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Asai R, Kato A, Kawaguchi Y. Epstein-Barr virus protein kinase BGLF4 interacts with viral transactivator BZLF1 and regulates its transactivation activity. J Gen Virol 2009; 90:1575-1581. [PMID: 19321754 DOI: 10.1099/vir.0.010462-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
BGLF4 is a serine/threonine protein kinase encoded by Epstein-Barr virus. One of the physiological substrates of BGLF4 is viral transactivator BZLF1. In the present study, it was demonstrated that alanine substitution of the serine residue at position 209 (S209A) in BZLF1 eliminated phosphorylation of the protein by BGLF4 in vitro. The S209A mutation in BZLF1, as well as a K102I mutation in BGLF4, which inactivated catalytic activity of the viral kinase, also inhibited formation of a stable BGLF4-BZLF1 complex and downregulation of BZLF1 autotransactivation activity mediated by BGLF4. These results indicate that formation of a stable complex of BGLF4-BZLF1 enables downregulation of BZLF1 autoregulation activity and it appears that BGLF4 phosphorylation of BZLF1 may be involved in these processes.
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Affiliation(s)
- Risa Asai
- Department of Virology, Nagoya University Graduate School of Medicine, Showa-ku, Nagoya 466-8550, Japan.,Division of Viral Infection, Department of Infectious Disease Control, International Research Center for Infectious Diseases, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo 108-8639, Japan
| | - Ai Kato
- Department of Virology, Nagoya University Graduate School of Medicine, Showa-ku, Nagoya 466-8550, Japan
| | - Yasushi Kawaguchi
- Department of Virology, Nagoya University Graduate School of Medicine, Showa-ku, Nagoya 466-8550, Japan.,Division of Viral Infection, Department of Infectious Disease Control, International Research Center for Infectious Diseases, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo 108-8639, Japan
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Hwang S, Kim KS, Flano E, Wu TT, Tong LM, Park AN, Song MJ, Sanchez DJ, O'Connell RM, Cheng G, Sun R. Conserved herpesviral kinase promotes viral persistence by inhibiting the IRF-3-mediated type I interferon response. Cell Host Microbe 2009; 5:166-78. [PMID: 19218087 DOI: 10.1016/j.chom.2008.12.013] [Citation(s) in RCA: 121] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2007] [Revised: 11/25/2008] [Accepted: 12/03/2008] [Indexed: 12/11/2022]
Abstract
A conserved herpesviral kinase, designated ORF36 in murine gamma-herpesvirus 68 (MHV-68), plays multiple vital roles in the viral life cycle. Here, we show by screening mutant viruses that ORF36 counteracts the antiviral type I interferon (IFN) response. ORF36 specifically binds to the activated form of interferon regulatory factor 3 (IRF-3) in the nucleus, inhibiting IRF-3 interaction with the cotranscriptional activator CBP and thereby suppressing the recruitment of RNA polymerase II to the interferon beta promoter. The anti-IFN function of ORF36 is conserved among herpesvirus subfamilies, although the conserved kinase activity is not absolutely required for this function. MHV-68 lacking ORF36 induces a greater interferon response and is attenuated in vitro and in vivo, where acute viral infection in the lung and latency in the spleen are compromised. Our data suggest that herpesviruses have evolved within their conserved kinase an anti-IFN activity critical for evasion of host immunity and for persistence.
