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Widman DG, Gornisiewicz S, Shacham S, Tamir S. In vitro toxicity and efficacy of verdinexor, an exportin 1 inhibitor, on opportunistic viruses affecting immunocompromised individuals. PLoS One 2018; 13:e0200043. [PMID: 30332435 PMCID: PMC6192554 DOI: 10.1371/journal.pone.0200043] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Accepted: 10/01/2018] [Indexed: 12/29/2022] Open
Abstract
Infection of immunocompromised individuals with normally benign opportunistic viruses is a major health burden globally. Infections with viruses such as Epstein-Barr virus (EBV), human cytomegalovirus (HCMV), Kaposi's sarcoma virus (KSHV), adenoviruses (AdV), BK virus (BKPyV), John Cunningham virus (JCPyV), and human papillomavirus (HPV) are significant concerns for the immunocompromised, including when these viruses exist as a co-infection with human immunodeficiency virus (HIV). These viral infections are more complicated in patients with a weakened immune system, and often manifest as malignancies resulting in significant morbidity and mortality. Vaccination is not an attractive option for these immune compromised individuals due to defects in their adaptive immune response. Verdinexor is part of a novel class of small molecules known as SINE (Selective Inhibitor of Nuclear Export) compounds. These small molecules demonstrate specificity for the nuclear export protein XPO1, to which they bind and block function, resulting in sequestration of XPO1-dependent proteins in the nucleus of the cell. In antiviral screening, verdinexor demonstrated varying levels of efficacy against all of the aforementioned viruses including previously with HIV. Studies by other labs have discussed likely mechanisms of action for verdinexor (ie. XPO1-dependence) against each virus. GLP toxicology studies suggest that anti-viral activity can be achieved at a tolerable dose range, based on the safety profile of a previous phase 1 clinical trial of verdinexor in healthy human volunteers. Taken together, these results indicate verdinexor has the potential to be a broad spectrum antiviral for immunocompromised subjects for which vaccination is a poor option.
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Affiliation(s)
- Douglas G. Widman
- Karyopharm Therapeutics, Department of Neurofegenerative and Infectious Diseases, Newton, Massachussets, United States of America
| | - Savanna Gornisiewicz
- Karyopharm Therapeutics, Department of Neurofegenerative and Infectious Diseases, Newton, Massachussets, United States of America
| | - Sharon Shacham
- Karyopharm Therapeutics, Department of Neurofegenerative and Infectious Diseases, Newton, Massachussets, United States of America
| | - Sharon Tamir
- Karyopharm Therapeutics, Department of Neurofegenerative and Infectious Diseases, Newton, Massachussets, United States of America
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2
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Beadle JR, Valiaeva N, Yang G, Yu JH, Broker TR, Aldern KA, Harden EA, Keith KA, Prichard MN, Hartman T, Buckheit RW, Chow LT, Hostetler KY. Synthesis and Antiviral Evaluation of Octadecyloxyethyl Benzyl 9-[(2-Phosphonomethoxy)ethyl]guanine (ODE-Bn-PMEG), a Potent Inhibitor of Transient HPV DNA Amplification. J Med Chem 2016; 59:10470-10478. [PMID: 27933957 DOI: 10.1021/acs.jmedchem.6b00659] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Human papillomavirus (HPV) high-risk genotypes such as HPV-16 and HPV-18 cause the majority of anogenital tract carcinomas, including cervical cancer, the second most common malignancy in women worldwide. Currently there are no approved antiviral agents that reduce or eliminate HPV and reverse virus-associated pathology. We synthesized and evaluated several alkoxyalkyl acyclic nucleoside phosphonate diesters and identified octadecyloxyethyl benzyl 9-[(2-phosphonomethoxy)ethyl]guanine (ODE-Bn-PMEG) as an active compound which strongly inhibited transient amplification of HPV-11, -16, and -18 origin-containing plasmid DNA in transfected cells at concentrations well below its cytotoxic concentrations. ODE-Bn-PMEG demonstrated increased uptake in human foreskin fibroblast cells and was readily converted in vitro to the active antiviral metabolite, PMEG diphosphate. The P-chiral enantiomers of ODE-Bn-PMEG were obtained and appeared to have equivalent antiviral activities against HPV. ODE-Bn-PMEG is a promising candidate for the local treatment of HPV-16 and HPV-18 and other high-risk types, an important unmet medical need.
