EXCLI JOURNAL 2023; 22:1113-1128. [PMID: 38054205 PMCID: PMC10694346 DOI: 10.17179/excli2023-6328] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Accepted: 10/18/2023] [Indexed: 12/07/2023]
Abstract
The virus interacts with its hosts by developing protein-protein interactions. Most viruses employ protein interactions to imitate the host protein: A viral protein with the same amino acid sequence or structure as the host protein attaches to the host protein's binding partner and interferes with the host protein's pathways. Being opportunistic, viruses have evolved to manipulate host cellular mechanisms by mimicking short linear motifs. In this review, we shed light on the current understanding of mimicry via short linear motifs and focus on viral mimicry by genetically different viral subtypes by providing recent examples of mimicry evidence and how high-throughput methods can be a reliable source to study SLiM-mediated viral mimicry.
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Affiliation(s)
- Sobia Idrees
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW, Australia
- Centre for Inflammation, Centenary Institute and the University of Technology Sydney, School of Life Sciences, Faculty of Science, Sydney, New South Wales, Australia
| | - Keshav Raj Paudel
- Centre for Inflammation, Centenary Institute and the University of Technology Sydney, School of Life Sciences, Faculty of Science, Sydney, New South Wales, Australia
| | - Tayyaba Sadaf
- Centre for Inflammation, Centenary Institute and the University of Technology Sydney, School of Life Sciences, Faculty of Science, Sydney, New South Wales, Australia
| | - Philip M. Hansbro
- Centre for Inflammation, Centenary Institute and the University of Technology Sydney, School of Life Sciences, Faculty of Science, Sydney, New South Wales, Australia
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3
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Tessier TM, Dodge MJ, MacNeil KM, Evans AM, Prusinkiewicz MA, Mymryk JS. Almost famous: Human adenoviruses (and what they have taught us about cancer). Tumour Virus Res 2021; 12:200225. [PMID: 34500123 PMCID: PMC8449131 DOI: 10.1016/j.tvr.2021.200225] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Revised: 08/25/2021] [Accepted: 09/03/2021] [Indexed: 12/11/2022] Open
Abstract
Papillomaviruses, polyomaviruses and adenoviruses are collectively categorized as the small DNA tumour viruses. Notably, human adenoviruses were the first human viruses demonstrated to be able to cause cancer, albeit in non-human animal models. Despite their long history, no human adenovirus is a known causative agent of human cancers, unlike a subset of their more famous cousins, including human papillomaviruses and human Merkel cell polyomavirus. Nevertheless, seminal research using human adenoviruses has been highly informative in understanding the basics of cell cycle control, gene expression, apoptosis and cell differentiation. This review highlights the contributions of human adenovirus research in advancing our knowledge of the molecular basis of cancer.
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Affiliation(s)
- Tanner M Tessier
- Department of Microbiology and Immunology, The University of Western Ontario, London, ON, Canada
| | - Mackenzie J Dodge
- Department of Microbiology and Immunology, The University of Western Ontario, London, ON, Canada
| | - Katelyn M MacNeil
- Department of Microbiology and Immunology, The University of Western Ontario, London, ON, Canada
| | - Andris M Evans
- Department of Microbiology and Immunology, The University of Western Ontario, London, ON, Canada
| | - Martin A Prusinkiewicz
- Department of Microbiology and Immunology, The University of Western Ontario, London, ON, Canada
| | - Joe S Mymryk
- Department of Microbiology and Immunology, The University of Western Ontario, London, ON, Canada; Department of Otolaryngology, Head & Neck Surgery, The University of Western Ontario, London, ON, Canada; Department of Oncology, The University of Western Ontario, London, ON, Canada; London Regional Cancer Program, Lawson Health Research Institute, London, ON, Canada.
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4
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Duan S, Pagano M. Ubiquitin ligases in cancer: Functions and clinical potentials. Cell Chem Biol 2021; 28:918-933. [PMID: 33974914 PMCID: PMC8286310 DOI: 10.1016/j.chembiol.2021.04.008] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Revised: 03/23/2021] [Accepted: 04/08/2021] [Indexed: 02/07/2023]
Abstract
Ubiquitylation, a highly regulated post-translational modification, controls many cellular pathways that are critical to cell homeostasis. Ubiquitin ligases recruit substrates and promote ubiquitin transfer onto targets, inducing proteasomal degradation or non-degradative signaling. Accumulating evidence highlights the critical role of dysregulated ubiquitin ligases in processes associated with the initiation and progression of cancer. Depending on the substrate specificity and biological context, a ubiquitin ligase can act either as a tumor promoter or as a tumor suppressor. In this review, we focus on the regulatory roles of ubiquitin ligases and how perturbations of their functions contribute to cancer pathogenesis. We also briefly discuss current strategies for targeting or exploiting ubiquitin ligases for cancer therapy.
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Affiliation(s)
- Shanshan Duan
- Department of Biochemistry and Molecular Pharmacology, NYU Grossman School of Medicine, New York, NY, USA; Laura and Isaac Perlmutter Cancer Center, NYU Grossman School of Medicine, New York, NY, USA
| | - Michele Pagano
- Department of Biochemistry and Molecular Pharmacology, NYU Grossman School of Medicine, New York, NY, USA; Laura and Isaac Perlmutter Cancer Center, NYU Grossman School of Medicine, New York, NY, USA; Howard Hughes Medical Institute, NYU Grossman School of Medicine, New York, NY, USA.
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5
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Aliabadi F, Sohrabi B, Mostafavi E, Pazoki-Toroudi H, Webster TJ. Ubiquitin-proteasome system and the role of its inhibitors in cancer therapy. Open Biol 2021; 11:200390. [PMID: 33906413 PMCID: PMC8080017 DOI: 10.1098/rsob.200390] [Citation(s) in RCA: 47] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Despite all the other cells that have the potential to prevent cancer development and metastasis through tumour suppressor proteins, cancer cells can upregulate the ubiquitin–proteasome system (UPS) by which they can degrade tumour suppressor proteins and avoid apoptosis. This system plays an extensive role in cell regulation organized in two steps. Each step has an important role in controlling cancer. This demonstrates the importance of understanding UPS inhibitors and improving these inhibitors to foster a new hope in cancer therapy. UPS inhibitors, as less invasive chemotherapy drugs, are increasingly used to alleviate symptoms of various cancers in malignant states. Despite their success in reducing the development of cancer with the lowest side effects, thus far, an appropriate inhibitor that can effectively inactivate this system with the least drug resistance has not yet been fully investigated. A fundamental understanding of the system is necessary to fully elucidate its role in causing/controlling cancer. In this review, we first comprehensively investigate this system, and then each step containing ubiquitination and protein degradation as well as their inhibitors are discussed. Ultimately, its advantages and disadvantages and some perspectives for improving the efficiency of these inhibitors are discussed.
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Affiliation(s)
- Fatemeh Aliabadi
- Physiology Research Center, Faculty of Medicine, Iran University of Medical Sciences, Tehran, Iran
| | - Beheshteh Sohrabi
- Department of Chemistry, Surface Chemistry Research Laboratory, Iran University of Science and Technology, PO Box 16846-13114, Tehran, Iran
| | - Ebrahim Mostafavi
- Department of Chemical Engineering, Northeastern University, Boston, MA 02115, USA.,Stanford Cardiovascular Institute, Stanford, CA, USA.,Department of Medicine, Stanford University School of Medicine, Stanford, CA, USA
| | - Hamidreza Pazoki-Toroudi
- Physiology Research Center, Faculty of Medicine, Iran University of Medical Sciences, Tehran, Iran.,Department of Physiology, Faculty of Medicine, Iran University of Medical Sciences, Tehran, Iran
| | - Thomas J Webster
- Department of Chemical Engineering, Northeastern University, Boston, MA 02115, USA
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6
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Seridi N, Hamidouche M, Belmessabih N, El Kennani S, Gagnon J, Martinez G, Coutton C, Marchal T, Chebloune Y. Immortalization of primary sheep embryo kidney cells. In Vitro Cell Dev Biol Anim 2021; 57:76-85. [PMID: 33415664 DOI: 10.1007/s11626-020-00520-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Accepted: 10/13/2020] [Indexed: 10/22/2022]
Abstract
Sheep primary epithelial cells are short-lived in cell culture systems. For long-term in vitro studies, primary cells need to be immortalized. This study aims to establish and characterize T immortalized sheep embryo kidney cells (TISEKC). In this study, we used fetal lamb kidneys to derive primary cultures of epithelial cells. We subsequently immortalized these cells using the large T SV40 antigen to generate crude TISEKC and isolate TISEKC clones. Among numerous clones of immortalized cells, the selected TISEKC-5 maintained active division and cell growth over 20 passages but lacked expression of the oncogenic large T SV40 antigen. Morphologically, TISEKC-5 maintained their epithelial aspect similar to the parental primary epithelial cells. However, their growth properties showed quite different patterns. Crude TISEKC, as well as the clones of TISEKC proliferated highly in culture compared to the parental primary cells. In the early passages, immortalized cells showed heterogeneous polyploidy but in the late passages the karyotype of immortalized cells became progressively stable, identical to that of the primary cells, because the TISEKC-5 cell line has lost the large SV40 T antigen expression, this cell line is a valuable tool for veterinary sciences and biotechnological productions.
