|
1
|
Topoisomerase IIβ-binding protein 1 activates expression of E2F1 and p73 in HPV-positive cells for genome amplification upon epithelial differentiation. Oncogene 2019; 38:3274-3287. [PMID: 30631149 PMCID: PMC6486426 DOI: 10.1038/s41388-018-0633-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Revised: 10/17/2018] [Accepted: 10/18/2018] [Indexed: 12/12/2022]
Abstract
High-risk human papillomaviruses (HPVs) constitutively activate the ataxia telangiectasia mutated (ATM) and the ataxia telangiectasia and Rad3-related (ATR) DNA damage repair pathways for viral genome amplification. HPVs activate these pathways through the immune regulator STAT-5. For the ATR pathway, STAT-5 increases expression of the topoisomerase IIβ-binding protein 1 (TopBP1), a scaffold protein that binds ATR and recruits it to sites of DNA damage. TopBP1 also acts as a transcriptional regulator and we investigated how this activity influenced the HPV life cycle. We determined that TopBP1 levels are increased in cervical intraepithelial neoplasias as well as cervical carcinomas, consistent with studies in HPV-positive cell lines. Suppression of TopBP1 by shRNAs impairs HPV genome amplification and activation of the ATR pathway but does not affect the total levels of ATR and CHK1. In contrast, knockdown reduces the expression of other DNA damage factors such as RAD51 and Mre11 but not BRCA2 or NBS1. Interestingly, TopBP1 positively regulates the expression of E2F1, a TopBP1 binding partner, and p73, in HPV positive cells in contrast to effects in other cell types. TopBP1 transcriptional activity is regulated by AKT and treatment with AKT inhibitors suppresses expression of E2F1 and p73 without interfering with ATR signaling. Importantly, the levels of p73 are elevated in HPV-positive cells and knockdown impairs HPV genome amplification. This demonstrates that p73, like p63 and p53, is an important regulator of the HPV life cycle that is controlled by the transcriptional activating properties of the multifunctional TopBP1 protein.
Collapse
|
|
2
|
Hong SY. DNA damage response is hijacked by human papillomaviruses to complete their life cycle. J Zhejiang Univ Sci B 2017; 18:215-232. [PMID: 28271657 DOI: 10.1631/jzus.b1600306] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The DNA damage response (DDR) is activated when DNA is altered by intrinsic or extrinsic agents. This pathway is a complex signaling network and plays important roles in genome stability, tumor transformation, and cell cycle regulation. Human papillomaviruses (HPVs) are the main etiological agents of cervical cancer. Cervical cancer ranks as the fourth most common cancer among women and the second most frequent cause of cancer-related death worldwide. Over 200 types of HPVs have been identified and about one third of these infect the genital tract. The HPV life cycle is associated with epithelial differentiation. Recent studies have shown that HPVs deregulate the DDR to achieve a productive life cycle. In this review, I summarize current findings about how HPVs mediate the ataxia-telangiectasia mutated kinase (ATM) and the ATM-and RAD3-related kinase (ATR) DDRs, and focus on the roles that ATM and ATR signalings play in HPV viral replication. In addition, I demonstrate that the signal transducer and activator of transcription-5 (STAT)-5, an important immune regulator, can promote ATM and ATR activations through different mechanisms. These findings may provide novel opportunities for development of new therapeutic targets for HPV-related cancers.
