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Wu CC, Chen MS, Lee TY, Cheng YJ, Tsou HH, Huang TS, Cho DY, Chen JY. Screening and identification of emodin as an EBV DNase inhibitor to prevent its biological functions. Virol J 2023; 20:148. [PMID: 37443068 PMCID: PMC10339607 DOI: 10.1186/s12985-023-02107-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Accepted: 06/21/2023] [Indexed: 07/15/2023] Open
Abstract
BACKGROUND The Epstein-Barr virus (EBV) is a prevalent oncovirus associated with a variety of human illnesses. BGLF5, an EBV DNase with alkaline nuclease (AN) activity, plays important roles in the viral life cycle and progression of human malignancies and has been suggested as a possible diagnostic marker and target for cancer therapy. Methods used conventionally for the detection of AN activity, radioactivity-based nuclease activity assay and DNA digestion detection by gel electrophoresis, are not suitable for screening AN inhibitors; the former approach is unsafe, and the latter is complicated. In the present study, a fluorescence-based nuclease activity assay was used to screen several natural compounds and identify an EBV DNase inhibitor. RESULTS Fluorescence-based nuclease activity assays, in which the DNA substrate is labelled with PicoGreen dye, are cheaper, safer, and easier to perform. Herein, the results of the fluorescence-based nuclease activity assay were consistent with the results of the two conventional methods. In addition, the PicoGreen-labelling method was applied for the biochemical characterisation of viral nucleases. Using this approach, we explored EBV DNase inhibitors. After several rounds of screening, emodin, an anthraquinone derivative, was found to possess significant anti-EBV DNase activity. We verified the efficacy of emodin using the conventional DNA-cleavage assay. Furthermore, using comet assay and micronucleus formation detection, we confirmed that emodin can inhibit DNase-induced DNA damage and genomic instability. Additionally, emodin treatment inhibited EBV production. CONCLUSIONS Using a PicoGreen-mediated nuclease activity assay, we successfully demonstrated that emodin has the potential to inhibit EBV DNase nuclease activity. Emodin also inhibits EBV DNase-related biological functions, suggesting that it is a potential inhibitor of EBV DNase.
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Affiliation(s)
- Chung-Chun Wu
- Translational Cell Therapy Center, Department of Medical Research, China Medical University Hospital, No. 2, Yude Rd., North Dist, Taichung City, 40447, Taiwan.
| | - Mei-Shu Chen
- National Institute of Cancer Research, National Health Research Institutes, No.35, Keyan Road, Zhunan Town, Miaoli County, Taiwan
| | - Ting-Ying Lee
- Translational Cell Therapy Center, Department of Medical Research, China Medical University Hospital, No. 2, Yude Rd., North Dist, Taichung City, 40447, Taiwan
| | - Yu-Jhen Cheng
- National Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Zhunan, Taiwan
| | - Hsiao-Hui Tsou
- Institute of Population Health Sciences, National Health Research Institutes, Zhunan, Taiwan
| | - Tze-Sing Huang
- National Institute of Cancer Research, National Health Research Institutes, No.35, Keyan Road, Zhunan Town, Miaoli County, Taiwan
| | - Der-Yang Cho
- Translational Cell Therapy Center, Department of Medical Research, China Medical University Hospital, No. 2, Yude Rd., North Dist, Taichung City, 40447, Taiwan
| | - Jen-Yang Chen
- National Institute of Cancer Research, National Health Research Institutes, No.35, Keyan Road, Zhunan Town, Miaoli County, Taiwan.
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Kuchta AL, Parikh H, Zhu Y, Kellogg GE, Parris DS, McVoy MA. Structural modelling and mutagenesis of human cytomegalovirus alkaline nuclease UL98. J Gen Virol 2011; 93:130-138. [PMID: 21900421 DOI: 10.1099/vir.0.034876-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Human cytomegalovirus encodes an alkaline nuclease, UL98, that is highly conserved among herpesviruses and has both endonuclease (endo) and exonuclease (exo) activities. This protein is thought to be important for viral replication and therefore represents a potential target for antiviral development; however, little is known about its structure or role in viral replication. Comparative structural modelling was used to build a model of UL98 based on the known structure of shutoff and exonuclease protein from Kaposi's sarcoma-associated herpesvirus. The model predicts that UL98 residues D254, E278 and K280 represent the critical aspartic acid, glutamic acid and lysine active-site residues, respectively, while R164 and S252 correspond to residues proposed to bind the 5' phosphate of the DNA substrate. UL98 with an amino-terminal hexahistidine tag was expressed in Escherichia coli, purified by affinity chromatography and confirmed to have exo and endo activities. Amino acid substitutions D254A, E278A, K280A and S252A virtually eliminated exo and endo activities, whereas R164A retained full endo activity but only 10 % of the exo activity compared with the wild-type enzyme. A mutant virus lacking UL98 was viable but severely attenuated for replication, while one expressing UL98(R164A) replicated normally. These results confirm the utility of the model in representing the active-site region of UL98 and suggest a mechanism for the differentiation of endonuclease and exonuclease activities. These findings could facilitate the exploration of the roles of alkaline nucleases in herpesvirus replication and the rational design of inhibitors that target their enzymic activities.