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Affiliation(s)
- James R Beadle
- University of California, San Diego , La Jolla, California 92093, United States
| | - Nadejda Valiaeva
- University of California, San Diego , La Jolla, California 92093, United States
| | - Guang Yang
- University of Alabama at Birmingham , Birmingham, Alabama 35233, United States
| | - Jei-Hwa Yu
- University of Alabama at Birmingham , Birmingham, Alabama 35233, United States
| | - Thomas R Broker
- University of Alabama at Birmingham , Birmingham, Alabama 35233, United States
| | - Kathy A Aldern
- University of California, San Diego , La Jolla, California 92093, United States
| | - Emma A Harden
- University of Alabama at Birmingham , Birmingham, Alabama 35233, United States
| | - Kathy A Keith
- University of Alabama at Birmingham , Birmingham, Alabama 35233, United States
| | - Mark N Prichard
- University of Alabama at Birmingham , Birmingham, Alabama 35233, United States
| | - Tracy Hartman
- ImQuest BioSciences , Frederick, Maryland 21704, United States
| | | | - Louise T Chow
- University of Alabama at Birmingham , Birmingham, Alabama 35233, United States
| | - Karl Y Hostetler
- University of California, San Diego , La Jolla, California 92093, United States.,Antiva Biosciences, Inc. , South San Francisco, California 94080, United States
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3
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Requirement for the E1 Helicase C-Terminal Domain in Papillomavirus DNA Replication In Vivo. J Virol 2016; 90:3198-211. [PMID: 26739052 DOI: 10.1128/jvi.03127-15] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Accepted: 12/31/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED The papillomavirus (PV) E1 helicase contains a conserved C-terminal domain (CTD), located next to its ATP-binding site, whose function in vivo is still poorly understood. The CTD is comprised of an alpha helix followed by an acidic region (AR) and a C-terminal extension termed the C-tail. Recent biochemical studies on bovine papillomavirus 1 (BPV1) E1 showed that the AR and C-tail regulate the oligomerization of the protein into a double hexamer at the origin. In this study, we assessed the importance of the CTD of human papillomavirus 11 (HPV11) E1 in vivo, using a cell-based DNA replication assay. Our results indicate that combined deletion of the AR and C-tail drastically reduces DNA replication, by 85%, and that further truncation into the alpha-helical region compromises the structural integrity of the E1 helicase domain and its interaction with E2. Surprisingly, removal of the C-tail alone or mutation of highly conserved residues within the domain still allows significant levels of DNA replication (55%). This is in contrast to the absolute requirement for the C-tail reported for BPV1 E1 in vitro and confirmed here in vivo. Characterization of chimeric proteins in which the AR and C-tail from HPV11 E1 were replaced by those of BPV1 indicated that while the function of the AR is transferable, that of the C-tail is not. Collectively, these findings define the contribution of the three CTD subdomains to the DNA replication activity of E1 in vivo and suggest that the function of the C-tail has evolved in a PV type-specific manner. IMPORTANCE While much is known about hexameric DNA helicases from superfamily 3, the papillomavirus E1 helicase contains a unique C-terminal domain (CTD) adjacent to its ATP-binding site. We show here that this CTD is important for the DNA replication activity of HPV11 E1 in vivo and that it can be divided into three functional subdomains that roughly correspond to the three conserved regions of the CTD: an alpha helix, needed for the structural integrity of the helicase domain, followed by an acidic region (AR) and a C-terminal tail (C-tail) that have been shown to regulate the oligomerization of BPV1 E1 in vitro. Characterization of E1 chimeras revealed that, while the function of the AR could be transferred from BPV1 E1 to HPV11 E1, that of the C-tail could not. These results suggest that the E1 CTD performs multiple functions in DNA replication, some of them in a virus type-specific manner.