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Affiliation(s)
- Seungmin Hwang
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA 90095, USA
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Epstein-Barr virus BGLF4 kinase suppresses the interferon regulatory factor 3 signaling pathway. J Virol 2008; 83:1856-69. [PMID: 19052084 DOI: 10.1128/jvi.01099-08] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The BGLF4 protein kinase of Epstein-Barr virus (EBV) is a member of the conserved family of herpesvirus protein kinases which, to some extent, have a function similar to that of the cellular cyclin-dependent kinase in regulating multiple cellular and viral substrates. In a yeast two-hybrid screening assay, a splicing variant of interferon (IFN) regulatory factor 3 (IRF3) was found to interact with the BGLF4 protein. This interaction was defined further by coimmunoprecipitation in transfected cells and glutathione S-transferase (GST) pull-down in vitro. Using reporter assays, we show that BGLF4 effectively suppresses the activities of the poly(I:C)-stimulated IFN-beta promoter and IRF3-responsive element. Moreover, BGLF4 represses the poly(I:C)-stimulated expression of endogenous IFN-beta mRNA and the phosphorylation of STAT1 at Tyr701. In searching for a possible mechanism, BGLF4 was shown not to affect the dimerization, nuclear translocation, or CBP recruitment of IRF3 upon poly(I:C) treatment. Notably, BGLF4 reduces the amount of active IRF3 recruited to the IRF3-responsive element containing the IFN-beta promoter region in a chromatin immunoprecipitation assay. BGLF4 phosphorylates GST-IRF3 in vitro, but Ser339-Pro340 phosphorylation-dependent, Pin1-mediated downregulation is not responsible for the repression. Most importantly, we found that three proline-dependent phosphorylation sites at Ser123, Ser173, and Thr180, which cluster in a region between the DNA binding and IRF association domains of IRF3, contribute additively to the BGLF4-mediated repression of IRF3(5D) transactivation activity. IRF3 signaling is activated in reactivated EBV-positive NA cells, and the knockdown of BGLF4 further stimulates IRF3-responsive reporter activity. The data presented here thus suggest a novel mechanism by which herpesviral protein kinases suppress host innate immune responses and facilitate virus replication.
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Epstein-Barr virus BGLF4 kinase induces disassembly of the nuclear lamina to facilitate virion production. J Virol 2008; 82:11913-26. [PMID: 18815303 DOI: 10.1128/jvi.01100-08] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
DNA viruses adopt various strategies to modulate the cellular environment for efficient genome replication and virion production. Previously, we demonstrated that the BGLF4 kinase of Epstein-Barr virus (EBV) induces premature chromosome condensation through the activation of condensin and topoisomerase IIalpha (C. P. Lee, J. Y. Chen, J. T. Wang, K. Kimura, A. Takemoto, C. C. Lu, and M. R. Chen, J. Virol. 81:5166-5180, 2007). In this study, we show that BGLF4 interacts with lamin A/C and phosphorylates lamin A protein in vitro. Using a green fluorescent protein (GFP)-lamin A system, we found that Ser-22, Ser-390, and Ser-392 of lamin A are important for the BGLF4-induced disassembly of the nuclear lamina and the EBV reactivation-mediated redistribution of nuclear lamin. Virion production and protein levels of two EBV primary envelope proteins, BFRF1 and BFLF2, were reduced significantly by the expression of GFP-lamin A(5A), which has five Ser residues replaced by Ala at amino acids 22, 390, 392, 652, and 657 of lamin A. Our data indicate that BGLF4 kinase phosphorylates lamin A/C to promote the reorganization of the nuclear lamina, which then may facilitate the interaction of BFRF1 and BFLF2s and subsequent virion maturation. UL kinases of alpha- and betaherpesviruses also induce the disassembly of the nuclear lamina through similar sites on lamin A/C, suggesting a conserved mechanism for the nuclear egress of herpesviruses.
