1
|
Fan Y, Sanyal S, Bruzzone R. Breaking Bad: How Viruses Subvert the Cell Cycle. Front Cell Infect Microbiol 2018; 8:396. [PMID: 30510918 PMCID: PMC6252338 DOI: 10.3389/fcimb.2018.00396] [Citation(s) in RCA: 90] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Accepted: 10/22/2018] [Indexed: 01/10/2023] Open
Abstract
Interactions between the host and viruses during the course of their co-evolution have not only shaped cellular function and the immune system, but also the counter measures employed by viruses. Relatively small genomes and high replication rates allow viruses to accumulate mutations and continuously present the host with new challenges. It is therefore, no surprise that they either escape detection or modulate host physiology, often by redirecting normal cellular pathways to their own advantage. Viruses utilize a diverse array of strategies and molecular targets to subvert host cellular processes, while evading detection. These include cell-cycle regulation, major histocompatibility complex-restricted antigen presentation, intracellular protein transport, apoptosis, cytokine-mediated signaling, and humoral immune responses. Moreover, viruses routinely manipulate the host cell cycle to create a favorable environment for replication, largely by deregulating cell cycle checkpoints. This review focuses on our current understanding of the molecular aspects of cell cycle regulation that are often targeted by viruses. Further study of their interactions should provide fundamental insights into cell cycle regulation and improve our ability to exploit these viruses.
Collapse
Affiliation(s)
- Ying Fan
- HKU-Pasteur Research Pole, LKS Faculty of Medicine, School of Public Health, The University of Hong Kong, Hong Kong, Hong Kong.,MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Sumana Sanyal
- HKU-Pasteur Research Pole, LKS Faculty of Medicine, School of Public Health, The University of Hong Kong, Hong Kong, Hong Kong.,LKS Faculty of Medicine, School of Biomedical Sciences, The University of Hong Kong, Hong Kong, Hong Kong
| | - Roberto Bruzzone
- HKU-Pasteur Research Pole, LKS Faculty of Medicine, School of Public Health, The University of Hong Kong, Hong Kong, Hong Kong.,Department of Cell Biology and Infection, Institut Pasteur, Paris, France
| |
Collapse
|
2
|
Stuber G, Flaberg E, Petranyi G, Otvös R, Rökaeus N, Kashuba E, Wiman KG, Klein G, Szekely L. PRIMA-1MET induces nucleolar translocation of Epstein-Barr virus-encoded EBNA-5 protein. Mol Cancer 2009; 8:23. [PMID: 19323829 PMCID: PMC2667484 DOI: 10.1186/1476-4598-8-23] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2008] [Accepted: 03/26/2009] [Indexed: 12/14/2022] Open
Abstract
The low molecular weight compound, PRIMA-1MET restores the transcriptional transactivation function of certain p53 mutants in tumor cells. We have previously shown that PRIMA-1MET induces nucleolar translocation of p53, PML, CBP and Hsp70. The Epstein-Barr virus encoded, latency associated antigen EBNA-5 (also known as EBNA-LP) is required for the efficient transformation of human B lymphocytes by EBV. EBNA-5 associates with p53-hMDM2-p14ARF complexes. EBNA-5 is a nuclear protein that translocates to the nucleolus upon heat shock or inhibition of proteasomes along with p53, hMDM2, Hsp70, PML and proteasome subunits. Here we show that PRIMA-1MET induces the nucleolar translocation of EBNA-5 in EBV transformed B lymphoblasts and in transfected tumor cells. The PRIMA-1MET induced translocation of EBNA-5 is not dependent on the presence of mutant p53. It also occurs in p53 null cells or in cells that express wild type p53. Both the native and the EGFP or DSRed conjugated EBNA-5 respond to PRIMA-1MET treatment in the same way. Image analysis of DSRed-EBNA-5 expressing cells, using confocal fluorescence time-lapse microscopy showed that the nucleolar translocation requires several hours to complete. FRAP (fluorescence recovery after photobleaching) and FLIP (fluorescence loss in photobleaching) measurements on live cells showed that the nucleolar translocation was accompanied by the formation of EBNA-5 aggregates. The process is reversible since the aggregates are dissolved upon removal of PRIMA-1MET. Our results suggest that mutant p53 is not the sole target of PRIMA-1MET. We propose that PRIMA-1MET may reversibly inhibit cellular chaperons that prevent the aggregation of misfolded proteins, and that EBNA-5 may serve as a surrogate drug target for elucidating the precise molecular action of PRIMA-1MET.
Collapse
Affiliation(s)
- György Stuber
- Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institute, Stockholm, Sweden.
| | | | | | | | | | | | | | | | | |
Collapse
|
3
|
Epstein-Barr virus in lymphoproliferative processes: an update for the diagnostic pathologist. Adv Anat Pathol 2009; 16:40-55. [PMID: 19098466 DOI: 10.1097/pap.0b013e3181916029] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The Epstein-Barr virus is an orally transmitted herpesvirus that is widespread in human populations and exhibits marked B-cell tropism. It is associated with more human neoplasms than any other known virus, and its role in the pathogenesis of such neoplasms has been the subject of intense investigation. This review presents an overview and update of the biology of Epstein-Barr virus and the diagnostic features of lymphoproliferative disorders associated with this intriguing human pathogen.
Collapse
|
4
|
Forsman A, Rüetschi U, Ekholm J, Rymo L. Identification of intracellular proteins associated with the EBV-encoded nuclear antigen 5 using an efficient TAP procedure and FT-ICR mass spectrometry. J Proteome Res 2008; 7:2309-19. [PMID: 18457437 DOI: 10.1021/pr700769e] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Epstein-Barr virus nuclear antigen 5 (EBNA5) is one of the first viral proteins detected after primary EBV infection and has been shown to be required for efficient transformation of B lymphocytes. EBNA5 is a protein that has many suggested functions but the underlying biology remains to be clarified. To gain further insight into the biological roles of the proposed multifunctional EBNA5, we isolated EBNA5 containing protein complexes using a modified tandem affinity purification (TAP) method and identified the protein components by LC-MS/MS analysis of tryptic digests on a LTQ-FT-ICR mass spectrometer. The modified TAP tag contained a Protein A domain and a StrepTagII sequence separated by two Tobacco Etch Virus protease cleavage sites and was fused to the C-terminus of EBNA5. Our results confirmed the wide applicability of this two-step affinity purification strategy for purification of protein complexes in mammalian cells. A total of 147 novel putative EBNA5 interaction partners were identified, 37 of which were validated with LC-MS/MS in split-tag experiments or in co-immuno precipitates from HEK293 cell extracts. This subgroup included the Bcl2-associated Athanogene 2 (BAG2) co-chaperone involved in protein folding and renaturation, the 26S proteasome subunit 2 involved in regulation of ubiquitin/proteasome protein degradation, and the heterogeneous ribonucleoprotein M (hnRNP M) involved in pre-mRNA processing. These EBNA5 interactors were further verified by co-immunoprecipitations from cell extracts of three EBV-positive lymphoblastoid lines. The combination of the Hsp70, Hsc70, BAG2 and 26S proteasome subunit 2 interactors suggests that EBNA5 might have a functional relationship with protein quality control systems that recognize proteins with abnormal structures and either refold them to normal conformation or target them for degradation. Our study also confirms previously identified interactors including HA95, Hsp70, Hsc70, Hsp27, HAX-1, Prolyl 4-hydroxylase, S3a, and alpha- and beta-tubulin.