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Affiliation(s)
- N Seridi
- Laboratory of Molecular and Cellular Biology, Unit of Genetics, Faculty of Biological Sciences, University of Sciences and Technology "Houari Boumediene", Algiers, Algeria
| | - M Hamidouche
- Laboratory of Production and Development of Viral Veterinary Vaccines, Pasteur Institute of Algeria, Algiers, Algeria
| | - N Belmessabih
- Laboratory of Production and Development of Viral Veterinary Vaccines, Pasteur Institute of Algeria, Algiers, Algeria
| | - S El Kennani
- INRAE/UGA USC 1450, Pathogenesis and Lentivirus Vaccination Laboratory, PAVAL Lab, Université Grenoble Alpes, 38041, Grenoble Cedex 9, France
| | - J Gagnon
- INRAE/UGA USC 1450, Pathogenesis and Lentivirus Vaccination Laboratory, PAVAL Lab, Université Grenoble Alpes, 38041, Grenoble Cedex 9, France
| | - G Martinez
- CHU Grenoble Alpes, UM de Génétique Chromosomique, Grenoble, France.,INSERM U1209, CNRS UMR 5309, Institute for Advanced Biosciences, Université Grenoble Alpes, 38000, Grenoble, France
| | - C Coutton
- CHU Grenoble Alpes, UM de Génétique Chromosomique, Grenoble, France.,INSERM U1209, CNRS UMR 5309, Institute for Advanced Biosciences, Université Grenoble Alpes, 38000, Grenoble, France
| | - T Marchal
- VetAgro Sup, UPSP ICE 2011.03.101, Laboratoire d'Histopathologie, Université de Lyon, Marcy-l'Etoile, France
| | - Y Chebloune
- INRAE/UGA USC 1450, Pathogenesis and Lentivirus Vaccination Laboratory, PAVAL Lab, Université Grenoble Alpes, 38041, Grenoble Cedex 9, France.
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7
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Fifty Years of JC Polyomavirus: A Brief Overview and Remaining Questions. Viruses 2020; 12:v12090969. [PMID: 32882975 PMCID: PMC7552028 DOI: 10.3390/v12090969] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Revised: 08/28/2020] [Accepted: 08/30/2020] [Indexed: 12/11/2022] Open
Abstract
In the fifty years since the discovery of JC polyomavirus (JCPyV), the body of research representing our collective knowledge on this virus has grown substantially. As the causative agent of progressive multifocal leukoencephalopathy (PML), an often fatal central nervous system disease, JCPyV remains enigmatic in its ability to live a dual lifestyle. In most individuals, JCPyV reproduces benignly in renal tissues, but in a subset of immunocompromised individuals, JCPyV undergoes rearrangement and begins lytic infection of the central nervous system, subsequently becoming highly debilitating-and in many cases, deadly. Understanding the mechanisms allowing this process to occur is vital to the development of new and more effective diagnosis and treatment options for those at risk of developing PML. Here, we discuss the current state of affairs with regards to JCPyV and PML; first summarizing the history of PML as a disease and then discussing current treatment options and the viral biology of JCPyV as we understand it. We highlight the foundational research published in recent years on PML and JCPyV and attempt to outline which next steps are most necessary to reduce the disease burden of PML in populations at risk.
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Merkel cell polyomavirus Tumor antigens expressed in Merkel cell carcinoma function independently of the ubiquitin ligases Fbw7 and β-TrCP. PLoS Pathog 2019; 15:e1007543. [PMID: 30689667 PMCID: PMC6366716 DOI: 10.1371/journal.ppat.1007543] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Revised: 02/07/2019] [Accepted: 12/19/2018] [Indexed: 02/01/2023] Open
Abstract
Merkel cell polyomavirus (MCPyV) accounts for 80% of all Merkel cell carcinoma (MCC) cases through expression of two viral oncoproteins: the truncated large T antigen (LT-t) and small T antigen (ST). MCPyV ST is thought to be the main driver of cellular transformation and has also been shown to increase LT protein levels through the activity of its Large-T Stabilization Domain (LSD). The ST LSD was reported to bind and sequester several ubiquitin ligases, including Fbw7 and β-TrCP, and thereby stabilize LT-t and several other Fbw7 targets including c-Myc and cyclin E. Therefore, the ST LSD is thought to contribute to transformation by promoting the accumulation of these oncoproteins. Targets of Fbw7 and β-TrCP contain well-defined, conserved, phospho-degrons. However, as neither MCPyV LT, LT-t nor ST contain the canonical Fbw7 phospho-degron, we sought to further investigate the proposed model of ST stabilization of LT-t and transformation. In this study, we provide several lines of evidence that fail to support a specific interaction between MCPyV T antigens and Fbw7 or β-TrCP by co-immunoprecipitation or functional consequence. Although MCPyV ST does indeed increase LT protein levels through its Large-T Stabilization domain (LSD), this is accomplished independently of Fbw7. Therefore, our study indicates a need for further investigation into the role and mechanism(s) of MCPyV T antigens in viral replication, latency, transformation, and tumorigenesis. Merkel cell carcinoma (MCC) is a very aggressive and deadly neuroendocrine skin cancer. Merkel cell polyomavirus (MCPyV) contributes to the development and maintenance of 80% of MCCs through the expression of its truncated large tumor antigen (LT-t) and small tumor antigen (ST). MCPyV ST is thought to be primarily responsible for transformation and tumorigenesis through many mechanisms including stabilization of MCPyV LT-t and other cellular proteins involved in proliferation such as c-Myc. As c-Myc is a known target substrate, and MCPyV LT-t is a proposed target substrate, of the ubiquitin ligase Fbw7, it is currently thought that ST stabilizes these proteins and transforms cells through binding and perturbing the function of Fbw7. However, neither MCPyV LT-t nor ST contain a canonical Fbw7 degron sequence necessary for this interaction. MCPyV LT-t, found in MCCs, does not bind to, nor is targeted by, Fbw7. However, an ill-defined, unidirectional interaction between MCPyV LT, ST, and Fbw7 was observed, but had no functional consequence. Therefore, this study calls for further investigation into the mechanism(s) by which MCPyV ST leads to the development and maintenance of MCC.
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9
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Yeh CH, Bellon M, Nicot C. FBXW7: a critical tumor suppressor of human cancers. Mol Cancer 2018; 17:115. [PMID: 30086763 PMCID: PMC6081812 DOI: 10.1186/s12943-018-0857-2] [Citation(s) in RCA: 324] [Impact Index Per Article: 54.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Accepted: 07/16/2018] [Indexed: 12/14/2022] Open
Abstract
The ubiquitin-proteasome system (UPS) is involved in multiple aspects of cellular processes, such as cell cycle progression, cellular differentiation, and survival (Davis RJ et al., Cancer Cell 26:455-64, 2014; Skaar JR et al., Nat Rev Drug Discov 13:889-903, 2014; Nakayama KI and Nakayama K, Nat Rev Cancer 6:369-81, 2006). F-box and WD repeat domain containing 7 (FBXW7), also known as Sel10, hCDC4 or hAgo, is a member of the F-box protein family, which functions as the substrate recognition component of the SCF E3 ubiquitin ligase. FBXW7 is a critical tumor suppressor and one of the most commonly deregulated ubiquitin-proteasome system proteins in human cancer. FBXW7 controls proteasome-mediated degradation of oncoproteins such as cyclin E, c-Myc, Mcl-1, mTOR, Jun, Notch and AURKA. Consistent with the tumor suppressor role of FBXW7, it is located at chromosome 4q32, a genomic region deleted in more than 30% of all human cancers (Spruck CH et al., Cancer Res 62:4535-9, 2002). Genetic profiles of human cancers based on high-throughput sequencing have revealed that FBXW7 is frequently mutated in human cancers. In addition to genetic mutations, other mechanisms involving microRNA, long non-coding RNA, and specific oncogenic signaling pathways can inactivate FBXW7 functions in cancer cells. In the following sections, we will discuss the regulation of FBXW7, its role in oncogenesis, and the clinical implications and prognostic value of loss of function of FBXW7 in human cancers.
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Affiliation(s)
- Chien-Hung Yeh
- Department of Pathology and Laboratory Medicine, Center for Viral Pathogenesis, University of Kansas Medical Center, 3901 Rainbow Boulevard, Kansas City, KS, 66160, USA
| | - Marcia Bellon
- Department of Pathology and Laboratory Medicine, Center for Viral Pathogenesis, University of Kansas Medical Center, 3901 Rainbow Boulevard, Kansas City, KS, 66160, USA
| | - Christophe Nicot
- Department of Pathology and Laboratory Medicine, Center for Viral Pathogenesis, University of Kansas Medical Center, 3901 Rainbow Boulevard, Kansas City, KS, 66160, USA.
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10
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DeCaprio JA. Merkel cell polyomavirus and Merkel cell carcinoma. Philos Trans R Soc Lond B Biol Sci 2018; 372:rstb.2016.0276. [PMID: 28893943 DOI: 10.1098/rstb.2016.0276] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/09/2017] [Indexed: 12/27/2022] Open
Abstract
Merkel cell polyomavirus (MCPyV) causes the highly aggressive and relatively rare skin cancer known as Merkel cell carcinoma (MCC). MCPyV also causes a lifelong yet relatively innocuous infection and is one of 14 distinct human polyomaviruses species. Although polyomaviruses typically do not cause illness in healthy individuals, several can cause catastrophic diseases in immunocompromised hosts. MCPyV is the only polyomavirus clearly associated with human cancer. How MCPyV causes MCC and what oncogenic events must transpire to enable this virus to cause MCC is the focus of this essay.This article is part of the themed issue 'Human oncogenic viruses'.
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Affiliation(s)
- James A DeCaprio
- Department of Medical Oncology, Dana-Farber Cancer Institute, 450 Brookline Avenue, Boston, MA 02215, USA .,Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, 450 Brookline Avenue, Boston, MA 02215, USA
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11
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Assetta B, Atwood WJ. The biology of JC polyomavirus. Biol Chem 2017; 398:839-855. [PMID: 28493815 DOI: 10.1515/hsz-2016-0345] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2016] [Accepted: 04/20/2017] [Indexed: 02/06/2023]
Abstract
JC polyomavirus (JCPyV) is the causative agent of a fatal central nervous system demyelinating disease known as progressive multifocal leukoencephalopathy (PML). PML occurs in people with underlying immunodeficiency or in individuals being treated with potent immunomodulatory therapies. JCPyV is a DNA tumor virus with a double-stranded DNA genome and encodes a well-studied oncogene, large T antigen. Its host range is highly restricted to humans and only a few cell types support lytic infection in vivo or in vitro. Its oncogenic potential in humans has not been firmly established and the international committee on oncogenic viruses lists JCPyV as possibly carcinogenic. Significant progress has been made in understanding the biology of JCPyV and here we present an overview of the field and discuss some important questions that remain unanswered.