Collapse
Affiliation(s)
- Shi-Yuan Hong
- Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| |
Collapse
|
|
3
|
Mengual-Chuliá B, Bedhomme S, Lafforgue G, Elena SF, Bravo IG. Assessing parallel gene histories in viral genomes. BMC Evol Biol 2016; 16:32. [PMID: 26847371 PMCID: PMC4743424 DOI: 10.1186/s12862-016-0605-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Accepted: 01/29/2016] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND The increasing abundance of sequence data has exacerbated a long known problem: gene trees and species trees for the same terminal taxa are often incongruent. Indeed, genes within a genome have not all followed the same evolutionary path due to events such as incomplete lineage sorting, horizontal gene transfer, gene duplication and deletion, or recombination. Considering conflicts between gene trees as an obstacle, numerous methods have been developed to deal with these incongruences and to reconstruct consensus evolutionary histories of species despite the heterogeneity in the history of their genes. However, inconsistencies can also be seen as a source of information about the specific evolutionary processes that have shaped genomes. RESULTS The goal of the approach here proposed is to exploit this conflicting information: we have compiled eleven variables describing phylogenetic relationships and evolutionary pressures and submitted them to dimensionality reduction techniques to identify genes with similar evolutionary histories. To illustrate the applicability of the method, we have chosen two viral datasets, namely papillomaviruses and Turnip mosaic virus (TuMV) isolates, largely dissimilar in genome, evolutionary distance and biology. Our method pinpoints viral genes with common evolutionary patterns. In the case of papillomaviruses, gene clusters match well our knowledge on viral biology and life cycle, illustrating the potential of our approach. For the less known TuMV, our results trigger new hypotheses about viral evolution and gene interaction. CONCLUSIONS The approach here presented allows turning phylogenetic inconsistencies into evolutionary information, detecting gene assemblies with similar histories, and could be a powerful tool for comparative pathogenomics.
Collapse
Affiliation(s)
- Beatriz Mengual-Chuliá
- Infections and Cancer Laboratory, Catalan Institute of Oncology (ICO), Barcelona, Spain.,Bellvitge Institute of Biomedical Research (IDIBELL), Barcelona, Spain
| | - Stéphanie Bedhomme
- Infections and Cancer Laboratory, Catalan Institute of Oncology (ICO), Barcelona, Spain.,Bellvitge Institute of Biomedical Research (IDIBELL), Barcelona, Spain.,Centre d'Ecologie Fonctionnelle et Evolutive, UMR CNRS 5175, Montpellier, France
| | - Guillaume Lafforgue
- Centre d'Ecologie Fonctionnelle et Evolutive, UMR CNRS 5175, Montpellier, France.,Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas-Universidad Politécnica de Valencia, València, Spain
| | - Santiago F Elena
- Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas-Universidad Politécnica de Valencia, València, Spain.,I2SysBio, Consejo Superior de Investigaciones Científicas-Universitat de València, València, Spain.,The Santa Fe Institute, Santa Fe, NM, USA
| | - Ignacio G Bravo
- Infections and Cancer Laboratory, Catalan Institute of Oncology (ICO), Barcelona, Spain. .,MIVEGEC (UMR CNRS 5290, IRD 224, UM), National Center for Scientific Research (CNRS), Montpellier, France. .,National Center for Scientific Research (CNRS), Maladies Infectieuses et Vecteurs: Ecologie, Génétique, Evolution et Contrôle (MIVEGEC), UMR CNRS 5290, IRD 224, UM, 911 Avenue Agropolis, BP 64501, 34394, Montpellier, Cedex 5, France.