Collapse
Affiliation(s)
- Alma Forsman
- Department of Clinical Chemistry and Transfusion Medicine, Institute of Biomedicine, Sahlgrenska Academy, Sahlgrenska University Hospital, University of Gothenburg, Gothenburg, Sweden
| | | | | | | |
Collapse
|
5
|
Bajaj BG, Murakami M, Robertson ES. Molecular biology of EBV in relationship to AIDS-associated oncogenesis. Cancer Treat Res 2007; 133:141-62. [PMID: 17672040 DOI: 10.1007/978-0-387-46816-7_5] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Epstein-Barr virus (EBV) is a gammaherpesvirus of the Lymphocryptovirus genus, which infects greater than 90% of the world's population. Infection is nonsymptomatic in healthy individuals, but has been associated with a number of lymphoproliferative disorders when accompanied by immunosuppression. Like all herpesviruses, EBV has both latent and lytic replication programs, which allows it to evade immune clearance and persist for the lifetime of the host. Latent infection is characterized by replication of the viral genome as an integral part of the host cell chromosomes, and the absence of production of infectious virus. A further layer of complexity is added in that EBV can establish three distinct latency programs, in each of which a specific set of viral antigens is expressed. In most malignant disorders associated with EBV, the virus replicates using one of these three latency programs. In the most aggressive latency program, only 11 of the hitherto 85 identified open reading frames in the EBV genome are expressed. The other two latency programs express even smaller subsets of this repertoire of latent genes. The onset of the AIDS pandemic and the corresponding increase in individuals with acquired immunodeficiency resulted in a sharp increase in EBV-mediated AIDS-associated malignancies. This has sparked a renewed interest in EBV biology and pathogenesis.
Collapse
Affiliation(s)
- Bharat G Bajaj
- Department of Microbiology, Abramson Comprehensive Cancer Center, University of Pennsylvania Medical School, Philadelphia, PA, USA
| | | | | |
Collapse
|
6
|
Shaku F, Matsuda G, Furuya R, Kamagata C, Igarashi M, Tanaka M, Kanamori M, Nishiyama Y, Yamamoto N, Kawaguchi Y. Development of a monoclonal antibody against Epstein-Barr virus nuclear antigen leader protein (EBNA-LP) that can detect EBNA-LP expressed in P3HR1 cells. Microbiol Immunol 2005; 49:477-83. [PMID: 15905610 DOI: 10.1111/j.1348-0421.2005.tb03743.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A mouse monoclonal antibody, LP4D3, was raised against purified Epstein-Barr virus nuclear antigen leader protein (EBNA-LP) fused to glutathione-S-transferase. The antibody detected endogenous and exogenous EBNA-LP in immunoblotting, immunofluorescence and immunoprecipitation assays, and the epitope of the antibody was mapped in the W2 domain of EBNA-LP. While another monoclonal antibody to EBNA-LP, JF186, which is widely used for analyses of the viral protein, did not react with truncated forms of EBNA-LP expressed in P3HR1 cells, as reported earlier, the LP4D3 antibody did. The LP4D3 antibody will be a useful tool for further studies of EBNA-LP, especially investigations into the phenotypes of mutant EBNA-LP expressed in P3HR1 cells.
Collapse
Affiliation(s)
- Fumio Shaku
- Department of Cell Regulation, Medical Research Institute, Tokyo, Japan
| | | | | | | | | | | | | | | | | | | |
Collapse
|
7
|
Ling PD, Peng RS, Nakajima A, Yu JH, Tan J, Moses SM, Yang WH, Zhao B, Kieff E, Bloch KD, Bloch DB. Mediation of Epstein-Barr virus EBNA-LP transcriptional coactivation by Sp100. EMBO J 2005; 24:3565-75. [PMID: 16177824 PMCID: PMC1276704 DOI: 10.1038/sj.emboj.7600820] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2005] [Accepted: 08/25/2005] [Indexed: 12/15/2022] Open
Abstract
The Epstein-Barr virus (EBV) EBNA-LP protein is important for EBV-mediated B-cell immortalization and is a potent gene-specific coactivator of the viral transcriptional activator, EBNA2. The mechanism(s) by which EBNA-LP functions as a coactivator remains an important question in the biology of EBV-induced B-cell immortalization. In this study, we found that EBNA-LP interacts with the promyelocytic leukemia nuclear body (PML NB)-associated protein Sp100 and displaces Sp100 and heterochromatin protein 1alpha (HP1alpha) from PML NBs. Interaction between EBNA-LP and Sp100 was mediated through conserved region 3 in EBNA-LP and the PML NB targeting domain in Sp100. Overexpression of Sp100 lacking the N-terminal PML NB targeting domain, but not a mutant form of Sp100 lacking the HP1alpha interaction domain, was sufficient to coactivate EBNA2 in a gene-specific manner independent of EBNA-LP. These findings suggest that Sp100 is a major mediator of EBNA-LP coactivation. These studies indicate that modulation of PML NB-associated proteins may be important for establishment of latent viral infections, and also identify a convenient model system to investigate the functions of Sp100.
Collapse
Affiliation(s)
- Paul D Ling
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX, USA
| | - Rong Sheng Peng
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX, USA
| | - Ayako Nakajima
- Department of Medicine, Harvard Medical School and Center for Immunology and Inflammatory Diseases of the General Medical Services, Massachusetts General Hospital, Boston, MA, USA
| | - Jiang H Yu
- Department of Medicine, Harvard Medical School and Center for Immunology and Inflammatory Diseases of the General Medical Services, Massachusetts General Hospital, Boston, MA, USA
| | - Jie Tan
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX, USA
| | - Stephanie M Moses
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX, USA
| | - Wei-Hong Yang
- Department of Medicine, Harvard Medical School and Center for Immunology and Inflammatory Diseases of the General Medical Services, Massachusetts General Hospital, Boston, MA, USA
| | - Bo Zhao
- Departments of Medicine and Microbiology and Molecular Genetics, Channing Laboratory, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| | - Elliott Kieff
- Departments of Medicine and Microbiology and Molecular Genetics, Channing Laboratory, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| | - Kenneth D Bloch
- Department of Medicine, Harvard Medical School and Cardiovascular Research Center of the General Medical Services, Massachusetts General Hospital, Boston, MA, USA
| | - Donald B Bloch
- Department of Medicine, Harvard Medical School and Center for Immunology and Inflammatory Diseases of the General Medical Services, Massachusetts General Hospital, Boston, MA, USA
| |
Collapse
|
8
|
Peng R, Moses SC, Tan J, Kremmer E, Ling PD. The Epstein-Barr virus EBNA-LP protein preferentially coactivates EBNA2-mediated stimulation of latent membrane proteins expressed from the viral divergent promoter. J Virol 2005; 79:4492-505. [PMID: 15767449 PMCID: PMC1061541 DOI: 10.1128/jvi.79.7.4492-4505.2005] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The mechanistic contribution of the Epstein-Barr virus (EBV) EBNA-LP protein to B-cell immortalization remains an enigma. However, previous studies have indicated that EBNA-LP may contribute to immortalization by enhancing EBNA2-mediated transcriptional activation of the LMP-1 gene. To gain further insight into the potential role EBNA-LP has in EBV-mediated B-cell immortalization, we asked whether it is a global or gene-specific coactivator of EBNA2 and whether coactivation requires interaction between these proteins. In type I Burkitt's lymphoma cells, we found that EBNA-LP strongly coactivated EBNA2 stimulation of LMP-1 and LMP2B RNAs, which are expressed from the viral divergent promoter. Surprisingly, the viral LMP2A gene and cellular CD21 and Hes-1 genes were induced by EBNA2 but showed no further induction after EBNA-LP coexpression. We also found that EBNA-LP did not stably interact with EBNA2 in coimmunoprecipitation assays, even though the conditions were adequate to observe specific interactions between EBNA2 and its cellular cofactor, CBF1. Colocalization between EBNA2 and EBNA-LP was not detectable in EBV-transformed cell lines or transfected type I Burkitt's cells. Finally, no significant interactions between EBNA2 and EBNA-LP were found with mammalian two-hybrid assays. From this data, we conclude that EBNA-LP is not a global coactivator of EBNA2 targets, but it preferentially coactivates EBNA2 stimulation of the viral divergent promoter. While this may require specific transient interactions between these proteins that only occur in the context of the divergent promoter, our data strongly suggest that EBNA-LP also cooperates with EBNA2 through mechanisms that do not require direct or indirect complex formation between these proteins.