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Affiliation(s)
- Alison L Kuchta
- Department of Pediatrics, Virginia Commonwealth University, Richmond, VA 23298, USA
| | - Hardik Parikh
- Department of Medicinal Chemistry, Virginia Commonwealth University, Richmond, VA 23298-0540, USA
| | - Yali Zhu
- Department of Molecular Virology, Immunology, and Medical Genetics, The Ohio State University, Columbus, OH 43210, USA
| | - Glen E Kellogg
- Department of Medicinal Chemistry, Virginia Commonwealth University, Richmond, VA 23298-0540, USA
| | - Deborah S Parris
- Department of Molecular Virology, Immunology, and Medical Genetics, The Ohio State University, Columbus, OH 43210, USA
| | - Michael A McVoy
- Department of Pediatrics, Virginia Commonwealth University, Richmond, VA 23298, USA
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Bagnéris C, Briggs LC, Savva R, Ebrahimi B, Barrett TE. Crystal structure of a KSHV-SOX-DNA complex: insights into the molecular mechanisms underlying DNase activity and host shutoff. Nucleic Acids Res 2011; 39:5744-56. [PMID: 21421561 PMCID: PMC3141240 DOI: 10.1093/nar/gkr111] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The early lytic phase of Kaposi’s sarcoma herpesvirus infection is characterized by viral replication and the global degradation (shutoff) of host mRNA. Key to both activities is the virally encoded alkaline exonuclease KSHV SOX. While the DNase activity of KSHV SOX is required for the resolution of viral genomic DNA as a precursor to encapsidation, its exact involvement in host shutoff remains to be determined. We present the first crystal structure of a KSHV SOX–DNA complex that has illuminated the catalytic mechanism underpinning both its endo and exonuclease activities. We further illustrate that KSHV SOX, similar to its Epstein–Barr virus homologue, has an intrinsic RNase activity in vitro that although an element of host shutoff, cannot solely account for the phenomenon.
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Affiliation(s)
- Claire Bagnéris
- Institute of Structural and Molecular Biology, Crystallography, Department of Biological Sciences, Birkbeck College, Malet Street, London WC1E 7HX , UK
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Rowe M, Zuo J. Immune responses to Epstein-Barr virus: molecular interactions in the virus evasion of CD8+ T cell immunity. Microbes Infect 2010; 12:173-81. [PMID: 20004735 PMCID: PMC2832755 DOI: 10.1016/j.micinf.2009.12.001] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2009] [Accepted: 12/01/2009] [Indexed: 12/21/2022]
Abstract
Persistent viruses have mechanisms for modulating the host immune responses that are essential for achieving a lifelong virus–host balance while minimizing the viral pathogenicity. Here we review some of the immune-modulating mechanisms evolved by the ubiquitous but potentially oncogenic Epstein–Barr virus, with particular emphasis on the molecular mechanisms of genes interfering with HLA class I antigen presentation.
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Affiliation(s)
- Martin Rowe
- Cancer Research UK Birmingham Cancer Centre, University of Birmingham, College of Medical and Dental Sciences, Vincent Drive, Edgbaston, Birmingham B15 2TT, United Kingdom.
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Rennekamp AJ, Lieberman PM. Initiation of lytic DNA replication in Epstein-Barr virus: search for a common family mechanism. Future Virol 2010; 5:65-83. [PMID: 22468146 PMCID: PMC3314400 DOI: 10.2217/fvl.09.69] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Herpesviruses are a complex family of dsDNA viruses that are a major cause of human disease. All family members share highly related viral replication proteins, such as DNA polymerase, ssDNA-binding proteins and processivity factors. Consequently, it is generally thought that lytic replication occurs through a common and conserved mechanism. However, considerable evidence indicates that proteins controlling initiation of DNA replication vary greatly among the herepesvirus subfamilies. In this article, we focus on some of the known mechanisms that regulate Epstein-Barr virus lytic-cycle replication, and compare this to other herpesvirus family members. Our reading of the literature leads us to conclude that diverse viral mechanisms generate a common nucleoprotein prereplication structure that can be recognized by a highly conserved family of viral replication enzymes.