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Lentz MR, Shideler T. Phosphorylation of bovine papillomavirus E1 by the protein kinase CK2 near the nuclear localization signal does not influence subcellular distribution of the protein in dividing cells. Arch Virol 2015; 161:165-9. [PMID: 26467928 DOI: 10.1007/s00705-015-2641-6] [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: 05/26/2015] [Accepted: 10/07/2015] [Indexed: 11/25/2022]
Abstract
The bovine papillomavirus E1 helicase is essential for viral replication. In dividing cells, DNA replication maintains, but does not increase, the viral genome copy number. Replication is limited by low E1 expression and an E1 nucleocytoplasmic shuttling mechanism. Shuttling is controlled in part by phosphorylation of E1 by cellular kinases. Here we investigate conserved sites for phosphorylation by kinase CK2 within the E1 nuclear localization signal. When these CK2 sites are mutated to either alanine or aspartic acid, no change in replication phenotype is observed, and there is no effect on the subcellular distribution of E1, which remains primarily nuclear. This demonstrates that phosphorylation of E1 by CK2 at these sites is not a factor in regulating viral DNA replication in dividing cells.
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Affiliation(s)
- Michael R Lentz
- Department of Biology, University of North Florida, 1 UNF Drive, Jacksonville, FL, 32224, USA.
| | - Tess Shideler
- Department of Biology, University of North Florida, 1 UNF Drive, Jacksonville, FL, 32224, USA
- Department of Pathology, University of New Mexico, Albuquerque, NM, 87131, USA
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5
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Schwartz S. Papillomavirus transcripts and posttranscriptional regulation. Virology 2013; 445:187-96. [PMID: 23706315 DOI: 10.1016/j.virol.2013.04.034] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Revised: 04/26/2013] [Accepted: 04/29/2013] [Indexed: 11/19/2022]
Abstract
Papillomavirus gene expression is strictly linked to the differentiation state of the infected cell and is highly regulated at the level of transcription and RNA processing. All papillomaviruses make extensive use of alternative mRNA polyadenylation and splicing to control gene expression. This chapter contains a compilation of all known alternatively spliced papillomavirus mRNAs and it summarizes our current knowledge of viral RNA elements, and viral and cellular factors that control papillomavirus mRNA processing.
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Affiliation(s)
- Stefan Schwartz
- Department of Laboratory Medicine, Section of Medical Microbiology, Lund University, BMC-B13, Sölvegatan 19, 223 62 Lund, Sweden.
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6
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Regulation of human papillomavirus gene expression by splicing and polyadenylation. Nat Rev Microbiol 2013; 11:239-51. [DOI: 10.1038/nrmicro2984] [Citation(s) in RCA: 115] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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HPV-16 E2 contributes to induction of HPV-16 late gene expression by inhibiting early polyadenylation. EMBO J 2012; 31:3212-27. [PMID: 22617423 DOI: 10.1038/emboj.2012.147] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2011] [Accepted: 04/24/2012] [Indexed: 11/08/2022] Open
Abstract
We provide evidence that the human papillomavirus (HPV) E2 protein regulates HPV late gene expression. High levels of E2 caused a read-through at the early polyadenylation signal pAE into the late region of the HPV genome, thereby inducing expression of L1 and L2 mRNAs. This is a conserved property of E2 of both mucosal and cutaneous HPV types. Induction could be reversed by high levels of HPV-16 E1 protein, or by the polyadenylation factor CPSF30. HPV-16 E2 inhibited polyadenylation in vitro by preventing the assembly of the CPSF complex. Both the N-terminal and hinge domains of E2 were required for induction of HPV late gene expression in transfected cells as well as for inhibition of polyadenylation in vitro. Finally, overexpression of HPV-16 E2 induced late gene expression from a full-length genomic clone of HPV-16. We speculate that the accumulation of high levels of E2 during the viral life cycle, not only turns off the expression of the pro-mitotic viral E6 and E7 genes, but also induces the expression of the late HPV genes L1 and L2.