Collapse
Affiliation(s)
- Rongsheng Peng
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX 77030, USA
| | | | | | | | | |
Collapse
|
9
|
Kanamori M, Watanabe S, Honma R, Kuroda M, Imai S, Takada K, Yamamoto N, Nishiyama Y, Kawaguchi Y. Epstein-Barr virus nuclear antigen leader protein induces expression of thymus- and activation-regulated chemokine in B cells. J Virol 2004; 78:3984-93. [PMID: 15047814 PMCID: PMC374277 DOI: 10.1128/jvi.78.8.3984-3993.2004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Epstein-Barr virus (EBV) nuclear antigen leader protein (EBNA-LP) plays a critical role in transformation of primary B lymphocytes to continuously proliferating lymphoblastoid cell lines (LCLs). To identify cellular genes in B cells whose expression is regulated by EBNA-LP, we performed microarray expression profiling on an EBV-negative human B-cell line, BJAB cells, that were transduced by a retroviral vector expressing the EBV EBNA-LP (BJAB-LP cells) and on BJAB cells that were transduced with a control vector (BJAB-vec cells). Microarray analysis led to the identification of a cellular gene encoding the CC chemokine TARC as a novel target gene that was induced by EBNA-LP. The levels of TARC mRNA expression and TARC secretion were significantly up-regulated in BJAB-LP compared with BJAB-vec cells. Induction of TARC was also observed when a subline of BJAB cells was converted by a recombinant EBV. Among the EBV-infected B-cell lines with the latency III phenotype that were tested, the LCLs especially secreted significantly high levels of TARC. The level of TARC secretion appeared to correlate with the level of full-length EBNA-LP expression. These results indicate that EBV infection induces TARC expression in B cells and that EBNA-LP is one of the viral gene products responsible for the induction.
Collapse
Affiliation(s)
- Mikiko Kanamori
- Department of Virology, Nagoya University Graduate School of Medicine, Showa-ku, Nagoya 466-8550, Japan
| | | | | | | | | | | | | | | | | |
Collapse
|
10
|
Kato K, Yokoyama A, Tohya Y, Akashi H, Nishiyama Y, Kawaguchi Y. Identification of protein kinases responsible for phosphorylation of Epstein-Barr virus nuclear antigen leader protein at serine-35, which regulates its coactivator function. J Gen Virol 2004; 84:3381-3392. [PMID: 14645919 DOI: 10.1099/vir.0.19454-0] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Epstein-Barr virus (EBV) nuclear antigen leader protein (EBNA-LP) is a phosphoprotein suggested to play important roles in EBV-induced immortalization. Earlier studies have shown that the major site of phosphorylation of EBNA-LP by cellular kinase(s) is a serine residue at position 35 (Ser-35) and that the phosphorylation of Ser-35 is critical for regulation of the coactivator function of EBNA-LP (Yokoyama et al., J Virol 75, 5119-5128, 2001). In the present study, we have attempted to identify protein kinase(s) responsible for the phosphorylation of EBNA-LP at Ser-35. A purified chimeric protein consisting of glutathione S-transferase (GST) fused to a domain of EBNA-LP containing Ser-35 was found to be specifically phosphorylated by purified cdc2 in vitro, while GST fused to a mutated domain of EBNA-LP in which Ser-35 was replaced with alanine was not. In addition, overexpression of cdc2 in mammalian cells caused a significant increase in the phosphorylation of EBNA-LP, while this increased phosphorylation was eliminated if Ser-35 of EBNA-LP was replaced with alanine. These results indicate that the cellular protein kinase cdc2 mediates the phosphorylation of EBNA-LP at Ser-35. Recently, we reported that cdc2 and conserved protein kinases encoded by herpesviruses phosphorylate the same amino acid residue of target proteins (Kawaguchi et al., J Virol 77, 2359-2368, 2003). Consistent with this, the EBV-encoded conserved protein kinase BGLF4 specifically mediated the phosphorylation of EBNA-LP at Ser-35. These results indicate that the coactivator function of EBNA-LP can be regulated by the activity of these cellular and viral protein kinases.
Collapse
Affiliation(s)
- Kentaro Kato
- Department of Veterinary Microbiology, Graduate School of Agricultural and Life Science, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
- Department of Cell Regulation, Medical Research Institute, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo 113-8510, Japan
| | - Akihiko Yokoyama
- Department of Cell Regulation, Medical Research Institute, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo 113-8510, Japan
| | - Yukinobu Tohya
- Department of Veterinary Microbiology, Graduate School of Agricultural and Life Science, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Hiroomi Akashi
- Department of Veterinary Microbiology, Graduate School of Agricultural and Life Science, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Yukihiro Nishiyama
- Department of Virology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan
| | - Yasushi Kawaguchi
- PRESTO, Japan Science and Technology Corporation, Tachikawa, Tokyo 190-0012, Japan
- Department of Virology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan
- Department of Cell Regulation, Medical Research Institute, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo 113-8510, Japan
| |
Collapse
|
11
|
Li H, Minarovits J. Host cell-dependent expression of latent Epstein-Barr virus genomes: regulation by DNA methylation. Adv Cancer Res 2003; 89:133-56. [PMID: 14587872 DOI: 10.1016/s0065-230x(03)01004-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Epstein-Barr virus (EBV) is a ubiquitous human gammaherpesvirus associated with a wide spectrum of malignant neoplasms. Expression of latent (growth transformation-associated) EBV genes is host cell specific. Transcripts for EBV-encoded nuclear antigens (EBNAs) are initiated at one of the alternative promoters: Wp, Cp (for EBNA1-6), or Qp (for EBNA1 only). Wp is active shortly after EBV infection of human B cells in vitro but is progressively methylated and silenced in established lymphoblastoid cell lines (LCLs). In parallel Cp, an unmethylated, lymphoid-specific promoter is switched on. In contrast, Cp is methylated and silent in Burkitt's lymphoma (BL) cell lines, which keep the phenotype of BL biopsy cells (group I BL lines). These cells use Qp for the initiation of EBNA1 messages. Qp is unmethylated both in group I BLs (Qp on) and in LCLs (Qp off). Thus, DNA methylation does not play a role in silencing Qp. In LCLs and nasopharyngeal carcinoma (NPC) cells, transcripts for latent membrane protein 1 (LMP1) are initiated from LMP1p, a promoter regulated by CpG methylation. LMPlp is silent in group I BL lines but can be activated by demethylating agents. Promoter silencing by CpG methylation involves both direct interference with transcription factor binding (Wp, Cp) and indirect mechanisms involving the recruitment of histone deacetylases (LMPlp). A dyad symmetry sequence(DS) within oriP (the latent origin of EBV replication) and intragenic RNA polymerase III control regions of EBER 1 and 2 transcription units are invariably unmethylated in EBV-carrying cells.