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Affiliation(s)
- Andrew J Rennekamp
- The Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA and The University of Pennsylvania, Biomedical Graduate Program in Cell & Molecular Biology, The School of Medicine, Philadelphia, PA 19104, USA, Tel.: +1 215 898 9523, Fax: +1 251 898 0663,
| | - Paul M Lieberman
- The Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA, Tel.: +1 215 898 9491, Fax: +1 215 898 0663,
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Wu CC, Liu MT, Chang YT, Fang CY, Chou SP, Liao HW, Kuo KL, Hsu SL, Chen YR, Wang PW, Chen YL, Chuang HY, Lee CH, Chen M, Wayne Chang WS, Chen JY. Epstein-Barr virus DNase (BGLF5) induces genomic instability in human epithelial cells. Nucleic Acids Res 2009; 38:1932-49. [PMID: 20034954 PMCID: PMC2847232 DOI: 10.1093/nar/gkp1169] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Epstein–Barr Virus (EBV) DNase (BGLF5) is an alkaline nuclease and has been suggested to be important in the viral life cycle. However, its effect on host cells remains unknown. Serological and histopathological studies implied that EBV DNase seems to be correlated with carcinogenesis. Therefore, we investigate the effect of EBV DNase on epithelial cells. Here, we report that expression of EBV DNase induces increased formation of micronucleus, an indicator of genomic instability, in human epithelial cells. We also demonstrate, using γH2AX formation and comet assay, that EBV DNase induces DNA damage. Furthermore, using host cell reactivation assay, we find that EBV DNase expression repressed damaged DNA repair in various epithelial cells. Western blot and quantitative PCR analyses reveal that expression of repair-related genes is reduced significantly in cells expressing EBV DNase. Host shut-off mutants eliminate shut-off expression of repair genes and repress damaged DNA repair, suggesting that shut-off function of BGLF5 contributes to repression of DNA repair. In addition, EBV DNase caused chromosomal aberrations and increased the microsatellite instability (MSI) and frequency of genetic mutation in human epithelial cells. Together, we propose that EBV DNase induces genomic instability in epithelial cells, which may be through induction of DNA damage and also repression of DNA repair, subsequently increases MSI and genetic mutations, and may contribute consequently to the carcinogenesis of human epithelial cells.
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Affiliation(s)
- Chung-Chun Wu
- National Institute of Cancer Research, National Health Research Institutes, Zhunan, Taiwan
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A bridge crosses the active-site canyon of the Epstein-Barr virus nuclease with DNase and RNase activities. J Mol Biol 2009; 391:717-28. [PMID: 19538972 DOI: 10.1016/j.jmb.2009.06.034] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2009] [Revised: 05/29/2009] [Accepted: 06/12/2009] [Indexed: 11/24/2022]
Abstract
Epstein-Barr virus, a double-stranded DNA (dsDNA) virus, is a major human pathogen from the herpesvirus family. The nuclease is one of the lytic cycle proteins required for successful viral replication. In addition to the previously described endonuclease and exonuclease activities on single-stranded DNA and dsDNA substrates, we observed an RNase activity for Epstein-Barr virus nuclease in the presence of Mn(2+), giving a possible explanation for its role in host mRNA degradation. Its crystal structure shows a catalytic core of the D-(D/E)XK nuclease superfamily closely related to the exonuclease from bacteriophage lambda with a bridge across the active-site canyon. This bridge may reduce endonuclease activity, ensure processivity or play a role in strand separation of dsDNA substrates. As the DNA strand that is subject to cleavage is likely to make a sharp turn in front of the bridge, endonuclease activity on single-stranded DNA stretches appears to be possible, explaining the cleavage of circular substrates.