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The papillomavirus E1 helicase activates a cellular DNA damage response in viral replication foci. J Virol 2011; 85:8981-95. [PMID: 21734054 DOI: 10.1128/jvi.00541-11] [Citation(s) in RCA: 146] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The papillomavirus E1 and E2 proteins are essential for viral genome replication. E1 is a helicase that unwinds the viral origin and recruits host cellular factors to replicate the viral genome. E2 is a transcriptional regulator that helps recruit the E1 helicase to the origin and also plays a role in genome partitioning. We find that when coexpressed, the E1 and E2 proteins from several papillomavirus types localize to defined nuclear foci and result in growth suppression of the host cells. Growth suppression was due primarily to E1 protein function, and nuclear expression of E1 was accompanied by activation of a DNA damage response, resulting in phosphorylation of ATM, Chk2, and H2AX. Growth suppression and ATM activation required the ATPase and origin-specific binding functions of the E1 protein and resulted in active DNA repair, as evidenced by incorporation of nucleotide analogs and detection of free DNA ends. In the presence of the E2 protein, these activities became localized to nuclear foci. We postulate that these foci represent viral replication factories and that a cellular DNA damage response is activated to facilitate replication of viral DNA.
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Abstract
Human papillomaviruses (HPVs), members of a very large family of small DNA viruses, cause both benign papillomas and malignant tumors. While most research on these viruses over the past 30 years has focused on their oncogenic properties in the genital tract, they also play an important role in diseases of the upper aerodigestive tract. Rapidly accelerating advances in knowledge have increased our understanding of the biology of these viruses and this knowledge, in turn, is being applied to new approaches to prevent, diagnose, and treat HPV-induced diseases. In this introductory article, we provide an overview of the structure and life cycle of the mucosal HPVs and their interactions with their target tissues and cells. Finally, we provide our thoughts about treatments for HPV-induced diseases, present and future.
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Fradet-Turcotte A, Brault K, Titolo S, Howley PM, Archambault J. Characterization of papillomavirus E1 helicase mutants defective for interaction with the SUMO-conjugating enzyme Ubc9. Virology 2009; 395:190-201. [PMID: 19836047 DOI: 10.1016/j.virol.2009.09.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2009] [Revised: 06/17/2009] [Accepted: 09/16/2009] [Indexed: 12/31/2022]
Abstract
The E1 helicase from BPV and HPV16 interacts with Ubc9 to facilitate viral genome replication. We report that HPV11 E1 also interacts with Ubc9 in vitro and in the yeast two-hybrid system. Residues in E1 involved in oligomerization (353-435) were sufficient for binding to Ubc9 in vitro, but the origin-binding and ATPase domains were additionally required in yeast. Nuclear accumulation of BPV E1 was shown previously to depend on its interaction with Ubc9 and sumoylation on lysine 514. In contrast, HPV11 and HPV16 E1 mutants defective for Ubc9 binding remained nuclear even when the SUMO pathway was inhibited. Furthermore, we found that K514 in BPV E1 and the analogous K559 in HPV11 E1 are not essential for nuclear accumulation of E1. These results suggest that the interaction of E1 with Ubc9 is not essential for its nuclear accumulation but, rather, depends on its oligomerization and binding to DNA and ATP.