Collapse
Affiliation(s)
- Hul Li
- Microbiological Research Group, National Center for Epidemiology, H-1529 Budapest, Hungary
| | | |
Collapse
|
12
|
Abstract
Epstein-Barr virus (EBV) is a ubiquitous human herpesvirus associated with the development of both lymphoid and epithelial tumours. As a common virus infection, EBV appears to have evolved to exploit the process of B cell development to persist as a life-long asymptomatic infection. However, the virus can contribute to oncogenesis as evidenced by its frequent detection in certain tumours, namely Burkitt's lymphoma (BL), post-transplant B cell lymphomas, Hodgkin's disease (HD) and nasopharyngeal carcinoma (NPC), and by its unique ability to efficiently transform resting B cells in vitro into permanently growing lymphoblastoid cell lines (LCLs). These transforming effects are associated with the restricted expression of EBV genes such that only a subset of so-called latent virus proteins are expressed in virus infected tumours and in LCLs. Distinct forms of EBV latency are manifest in the different tumours and these appear to be a vestige of the pattern of latent gene expression used by the virus during the establishment of persistent infection within the B cell pool. This review summarises our current knowledge of EBV latent gene function and how this relates to the role of the virus in the aetiology of different tumours.
Collapse
Affiliation(s)
- Lawrence S Young
- Cancer Research UK Institute for Cancer Studies, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
| | | |
Collapse
|
13
|
Kashuba E, Mattsson K, Pokrovskaja K, Kiss C, Protopopova M, Ehlin-Henriksson B, Klein G, Szekely L. EBV-encoded EBNA-5 associates with P14ARF in extranucleolar inclusions and prolongs the survival of P14ARF-expressing cells. Int J Cancer 2003; 105:644-53. [PMID: 12740913 DOI: 10.1002/ijc.11124] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Epstein-Barr virus (EBV) carrying lymphoblastoid cells of normal origin express the full program of all 9 virus-encoded, growth transformation associated proteins. They have an intact p53 pathway as a rule. This raises the question of whether any of the viral proteins impair the pathway functionally. Using a yeast 2-hybrid system, we have shown that EBNA-5 but not the other EBNAs interacts with the p14ARF protein, a regulator of the p53 pathway. The interaction was confirmed in vitro using a GST pull-down assay. Moreover, expression of EBNA-5 increased the survival of p14ARF-transfected cells. EBV infection of resting B cells induced the expression of p14ARF mRNA without increased level of the protein. A fraction of the p14ARF localized to the nucleoli but the bulk of the protein accumulated in nuclear but extranucleolar inclusions. Formation of the extranucleolar inclusions led to complete relocalization of EBNA-5 from nucleoplasm to these structures. The inclusions also contained p53 and HDM2, and were surrounded by PML bodies and proteasomes, which suggests that these inclusions could be targets for proteasome dependent protein degradation.
Collapse
Affiliation(s)
- Elena Kashuba
- Microbiology and Tumor Biology Center (MTC), Karolinska Institute, Nobels vag 16, Box 280, S-171 77 Stockholm, Sweden.
| | | | | | | | | | | | | | | |
Collapse
|
14
|
Igarashi M, Kawaguchi Y, Hirai K, Mizuno F. Physical interaction of Epstein-Barr virus (EBV) nuclear antigen leader protein (EBNA-LP) with human oestrogen-related receptor 1 (hERR1): hERR1 interacts with a conserved domain of EBNA-LP that is critical for EBV-induced B-cell immortalization. J Gen Virol 2003; 84:319-327. [PMID: 12560563 DOI: 10.1099/vir.0.18615-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Epstein-Barr virus (EBV) nuclear antigen leader protein (EBNA-LP) consists of W1W2 repeats and a unique C-terminal Y1Y2 domain and plays a critical role in EBV-induced transformation. To identify the cellular proteins associating with EBNA-LP, we performed a yeast two-hybrid screen using EBNA-LP cDNA containing a single W1W2 domain as bait and an EBV-transformed human peripheral blood lymphocyte cDNA library as the source of cellular genes. Our results were as follows. (i) A cDNA in the positive yeast colony was found to encode a cellular protein, human oestrogen-related receptor 1 (hERR1), which is a constitutive transcriptional activator of the various types of oestrogen response elements. (ii) A purified chimeric protein consisting of glutathione S-transferase (GST) fused to hERR1 specifically formed complexes with EBNA-LPs containing one (EBNA-LPR1), two (EBNA-LPR2) or four W1W2 repeats (EBNA-LPR4) transiently expressed in COS-7 cells. Reciprocally, GST fused to EBNA-LPR1 or EBNA-LPR2 pulled down hERR1 transiently expressed in COS-7 cells. (iii) Mutational analyses of EBNA-LP revealed that the Y2 domain of EBNA-LP is responsible for the interaction with hERR1 and two leucines in the Y2 domain (Leu-78 and -82), which are conserved among a subset of primate gammaherpesviruses, are interactive sites for hERR1. So far, it has been reported that the only domain of EBNA-LP critical for EBV-induced transformation is the Y1Y2 domain. Potential roles of hERR1 in EBV-induced transformation are discussed.
Collapse
Affiliation(s)
- Mie Igarashi
- Department of Microbiology, Tokyo Medical University, 6-1-1, Shinjuku, Shinjuku-ku, Tokyo 160-8402, Japan
- Department of Tumor Virology, Medical Research Institute, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo 113-8510, Japan
| | - Yasushi Kawaguchi
- Department of Tumor Virology, Medical Research Institute, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo 113-8510, Japan
| | - Kanji Hirai
- Department of Tumor Virology, Medical Research Institute, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo 113-8510, Japan
| | - Fumio Mizuno
- Department of Microbiology, Tokyo Medical University, 6-1-1, Shinjuku, Shinjuku-ku, Tokyo 160-8402, Japan
| |
Collapse
|
15
|
Abstract
Ribosome biogenesis is both necessary for cellular adaptation, growth, and proliferation as well as a major energetic and biosynthetic demand upon cells. For these reasons, ribosome biogenesis requires precise regulation to balance supply and demand. The complexity of ribosome biogenesis gives rise to many steps and opportunities where regulation could take place. For trans-acting factors involved in ribosome biogenesis in the nucleolus, there may be a dynamic coordination, both spatially and temporally, that regulates their functions from the transcription of rDNA to the assembly and export of preribosomal particles. Here we summarize most of the described regulations on ribosome biogenesis in the nucleolus. However, these may represent only a small fraction of a larger picture. Further studies are required to determine the initial signals, signal transduction pathways utilized, and the specific targets of these regulatory modifications and how these are used to control ribosome biogenesis as a whole.
Collapse
Affiliation(s)
- D J Leary
- Department of Cell and Molecular Biology, Northwestern University Medical School, 300 E. Chicago Ave, Chicago, IL 60611, USA
| | | |
Collapse
|
16
|
Bandobashi K, Maeda A, Teramoto N, Nagy N, Székely L, Taguchi H, Miyoshi I, Klein G, Klein E. Intranuclear localization of the transcription coadaptor CBP/p300 and the transcription factor RBP-Jk in relation to EBNA-2 and -5 in B lymphocytes. Virology 2001; 288:275-82. [PMID: 11601899 DOI: 10.1006/viro.2001.1103] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have studied the expression and the localization of the cellular proteins CBP/p300 and RBP-Jk in in vitro EBV-infected human B lymphocytes in relation to the EBNA-2 and EBNA-5 proteins. We found that the level of CBP/p300 was elevated drastically by EBV infection and also after activation by CD40 ligation. Thus the increase in CBP/p300 expression in the EBV-infected cells is related to the virus-induced activation and proliferation of the cells. EBNA-2 and RBP-Jk colocalized in the nucleoplasm, which is in accordance with their functional interaction. We confirmed earlier reports about the presence and colocalization of EBNA-5 and CBP in the nuclear POD bodies. On the other hand, neither EBNA-2 nor p300 was detected in the PODs. The expression of these two proteins overlapped in some distinct dots of the nucleoplasm. Taken together, the different patterns of CBP and p300 expression and their different localization in relation to the PML bodies and two EBV-encoded proteins in the B cells may provide some clue to their distinct functional roles.