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Fang CY, Lee CH, Wu CC, Chang YT, Yu SL, Chou SP, Huang PT, Chen CL, Hou JW, Chang Y, Tsai CH, Takada K, Chen JY. Recurrent chemical reactivations of EBV promotes genome instability and enhances tumor progression of nasopharyngeal carcinoma cells. Int J Cancer 2009; 124:2016-25. [PMID: 19132751 DOI: 10.1002/ijc.24179] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Nasopharyngeal carcinoma (NPC) is an endemic malignancy prevalent in South East Asia. Epidemiological studies have associated this disease closely with Epstein-Barr virus (EBV) infection. Previous studies also showed that EBV reactivation is implicated in the progression of NPC. Thus, we proposed that recurrent reactivations of EBV may be important for its pathogenic role. In this study, NPC cell lines latently infected with EBV, NA and HA, and the corresponding EBV-negative NPC cell lines, NPC-TW01 (TW01) and HONE-1, were treated with 12-O-tetradecanoylphorbol-13-acetate (TPA) and sodium n-butyrate (SB) for lytic cycle induction. A single treatment with TPA/SB revealed that DNA double-strand breaks and formation of micronuclei (a marker for genome instability) were associated with EBV reactivation in NA and HA cells. Examination of EBV early genes had identified several lytic proteins, particularly EBV DNase, as potent activators that induced DNA double-strand breaks and contribute to genome instability. Recurrent reactivations of EBV in NA and HA cells resulted in a marked increase of genome instability. In addition, the degree of chromosomal aberrations, as shown by chromosome structural variants and DNA copy-number alterations, is proportional to the frequency of TPA/SB-induced EBV reactivation. Whereas these DNA abnormalities were limited in EBV-negative TW01 cells with mock or TPA/SB treatment, and were few in mock-treated NA cells. The invasiveness and tumorigenesis assays also revealed a profound increase in both characteristics of the repeatedly reactivated NA cells. These results suggest that recurrent EBV reactivations may result in accumulation of genome instability and promote the tumor progression of NPC.
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Affiliation(s)
- Chih-Yeu Fang
- National Institute of Cancer Research, National Health Research Institutes, Zhunan, Taiwan
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Hsiang CY, Ho TY. Emodin is a novel alkaline nuclease inhibitor that suppresses herpes simplex virus type 1 yields in cell cultures. Br J Pharmacol 2008; 155:227-35. [PMID: 18552872 PMCID: PMC2538697 DOI: 10.1038/bjp.2008.242] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND AND PURPOSE Most antiviral therapies directed against herpes simplex virus (HSV) infections are limited to a small group of nucleoside analogues that target the viral polymerase. Extensive clinical use of these drugs has led to the emergence of resistant viral strains, mainly in immunocompromised patients. This highlights the need for the development of new anti-herpesviral drugs with novel targets. Herein the effects of a plant anthraquinone, emodin, on the HSV-1 alkaline nuclease activity and virus yields were investigated. EXPERIMENTAL APPROACH HSV-1 alkaline nuclease activity was examined by nuclease activity assay. Inhibition of virus yields was measured by plaque reduction assay and immunohistochemical staining. Interaction between emodin and alkaline nuclease was analysed by docking technology. KEY RESULTS Emodin specifically inhibited the nuclease activity of HSV-1 UL12 alkaline nuclease in a biochemical assay. Plaque reduction assay revealed that emodin reduced the plaque formation with an EC(50) of 21.5+/-4.4 muM. Immunohistochemical staining using the anti-nucleocapsid protein antibody demonstrated that emodin induced the accumulation of viral nucleocapsids in the nucleus in a dose-dependent manner. Docking analysis further suggested that the inhibitory effect of emodin on the UL12 activity may result from the interaction between emodin and critical catalytic amino acid residues of UL12. CONCLUSIONS AND IMPLICATIONS Our findings suggest that emodin is a potent anti-HSV agent that inhibits the yields of HSV-1 via the suppression of a novel target, UL12.
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Affiliation(s)
- C-Y Hsiang
- Department of Microbiology, China Medical University, Taichung, Taiwan
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Hu HP, Hsieh SC, King CC, Wang WK. Characterization of retrovirus-based reporter viruses pseudotyped with the precursor membrane and envelope glycoproteins of four serotypes of dengue viruses. Virology 2007; 368:376-87. [PMID: 17662331 PMCID: PMC7126519 DOI: 10.1016/j.virol.2007.06.026] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2007] [Revised: 05/14/2007] [Accepted: 06/19/2007] [Indexed: 11/16/2022]
Abstract
In this study, we successfully established retrovirus-based reporter viruses pseudotyped with the precursor membrane and envelope (PrM/E) proteins of each of the four serotypes of dengue viruses, which caused the most important arboviral diseases in this century. Co-sedimentation of the dengue E protein and HIV-1 core proteins by sucrose gradient analysis of the pseudotype reporter virus of dengue virus type 2, D2(HIVluc), and detection of HIV-1 core proteins by immunoprecipitation with anti-E monoclonal antibody suggested that dengue viral proteins were incorporated into the pseudotype viral particles. The infectivity in target cells, as assessed by the luciferase activity, can be inhibited by the lysosomotropic agents, suggesting a pH-dependent mechanism of entry. Amino acid substitutions of the leucine at position 107, a critical residue at the fusion loop of E protein, with lysine resulted in severe impairment in infectivity, suggesting that entry of the pseudotype reporter virus is mediated through the fusogenic properties of E protein. With more and more dengue viral sequences available from different outbreaks worldwide, this sensitive and convenient tool has the potential to facilitate molecular characterization of the PrM/E proteins of dengue field isolates.