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12
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Abstract
Ubiquitin E3 ligases control every aspect of eukaryotic biology by promoting protein ubiquitination and degradation. At the end of a three-enzyme cascade, ubiquitin ligases mediate the transfer of ubiquitin from an E2 ubiquitin-conjugating enzyme to specific substrate proteins. Early investigations of E3s of the RING (really interesting new gene) and HECT (homologous to the E6AP carboxyl terminus) types shed light on their enzymatic activities, general architectures, and substrate degron-binding modes. Recent studies have provided deeper mechanistic insights into their catalysis, activation, and regulation. In this review, we summarize the current progress in structure-function studies of ubiquitin ligases as well as exciting new discoveries of novel classes of E3s and diverse substrate recognition mechanisms. Our increased understanding of ubiquitin ligase function and regulation has provided the rationale for developing E3-targeting therapeutics for the treatment of human diseases.
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Affiliation(s)
- Ning Zheng
- Howard Hughes Medical Institute and Department of Pharmacology, University of Washington, Seattle, Washington 98195; ,
| | - Nitzan Shabek
- Howard Hughes Medical Institute and Department of Pharmacology, University of Washington, Seattle, Washington 98195; ,
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13
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Vriend J, Ghavami S, Marzban H. The role of the ubiquitin proteasome system in cerebellar development and medulloblastoma. Mol Brain 2015; 8:64. [PMID: 26475605 PMCID: PMC4609148 DOI: 10.1186/s13041-015-0155-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Accepted: 10/08/2015] [Indexed: 01/12/2023] Open
Abstract
Cerebellar granule cells precursors are derived from the upper rhombic lip and migrate tangentially independent of glia along the subpial stream pathway to form the external germinal zone. Postnatally, granule cells migrate from the external germinal zone radially through the Purkinje cell layer, guided by Bergmann glia fibers, to the internal granular cell layer. Medulloblastomas (MBs) are the most common malignant childhood brain tumor. Many of these tumors develop from precursor cells of the embryonic rhombic lips. Four main groups of MB are recognized. The WNT group of MBs arise primarily from the lower rhombic lip and embryonic brainstem. The SHH group of MBs originate from cerebellar granule cell precursors in the external germinal zone of the embryonic cerebellum. The cellular origins of type 3 and type 4 MBs are not clear. Several ubiquitin ligases are revealed to be significant factors in development of the cerebellum as well as in the initiation and maintenance of MBs. Proteasome dysfunction at a critical stage of development may be a major factor in determining whether progenitor cells which are destined to become granule cells differentiate normally or become MB cells. We propose the hypothesis that proteasomal activity is essential to regulate the critical transition between proliferating granule cells and differentiated granule cells and that proteasome dysfunction may lead to MB. Proteasome dysfunction could also account for various mutations in MBs resulting from deficiencies in DNA checkpoint and repair mechanisms prior to development of MBs. Data showing a role for the ubiquitin ligases β-TrCP, FBW7, Huwe1, and SKP2 in MBs suggest the possibility of a classification of MBs based on the expression (over expression or under expression) of specific ubiquitin ligases which function as oncogenes, tumor suppressors or cell cycle regulators.
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Affiliation(s)
- Jerry Vriend
- Department of Human Anatomy and Cell Science, Rm129, BMSB, 745 Bannatyne Avenue, Winnipeg, MB, Canada
| | - Saeid Ghavami
- Department of Human Anatomy and Cell Science, Rm129, BMSB, 745 Bannatyne Avenue, Winnipeg, MB, Canada.,Children's Hospital Research Institute of Manitoba (CHRIM), College of Medicine, Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, R3E 0J9, Canada
| | - Hassan Marzban
- Department of Human Anatomy and Cell Science, Rm129, BMSB, 745 Bannatyne Avenue, Winnipeg, MB, Canada. .,Children's Hospital Research Institute of Manitoba (CHRIM), College of Medicine, Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, R3E 0J9, Canada.
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14
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Xu W, Taranets L, Popov N. Regulating Fbw7 on the road to cancer. Semin Cancer Biol 2015; 36:62-70. [PMID: 26459133 DOI: 10.1016/j.semcancer.2015.09.005] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Accepted: 09/13/2015] [Indexed: 12/22/2022]
Abstract
The F-box protein Fbw7 targets for degradation critical cellular regulators, thereby controlling essential processes in cellular homeostasis, including cell cycle, differentiation and apoptosis. Most Fbw7 substrates are strongly associated with tumorigenesis and Fbw7 can either suppress or promote tumor development in mouse models. Fbw7 activity is controlled at different levels, resulting in specific and tunable regulation of the abundance and activity of its substrates. Here we highlight recent studies on the role of Fbw7 in controlling tumorigenesis and on the mechanisms that modulate Fbw7 function.
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Affiliation(s)
- Wenshan Xu
- Department of Radiation Oncology and Comprehensive Cancer Center Mainfranken, University Hospital Würzburg, Versbacher Str. 5, 97078 Würzburg, Germany
| | - Lyudmyla Taranets
- Department of Radiation Oncology and Comprehensive Cancer Center Mainfranken, University Hospital Würzburg, Versbacher Str. 5, 97078 Würzburg, Germany
| | - Nikita Popov
- Department of Radiation Oncology and Comprehensive Cancer Center Mainfranken, University Hospital Würzburg, Versbacher Str. 5, 97078 Würzburg, Germany.
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15
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Zhou Z, He C, Wang J. Regulation mechanism of Fbxw7-related signaling pathways (Review). Oncol Rep 2015; 34:2215-24. [PMID: 26324296 DOI: 10.3892/or.2015.4227] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Accepted: 05/29/2015] [Indexed: 11/05/2022] Open
Abstract
F-box and WD repeat domain-containing 7 (Fbxw7), the substrate-recognition component of SCFFbxw7 complex, is thought to be a tumor suppressor involved in cell growth, proliferation, differentiation and survival. Although an increasing number of ubiquitin substrates of Fbxw7 have been identified, the best characterized substrates are cyclin E and c-Myc. Fbxw7/cyclin E and Fbxw7/c-Myc pathways are tightly regulated by multiple regulators. Fbxw7 has been identified as a tumor suppressor in hepatocellular carcinoma. This review focused on the regulation of Fbxw7/cyclin E and Fbxw7/c-Myc pathways and discussed findings to gain a better understanding of the role of Fbxw7 in hepatocellular carcinoma.
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Affiliation(s)
- Zhenyu Zhou
- Department of Hepatobiliary Surgery, Sun Yat-sen Memorial Hospital, Sun Yat‑sen University, Guangzhou, Guangdong 510120, P.R. China
| | - Chuanchao He
- Department of Hepatobiliary Surgery, Sun Yat-sen Memorial Hospital, Sun Yat‑sen University, Guangzhou, Guangdong 510120, P.R. China
| | - Jie Wang
- Department of Hepatobiliary Surgery, Sun Yat-sen Memorial Hospital, Sun Yat‑sen University, Guangzhou, Guangdong 510120, P.R. China
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16
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Fekrmandi F, Wang TT, White JH. The hormone-bound vitamin D receptor enhances the FBW7-dependent turnover of NF-κB subunits. Sci Rep 2015; 5:13002. [PMID: 26269414 PMCID: PMC4534774 DOI: 10.1038/srep13002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Accepted: 07/06/2015] [Indexed: 01/14/2023] Open
Abstract
Signaling by hormonal vitamin D, 1,25-dihydroxyvitamin D (1,25D) has attracted increasing interest because of its non-classical actions, particularly its putative anticancer properties and its role in controlling immune system function. Notably, the hormone-bound vitamin D receptor (VDR) suppresses signaling by pro-inflammatory NF-κB transcription factors, although the underlying mechanisms have remained elusive. Recently, the VDR was shown to enhance the turnover of the oncogenic transcription factor cMYC mediated by the E3 ligase and tumor suppressor FBW7. As FBW7 also controls the turnover of the p100 (NF-κB2) subunit of the family, we determined whether the 1,25D enhanced FBW7-dependent turnover of NF-κB subunits p100, p105 (NF-κB1) and p65 (RELA). Protein levels of all three subunits declined markedly in the presence of 1,25D in multiple cell lines in the absence of substantial changes in mRNA expression. The VDR coimmunoprecipitated with all three subunits, and 1,25D treatment accelerated subunit turnover in cycloheximide-treated cells. Importantly, we observed an association of FBW7 with p105 and p65, as well as p100, and knockdown of FBW7 eliminated 1,25D-dependent subunit turnover. Moreover, expression of NF-κB target genes was elevated in FBW7-depleted cells. These results reveal that 1,25D signaling suppresses NF-κB function by enhancing FBW7-dependent subunit turnover.
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Affiliation(s)
- Fatemeh Fekrmandi
- Departments of Medicine, McGill University, Montreal, Quebec, Canada
| | | | - John H White
- 1] Departments of Medicine, McGill University, Montreal, Quebec, Canada [2] Physiology, McGill University, Montreal, Quebec, Canada
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Targeting Cullin-RING E3 ubiquitin ligases for drug discovery: structure, assembly and small-molecule modulation. Biochem J 2015; 467:365-86. [PMID: 25886174 PMCID: PMC4403949 DOI: 10.1042/bj20141450] [Citation(s) in RCA: 164] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
In the last decade, the ubiquitin–proteasome system has emerged as a valid target for the development of novel therapeutics. E3 ubiquitin ligases are particularly attractive targets because they confer substrate specificity on the ubiquitin system. CRLs [Cullin–RING (really interesting new gene) E3 ubiquitin ligases] draw particular attention, being the largest family of E3s. The CRLs assemble into functional multisubunit complexes using a repertoire of substrate receptors, adaptors, Cullin scaffolds and RING-box proteins. Drug discovery targeting CRLs is growing in importance due to mounting evidence pointing to significant roles of these enzymes in diverse biological processes and human diseases, including cancer, where CRLs and their substrates often function as tumour suppressors or oncogenes. In the present review, we provide an account of the assembly and structure of CRL complexes, and outline the current state of the field in terms of available knowledge of small-molecule inhibitors and modulators of CRL activity. A comprehensive overview of the reported crystal structures of CRL subunits, components and full-size complexes, alone or with bound small molecules and substrate peptides, is included. This information is providing increasing opportunities to aid the rational structure-based design of chemical probes and potential small-molecule therapeutics targeting CRLs.