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Wang Y, Azuma Y, Moore D, Osheroff N, Neufeld KL. Interaction between tumor suppressor adenomatous polyposis coli and topoisomerase IIalpha: implication for the G2/M transition. Mol Biol Cell 2008; 19:4076-85. [PMID: 18632987 DOI: 10.1091/mbc.e07-12-1296] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The tumor suppressor adenomatous polyposis coli (APC) is implicated in regulating multiple stages of the cell cycle. APC participation in G1/S is attributed to its recognized role in Wnt signaling. APC function in the G2/M transition is less well established. To identify novel protein partners of APC that regulate the G2/M transition, APC was immunoprecipitated from colon cell lysates and associated proteins were analyzed by matrix-assisted laser desorption ionization/time of flight (MALDI-TOF). Topoisomerase IIalpha (topo IIalpha) was identified as a potential binding partner of APC. Topo IIalpha is a critical regulator of G2/M transition. Evidence supporting an interaction between endogenous APC and topo IIalpha was obtained by coimmunoprecipitation, colocalization, and Förster resonance energy transfer (FRET). The 15-amino acid repeat region of APC (M2-APC) interacted with topo IIalpha when expressed as a green fluorescent protein (GFP)-fusion protein in vivo. Although lacking defined nuclear localization signals (NLS) M2-APC predominantly localized to the nucleus. Furthermore, cells expressing M2-APC displayed condensed or fragmented nuclei, and they were arrested in the G2 phase of the cell cycle. Although M2-APC contains a beta-catenin binding domain, biochemical studies failed to implicate beta-catenin in the observed phenotype. Finally, purified recombinant M2-APC enhanced topo IIalpha activity in vitro. Together, these data support a novel role for APC in the G2/M transition, potentially through association with topo IIalpha.
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Affiliation(s)
- Yang Wang
- Department of Molecular Biosciences, University of Kansas, Lawrence, KS 66045, USA
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Abstract
Many viruses introduce DNA into the host-cell nucleus, where they must either embrace or confront chromatin factors as a support or obstacle to completion of their life cycle. Compared to the eukaryotic cell, viruses have compact and rapidly evolving genomes. Despite their smaller size, viruses have complex life cycles that involve dynamic changes in DNA structure. Nuclear entry, transcription, replication, genome stabilization, and virion packaging involve complex changes in chromosome organization and structure. Chromatin dynamics and epigenetic modifications play major roles in viral and host chromosome biology. In some cases, viruses may use novel or viral-specific epigenetic modifying activities, which may reflect variant pathways that distinguish their behavior from the bulk of the cellular chromosome. This review examines several recent discoveries that highlight the role of chromatin dynamics in the life cycle of DNA viruses.
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Yang PW, Chang SS, Tsai CH, Chao YH, Chen MR. Effect of phosphorylation on the transactivation activity of Epstein-Barr virus BMRF1, a major target of the viral BGLF4 kinase. J Gen Virol 2008; 89:884-895. [PMID: 18343828 DOI: 10.1099/vir.0.83546-0] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Modification of human herpesvirus DNA polymerase processivity factors (PFs) by phosphorylation occurs frequently during viral lytic replication. However, functional regulation of the herpesvirus PFs through phosphorylation is not well understood. In addition to processivity, the PF BMRF1 of Epstein-Barr virus can function as a transactivator to activate the BHLF1 promoter within the lytic origin of replication (oriLyt), which is assumed to facilitate DNA replication through remodelling viral chromatin structure. BMRF1 is known to be phosphorylated by the viral BGLF4 kinase, but its impact on BMRF1 function is unclear. Seven candidate BGLF4 target sites were predicted within a proline-rich region between the DNA-processivity and nuclear-localization domains of BMRF1. We show that four of these residues, Ser-337, Thr-344, Ser-349 and Thr-355, are responsible for the BGLF4-induced hyperphosphorylation of BMRF1. In functional analyses, a phosphorylation-mimicking mutant of BMRF1 shows similar nuclear localization, as well as DNA-binding ability, to the wild type; however, it displays stronger synergistic activation of the BHLF1 promoter with Zta. Notably, BGLF4 downregulates BMRF1 transactivation and enhances the transactivation activity of Zta and the synergistic activation of BMRF1 and Zta on the BHLF1 promoter. Our findings suggest that BGLF4 may modulate the activation of the oriLyt BHLF1 promoter coordinately through multiple mechanisms to facilitate optimal oriLyt-dependent viral DNA replication.