| |
Collapse
|
|
4
|
Torres-Poveda K, Bahena-Román M, Madrid-González C, Burguete-García AI, Bermúdez-Morales VH, Peralta-Zaragoza O, Madrid-Marina V. Role of IL-10 and TGF-β1 in local immunosuppression in HPV-associated cervical neoplasia. World J Clin Oncol 2014; 5:753-763. [PMID: 25302175 PMCID: PMC4129538 DOI: 10.5306/wjco.v5.i4.753] [Citation(s) in RCA: 110] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/28/2013] [Revised: 04/05/2014] [Accepted: 05/19/2014] [Indexed: 02/06/2023] Open
Abstract
Cervical cancer is a worldwide disease that constitutes a significant public health problem, especially in developing countries, not only due to its high incidence but also because the most affected population comprises women who belong to marginalized socio-economic classes. Clinical and molecular research has identified immunological impairment in squamous intraepithelial cervical lesions and cervical cancer patients. Human Papillomavirus (HPV) has several mechanisms for avoiding the immune system: it down-regulates the expression of interferon and upregulates interleukin (IL)-10 and transforming growth factor (TGF)-β1 to produce a local immunosuppressive environment, which, along with altered tumor surface antigens, forms an immunosuppressive network that inhibits the antitumor immune response. In this review we analyzed the available data on several deregulated cellular immune functions in patients with NIC I, NIC II and NIC III and cervical cancer. The effects of immunosuppressive cytokines on innate immune response, T-cell activation and cellular factors that promote tumor cell proliferation in cervical cancer patients are summarized. We discuss the functional consequences of HPV E2, E6, and E7 protein interactions with IL-10 and TGF-β1 promoters in the induction of these cytokines and postulate its effect on the cellular immune response in squamous intraepithelial cervical lesions and cervical cancer patients. This review provides a comprehensive picture of the immunological functions of IL-10 and TGF-β1 in response to HPV in humans.
Collapse
|
|
5
|
Hong S, Laimins LA. Regulation of the life cycle of HPVs by differentiation and the DNA damage response. Future Microbiol 2014; 8:1547-57. [PMID: 24266355 DOI: 10.2217/fmb.13.127] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
HPVs are the causative agents of cervical and other anogenital cancers. HPVs infect stratified epithelia and link their productive life cycles to cellular differentiation. Low levels of viral genomes are stably maintained in undifferentiated cells and productive replication or amplification is restricted to differentiated suprabasal cells. Amplification is dependent on the activation of the ATM DNA damage factors that are recruited to viral replication centers and inhibition of this pathway blocks productive replication. The STAT-5 protein appears to play a critical role in mediating activation of the ATM pathway in HPV-positive cells. While HPVs need to activate the DNA damage pathway for replication, cervical cancers contain many genomic alterations suggesting that this pathway is circumvented during progression to malignancy.
Collapse
Affiliation(s)
- Shiyuan Hong
- Department of Microbiology-Immunology, Northwestern University, Feinberg, School of Medicine, Chicago Avenue, Morton 6-681, Chicago, IL 60611, USA
| | | |
Collapse
|
|
6
|
Abstract
The papillomavirus E2 proteins are pivotal to the viral life cycle and have well characterized functions in transcriptional regulation, initiation of DNA replication and partitioning the viral genome. The E2 proteins also function in vegetative DNA replication, post-transcriptional processes and possibly packaging. This review describes structural and functional aspects of the E2 proteins and their binding sites on the viral genome. It is intended to be a reference guide to this viral protein.
Collapse
Affiliation(s)
- Alison A McBride
- Laboratory of Viral Diseases, National Institute of Allergy and Infectious Disease, National Institutes of Health, Bethesda, MD 20892, USA.
| |
Collapse
|
|
7
|
Kajitani N, Satsuka A, Kawate A, Sakai H. Productive Lifecycle of Human Papillomaviruses that Depends Upon Squamous Epithelial Differentiation. Front Microbiol 2012; 3:152. [PMID: 22536200 PMCID: PMC3334820 DOI: 10.3389/fmicb.2012.00152] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2011] [Accepted: 04/02/2012] [Indexed: 12/26/2022] Open
Abstract
Human papillomaviruses (HPVs) target the stratified epidermis, and can causes diseases ranging from benign condylomas to malignant tumors. Infections of HPVs in the genital tract are among the most common sexually transmitted diseases, and a major risk factor for cervical cancer. The virus targets epithelial cells in the basal layer of the epithelium, while progeny virions egress from terminally differentiated cells in the cornified layer, the surface layer of the epithelium. In infected basal cells, the virus maintains its genomic DNA at low-copy numbers, at which the viral productive lifecycle cannot proceed. Progression of the productive lifecycle requires differentiation of the host cell, indicating that there is tight crosstalk between viral replication and host differentiation programs. In this review, we discuss the regulation of the HPV lifecycle controlled by the differentiation program of the host cells.