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Abstract
FBW7 (F-box and WD repeat domain-containing 7) or Fbxw7 is a tumor suppressor, which promotes the ubiquitination and subsequent degradation of numerous oncoproteins including Mcl-1, Cyclin E, Notch, c- Jun, and c-Myc. In turn, FBW7 is regulated by multiple upstream factors including p53, C/EBP-δ, EBP2, Pin1, Hes-5 and Numb4 as well as by microRNAs such as miR-223, miR-27a, miR-25, and miR-129-5p. Given that the Fbw7 tumor suppressor is frequently inactivated or deleted in various human cancers, targeting FBW7 regulators is a promising anti-cancer therapeutic strategy.
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Duro N, Miskei M, Fuxreiter M. Fuzziness endows viral motif-mimicry. MOLECULAR BIOSYSTEMS 2015; 11:2821-9. [DOI: 10.1039/c5mb00301f] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The local dynamics of host and viral peptide motifs suggests a different scenario for partner recognition. Host peptide motifs serve as molecular recognition elements, while viral motifs preserve the structural heterogeneity and remain fuzzy when bound to the host.
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Affiliation(s)
- Norbert Duro
- MTA-DE Momentum
- Laboratory of Protein Dynamics
- Department of Biochemistry and Molecular Biology
- University of Debrecen
- Hungary
| | - Marton Miskei
- MTA-DE Momentum
- Laboratory of Protein Dynamics
- Department of Biochemistry and Molecular Biology
- University of Debrecen
- Hungary
| | - Monika Fuxreiter
- MTA-DE Momentum
- Laboratory of Protein Dynamics
- Department of Biochemistry and Molecular Biology
- University of Debrecen
- Hungary
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20
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Removal of a small C-terminal region of JCV and SV40 large T antigens has differential effects on transformation. Virology 2014; 468-470:47-56. [PMID: 25129438 DOI: 10.1016/j.virol.2014.07.038] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2014] [Revised: 06/23/2014] [Accepted: 07/21/2014] [Indexed: 01/12/2023]
Abstract
The large T antigen (LT) protein of JCV and SV40 polyomaviruses is required to induce tumors in rodents and transform cells in culture. When both LTs are compared side-by-side in cell culture assays, SV40 shows a more robust transformation phenotype even though the LT sequences are highly conserved. A complete understanding of SV40׳s enhanced transforming capabilities relative to JCV is lacking. When the least conserved region of the LT proteins, the variable linker and host range region (VHR), was removed, changes in T antigen expression and cellular p53 post-translational modifications occurred, but interaction with the pRB pathway was unaffected. Transformation assessed by growth in low serum was reduced after VHR truncation of the SV40, but not the JCV, T antigen. Conversely, anchorage independent transformation was enhanced only by truncation of the JCV VHR. This is the first report to link the SV40 or JCV VHR region to transformation potential.
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Van Roey K, Uyar B, Weatheritt RJ, Dinkel H, Seiler M, Budd A, Gibson TJ, Davey NE. Short Linear Motifs: Ubiquitous and Functionally Diverse Protein Interaction Modules Directing Cell Regulation. Chem Rev 2014; 114:6733-78. [DOI: 10.1021/cr400585q] [Citation(s) in RCA: 293] [Impact Index Per Article: 29.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Kim Van Roey
- Structural
and Computational Biology Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Bora Uyar
- Structural
and Computational Biology Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Robert J. Weatheritt
- MRC
Laboratory of Molecular Biology (LMB), Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, United Kingdom
| | - Holger Dinkel
- Structural
and Computational Biology Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Markus Seiler
- Structural
and Computational Biology Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Aidan Budd
- Structural
and Computational Biology Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Toby J. Gibson
- Structural
and Computational Biology Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Norman E. Davey
- Structural
and Computational Biology Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, 69117 Heidelberg, Germany
- Department
of Physiology, University of California, San Francisco, San Francisco, California 94143, United States
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22
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Luan Y, Wang P. FBW7-mediated ubiquitination and degradation of KLF5. World J Biol Chem 2014; 5:216-223. [PMID: 24921010 PMCID: PMC4050114 DOI: 10.4331/wjbc.v5.i2.216] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Revised: 01/15/2014] [Accepted: 03/18/2014] [Indexed: 02/05/2023] Open
Abstract
Krüppel-like factor (KLF) family proteins are transcription factors that regulate numerous cellular functions, such as cell proliferation, differentiation, and cell death. Posttranslational modification of KLF proteins is important for their transcriptional activities and biological functions. One KLF family member with important roles in cell proliferation and tumorigenesis is KLF5. The function of KLF5 is tightly controlled by post-translational modifications, including SUMOylation, phosphorylation, and ubiquitination. Recent studies from our lab and others’ have demonstrated that the tumor suppressor FBW7 is an essential E3 ubiquitin ligase that targets KLF5 for ubiquitination and degradation. KLF5 contains functional Cdc4 phospho-degrons (CPDs), which are required for its interaction with FBW7. Mutation of CPDs in KLF5 blocks the ubiquitination and degradation of KLF5 by FBW7. The protein kinase Glycogen synthase kinase 3β is involved in the phosphorylation of KLF5 CPDs. In both cancer cell lines and mouse models, it has been shown that FBW7 regulates the expression of KLF5 target genes through the modulation of KLF5 stability. In this review, we summarize the current progress on delineating FBW7-mediated KLF5 ubiquitination and degradation.
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Kwun HJ, Shuda M, Feng H, Camacho CJ, Moore PS, Chang Y. Merkel cell polyomavirus small T antigen controls viral replication and oncoprotein expression by targeting the cellular ubiquitin ligase SCFFbw7. Cell Host Microbe 2014; 14:125-35. [PMID: 23954152 DOI: 10.1016/j.chom.2013.06.008] [Citation(s) in RCA: 130] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Revised: 05/09/2013] [Accepted: 06/10/2013] [Indexed: 10/26/2022]
Abstract
Merkel cell polyomavirus (MCV) causes an aggressive human skin cancer, Merkel cell carcinoma, through expression of small T (sT) and large T (LT) viral oncoproteins. MCV sT is also required for efficient MCV DNA replication by the multifunctional MCV LT helicase protein. We find that LT is targeted for proteasomal degradation by the cellular SCF(Fbw7) E3 ligase, which can be inhibited by sT through its LT-stabilization domain (LSD). Consequently, sT also stabilizes cellular SCF(Fbw7) targets, including the cell-cycle regulators c-Myc and cyclin E. Mutating the sT LSD decreases LT protein levels and eliminates synergism in MCV DNA replication as well as sT-induced cell transformation. SCF(Fbw7) knockdown mimics sT-mediated stabilization of LT, but this knockdown is insufficient to fully reconstitute the transforming activity of a mutant LSD sT protein. Thus, MCV has evolved a regulatory system involving SCF(Fbw7) that controls viral replication but also contributes to host cell transformation.
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Affiliation(s)
- Hyun Jin Kwun
- Cancer Virology Program, University of Pittsburgh, Pittsburgh, PA 15213, USA
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Two independent regions of simian virus 40 T antigen increase CBP/p300 levels, alter patterns of cellular histone acetylation, and immortalize primary cells. J Virol 2013; 87:13499-509. [PMID: 24089570 DOI: 10.1128/jvi.02658-13] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Simian virus 40 (SV40) large T antigen (SVT) interferes with normal cell regulation and thus has been used to identify cellular components controlling proliferation and homeostasis. We have previously shown that SVT-mediated transformation requires interaction with the histone acetyltransferases (HATs) CBP/p300 and now report that the ectopic expression of SVT in several cell types in vivo and in vitro results in a significant increase in the steady-state levels of CBP/p300. Furthermore, SVT-expressing cells contain higher levels of acetylated CBP/p300, a modification that has been linked to increased HAT activity. Concomitantly, the acetylation levels of histone residues H3K56 and H4K12 are markedly increased in SVT-expressing cells. Other polyomavirus-encoded large T antigens also increase the levels of CBP/p300 and sustain a rise in the acetylation levels of H3K56 and H4K12. SVT does not affect the transcription of CBP/p300, but rather, alters their overall levels through increasing the loading of CBP/p300 mRNAs onto polysomes. Two distinct regions within SVT, one located in the amino terminus and one in the carboxy terminus, can independently alter both the levels of CBP/p300 and the loading of CBP/p300 transcripts onto polysomes. Within the amino-terminal fragment, a functional J domain is necessary for increasing CBP/p300 and specific histone acetylation levels, as well as for immortalizing primary cells. These studies uncover the action of polyomavirus T antigens on cellular CBP/p300 and suggest that additional mechanisms are used by T antigens to induce cell immortalization and transformation.
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Lagatie O, Tritsmans L, Stuyver LJ. The miRNA world of polyomaviruses. Virol J 2013; 10:268. [PMID: 23984639 PMCID: PMC3765807 DOI: 10.1186/1743-422x-10-268] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Accepted: 08/27/2013] [Indexed: 12/20/2022] Open
Abstract
Polyomaviruses are a family of non-enveloped DNA viruses infecting several species, including humans, primates, birds, rodents, bats, horse, cattle, raccoon and sea lion. They typically cause asymptomatic infection and establish latency but can be reactivated under certain conditions causing severe diseases. MicroRNAs (miRNAs) are small non-coding RNAs that play important roles in several cellular processes by binding to and inhibiting the translation of specific mRNA transcripts. In this review, we summarize the current knowledge of microRNAs involved in polyomavirus infection. We review in detail the different viral miRNAs that have been discovered and the role they play in controlling both host and viral protein expression. We also give an overview of the current understanding on how host miRNAs may function in controlling polyomavirus replication, immune evasion and pathogenesis.