Collapse
Affiliation(s)
- K Bandobashi
- Microbiology and Tumor Biology Center, Karolinska Institute, S-171 77 Stockholm, Sweden.
| | | | | | | | | | | | | | | | | |
Collapse
|
17
|
Yokoyama A, Tanaka M, Matsuda G, Kato K, Kanamori M, Kawasaki H, Hirano H, Kitabayashi I, Ohki M, Hirai K, Kawaguchi Y. Identification of major phosphorylation sites of Epstein-Barr virus nuclear antigen leader protein (EBNA-LP): ability of EBNA-LP to induce latent membrane protein 1 cooperatively with EBNA-2 is regulated by phosphorylation. J Virol 2001; 75:5119-28. [PMID: 11333893 PMCID: PMC114917 DOI: 10.1128/jvi.75.11.5119-5128.2001] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Epstein-Barr virus (EBV) nuclear antigen leader protein (EBNA-LP) is a phosphoprotein suggested to play important roles in EBV-induced immortalization of B cells. One of the potential functions of EBNA-LP is a cooperative induction with EBNA-2 of viral and cellular gene expression, including that of the genes for viral latent membrane protein 1 (LMP-1) and cellular cyclin D2. We report here that the phosphorylation of EBNA-LP by cellular kinase(s) is critical to its ability to cooperate with EBNA-2 in up-regulating the expression of LMP-1 in a B-lymphoma cell line. Our conclusion is based on the following observations. (i) Mass-spectrometric analysis of purified EBNA-LP and mutational analyses of EBNA-LP revealed that the serine residue at position 35 in the W2 repeat domain is the major phosphorylation site of EBNA-LP in vivo. (ii) Substitutions of this site in each W2 repeat domain with alanine markedly reduced the ability of the protein to induce LMP-1 expression in combination with EBNA-2 in Akata cells. (iii) Replacement at the major phosphorylation sites with glutamic acids restored the wild-type phenotype. It is well established that this substitution mimics constitutive phosphorylation. These results indicated that the coactivator function of EBNA-LP is regulated by phosphorylation.
Collapse
Affiliation(s)
- A Yokoyama
- Department of Tumor Virology, Division of Virology and Immunology, Medical Research Institute, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo 113-8510, Japan
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
18
|
Yokoyama A, Kawaguchi Y, Kitabayashi I, Ohki M, Hirai K. The conserved domain CR2 of Epstein-Barr virus nuclear antigen leader protein is responsible not only for nuclear matrix association but also for nuclear localization. Virology 2001; 279:401-13. [PMID: 11162796 DOI: 10.1006/viro.2000.0715] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
There is a growing body of evidence for the importance of the nuclear matrix in various nuclear events including gene expression and DNA replication. Epstein-Barr virus (EBV) nuclear antigen leader protein (EBNA-LP) is a nuclear matrix-associated protein that has been suggested to play an important role in EBV-induced transformation. To define the biological significance of the association of EBNA-LP with the nuclear matrix, we mapped the domain of EBNA-LP responsible for nuclear matrix association and investigated the functions of the EBNA-LP mutant mutagenized by substitution of alanines for the cluster of arginine residues in the mapped region. The results of the present study were as follows. (i) Transiently expressed EBNA-LP in COS-7 or BOSC23 cells was associated with the nuclear matrix, similarly to that in EBV-infected B cells. (ii) Mutational analysis of EBNA-LP revealed that a 10-amino acid segment of EBNA-LP is critical for nuclear matrix association of the protein. Interestingly, the identified region overlapped with the region CR2 of EBNA-LP conserved among a subset of primate gammaherpesviruses. The identified segment is referred to as EBNA-LP NMTS (nuclear matrix targeting signal). (iii) The EBNA-LP mutant with the arginine to alanine substitutions in NMTS was no longer localized not only to the nuclear matrix but also to the nucleus. (iv) The EBNA-LP mutant lacked its ability to coactivate EBNA-2-dependent transactivation. These results indicated that EBNA-LP needs to be localized in the nucleus and/or associated with the nuclear matrix through CR2 to elicit its function such as the coactivation of the EBNA-2-dependent transcriptional activation.
Collapse
Affiliation(s)
- A Yokoyama
- Department of Tumor Virology, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, 1-5-45, Yushima, Bunkyo-ku, 113-8510, Japan
| | | | | | | | | |
Collapse
|
19
|
Peng R, Tan J, Ling PD. Conserved regions in the Epstein-Barr virus leader protein define distinct domains required for nuclear localization and transcriptional cooperation with EBNA2. J Virol 2000; 74:9953-63. [PMID: 11024123 PMCID: PMC102033 DOI: 10.1128/jvi.74.21.9953-9963.2000] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Epstein-Barr virus (EBV) EBNA-LP is a latent protein whose function is not fully understood. Recent studies have shown that EBNA-LP may be an important EBNA2 cofactor by enhancing EBNA2 stimulation of the latency C and LMP-1 promoters. To further our understanding of EBNA-LP function, we have introduced a series of mutations into evolutionarily conserved regions and tested the mutant proteins for the ability to enhance EBNA2 stimulation of the latency C and LMP-1 promoters. Three conserved regions (CR1 to CR3) are located in the repeat domains that are essential for the EBNA2 cooperativity function. In addition, three serine residues are also well conserved in the repeat domains. Clustered alanine mutations were introduced into CR1 to CR3, and the conserved serines were also changed to alanine residues in an EBNA-LP with two repeats, which is the minimal protein able to cooperate with EBNA2. Mutations introduced into CR1a had no effect on EBNA-LP function, while mutations introduced into CR1b resulted in EBNA-LP with slightly decreased activity. Mutations in CR1c and CR2 resulted in proteins that no longer localized exclusively to the nucleus and also had no EBNA2 cooperation activity. Mutations introduced into conserved serines S5/71 resulted in proteins with slightly higher activity, while mutations introduced into conserved serines S35/101 or in CR3 (which contains S60/126) resulted in EBNA-LP proteins with substantially reduced activity. The potential karyophilic signals within EBNA-LP CR1c and CR2 were also examined by introducing oligonucleotides encoding these positively charged amino acid groupings into a cytoplasmic test protein, herpes simplex virus DeltaIE175, and by examining the intracellular localization of the resulting proteins. This assay identified a strong nuclear localization signal between EBNA-LP amino acids 43 and 50 (109 to 117 in the second W repeat) comprising CR2, while EBNA-LP amino acids 29 to 36 (91 to 98 in the second W repeat) were unable to function independently as a nuclear localization signal. However, a combination of amino acids 29 to 50 resulted in more efficient nuclear localization than with amino acids 43 to 50 alone. These results indicate that EBNA-LP has a bipartite nuclear localization signal and that efficient nuclear localization is essential for EBNA2 cooperativity function. Interestingly, EBNA-LP with only a single repeat localized exclusively to the cytoplasm, providing an explanation for why this isoform has no activity. In addition, two conserved serine residues which are distinct from nuclear import functions are important for EBNA2 cooperativity function.
Collapse
Affiliation(s)
- R Peng
- Division of Molecular Virology, Baylor College of Medicine, Houston, Texas 77030, USA
| | | | | |
Collapse
|
20
|
Young LS, Dawson CW, Eliopoulos AG. The expression and function of Epstein-Barr virus encoded latent genes. Mol Pathol 2000; 53:238-47. [PMID: 11091847 PMCID: PMC1186976 DOI: 10.1136/mp.53.5.238] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/25/2000] [Indexed: 01/15/2023]
Abstract
The association of Epstein-Barr virus (EBV) with various malignancies is well established but the pattern of EBV latent gene expression in these different tumours is variable, reflecting distinct aspects of the virus-cell interaction. These different forms of EBV latency are associated with phenotypic variation and highlight the influence of EBV latent proteins on cell growth and survival. The EBV latent proteins have distinct functions associated with the maintenance of EBV infection and the control of various signalling and transcriptional pathways that facilitate the proliferation and survival of infected cells. Understanding the function of these EBV latent proteins will not only provide insight into the mechanisms governing fundamental cell processes but will also identify targets for novel treatment.