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Affiliation(s)
- Amélie Fradet-Turcotte
- Laboratory of Molecular Virology, Institut de Recherches Cliniques de Montréal and Department of Biochemistry, University of Montreal, 110 Pine Avenue West, Montreal, Quebec, Canada H2W 1R7
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11
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Côté-Martin A, Moody C, Fradet-Turcotte A, D'Abramo CM, Lehoux M, Joubert S, Poirier GG, Coulombe B, Laimins LA, Archambault J. Human papillomavirus E1 helicase interacts with the WD repeat protein p80 to promote maintenance of the viral genome in keratinocytes. J Virol 2008; 82:1271-83. [PMID: 18032488 PMCID: PMC2224424 DOI: 10.1128/jvi.01405-07] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2007] [Accepted: 11/12/2007] [Indexed: 02/02/2023] Open
Abstract
Due to the limited coding capacity of their small genomes, human papillomaviruses (HPV) rely extensively on host factors for the completion of their life cycles. Accordingly, most HPV proteins, including the replicative helicase E1, engage in multiple protein interactions. The fact that conserved regions of E1 have not yet been ascribed a function prompted us to use tandem affinity protein purification (TAP) coupled to mass spectrometry to identify novel targets of this helicase. This method led to the discovery of a novel interaction between the N-terminal 40 amino acids of HPV type 11 (HPV11) E1 and the cellular WD repeat protein p80 (WDR48). We found that interaction with p80 is conserved among E1 proteins from anogenital HPV but not among cutaneous or animal types. Colocalization studies showed that E1 can redistribute p80 from the cytoplasm to the nucleus in a manner that is dependent on the E1 nuclear localization signal. Three amino acid substitutions in E1 proteins from HPV11 and -31 were identified that abrogate binding to p80 and its relocalization to the nucleus. In HPV31 E1, these substitutions reduced but did not completely abolish transient viral DNA replication. HPV31 genomes encoding two of the mutant E1 proteins were not maintained as episomes in immortalized primary keratinocytes, whereas one encoding the third mutant protein was maintained at a very low copy number. These findings suggest that the interaction of E1 with p80 is required for efficient maintenance of the viral episome in undifferentiated keratinocytes.
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Affiliation(s)
- Alexandra Côté-Martin
- Laboratory of Molecular Virology, Institut de Recherches Cliniques de Montréal, 110 Pine Avenue West, Montreal, Quebec, Canada
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Kisseljov F, Sakharova O, Kondratjeva T. Chapter 2 Cellular and Molecular Biological Aspects of Cervical Intraepithelial Neoplasia. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2008; 271:35-95. [DOI: 10.1016/s1937-6448(08)01202-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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13
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Poppelreuther S, Iftner T, Stubenrauch F. A novel splice donor site at nt 1534 is required for long-term maintenance of HPV31 genomes. Virology 2008; 370:93-101. [PMID: 17904182 DOI: 10.1016/j.virol.2007.08.026] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2007] [Revised: 07/13/2007] [Accepted: 08/22/2007] [Indexed: 11/28/2022]
Abstract
Human papillomaviruses (HPV) are small double-stranded DNA viruses that replicate as low copy number nuclear plasmids during the persistent phase. HPV only possess nine open reading frames but extend their coding capabilities by alternative RNA splicing. We have identified in cell lines with replicating HPV31 genomes viral transcripts that connect the novel splice donor (SD) sites at nt 1426 and 1534 within the E1 replication gene to known splice acceptors at nt 3295 or 3332 within the E2/E4 region. These transcripts are polyadenylated and are present at low amounts in the non-productive and productive phase of the viral life cycle. Mutation of the novel splice sites in the context of HPV31 genomes revealed that the inactivation of SD1534 had only minor effects in short-term replication assays but displayed a low copy number phenotype in long-term cultures which might be due to the expression of alternative E1;E4 or yet unknown viral proteins. This suggests a regulatory role for minor splice sites within E1 for papillomavirus replication.
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Affiliation(s)
- Sven Poppelreuther
- Sektion Experimentelle Virologie, Institut für Medizinische Virologie und Epidemiologie der Viruskrankheiten, Universitaetsklinikum Tuebingen, Elfriede-Aulhorn-Str. 6, 72076 Tuebingen, Germany
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Kadaja M, Sumerina A, Verst T, Ojarand M, Ustav E, Ustav M. Genomic instability of the host cell induced by the human papillomavirus replication machinery. EMBO J 2007; 26:2180-91. [PMID: 17396148 PMCID: PMC1852791 DOI: 10.1038/sj.emboj.7601665] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2006] [Accepted: 03/05/2007] [Indexed: 12/18/2022] Open
Abstract
Development of invasive cervical cancer upon infection by 'high-risk' human papillomavirus (HPV) in humans is a stepwise process in which some of the initially episomal 'high-risk' type of HPVs (HR-HPVs) integrate randomly into the host cell genome. We show that HPV replication proteins E1 and E2 are capable of inducing overamplification of the genomic locus where HPV origin has been integrated. Clonal analysis of the cells in which the replication from integrated HPV origin was induced showed excision, rearrangement and de novo integration of the HPV containing and flanking cellular sequences. These data suggest that papillomavirus replication machinery is capable of inducing genomic changes of the host cell that may facilitate the formation of the HPV-dependent cancer cell.