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Affiliation(s)
- Ole Lagatie
- Janssen Diagnostics, Turnhoutseweg 30, Beerse 2340, Belgium.
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Luo H, Zhang Z, Zheng Z, Ke X, Zhang X, Li Q, Liu Y, Bai B, Mao P, Hu Q, Wang H. Human bocavirus VP2 upregulates IFN-β pathway by inhibiting ring finger protein 125-mediated ubiquitination of retinoic acid-inducible gene-I. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2013; 191:660-9. [PMID: 23772026 DOI: 10.4049/jimmunol.1202933] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Precise regulation of innate immunity is crucial for maintaining optimal immune responses against infections. Whereas positive regulation of IFN signaling elicits rapid type I IFNs, negative regulation is equally important in preventing the production of superfluous IFNs that can be hazardous to the host. The positive regulators of IFN pathway are known to be the main targets of viruses to antagonize the innate immune system. Whether viruses target the negative regulators of IFN pathway remains to be fully investigated. In this study, we report that the structural protein VP2 of human Bocavirus modulates IFN pathway by targeting the ring finger protein 125 (RNF125), a negative regulator of type I IFN signaling, which conjugates Lys(48)-linked ubiquitination to retinoic acid-inducible gene-I (RIG-I) and subsequently leads to the proteasome-dependent degradation of RIG-I. VP2 not only upregulated Sendai virus (SeV)-induced IFNB promoter activity, but also enhanced SeV-induced IFN-β production at both mRNA and protein levels. In agreement, the level of Ser(396)-phosphorylated IFN regulatory factor 3 stimulated by SeV was enhanced in the presence of VP2. Furthermore, VP2 was demonstrated to physically interact with RNF125, resulting in the reduction of RNF125-mediated ubiquitination and proteasome-dependent degradation of RIG-I. Additional study indicated that endogenous RIG-I degradation was decreased in VP2-expressing cells. Our study delineates a unique phenomenon for aberrant activation of IFN regulatory factor 3 pathway and may represent a new mechanism underlying viral manipulation of the host immune system.
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Affiliation(s)
- Huanle Luo
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China
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Gummlich L, Rabien A, Jung K, Dubiel W. Deregulation of the COP9 signalosome–cullin-RING ubiquitin-ligase pathway: Mechanisms and roles in urological cancers. Int J Biochem Cell Biol 2013; 45:1327-37. [DOI: 10.1016/j.biocel.2013.03.023] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Revised: 03/21/2013] [Accepted: 03/22/2013] [Indexed: 12/22/2022]
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Abstract
During the past 6 years, focused virus hunting has led to the discovery of nine new human polyomaviruses, including Merkel cell polyomavirus, which has been linked to Merkel cell carcinoma, a lethal skin cell cancer. The discovery of so many new and highly divergent human polyomaviruses raises key questions regarding their evolution, tropism, latency, reactivation, immune evasion and contribution to disease. This Review describes the similarities and differences among the new human polyomaviruses and discusses how these viruses might interact with their human host.
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Affiliation(s)
- James A DeCaprio
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts 02215, USA.
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29
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Fine DA, Rozenblatt-Rosen O, Padi M, Korkhin A, James RL, Adelmant G, Yoon R, Guo L, Berrios C, Zhang Y, Calderwood MA, Velmurgan S, Cheng J, Marto JA, Hill DE, Cusick ME, Vidal M, Florens L, Washburn MP, Litovchick L, DeCaprio JA. Identification of FAM111A as an SV40 host range restriction and adenovirus helper factor. PLoS Pathog 2012; 8:e1002949. [PMID: 23093934 PMCID: PMC3475652 DOI: 10.1371/journal.ppat.1002949] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2010] [Accepted: 08/22/2012] [Indexed: 11/18/2022] Open
Abstract
The small genome of polyomaviruses encodes a limited number of proteins that are highly dependent on interactions with host cell proteins for efficient viral replication. The SV40 large T antigen (LT) contains several discrete functional domains including the LXCXE or RB-binding motif, the DNA binding and helicase domains that contribute to the viral life cycle. In addition, the LT C-terminal region contains the host range and adenovirus helper functions required for lytic infection in certain restrictive cell types. To understand how LT affects the host cell to facilitate viral replication, we expressed full-length or functional domains of LT in cells, identified interacting host proteins and carried out expression profiling. LT perturbed the expression of p53 target genes and subsets of cell-cycle dependent genes regulated by the DREAM and the B-Myb-MuvB complexes. Affinity purification of LT followed by mass spectrometry revealed a specific interaction between the LT C-terminal region and FAM111A, a previously uncharacterized protein. Depletion of FAM111A recapitulated the effects of heterologous expression of the LT C-terminal region, including increased viral gene expression and lytic infection of SV40 host range mutants and adenovirus replication in restrictive cells. FAM111A functions as a host range restriction factor that is specifically targeted by SV40 LT. Viruses have evolved numerous mechanisms to counteract host cell defenses to facilitate productive infection. Simian Virus 40 (SV40) replication depends on specific interactions between large T antigen (LT) and a wide variety of host cell proteins. Although the LT C-terminal region has no evident enzymatic activity, mutations or deletions of this region significantly reduce the ability of the virus to replicate in restrictive cell types. Here, we identified host proteins that bind to LT and determined that the LT C-terminal region binds specifically to FAM111A. This physical interaction was required for efficient viral replication and sustained viral gene expression in restrictive cell types. In addition, RNAi-mediated knockdown of FAM111A levels in restrictive cells restored lytic infection of SV40 host range mutants and human adenovirus. These results indicate that FAM111A plays an important role in viral host range restriction. Our study provides insights into the viral-host perturbations caused by SV40 LT and the interaction of viruses with host restriction factors.
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Affiliation(s)
- Debrah A. Fine
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Program in Virology, Harvard University Graduate School of Arts and Sciences, Division of Medical Sciences, Boston, Massachusetts, United States of America
- Genomic Analysis of Network Perturbations Center of Excellence in Genomic Science, Center for Cancer Systems Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
| | - Orit Rozenblatt-Rosen
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Genomic Analysis of Network Perturbations Center of Excellence in Genomic Science, Center for Cancer Systems Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
| | - Megha Padi
- Genomic Analysis of Network Perturbations Center of Excellence in Genomic Science, Center for Cancer Systems Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Center for Cancer Computational Biology, Department of Biostatistics and Computational Biology and Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Department of Biostatistics, Harvard School of Public Health, Boston, Massachusetts, United States of America
| | - Anna Korkhin
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Genomic Analysis of Network Perturbations Center of Excellence in Genomic Science, Center for Cancer Systems Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
| | - Robert L. James
- Genomic Analysis of Network Perturbations Center of Excellence in Genomic Science, Center for Cancer Systems Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Center for Cancer Systems Biology and Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
| | - Guillaume Adelmant
- Genomic Analysis of Network Perturbations Center of Excellence in Genomic Science, Center for Cancer Systems Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Blais Proteomics Center and Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Rosa Yoon
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Program in Virology, Harvard University Graduate School of Arts and Sciences, Division of Medical Sciences, Boston, Massachusetts, United States of America
| | - Luxuan Guo
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Christian Berrios
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Program in Virology, Harvard University Graduate School of Arts and Sciences, Division of Medical Sciences, Boston, Massachusetts, United States of America
| | - Ying Zhang
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - Michael A. Calderwood
- Genomic Analysis of Network Perturbations Center of Excellence in Genomic Science, Center for Cancer Systems Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Center for Cancer Systems Biology and Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Soundarapandian Velmurgan
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
| | - Jingwei Cheng
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Jarrod A. Marto
- Genomic Analysis of Network Perturbations Center of Excellence in Genomic Science, Center for Cancer Systems Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Blais Proteomics Center and Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - David E. Hill
- Genomic Analysis of Network Perturbations Center of Excellence in Genomic Science, Center for Cancer Systems Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Center for Cancer Systems Biology and Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Michael E. Cusick
- Genomic Analysis of Network Perturbations Center of Excellence in Genomic Science, Center for Cancer Systems Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Center for Cancer Systems Biology and Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Marc Vidal
- Genomic Analysis of Network Perturbations Center of Excellence in Genomic Science, Center for Cancer Systems Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Center for Cancer Systems Biology and Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Laurence Florens
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - Michael P. Washburn
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
- Department of Pathology and Laboratory Medicine, The University of Kansas Medical Center, Kansas City, Kansas, United States of America
| | - Larisa Litovchick
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Genomic Analysis of Network Perturbations Center of Excellence in Genomic Science, Center for Cancer Systems Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - James A. DeCaprio
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Program in Virology, Harvard University Graduate School of Arts and Sciences, Division of Medical Sciences, Boston, Massachusetts, United States of America
- Genomic Analysis of Network Perturbations Center of Excellence in Genomic Science, Center for Cancer Systems Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
- * E-mail:
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An ac34 deletion mutant of Autographa californica nucleopolyhedrovirus exhibits delayed late gene expression and a lack of virulence in vivo. J Virol 2012; 86:10432-43. [PMID: 22787232 DOI: 10.1128/jvi.00779-12] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Ac34 and its homologs are highly conserved in all sequenced alphabaculoviruses. In this paper, we show that ac34 transcripts were detected from 6 to 48 h postinfection (p.i.) in Autographa californica nucleopolyhedrovirus (AcMNPV)-infected Sf9 cells. Ac34 localized to both the cytoplasm and the nuclei of infected cells but was not a viral structural protein. To determine the function of ac34 in the viral life cycle, an ac34 knockout AcMNPV (vAc34KO) was constructed. Compared with wild-type and repair viruses, vAc34KO exhibited an approximately 100-fold reduction in infectious virus production. Further investigations showed that the ac34 deletion did not affect the replication of viral DNA, polyhedron formation, or nucleocapsid assembly but delayed the expression of late genes, such as vp39, 38k, and p6.9. Bioassays revealed that vAc34KO was unable to establish a fatal infection in Trichoplusia ni larvae via per os inoculation. Few infectious progeny viruses were detected in the hemolymph of the infected larvae, indicating that the replication of vAc34KO was attenuated. These results suggest that Ac34 is an activator protein that promotes late gene expression and is essential for the pathogenicity of AcMNPV.