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Affiliation(s)
- Pei-Wen Yang
- Graduate Institute and Department of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan, ROC
| | - Shih-Shin Chang
- Graduate Institute and Department of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan, ROC
| | - Ching-Hwa Tsai
- Graduate Institute and Department of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan, ROC
| | - Yi-Hsin Chao
- Graduate Institute and Department of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan, ROC
| | - Mei-Ru Chen
- Graduate Institute and Department of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan, ROC
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Lu CC, Chen YC, Wang JT, Yang PW, Chen MR. Xeroderma pigmentosum C is involved in Epstein Barr virus DNA replication. J Gen Virol 2008; 88:3234-3243. [PMID: 18024891 DOI: 10.1099/vir.0.83212-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Cellular mismatch and base-excision repair machineries have been shown to be involved in Epstein-Barr Virus (EBV) lytic DNA replication. We report here that nucleotide-excision repair (NER) may also play an important role in EBV lytic DNA replication. Firstly, the EBV BGLF4 kinase interacts with xeroderma pigmentosum C (XPC), the critical DNA damage-recognition factor of NER, in yeast and in vitro, as demonstrated by yeast two-hybrid and glutathione S-transferase pull-down assays. Simultaneously, XPC was shown, by indirect immunofluorescence and co-immunoprecipitation assays, to interact and colocalize with BGLF4 in EBV-positive NA cells undergoing lytic viral replication. In addition, the efficiency of EBV DNA replication was reduced about 30-40 % by an XPC small interfering RNA. Expression of BGLF4 enhances cellular DNA-repair activity in p53-defective H1299/bcl2 cells in a host-cell reactivation assay. This enhancement was not observed in the XPC-mutant cell line XP4PA-SV unless complemented by ectopic XPC, suggesting that BGLF4 may stimulate DNA repair in an XPC-dependent manner. Overall, we suggest that the interaction of BGLF4 and XPC may be involved in DNA replication and repair and thereby enhance the efficiency of viral DNA replication.
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Affiliation(s)
- Chih-Chung Lu
- Graduate Institute and Department of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan 100, PR China
| | - Yi-Chun Chen
- Graduate Institute and Department of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan 100, PR China
| | - Jiin-Tarng Wang
- Graduate Institute and Department of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan 100, PR China
| | - Pei-Wen Yang
- Graduate Institute and Department of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan 100, PR China
| | - Mei-Ru Chen
- Graduate Institute and Department of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan 100, PR China
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Gershburg E, Pagano JS. Conserved herpesvirus protein kinases. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2007; 1784:203-12. [PMID: 17881303 PMCID: PMC2265104 DOI: 10.1016/j.bbapap.2007.08.009] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2007] [Revised: 08/08/2007] [Accepted: 08/09/2007] [Indexed: 11/21/2022]
Abstract
Conserved herpesviral protein kinases (CHPKs) are a group of enzymes conserved throughout all subfamilies of Herpesviridae. Members of this group are serine/threonine protein kinases that are likely to play a conserved role in viral infection by interacting with common host cellular and viral factors; however, along with a conserved role, individual kinases may have unique functions in the context of viral infection in such a way that they are only partially replaceable even by close homologues. Recent studies demonstrated that CHPKs are crucial for viral infection and suggested their involvement in regulation of numerous processes at various infection steps (primary infection, nuclear egress, tegumentation), although the mechanisms of this regulation remain unknown. Notwithstanding, recent advances in discovery of new CHPK targets, and studies of CHPK knockout phenotypes have raised their attractiveness as targets for antiviral therapy. A number of compounds have been shown to inhibit the activity of human cytomegalovirus (HCMV)-encoded UL97 protein kinase and exhibit a pronounced antiviral effect, although the same compounds are inactive against Epstein-Barr virus (EBV)-encoded protein kinase BGLF4, illustrating the fact that low homology between the members of this group complicates development of compounds targeting the whole group, and suggesting that individualized, structure-based inhibitor design will be more effective. Determination of CHPK structures will greatly facilitate this task.
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Affiliation(s)
- Edward Gershburg
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
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