Collapse
Affiliation(s)
- L S Young
- CRC Institute for Cancer Studies, University of Birmingham Medical School, UK.
| | | | | |
Collapse
|
21
|
Peng R, Gordadze AV, Fuentes Pananá EM, Wang F, Zong J, Hayward GS, Tan J, Ling PD. Sequence and functional analysis of EBNA-LP and EBNA2 proteins from nonhuman primate lymphocryptoviruses. J Virol 2000; 74:379-89. [PMID: 10590127 PMCID: PMC111549 DOI: 10.1128/jvi.74.1.379-389.2000] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The Epstein-Barr virus (EBV) EBNA-LP and EBNA2 proteins are the first to be synthesized during establishment of latent infection in B lymphocytes. EBNA2 is a key transcriptional regulator of both viral and cellular gene expression and is essential for EBV-induced immortalization of B lymphocytes. EBNA-LP is also important for EBV-induced immortalization of B lymphocytes, but far less is known about the functional domains and cellular cofactors that mediate EBNA-LP function. While recent studies suggest that serine phosphorylation of EBNA-LP and coactivation of EBNA2-mediated transactivation are important, more detailed mutational and genetic studies are complicated by the repeat regions that comprise the majority of the EBNA-LP sequence. Therefore, we have used a comparative approach by studying the EBNA-LP homologues from baboon and rhesus macaque lymphocryptoviruses (LCVs) (baboon LCV and rhesus LCV). The predicted baboon and rhesus LCV EBNA-LP amino acid sequences are 61 and 64% identical to the EBV EBNA-LP W1 and W2 exons and 51% identical to the EBV EBNA-LP Y1 and Y2 exons. Five evolutionarily conserved regions can be defined, and four of eight potential serine residues are conserved among all three EBNA-LPs. The major internal repeat sequence also revealed a highly conserved Wp EBNA promoter with strong conservation of upstream activating sequences important for Wp transcriptional regulation. To test whether transcriptional coactivating properties were common to the rhesus LCV EBNA-LP, a rhesus LCV EBNA2 homologue was cloned and expressed. The rhesus LCV EBNA2 transcriptionally transactivates EBNA2-responsive promoters through a CBF1-dependent mechanism. The rhesus LCV EBNA-LP was able to further enhance rhesus LCV or EBV EBNA2 transactivation 5- to 12-fold. Thus, there is strong structural and functional conservation among the simian EBNA-LP homologues. Identification of evolutionarily conserved serine residues and regions in EBNA-LP homologues provides important clues for identifying the cellular cofactors and molecular mechanisms mediating these conserved viral functions.
Collapse
Affiliation(s)
- R Peng
- Division of Molecular Virology, Baylor College of Medicine, Houston, Texas 77030, USA
| | | | | | | | | | | | | | | |
Collapse
|
22
|
Abstract
Two regions of the EBNA-3A protein of Epstein-Barr virus were shown to be capable of binding to the cell protein RBP-Jk (also known as CBF-1), a component of the Notch signaling pathway. Consistent with this binding, EBNA-3A inhibited reporter gene expression from plasmids containing RBP-Jk DNA binding sites within their promoters, including the Cp promoter. When EBNA-3A was linked to a GAL4 DNA binding domain, it repressed the activity of a promoter containing GAL4 binding sites at all plasmid concentrations tested. However, a deletion mutant of EBNA-3A lacking amino acids 100 to 364 showed a biphasic response in the GAL4 assay: it inhibited transcription at low DNA concentrations but activated it at high DNA concentrations. There appears to be a gene activation function within EBNA-3A that is masked in the full-length protein in this assay. Current models for EBNA-3 function have stressed transcription repression through binding to RBP-Jk, but we consider an alternative scheme in which the role of the binding of EBNA-3A, -3B, and -3C to RBP-Jk is to buffer the levels of active EBNA-3 protein. We have also found that the behavior of EBNA-3A in a cell fractionation procedure that distinguishes insoluble matrix from soluble cell fractions is modified by EBNA-LP, indicating a further novel level of interplay between the EBNA proteins.
Collapse
Affiliation(s)
- I Cludts
- Ludwig Institute for Cancer Research, Imperial College School of Medicine at St. Mary's, London, United Kingdom
| | | |
Collapse
|
23
|
Alcalay M, Tomassoni L, Colombo E, Stoldt S, Grignani F, Fagioli M, Szekely L, Helin K, Pelicci PG. The promyelocytic leukemia gene product (PML) forms stable complexes with the retinoblastoma protein. Mol Cell Biol 1998; 18:1084-93. [PMID: 9448006 PMCID: PMC108821 DOI: 10.1128/mcb.18.2.1084] [Citation(s) in RCA: 137] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/1997] [Accepted: 10/24/1997] [Indexed: 02/05/2023] Open
Abstract
PML is a nuclear protein with growth-suppressive properties originally identified in the context of the PML-retinoic acid receptor alpha (RAR alpha) fusion protein of acute promyelocytic leukemia. PML localizes within distinct nuclear structures, called nuclear bodies, which are disrupted by the expression of PML-RAR alpha. We report that PML colocalizes with the nonphosphorylated fraction of the retinoblastoma protein (pRB) within nuclear bodies and that pRB is delocalized by PML-RAR alpha expression. Both PML and PML-RAR alpha form complexes with the nonphosphorylated form of pRB in vivo, and they interact with the pocket region of pRB. The regions of PML and PML-RAR alpha involved in pRB binding differ; in fact, the B boxes and the C-terminal region of PML, the latter of which is not present in PML-RAR alpha, are essential for the formation of stable complexes with pRB. Functionally, PML abolishes activation of glucocorticoid receptor-regulated transcription by pRB, whereas PML-RAR alpha further increases it. Our results suggest that PML may be part of transcription-regulatory complexes and that the oncogenic potential of the PML-RAR alpha protein may derive from the alteration of PML-regulated transcription.
Collapse
Affiliation(s)
- M Alcalay
- Department of Experimental Oncology, European Institute of Oncology, Milan, Italy.
| | | | | | | | | | | | | | | | | |
Collapse
|
24
|
Abstract
Nuclear dots (NDs), alternatively designated nuclear bodies (NBs), PML oncogenic domains (PODs), nuclear domain 10 (ND10) or Kr-bodies, became a major topic for researchers in many fields only recently. Originally described as an autoantigenic target in patients with primary biliary cirrhosis, they are now also known to play a role in development of acute promyelocytic leukemia (APL) and possibly other forms of neoplasia. Size, number and composition of NDs are regulated throughout the cell cycle. Infection with herpes simplex virus, adenovirus, cytomegalovirus, Epstein-Barr-virus, influenza virus and human T cell lymphotropic virus type I (HTLV I) strongly modifies ND structure through viral regulatory proteins. Due to this finding and because at least three of the cellular ND proteins are highly interferon-inducible, a function of NDs in early viral infection or in antiviral response has been postulated. Functional data are currently available only for two of the ND-associated proteins. The Sp100 protein seems to have transcriptional transactivating property, whereas the promyelocytic leukemia protein (PML) was reported to suppress growth and transformation. Here, we give a brief overview of the data currently available on NDs. Thus, we hope to link seemingly unrelated findings in the literature on oncology, virology, cell biology and immunology.