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Proteasome-dependent disruption of the E3 ubiquitin ligase anaphase-promoting complex by HCMV protein pUL21a. PLoS Pathog 2012; 8:e1002789. [PMID: 22792066 PMCID: PMC3390409 DOI: 10.1371/journal.ppat.1002789] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2011] [Accepted: 05/22/2012] [Indexed: 01/27/2023] Open
Abstract
The anaphase-promoting complex (APC) is an E3 ubiquitin ligase which controls ubiquitination and degradation of multiple cell cycle regulatory proteins. During infection, human cytomegalovirus (HCMV), a widespread pathogen, not only phosphorylates the APC coactivator Cdh1 via the multifunctional viral kinase pUL97, it also promotes degradation of APC subunits via an unknown mechanism. Using a proteomics approach, we found that a recently identified HCMV protein, pUL21a, interacted with the APC. Importantly, we determined that expression of pUL21a was necessary and sufficient for proteasome-dependent degradation of APC subunits APC4 and APC5. This resulted in APC disruption and required pUL21a binding to the APC. We have identified the proline-arginine amino acid pair at residues 109–110 in pUL21a to be critical for its ability to bind and regulate the APC. A point mutant virus in which proline-arginine were mutated to alanines (PR-AA) grew at wild-type levels. However, a double mutant virus in which the viral ability to regulate the APC was abrogated by both PR-AA point mutation and UL97 deletion was markedly more attenuated compared to the UL97 deletion virus alone. This suggests that these mutations are synthetically lethal, and that HCMV exploits two viral factors to ensure successful disruption of the APC to overcome its restriction on virus infection. This study reveals the HCMV protein pUL21a as a novel APC regulator and uncovers a unique viral mechanism to subvert APC activity. In this study, we report an intriguing mechanism used by human cytomegalovirus (HCMV) to regulate a cellular E3 ubiquitin ligase, the anaphase promoting complex (APC). The ability to hijack the ubiquitin-proteasome system for regulating protein degradation and to manipulate the cell cycle for viral genome synthesis is critical in many viral infections. The APC is a master cell cycle modulator that targets a number of regulatory proteins for proteasomal degradation. It can prevent cells from entry into S-phase, thus creating a hindrance for viruses needing to coerce cells into a cellular environment favorable for viral DNA synthesis. We have identified an HCMV protein, pUL21a, which uses a seemingly counterintuitive mechanism to regulate the APC. It interacts with the APC to target the subunits of this ubiquitin ligase for proteasomal degradation. This causes disruption of the complex and reduces its activity. Furthermore, a virus lacking pUL21a and pUL97, which is another HCMV-encoded APC regulator, was highly attenuated when compared to loss of UL97 alone, suggesting that HCMV uses two proteins to fully disarm the APC. This study identifies a herpesviral protein that uses a unique, proteasome-dependent mechanism to regulate the activity of this prominent cellular E3 ubiquitin ligase.
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Van Ghelue M, Khan MTH, Ehlers B, Moens U. Genome analysis of the new human polyomaviruses. Rev Med Virol 2012; 22:354-77. [PMID: 22461085 DOI: 10.1002/rmv.1711] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2011] [Revised: 01/31/2012] [Accepted: 02/08/2012] [Indexed: 11/09/2022]
Abstract
Polyomaviridae is a growing family of naked, double-stranded DNA viruses that infect birds and mammals. The last few years, several new members infecting birds or primates have been discovered, including seven human polyomaviruses: KI, WU, Merkel cell polyomavirus, HPyV6, HPyV7, trichodysplasia spinulosa-associated polyomavirus, and HPyV9. In addition, DNA and antibodies against the monkey lymphotropic polyomavirus have been detected in humans, indicating that this virus can also infect man. However, little is known about the route of infection, transmission, cell tropism, and, with the exception of Merkel cell polyomavirus and trichodysplasia spinulosa-associated polyomavirus, the pathogenicity of these viruses. This review compares the genomes of these emerging human polyomaviruses with previously known polyomaviruses detected in man, reports mutations in different isolates, and predicts structural and functional properties of their viral proteins.
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Affiliation(s)
- Marijke Van Ghelue
- Department of Medical Genetics, University Hospital Northern-Norway, Tromsø, Norway
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Abstract
The cullin family of ubiquitin ligases can potentially assemble hundreds of RING-type E3 complexes (CRLs) by utilizing different substrate receptors that share common interaction domains. Cullin receptors dictate substrate specificity, and cullin-mediated substrate degradation controls a wide range of cellular processes, including proliferation, differentiation, and apoptosis. Dysregulation of cullin activity has been shown to contribute to oncogenesis through the accumulation of oncoproteins or the excessive degradation of tumor suppressors. In this review, we will discuss cullin complexes and their substrates, the regulatory pathways that affect cullin activity, and the mechanisms by which cullins may facilitate or inhibit carcinogenesis.
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Affiliation(s)
- Jennifer Lee
- Department of Pathology and Laboratory Medicine, Weill Cornell Medical College and Weill Cornell Graduate School of Medical Sciences, New York, NY, USA
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Gustin JK, Moses AV, Früh K, Douglas JL. Viral takeover of the host ubiquitin system. Front Microbiol 2011; 2:161. [PMID: 21847386 PMCID: PMC3147166 DOI: 10.3389/fmicb.2011.00161] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2011] [Accepted: 07/14/2011] [Indexed: 01/29/2023] Open
Abstract
Like the other more well-characterized post-translational modifications (phosphorylation, methylation, acetylation, acylation, etc.), the attachment of the 76 amino acid ubiquitin (Ub) protein to substrates has been shown to govern countless cellular processes. As obligate intracellular parasites, viruses have evolved the capability to commandeer many host processes in order to maximize their own survival, whether it be to increase viral production or to ensure the long-term survival of latently infected host cells. The first evidence that viruses could usurp the Ub system came from the DNA tumor viruses and Adenoviruses, each of which use Ub to dysregulate the host cell cycle (Scheffner et al., 1990; Querido et al., 2001). Today, the list of viruses that utilize Ub includes members from almost every viral class, encompassing both RNA and DNA viruses. Among these, there are examples of Ub usage at every stage of the viral life cycle, involving both ubiquitination and de-ubiquitination. In addition to viruses that merely modify the host Ub system, many of the large DNA viruses encode their own Ub modifying machinery. In this review, we highlight the latest discoveries regarding the myriad ways that viruses utilize Ub to their advantage.
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Affiliation(s)
- Jean K Gustin
- Vaccine and Gene Therapy Institute, Oregon Health & Science University Beaverton, OR, USA
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Ou HD, May AP, O'Shea CC. The critical protein interactions and structures that elicit growth deregulation in cancer and viral replication. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2011; 3:48-73. [PMID: 21061422 DOI: 10.1002/wsbm.88] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
One of the greatest challenges in biomedicine is to define the critical targets and network interactions that are subverted to elicit growth deregulation in human cells. Understanding and developing rational treatments for cancer requires a definition of the key molecular targets and how they interact to elicit the complex growth deregulation phenotype. Viral proteins provide discerning and powerful probes to understand both how cells work and how they can be manipulated using a minimal number of components. The small DNA viruses have evolved to target inherent weaknesses in cellular protein interaction networks to hijack the cellular DNA and protein replication machinery. In the battle to escape the inevitability of senescence and programmed cell death, cancers have converged on similar mechanisms, through the acquisition and selection of somatic mutations that drive unchecked cellular replication in tumors. Understanding the dynamic mechanisms through which a minimal number of viral proteins promote host cells to undergo unscheduled and pathological replication is a powerful strategy to identify critical targets that are also disrupted in cancer. Viruses can therefore be used as tools to probe the system-wide protein-protein interactions and structures that drive growth deregulation in human cells. Ultimately this can provide a path for developing system context-dependent therapeutics. This review will describe ongoing experimental approaches using viruses to study pathways deregulated in cancer, with a particular focus on viral cellular protein-protein interactions and structures.
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Affiliation(s)
- Horng D Ou
- Molecular and Cell Biology Laboratory, Salk Institute for Biological Studies, La Jolla, CA, USA
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36
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Nucleolar targeting of the fbw7 ubiquitin ligase by a pseudosubstrate and glycogen synthase kinase 3. Mol Cell Biol 2011; 31:1214-24. [PMID: 21220517 DOI: 10.1128/mcb.01347-10] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
E3 ubiquitin ligases catalyze protein degradation by the ubiquitin-proteasome system, and their activity is tightly controlled. One level of regulation involves subcellular localization, and the Fbw7 tumor suppressor exemplifies this type of control. Fbw7 is the substrate-binding component of an SCF ubiquitin ligase that degrades critical oncoproteins. Alternative splicing produces three Fbw7 protein isoforms that occupy distinct compartments: Fbw7α is nucleoplasmic, Fbw7β is cytoplasmic, and Fbw7γ is nucleolar. We found that cancer-associated Fbw7 mutations that disrupt substrate binding prevent Fbw7γ nucleolar localization, implicating a substrate-like interaction in nucleolar targeting. We identified EBNA1-binding protein 2 (Ebp2) as the critical nucleolar factor that directly mediates Fbw7 nucleolar targeting. Ebp2 binds to Fbw7 like a substrate, and this is mediated by an Ebp2 degron that is phosphorylated by glycogen synthase kinase 3. However, despite these canonical substrate-like interactions, Fbw7 binding is largely uncoupled from Ebp2 turnover in vivo. Ebp2 thus acts like a pseudosubstrate that directly recruits Fbw7 to nucleoli.