Collapse
Affiliation(s)
- Naoko Kajitani
- Laboratory of Mammalian Molecular Biology, Graduate School of Biostudies, Kyoto University Kyoto, Japan
| | | | | | | |
Collapse
|
|
8
|
Abstract
Replication of the double-stranded, circular human papillomavirus (HPV) genomes requires the viral DNA replicase E1. Here, we report an initial characterization of the E1 cistron of HPV type 16 (HPV-16), the most common oncogenic mucosal HPV type found in cervical and some head and neck cancers. The first step in HPV DNA replication is an initial burst of plasmid viral DNA amplification. Complementation assays between HPV-16 genomes carrying mutations in the early genes confirmed that the expression of E1 was necessary for initial HPV-16 plasmid synthesis. The major early HPV-16 promoter, P97, was dispensable for E1 production in the initial amplification because cis mutations inactivating P97 did not affect the trans complementation of E1- mutants. In contrast, E1 expression was abolished by cis mutations in the splice donor site at nucleotide (nt) 226, the splice acceptor site at nt 409, or a TATAA box at nt 7890. The mapping of 5' mRNA ends using rapid amplification of cDNA ends defined a promoter with a transcription start site at HPV-16 nt 14, P14. P14-initiated mRNA levels were low and required intact TATAA (7890). E1 expression required the HPV-16 keratinocyte-dependent enhancer, since cis mutations in its AP-2 and TEF-1 motifs abolished the ability of the mutant genomes to complement E1- genomes, and it was further modulated by origin-proximal and -distal binding sites for the viral E2 gene products. We conclude that P14-initiated E1 expression is critical for and limiting in the initial amplification of the HPV-16 genome.
Collapse
|
|
9
|
Abstract
Papillomaviruses establish persistent infection in the dividing, basal epithelial cells of the host. The viral genome is maintained as a circular, double-stranded DNA, extrachromosomal element within these cells. Viral genome amplification occurs only when the epithelial cells differentiate and viral particles are shed in squames that are sloughed from the surface of the epithelium. There are three modes of replication in the papillomavirus life cycle. Upon entry, in the establishment phase, the viral genome is amplified to a low copy number. In the second maintenance phase, the genome replicates in dividing cells at a constant copy number, in synchrony with the cellular DNA. And finally, in the vegetative or productive phase, the viral DNA is amplified to a high copy number in differentiated cells and is destined to be packaged in viral capsids. This review discusses the cis elements and protein factors required for each stage of papillomavirus replication.
Collapse
Affiliation(s)
- Alison A McBride
- Laboratory of Viral Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| |
Collapse
|
|
10
|
Abstract
Carcinoma of the uterine cervix, a leading cause of cancer death in women worldwide, is initiated by infection with high-risk types of human papillomaviruses (HPVs). This review summarizes laboratory studies over the past 20 years that have elucidated the major features of the HPV life cycle, identified the functions of the viral proteins, and clarified the consequences of HPV infection for their host cells. This information has allowed the development of various strategies to prevent or treat infections, including prophylactic vaccination with virus-like particles, therapeutic vaccination against viral proteins expressed in cancer cells, and antiviral approaches to inhibit virus replication, spread, or pathogenesis. These strategies have the potential to cause a dramatic reduction in the incidence of cervical carcinoma and serve as the prototype for comprehensive efforts to combat virus-induced tumors.