Collapse
Affiliation(s)
- T Sternsdorf
- Heinrich-Pette-Institut für experimentelle Virologie und Immunologie, Universität Hamburg, Germany
| | | | | | | |
Collapse
|
25
|
Nitsche F, Bell A, Rickinson A. Epstein-Barr virus leader protein enhances EBNA-2-mediated transactivation of latent membrane protein 1 expression: a role for the W1W2 repeat domain. J Virol 1997; 71:6619-28. [PMID: 9261384 PMCID: PMC191940 DOI: 10.1128/jvi.71.9.6619-6628.1997] [Citation(s) in RCA: 104] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The Epstein-Barr virus (EBV)-encoded leader protein EBNA-LP is made up of several 66-amino-acid repeats (the W1W2 domains) linked to a unique 45-amino-acid C-terminal sequence (the Y1Y2 domain). This protein is highly expressed along with a second nuclear antigen, EBNA-2, during the initial stages of virus-induced B-cell transformation. While EBNA-2's essential role in transformation as a transcriptional activatory is well documented, very little is known about EBNA-LP function except that recombinant viruses lacking the EBNA-LP Y1Y2 exons show reduced, but still detectable, transforming ability. This was taken as evidence that EBNA-LP plays an auxiliary role but is not essential for transformation. A recent study showed that EBNA-LP could cooperate with EBNA-2 in activating cyclin D2 transcription in resting B cells (A.J. Sinclair, L Palmero, G. Peters, and P.J. Farrell, EMBO J. 13:3321-3328, 1994). Here we report that EBNA-LP can also cooperate with EBNA-2 in up-regulating expression of the major EBV effector protein of B-cell transformation, latent membrane protein 1 (LMP1). In transient-transfection assays, EBNA-LP enhanced the level of EBNA-2-induced LMP1 expression by 5- to 10-fold in one Latency I Burkitt's lymphoma cell line, Eli-BL, and was absolutely required, along with EBNA-2, to induce LMP1 in a second line, Akata-BL. These changes in LMP1 protein expression appeared to be reflected at the transcriptional level. A study of EBNA-LP mutants showed that this cooperative function mapped to the W1W2 repeat domain rather than to Y1Y2. Because a Y1Y2-deleted form of EBNA-LP may therefore retain some aspects of wild-type function, the original data from virus recombinants leave open the possibility that EBNA-LP is actually an essential transforming gene.
Collapse
Affiliation(s)
- F Nitsche
- CRC Institute for Cancer Studies, University of Birmingham, United Kingdom
| | | | | |
Collapse
|
26
|
Kitay MK, Rowe DT. Cell cycle stage-specific phosphorylation of the Epstein-Barr virus immortalization protein EBNA-LP. J Virol 1996; 70:7885-93. [PMID: 8892911 PMCID: PMC190860 DOI: 10.1128/jvi.70.11.7885-7893.1996] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
EBNA-LP is a viral nuclear oncoprotein implicated in the immortalization of B lymphocytes by Epstein-Barr virus. An analysis of EBNA-LP migration on polyacrylamide gels was performed with protein derived from the X50-7 lymphoblastoid cell line blocked by hydroxyurea or aphidicolin at the G1/S phase of the cell cycle or by nocodazole at the G2/M phase. More slowly migrating species of EBNA-LP were detected in G2/M phase-arrested cell extracts. Release from nocodazole G2/M block or treatment with phosphatase caused the more slowly migrating species of EBNA-LP to disappear. Analyses of 32PO(4)(3-)-labeled EBNA-LP protein immunoprecipitated from the drug-synchronized cells showed that phosphorylated EBNA-LP was present throughout the cell cycle but that phosphorylation increased in G2 and was maximal at G2/M. Phosphoamino acid analysis revealed that all phosphorylation was on serine residues only. The ability of EBNA-LP to be phosphorylated by p34(cdc2) kinase and casein kinase II exclusively on serines implicates these enzymes as being potentially involved in EBNA-LP phosphorylation.
Collapse
Affiliation(s)
- M K Kitay
- Department of Infectious Diseases and Microbiology, Graduate School of Public Health, University of Pittsburgh, Pennsylvania 15261, USA
| | | |
Collapse
|
27
|
Szekely L, Pokrovskaja K, Jiang WQ, de The H, Ringertz N, Klein G. The Epstein-Barr virus-encoded nuclear antigen EBNA-5 accumulates in PML-containing bodies. J Virol 1996; 70:2562-8. [PMID: 8642686 PMCID: PMC190102 DOI: 10.1128/jvi.70.4.2562-2568.1996] [Citation(s) in RCA: 95] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
EBNA-5 is one of the Epstein-Barr virus (EBV)-encoded nuclear proteins required for immortalization of human B lymphocytes. In the nuclei of EBV-transformed lymphoblastoid cell lines EBNA-5 is preferentially targetted to distinct nuclear foci. Previously we have shown (W.Q. Jiang, L. Szekely, V. Wendel-Hansen, N. Ringertz, G. Klein, and A. Rosen, Exp. Cell Res. 197:314-318, 1991) that the same foci also contained the retinoblastoma (Rb) protein. Using a similar double immunofluorescence technique, we now show that these foci colocalize with nuclear bodies positive for PML, the promyelocytic leukemia-associated protein. Artificial spreading of the chromatin by exposure to the forces of fluid surface tension disrupts this colocalization gradually, suggesting that the bodies consist of at least two subcomponents. Heat shock or metabolic stress induced by high cell density leads to the release of EBNA-5 from the PML-positive nuclear bodies and induces it to translocate to the nucleoli. In addition to their presence in nuclear bodies, both proteins are occasionally present in nuclear aggregates and doughnut-like structures in which PML is concentrated in an outer shell. Nuclear bodies with prominent PML staining are seen in resting B lymphocytes. This staining pattern does not change upon EBV infection. In freshly infected cells EBNA-5 antigens are first distributed throughout the nucleoplasm. After a few days intensely staining foci develop. These foci coincide with PML-positive nuclear bodies. At a later stage and in established lymphoblastoid cell lines EBNA-5 is almost exclusively present in the PML-positive nuclear foci. The colocalization is restricted to EBV-infected human lymphoblasts. The data presented indicate that the distinct EBNA-5 foci are not newly formed structures but the result of translocation of the viral protein to a specialized domain present already in the nuclei of uninfected cells.
Collapse
Affiliation(s)
- L Szekely
- Microbiology and Tumor Biology Center, Karolinska Institute, Stockholm, Sweden
| | | | | | | | | | | |
Collapse
|
28
|
Abstract
The purpose of this review is to bring attention to some additional work in the tumor virus/tumor suppressor field which may have been overshadowed by reports describing adenovirus, SV40, and HPV oncoprotein binding to pRB and p53. The data reviewed herein provide further support for the model that a common mechanism by which DNA tumor viruses transform cells involves inactivation of cellular proteins which function as negative regulators of cell growth.