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Washington MN, Kim JS, Weigel NL. 1α,25-dihydroxyvitamin D3 inhibits C4-2 prostate cancer cell growth via a retinoblastoma protein (Rb)-independent G1 arrest. Prostate 2011; 71:98-110. [PMID: 20632309 PMCID: PMC2966519 DOI: 10.1002/pros.21226] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
BACKGROUND The active metabolite of vitamin D, 1α,25-dihydroxyvitamin D(3) (1,25D) reduces the growth of several prostate cancer cell lines, most commonly by inducing a cell-cycle arrest in G(1). This is mediated, in part, through down-regulation of c-Myc, a positive regulator of the transcription factor, E2F. There is evidence that prostate cancer cells lacking functional retinoblastoma protein (Rb), a negative regulator of E2F activity, are poorly responsive to 1,25D treatment. Since up to 60% of prostate cancers demonstrate a loss of heterozygosity for Rb, we sought to determine whether Rb is required for the growth inhibitory effects of 1,25D. METHODS Using siRNA, Rb was reduced in C4-2 prostate cancer cells, and the response of cells to 1,25D treatment or depletion of c-myc measured by [(3)H]-thymidine incorporation and flow cytometry. The effects of 1,25D treatment on E2F levels and activity, and E2F target gene expression were also measured. RESULTS 1,25D treatment and c-Myc depletion both cause a G(1) arrest inhibiting C4-2 cell proliferation independently of Rb. 1,25D reduces c-Myc expression and causes a decrease in E2F and E2F target genes. Bcl-2, an E2F target and positive regulator of C4-2 cell growth, also is down-regulated by 1,25D independently of Rb. CONCLUSIONS Redundant growth inhibitory pathways compensate for the loss of Rb, and tumors lacking functional Rb may be responsive to 1,25D.
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Affiliation(s)
- Michele N Washington
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas 77030 USA
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Davey NE, Travé G, Gibson TJ. How viruses hijack cell regulation. Trends Biochem Sci 2010; 36:159-69. [PMID: 21146412 DOI: 10.1016/j.tibs.2010.10.002] [Citation(s) in RCA: 277] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2010] [Revised: 10/27/2010] [Accepted: 10/28/2010] [Indexed: 12/18/2022]
Abstract
Viruses, as obligate intracellular parasites, are the pathogens that have the most intimate relationship with their host, and as such, their genomes have been shaped directly by interactions with the host proteome. Every step of the viral life cycle, from entry to budding, is orchestrated through interactions with cellular proteins. Accordingly, viruses will hijack and manipulate these proteins utilising any achievable mechanism. Yet, the extensive interactions of viral proteomes has yielded a conundrum: how do viruses commandeer so many diverse pathways and processes, given the obvious spatial constraints imposed by their compact genomes? One important approach is slowly being revealed, the extensive mimicry of host protein short linear motifs (SLiMs).
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Affiliation(s)
- Norman E Davey
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany.
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Interaction and co-localization of JC virus large T antigen and the F-box protein β-transducin-repeat containing protein. Virology 2010; 410:119-28. [PMID: 21106215 DOI: 10.1016/j.virol.2010.10.038] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2010] [Revised: 09/29/2010] [Accepted: 10/29/2010] [Indexed: 11/24/2022]
Abstract
Lytic infection and transformation of cultured cells by JC virus (JCV) require five tumor proteins, which interact with factors regulating critical cellular processes. We demonstrate that JCV large T antigen (TAg) binds the F-box proteins β-transducin-repeat containing protein-1 and 2 (βTrCP1/2). These interactions involve a phosphodegron (DpSGX(2-4)pS) found in βTrCP substrates. TAg stability is unaltered, suggesting TAg is a pseudo-substrate. βTrCP and TAg co-localize in the cytoplasm, and a functional SCF complex is required. We examined whether TAg influences the levels of β-catenin, a βTrCP substrate. We were unable to demonstrate that TAg elevates β-catenin as previously reported, and a mutant TAg unable to bind βTrCP also had no detectable effect on β-catenin stability. Results presented in this study link JCV TAg to the cellular degradation complex, SCF(βTrCP1/2). Proteasomal degradation is essential for proper regulation of cellular functions, and interference with proteasomal pathways highlights possible JCV pathogenic and oncogenic mechanisms.
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40
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Regulation of the tumour suppressor Fbw7α by PKC-dependent phosphorylation and cancer-associated mutations. Biochem J 2010; 432:77-87. [DOI: 10.1042/bj20100799] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Fbw7 (F-box WD40 protein 7) is a major tumour suppressor, which mediates the degradation of several potent oncogenes. PKC (protein kinase C) comprises a serine/threonine kinase family that can promote transformation when dysregulated. In the present study, we investigated the relationship between Fbw7 and PKC. Multiple members of the PKC superfamily interact with the substrate-binding domain of Fbw7. However, we find no evidence for Fbw7-mediated degradation of PKC. Instead, we demonstrate that Fbw7 is a novel substrate for PKC. Two residues within the isoform-specific N-terminus of Fbw7α are phosphorylated in a PKC-dependent manner, both in vitro and in mammalian cells (Ser10 and Ser18). Mutational analyses reveal that phosphorylation of Fbw7α at Ser10 can regulate its nuclear localization. Cancer-associated mutations in nearby residues (K11R and the addition of a proline residue at position 16) influence Fbw7α localization in a comparable manner, suggesting that mislocalization of this protein may be of pathological significance. Together these results provide evidence for both physical and functional interactions between the PKC and Fbw7 families, and yield insights into the isoform-specific regulation of Fbw7α.
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Isobe T, Hattori T, Kitagawa K, Uchida C, Kotake Y, Kosugi I, Oda T, Kitagawa M. Adenovirus E1A inhibits SCF(Fbw7) ubiquitin ligase. J Biol Chem 2009; 284:27766-27779. [PMID: 19679664 DOI: 10.1074/jbc.m109.006809] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The SCF(Fbw7) ubiquitin ligase complex plays important roles in cell growth, survival, and differentiation via the ubiquitin-proteasome-mediated regulation of protein stability. Fbw7 (also known as Fbxw7, Sel-10, hCdc4, or hAgo), a substrate recognition subunit of SCF(Fbw7) ubiquitin ligase, facilitates the degradation of several proto-oncogene products by the proteasome. Given that mutations in Fbw7 are found in various types of human cancers, Fbw7 is considered to be a potent tumor suppressor. In the present study, we show that E1A, an oncogene product derived from adenovirus, interferes with the activity of the SCF(Fbw7) ubiquitin ligase. E1A interacted with SCF(Fbw7) and attenuated the ubiquitylation of its target proteins in vivo. Furthermore, using in vitro purified SCF(Fbw7) component proteins, we found that E1A directly bound to Roc1/Rbx1 and CUL1 and that E1A inhibited the ubiquitin ligase activity of the Roc1/Rbx1-CUL1 complex but not that of another RING-type ubiquitin ligase, Mdm2. Ectopically expressed E1A interacted with cellular endogenous Roc1/Rbx1 and CUL1 and decelerated the degradation of several protooncogene products that were degraded by SCF(Fbw7) ubiquitin ligase. Moreover, after wild-type adenovirus infection, adenovirus-derived E1A interacted with endogenous Roc1/Rbx1 and decelerated degradation of the endogenous target protein of SCF(Fbw7). These observations demonstrated that E1A perturbs protein turnover regulated by SCF(Fbw7) through the inhibition of SCF(Fbw7) ubiquitin ligase. Our findings may help to explain the mechanism whereby adenovirus infection induces unregulated proliferation.
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Affiliation(s)
- Tomoyasu Isobe
- Department of Biochemistry 1, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan
| | - Takayuki Hattori
- Department of Biochemistry 1, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan
| | - Kyoko Kitagawa
- Department of Biochemistry 1, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan
| | - Chiharu Uchida
- Department of Biochemistry 1, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan
| | - Yojiro Kotake
- Department of Biochemistry 1, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan
| | - Isao Kosugi
- Second Department of Pathology, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan
| | - Toshiaki Oda
- Department of Biochemistry 1, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan
| | - Masatoshi Kitagawa
- Department of Biochemistry 1, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan.
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Cheng J, DeCaprio JA, Fluck MM, Schaffhausen BS. Cellular transformation by Simian Virus 40 and Murine Polyoma Virus T antigens. Semin Cancer Biol 2009; 19:218-28. [PMID: 19505649 PMCID: PMC2694755 DOI: 10.1016/j.semcancer.2009.03.002] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2009] [Revised: 03/19/2009] [Accepted: 03/20/2009] [Indexed: 01/09/2023]
Abstract
Simian Virus 40 (SV40) and Mouse Polyoma Virus (PY) are small DNA tumor viruses that have been used extensively to study cellular transformation. The SV40 early region encodes three tumor antigens, large T (LT), small T (ST) and 17KT that contribute to cellular transformation. While PY also encodes LT and ST, the unique middle T (MT) generates most of the transforming activity. SV40 LT mediated transformation requires binding to the tumor suppressor proteins Rb and p53 in the nucleus and ST binding to the protein phosphatase PP2A in the cytoplasm. SV40 LT also binds to several additional cellular proteins including p300, CBP, Cul7, IRS1, Bub1, Nbs1 and Fbxw7 that contribute to viral transformation. PY MT transformation is dependent on binding to PP2A and the Src family protein tyrosine kinases (PTK) and assembly of a signaling complex on cell membranes that leads to transformation in a manner similar to Her2/neu. Phosphorylation of MT tyrosine residues activates key signaling molecules including Shc/Grb2, PI3K and PLCgamma1. The unique contributions of SV40 LT and ST and PY MT to cellular transformation have provided significant insights into our understanding of tumor suppressors, oncogenes and the process of oncogenesis.
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Affiliation(s)
- Jingwei Cheng
- Department of Medical Oncology, Dana-Farber Cancer Institute; Department of Medicine, Brigham and Women’s Hospital; and Harvard Medical School, Boston, MA 02115
| | - James A. DeCaprio
- Department of Medical Oncology, Dana-Farber Cancer Institute; Department of Medicine, Brigham and Women’s Hospital; and Harvard Medical School, Boston, MA 02115
- Center for Applied Cancer Science, Dana-Farber Cancer Institute, Boston, MA 02115
| | - Michele M. Fluck
- Department of Microbiology and Molecular Genetics, Interdepartmental Program in Cell and Molecular Biology, Michigan State University, East Lansing, MI 48824
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Isaacson MK, Ploegh HL. Ubiquitination, ubiquitin-like modifiers, and deubiquitination in viral infection. Cell Host Microbe 2009; 5:559-70. [PMID: 19527883 PMCID: PMC7103382 DOI: 10.1016/j.chom.2009.05.012] [Citation(s) in RCA: 224] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2009] [Accepted: 05/27/2009] [Indexed: 11/26/2022]
Abstract
Ubiquitin is important for nearly every aspect of cellular physiology. All viruses rely extensively on host machinery for replication; therefore, it is not surprising that viruses connect to the ubiquitin pathway at many levels. Viral involvement with ubiquitin occurs either adventitiously because of the unavoidable usurpation of cellular processes, or for some specific purpose selected for by the virus to enhance viral replication. Here, we review current knowledge of how the ubiquitin pathway alters viral replication and how viruses influence the ubiquitin pathway to enhance their own replication.