Collapse
Affiliation(s)
- Daniel DiMaio
- Department of Genetics, Yale University School of Medicine, New Haven, Connecticut 06510, USA
| | | |
Collapse
|
|
11
|
Narahari J, Fisk JC, Melendy T, Roman A. Interactions of the cellular CCAAT displacement protein and human papillomavirus E2 protein with the viral origin of replication can regulate DNA replication. Virology 2006; 350:302-11. [PMID: 16529788 DOI: 10.1016/j.virol.2006.01.047] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2005] [Revised: 01/18/2006] [Accepted: 01/31/2006] [Indexed: 01/19/2023]
Abstract
Previously, we and others have shown that CCAAT displacement protein (CDP) negatively regulates the papillomavirus promoters. Overexpression of CDP has been shown to inhibit high-risk human papillomavirus virus (HPV) and bovine papillomavirus DNA replication in vivo presumably through reduction in expression of viral replication proteins, E1 and E2. Sequence analysis of the HPV origin indicates several potential CDP-binding sites with one site overlapping the E1-binding site. Therefore, CDP could also negatively regulate papillomavirus replication directly by preventing the loading of the initiation complex. We show here that purified CDP inhibits in vitro HPV DNA replication. Footprint analysis demonstrated that CDP binds the E1-binding site and the TATA box, and that the binding of purified CDP to the E1-binding site is decreased by the addition of purified E2 protein. Consistent with this, E2-independent in vitro HPV replication is inhibited by CDP to a greater extent than E2-dependent replication. These results suggest that binding of E2 at the E2-binding site may play an important role in overcoming the inhibition of E1 initiation complex formation caused by the binding of negative regulators like CDP to the origin of replication.
Collapse
Affiliation(s)
- Janaki Narahari
- Department of Microbiology and Immunology, Indiana University School of Medicine and Walther Cancer Institute, Indianapolis, IN 46202, USA.
| | | | | | | |
Collapse
|
|
12
|
François A, Guilbaud M, Awedikian R, Chadeuf G, Moullier P, Salvetti A. The cellular TATA binding protein is required for rep-dependent replication of a minimal adeno-associated virus type 2 p5 element. J Virol 2005; 79:11082-94. [PMID: 16103159 PMCID: PMC1193596 DOI: 10.1128/jvi.79.17.11082-11094.2005] [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: 12/22/2022] Open
Abstract
The p5 promoter region of adeno-associated virus type 2 (AAV-2) is a multifunctional element involved in rep gene expression, Rep-dependent replication, and site-specific integration. We initially characterized a 350-bp p5 region by its ability to behave like a cis-acting replication element in the presence of Rep proteins and adenoviral factors. The objective of this study was to define the minimal elements within the p5 region required for Rep-dependent replication. Assays performed in transfected cells (in vivo) indicated that the minimal p5 element was composed by a 55-bp sequence (nucleotides 250 to 304 of wild-type AAV-2) containing the TATA box, the Rep binding site, the terminal resolution site present at the transcription initiation site (trs(+1)), and a downstream 17-bp region that could potentially form a hairpin structure localizing the trs(+1) at the top of the loop. Interestingly, the TATA box was absolutely required for in vivo but dispensable for in vitro, i.e., cell-free, replication. We also demonstrated that Rep binding and nicking at the trs(+1) was enhanced in the presence of the cellular TATA binding protein, and that overexpression of this cellular factor increased in vivo replication of the minimal p5 element. Together, these studies identified the minimal replication origin present within the AAV-2 p5 promoter region and demonstrated for the first time the involvement of the TATA box, in cis, and of the TATA binding protein, in trans, for Rep-dependent replication of this viral element.