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Affiliation(s)
- Hsien-Ping Hu
- Institute of Microbiology, College of Medicine, National Taiwan University, No 1 Sec1 Jen-Ai Rd, Taipei 100, Taiwan
| | - Szu-Chia Hsieh
- Institute of Microbiology, College of Medicine, National Taiwan University, No 1 Sec1 Jen-Ai Rd, Taipei 100, Taiwan
| | - Chwan-Chuen King
- Institute of Epidemiology, College of Public Health, National Taiwan University, No 1 Sec1 Jen-Ai Rd, Taipei 100, Taiwan
| | - Wei-Kung Wang
- Institute of Microbiology, College of Medicine, National Taiwan University, No 1 Sec1 Jen-Ai Rd, Taipei 100, Taiwan
- Department of Internal Medicine, National Taiwan University Hospital, No 7 Chung-Shan S Rd, Taipei 100, Taiwan
- Corresponding author. Institute of Microbiology, National Taiwan University, No 1 Sec1 Jen-Ai Rd, Taipei 100, Taiwan. Fax: +886 2 2391 5293.
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Rowe M, Glaunsinger B, van Leeuwen D, Zuo J, Sweetman D, Ganem D, Middeldorp J, Wiertz EJHJ, Ressing ME. Host shutoff during productive Epstein-Barr virus infection is mediated by BGLF5 and may contribute to immune evasion. Proc Natl Acad Sci U S A 2007; 104:3366-71. [PMID: 17360652 PMCID: PMC1805610 DOI: 10.1073/pnas.0611128104] [Citation(s) in RCA: 185] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Relatively little is known about immune evasion during the productive phase of infection by the gamma(1)-herpesvirus Epstein-Barr virus (EBV). The use of a unique system to isolate cells in lytic cycle allowed us to identify a host shutoff function operating in productively EBV-infected B cells. This impairment of protein synthesis results from mRNA degradation induced upon expression of the early lytic-cycle gene product BGLF5. Recently, a gamma(2)-herpesvirus, Kaposi sarcoma herpesvirus, has also been shown to encode a host shutoff function, indicating that host shutoff appears to be a general feature of gamma-herpesviruses. One of the consequences of host shutoff is a block in the synthesis of HLA class I and II molecules, reflected by reduced levels of these antigen-presenting complexes at the surface of cells in EBV lytic cycle. This effect could lead to escape from T cell recognition and elimination of EBV-producing cells, thereby allowing generation of viral progeny in the face of memory T cell responses.
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Affiliation(s)
- Martin Rowe
- *Division of Cancer Studies, University of Birmingham Medical School, Vincent Drive, Edgbaston, Birmingham B15 2TT, United Kingdom
| | - Britt Glaunsinger
- Howard Hughes Medical Institute, Departments of Microbiology and Medicine, University of California, San Francisco, CA 94143
| | - Daphne van Leeuwen
- Department of Medical Microbiology, Leiden University Medical Center, Albinusdreef 2, 2333 ZA Leiden, The Netherlands; and
| | - Jianmin Zuo
- *Division of Cancer Studies, University of Birmingham Medical School, Vincent Drive, Edgbaston, Birmingham B15 2TT, United Kingdom
| | - David Sweetman
- *Division of Cancer Studies, University of Birmingham Medical School, Vincent Drive, Edgbaston, Birmingham B15 2TT, United Kingdom
| | - Don Ganem
- Howard Hughes Medical Institute, Departments of Microbiology and Medicine, University of California, San Francisco, CA 94143
| | - Jaap Middeldorp
- Department of Pathology, Free University Medical Center, De Boelelaan 1117, 1081 HV Amsterdam, The Netherlands
| | - Emmanuel J. H. J. Wiertz
- Department of Medical Microbiology, Leiden University Medical Center, Albinusdreef 2, 2333 ZA Leiden, The Netherlands; and
- To whom correspondence should be addressed. E-mail:
| | - Maaike E. Ressing
- Department of Medical Microbiology, Leiden University Medical Center, Albinusdreef 2, 2333 ZA Leiden, The Netherlands; and
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