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Affiliation(s)
- Marisa K Isaacson
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA
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44
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A structure-guided mutational analysis of simian virus 40 large T antigen: identification of surface residues required for viral replication and transformation. J Virol 2009; 83:8781-8. [PMID: 19553311 DOI: 10.1128/jvi.00621-09] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Simian virus 40 large T antigen (TAg) transforms cells in culture and induces tumors in rodents. Genetic studies suggest that TAg interaction with the chaperone hsp70 and tumor suppressors pRb and p53 may not be sufficient to elicit complete transformation of cells. In order to identify additional cellular factors important for transformation, we designed mutations on the solvent-exposed surface of TAg. We hypothesized that surface residues would interact directly with cellular targets and that the mutation of these residues might disrupt this interaction without perturbing TAg's global structure. Using structural data, we identified 61 amino acids on the surface of TAg. Each surface amino acid was changed to an alanine. Furthermore, five patches containing clusters of charged amino acids on the surface of TAg were identified. Within these patches, we selectively mutated three to four charged amino acids and thus generated five mutants (patch mutants 1 to 5). We observed that while patch mutants 3 and 4 induced foci in REF52 cells, patch mutants 1 and 2 were deficient in focus formation. We determined that the patch 1 mutant is defective in p53 binding, thus explaining its defect in transformation. The patch 2 mutant can interact with the Rb family members and p53 like wild-type TAg but is unable to transform cells, suggesting that it is defective for action on an unknown cellular target essential for transformation. Our results suggest that the histone acetyltransferase CBP/p300 is one of the potential targets affected by the mutations in patch 2.
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45
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Wickliffe K, Williamson A, Jin L, Rape M. The multiple layers of ubiquitin-dependent cell cycle control. Chem Rev 2009; 109:1537-48. [PMID: 19146381 PMCID: PMC3206288 DOI: 10.1021/cr800414e] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Affiliation(s)
- Katherine Wickliffe
- University of California at Berkeley, Department of Molecular and Cell Biology, Berkeley, CA 94720, USA
| | - Adam Williamson
- University of California at Berkeley, Department of Molecular and Cell Biology, Berkeley, CA 94720, USA
| | - Lingyan Jin
- University of California at Berkeley, Department of Molecular and Cell Biology, Berkeley, CA 94720, USA
| | - Michael Rape
- University of California at Berkeley, Department of Molecular and Cell Biology, Berkeley, CA 94720, USA
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Delk NA, Hunt KK, Keyomarsi K. Altered subcellular localization of tumor-specific cyclin E isoforms affects cyclin-dependent kinase 2 complex formation and proteasomal regulation. Cancer Res 2009; 69:2817-25. [PMID: 19318554 DOI: 10.1158/0008-5472.can-08-4182] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In tumors, alternative translation and posttranslational proteolytic cleavage of full-length cyclin E (EL) produces tumorigenic low molecular weight cyclin E (LMW-E) isoforms that lack a portion of the EL amino-terminus containing a nuclear localization sequence. Therefore, we hypothesized that LMW-E isoforms have altered subcellular localization. To explore our hypothesis, we compared EL versus LMW-E localization in cell lysates and in vivo using fractionation and protein complementation assays. Our results reveal that LMW-E isoforms preferentially accumulate in the cytoplasm where they bind the cyclin E kinase partner, cyclin-dependent kinase 2 (Cdk2), and have associated kinase activity. The nuclear ubiquitin ligase Fbw7 targets Cdk2-bound cyclin E for degradation; thus, we examined if altered subcellular localization affected LMW-E degradation. We found that cytoplasmic LMW-E/Cdk2 was less susceptible to Fbw7-mediated degradation. One implication of our findings is that altered LMW-E and LMW-E/Cdk2 subcellular localization may lead to aberrant LMW-E protein interactions, regulation, and activity, ultimately contributing to LMW-E tumorigenicity.
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Affiliation(s)
- Nikki A Delk
- Department of Experimental Radiation Oncology, University of Texas at M. D. Anderson Cancer Center, Houston Texas 77030, USA
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Blanchette P, Branton PE. Manipulation of the ubiquitin-proteasome pathway by small DNA tumor viruses. Virology 2008; 384:317-23. [PMID: 19013629 DOI: 10.1016/j.virol.2008.10.005] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2008] [Accepted: 10/03/2008] [Indexed: 10/21/2022]
Abstract
Viruses have evolved to use cellular pathways to their advantage, including the ubiquitin-proteasome pathway of protein degradation. In several cases, viruses produce proteins that highjack cellular E3 ligases to modify their substrate specificity in order to eliminate unwanted cellular proteins, in particular inhibitors of the cell cycle. They can also inhibit E3 ligase to prevent specific protein degradation or even use the system to control the level of expression of their own proteins. In this review we explore the specific ways that small DNA tumor viruses exploit the ubiquitin-proteasome pathway for their own benefit.
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Tan Y, Sangfelt O, Spruck C. The Fbxw7/hCdc4 tumor suppressor in human cancer. Cancer Lett 2008; 271:1-12. [PMID: 18541364 DOI: 10.1016/j.canlet.2008.04.036] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2008] [Revised: 04/23/2008] [Accepted: 04/23/2008] [Indexed: 12/11/2022]
Abstract
Fbxw7/hCdc4 is a member of the F-box family of proteins, which function as interchangeable substrate recognition components of the SCF ubiquitin ligases. SCF(Fbxw7/hCdc4) targets several important oncoproteins including c-Myc, c-Jun, cyclin E1, and Notch, for ubiquitin-dependent proteolysis. Recent studies have shown that FBXW7/hCDC4 is mutated in a variety of human tumor types, suggesting that it is a general tumor suppressor in human cancer. Alteration of Fbxw7/hCdc4 function is linked to defects in differentiation, cellular proliferation, and genetic instability. In this review, we summarize what is known about Fbxw7/hCdc4-mediated degradation in the regulation of cellular proliferation and discuss how alteration of its function contributes to human tumorigenesis.
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Affiliation(s)
- YingMeei Tan
- Department of Tumor Cell Biology, Sidney Kimmel Cancer Center, San Diego, CA 92121, USA
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Finkin S, Aylon Y, Anzi S, Oren M, Shaulian E. Fbw7 regulates the activity of endoreduplication mediators and the p53 pathway to prevent drug-induced polyploidy. Oncogene 2008; 27:4411-21. [PMID: 18391985 DOI: 10.1038/onc.2008.77] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Fbw7 is a tumor suppressor that is mutated in numerous cancers. It encodes an E3 ubiquitin ligase, whose ability to decrease the levels of pivotal regulators of cell growth and proliferation underlies its tumor suppressor function. Here, we explore the consequences of Fbw7 inactivation on the outcome of chemotherapeutic treatments. When exposed to spindle toxins such as vinblastine and taxol, Fbw7-deficient cells undergo extensive mitotic slippage and endoreduplication, rendering them polyploid. A combined deregulation of several Fbw7 target proteins is required for this phenotype. Specifically, elevated expression of cyclin E and Aurora A in Fbw7-deficient cells is required for drug-induced polyploidy. However, overexpression of either cyclin E or Aurora A alone is not sufficient for drug-induced polyploidy. In addition, we demonstrate that Fbw7 deficiency limits the ability of p53 to respond to mitotic toxins but not to DNA damage. Furthermore, Fbw7 expression regulates the p53-dependent induction of genes such as Lats2 and p21 in response to vinblastine. Hence, we suggest that Fbw7 serves as a master regulator of the mitotic and tetraploidy checkpoints.
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Affiliation(s)
- S Finkin
- Department of Experimental Medicine and Cancer Research, Hebrew University Medical School, Jerusalem, Israel
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Epstein-Barr virus nuclear antigen 3C interacts with and enhances the stability of the c-Myc oncoprotein. J Virol 2008; 82:4082-90. [PMID: 18256156 DOI: 10.1128/jvi.02500-07] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Epstein-Barr virus (EBV) was the first human DNA virus to be associated with cancer. Its oncogenic potential was further demonstrated by its ability to transform primary B lymphocytes in vitro. EBV nuclear antigen 3C (EBNA3C) is one of a small subset of latent antigens critical for the transformation of human primary B lymphocytes. Although EBNA3C has been shown to modulate several cellular functions, additional targets involved in cellular transformation remain to be explored. EBNA3C can recruit key components of the SCF(Skp2) ubiquitin ligase complex. In this report, we show that EBNA3C residues 130 to 190, previously shown to bind to the SCF(Skp2) complex, also can strongly associate with the c-Myc oncoprotein. Additionally, the interaction of EBNA3C with c-Myc was mapped to the region of c-Myc that includes the highly conserved Skp2 binding domain. Skp2 has been shown to regulate c-Myc stability and also has been shown to function as a coactivator of transcription for c-Myc target genes. We now show that the EBV latent oncoprotein EBNA3C can stabilize c-Myc and that the recruitment of both c-Myc and its cofactor Skp2 to c-Myc-dependent promoters can enhance c-Myc-dependent transcription. This same region of EBNA3C also recruits and modulates the activity of retinoblastoma and p27, both major regulators of the mammalian cell cycle. The inclusion of c-Myc in the group of cellular targets modulated by this domain further accentuates the importance of these critical residues of EBNA3C in bypassing the cell cycle checkpoints.
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