Collapse
|
|
13
|
Deng SJ, Pearce KH, Dixon EP, Hartley KA, Stanley TB, Lobe DC, Garvey EP, Kost TA, Petty RL, Rocque WJ, Alexander KA, Underwood MR. Identification of peptides that inhibit the DNA binding, trans-activator, and DNA replication functions of the human papillomavirus type 11 E2 protein. J Virol 2004; 78:2637-41. [PMID: 14963172 PMCID: PMC369253 DOI: 10.1128/jvi.78.5.2637-2641.2003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Peptide antagonists of the human papillomavirus type 11 (HPV-11) E2-DNA association were identified using a filamentous bacteriophage random peptide library. Synthetic peptides antagonized the E2-DNA interaction, effectively blocked E2-mediated transcriptional activation of a reporter gene in cell culture, and inhibited E1-E2-mediated HPV-11 DNA replication in vitro. These peptides may prove to be useful tools for characterizing E2 function and for exploring the effectiveness of E2-inhibitor-based treatments for HPV-associated diseases.
Collapse
Affiliation(s)
- Su-Jun Deng
- Departments of Gene Expression and Protein Biochemistry, GlaxoSmithKline Research and Development, Research Triangle Park, North Carolina 27709, USA
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
|
14
|
Hou SY, Wu SY, Chiang CM. Transcriptional activity among high and low risk human papillomavirus E2 proteins correlates with E2 DNA binding. J Biol Chem 2002; 277:45619-29. [PMID: 12239214 DOI: 10.1074/jbc.m206829200] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The full-length E2 protein, encoded by human papillomaviruses (HPVs), is a sequence-specific transcription factor found in all HPVs, including cancer-causing high risk HPV types 16 and 18 and wart-inducing low risk HPV types 6 and 11. To investigate whether E2 proteins encoded by high risk HPVs may function differentially from E2 proteins encoded by low risk HPVs and animal papillomaviruses, we conducted comparative DNA-binding and transcription studies using electrophoretic mobility shift assays and cell-free transcription systems reconstituted with purified general transcription factors, cofactor, RNA polymerase II, and with E2 proteins encoded by HPV-16, HPV-18, HPV-11, and bovine papillomavirus type 1 (BPV-1). We found that although different types of E2 proteins all exhibited transactivation and repression activities, depending on the sequence context of the E2-binding sites, HPV-16 E2 shows stronger transcription activity and greater DNA-binding affinity than those displayed by the other E2 proteins. Surprisingly, HPV-18 E2 behaves more similarly to BPV-1 E2 than HPV-16 E2 in its functional properties. Our studies thus categorize HPV-18 E2 and BPV-1 E2 in the same protein family, a finding consistent with the available E2 structural data that separate the closely related HPV-16 and HPV-18 E2 proteins but classify together the more divergent BPV-1 and HPV-18 E2 proteins.
Collapse
Affiliation(s)
- Samuel Y Hou
- Department of Biochemistry, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106-4935, USA
| | | | | |
Collapse
|
|
15
|
Quadt I, Mainz D, Mans R, Kremer A, Knebel-Mörsdorf D. Baculovirus infection raises the level of TATA-binding protein that colocalizes with viral DNA replication sites. J Virol 2002; 76:11123-7. [PMID: 12368354 PMCID: PMC136646 DOI: 10.1128/jvi.76.21.11123-11127.2002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
During the infection cycle of Autographa californica multicapsid nuclear polyhedrosis virus, the TATA-binding protein (TBP) of the insect host cell likely participates in early viral transcription, which is mediated by the host RNA polymerase II. However, the role of TBP in late and very late viral transcription, which is accomplished by an alpha-amanitin-resistant RNA polymerase, is unclear. We observed a dramatic increase of TBP protein during the late phases of infection. TBP mRNA levels, however, were not coordinately increased. Indirect-immunofluorescence studies revealed a nuclear redistribution of TBP during infection. After labeling of viral replication centers with bromodeoxyuridine (BrdU), costaining of TBP and BrdU showed that TBP localized to viral DNA replication centers. These results suggest a putative role of TBP during late viral transcription, which may occur in close proximity to viral DNA replication.
Collapse
Affiliation(s)
- Ilja Quadt
- Max-Planck-Institute for Neurological Research and Department of Neurology, University of Cologne, D-50931 Cologne, Germany
| | | | | | | | | |
Collapse
|