Collapse
Affiliation(s)
- J W Ludlow
- Department of Biochemistry, School of Medicine and Dentistry, Rochester, NY 14642, USA
| | | |
Collapse
|
29
|
|
30
|
Affiliation(s)
- E S Razvi
- Department of Pathology, University of Massachusetts Medical Center, Worcester 01655, USA
| | | |
Collapse
|
31
|
Li SL, Biberfeld P, Ernberg I. DNA of lymphoma-associated herpesvirus (HVMF1) in SIV-infected monkeys (Macaca fascicularis) shows homologies to EBNA-1, -2 and -5 genes. Int J Cancer 1994; 59:287-95. [PMID: 7927931 DOI: 10.1002/ijc.2910590223] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
We have characterized a new Epstein-Barr-virus(EBV)-like herpesvirus associated with lymphomas of SIV-infected cynomolgus (Macaca fascicularis) monkeys and propose that this virus is designated herpesvirus macaca fascicularis I (HVMFI). Genomic regions in HVMF1 of potential significance for tumor pathogenesis were analyzed by Southern blotting, PCR and sequencing, and compared with human EBV DNA. Virus from 7 SIV-associated lymphomas and one lymphoma-derived cell line were shown to share homology with the EBNA1- and EBNA2-coding regions of EBV, while some homology to EBV-LMP1 was detectable only at low-stringency hybridization. Homologous regions to the long internal repeat (IR1; BamHI W), the EBER1 and 2 and the latent origin of DNA replication (oriP) could also be demonstrated in HVMF1. These coding regions, except IR1, showed restriction-enzyme maps different from those of EBV. Sequencing of the EBNA5 homologous region of HVMF1 DNA, corresponding to exons W1 and W2, showed 65% homology to the EBV exons W1 and W2, and 80% to the whole region including the intron. Since EBNA5 has been reported to bind tumor-suppressor proteins p53 and Rb in vitro, the HVMF1 homology could be important for the lymphomagenic capacity of this monkey herpesvirus.
Collapse
MESH Headings
- Amino Acid Sequence
- Animals
- Antigens, Viral/genetics
- Base Sequence
- DNA Replication
- DNA, Neoplasm/analysis
- DNA, Neoplasm/genetics
- DNA, Viral/analysis
- DNA, Viral/genetics
- DNA-Binding Proteins/genetics
- Epstein-Barr Virus Nuclear Antigens
- Exons
- HIV-1
- HIV-2
- Herpesviridae/chemistry
- Herpesviridae/genetics
- Herpesviridae Infections/complications
- Herpesviridae Infections/virology
- Herpesvirus 4, Human/genetics
- Lymphoma/complications
- Lymphoma/virology
- Lymphoma, AIDS-Related/virology
- Macaca fascicularis
- Molecular Sequence Data
- Nucleic Acid Hybridization
- Polymerase Chain Reaction
- Promoter Regions, Genetic
- RNA-Binding Proteins/genetics
- Repetitive Sequences, Nucleic Acid
- Sequence Homology, Nucleic Acid
- Simian Acquired Immunodeficiency Syndrome/complications
- Simian Acquired Immunodeficiency Syndrome/virology
- Tumor Cells, Cultured
- Viral Matrix Proteins/genetics
Collapse
Affiliation(s)
- S L Li
- Immunopathology Laboratory, Karolinska Institute, Stockholm, Sweden
| | | | | |
Collapse
|
32
|
Abstract
The first human tumour suppressor gene, the Retinoblastoma Susceptibility gene (RB1) was first demonstrated in retinoblastoma, a rare paediatric eye tumour which has been studied extensively over the last century. Genetic studies of retinoblastoma have yielded unique insights into familial cancer syndromes and the mechanisms of oncogenesis by tumour suppressor genes such as the RB1 gene. In this view, we will summarize past research into the genetics of retinoblastoma that led to the discovery of the RB1 gene and discuss the influence these results have had on the field of cancer research. In addition, we will discuss current research into RB1 as it relates to cancer and its potential for new therapies.
Collapse
Affiliation(s)
- E L Schubert
- Department of Molecular Genetics, University of Texas M.D. Anderson Cancer Center, Houston 77030
| | | | | |
Collapse
|
33
|
|
34
|
Abstract
At least three genetic changes are known to contribute to the genesis of Burkitt's lymphoma (BL): the Ig/myc translocation, the presence of Epstein-Barr virus (EBV) in the vast majority of the endemic and a minority of sporadic tumors, and a p53 mutation, present in approximately 60% of the BL-derived lines. Activation of c-myc by juxtaposition to Ig sequences is a universal common denominator in endemic and sporadic EBV positive and negative BLs. It acts by preventing the cell from leaving the cycling compartment and by facilitating immune escape. EBV probably acts by expanding the target cell population at risk and prolonging its life span. This, together with the malaria co-factor, would increase the risk of the translocation accident. The p53 mutation may be essential for the continued growth of the tumors where it occurs, since introduction of wild-type p53 leads to their apoptotic death.
Collapse
Affiliation(s)
- G Klein
- Department of Tumor Biology, Karolinska Institutet, Stockholm, Sweden
| |
Collapse
|
35
|
Szekely L, Selivanova G, Magnusson KP, Klein G, Wiman KG. EBNA-5, an Epstein-Barr virus-encoded nuclear antigen, binds to the retinoblastoma and p53 proteins. Proc Natl Acad Sci U S A 1993; 90:5455-9. [PMID: 8390666 PMCID: PMC46739 DOI: 10.1073/pnas.90.12.5455] [Citation(s) in RCA: 211] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Epstein-Barr virus (EBV) immortalized human lymphoblastoid cell lines express six virally encoded nuclear proteins, designated EBV nuclear antigens 1-6 (EBNA-1-6). We show that the EBNA-5 protein (alternatively designated EBNA-LP) that is required for B-cell transformation can form a molecular complex with the retinoblastoma (RB) and p53 tumor suppressor proteins. Using EBNA-5 deletion mutants, we have found that a 66-amino acid-long peptide, encoded by the W repeat of the EBV genome, is sufficient for binding. Point mutations of RB and p53 that inhibit their complexing with other DNA viral oncoproteins do not affect their binding to EBNA-5. p53 competes with RB for EBNA-5 binding. Our data suggest that the mechanisms involved in EBV transformation may include impairment of RB and p53 function.
Collapse
MESH Headings
- Amino Acid Sequence
- Antibodies, Monoclonal
- Antigens, Viral/biosynthesis
- Antigens, Viral/metabolism
- Binding Sites
- Blotting, Western
- Burkitt Lymphoma
- DNA-Binding Proteins/biosynthesis
- DNA-Binding Proteins/metabolism
- Epstein-Barr Virus Nuclear Antigens
- Glutathione Transferase/metabolism
- Herpesvirus 4, Human/immunology
- Herpesvirus 4, Human/metabolism
- Humans
- Leukemia, Promyelocytic, Acute
- Molecular Sequence Data
- Mutagenesis, Site-Directed
- Peptides/chemical synthesis
- Recombinant Fusion Proteins/metabolism
- Retinoblastoma Protein/metabolism
- Sequence Deletion
- Transfection
- Tumor Cells, Cultured
- Tumor Suppressor Protein p53/metabolism
Collapse
Affiliation(s)
- L Szekely
- Department of Tumor Biology, Karolinska Institute, Stockholm, Sweden
| | | | | | | | | |
Collapse
|
36
|
Abstract
Nuclear bodies (NBs) were first described in detail some 30 years ago, by conventional electron microscopy, as prominent interchromatin structures found primarily in the nuclei of malignant or hyperstimulated animal cells. Subsequent studies have shown that NBs are ubiquitous organelles, but they are numerically and morphologically quite varied. With the recent discovery of human autoantibodies against several key nuclear antigens present in some NBs, these structures are once again the subject of much attention. At least one class of NBs, coiled bodies, has been shown to be nucleolus-derived and to contain not only nucleolus-associated antigens, but also many of the snRNP components involved in pre-mRNA splicing. These data suggest that coiled bodies, and perhaps other NBs as well, are multifunctional and may be involved in the processing or transport of both pre-mRNA and pre-rRNA. Further evidence is provided showing that NBs constitute distinct nuclear domains whose functional significance is just now emerging.
Collapse
Affiliation(s)
- K Brasch
- Department of Biology, California State University, San Bernardino 92407-2397
| | | |
Collapse
|