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Affiliation(s)
- Meelis Kadaja
- Institute of Molecular and Cell Biology, University of Tartu, Tartu, Estonia
| | - Alina Sumerina
- Institute of Molecular and Cell Biology, University of Tartu, Tartu, Estonia
| | - Tatjana Verst
- Institute of Molecular and Cell Biology, University of Tartu, Tartu, Estonia
| | - Mari Ojarand
- Institute of Molecular and Cell Biology, University of Tartu, Tartu, Estonia
| | - Ene Ustav
- Institute of Technology, University of Tartu, Tartu, Estonia
| | - Mart Ustav
- Institute of Molecular and Cell Biology, University of Tartu, Tartu, Estonia
- Institute of Technology, University of Tartu, Tartu, Estonia
- Department of Biomedical Technology, Institute of Technology, University of Tartu and Estonian Biocentre, Nooruse 1, Tartu 50411, Estonia. Tel.: +372 737 4800; Fax: +372 737 4900; E-mail:
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Yu JH, Lin BY, Deng W, Broker TR, Chow LT. Mitogen-activated protein kinases activate the nuclear localization sequence of human papillomavirus type 11 E1 DNA helicase to promote efficient nuclear import. J Virol 2007; 81:5066-78. [PMID: 17344281 PMCID: PMC1900230 DOI: 10.1128/jvi.02480-06] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Human and animal papillomavirus DNA replicates as multicopy nuclear plasmids. Replication requires two viral proteins, the origin-recognition protein E2 and the replicative DNA helicase E1. Using genetic, biochemical, and immunofluorescence assays, we demonstrated that efficient nuclear import of the human papillomavirus (HPV) type 11 E1 protein depends on a codominant bipartite nuclear localization sequence (NLS) and on phosphorylation of the serine residues S89 and S93 by the mitogen-activated protein kinases (MAPKs), extracellular signal-regulated kinase, and c-Jun N-terminal protein kinase. The NLS and the MAPK substrates are located within a 50-amino-acid-long peptide near the amino terminus, previously designated the localization regulatory region (LRR). The downstream NLS overlaps the cyclin-binding motif RRL, which is necessary for phosphorylation by the cyclin-dependent kinases to inactivate a dominant nuclear export sequence, also in the LRR. Alanine mutations of the MAPK substrates significantly impaired nuclear import, whereas phospho-mimetic mutations partially restored nuclear import. We further identified two MAPK docking motifs near the C terminus of E1 that are conserved among E1 proteins of many HPVs and bovine papillomavirus type 1. Mutations of these MAPK docking motifs or addition of specific MAPK inhibitors significantly reduced nuclear import. Interestingly, a fraction of the NLS-minus E1 protein was cotransported with the E2 protein into the nucleus and supported transient viral DNA replication. In contrast, E1 proteins mutated in the MAPK docking motifs were completely inactive in transient replication, an indication that additional properties were adversely affected by those changes.
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Affiliation(s)
- Jei-Hwa Yu
- Department of Biochemistry and Molecular Genetics, McCallum Building, University of Alabama at Birmingham, 1918 University Boulevard, Birmingham, Alabama 35294-0005, USA
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Zheng ZM, Baker CC. Papillomavirus genome structure, expression, and post-transcriptional regulation. FRONT BIOSCI-LANDMRK 2006; 11:2286-302. [PMID: 16720315 PMCID: PMC1472295 DOI: 10.2741/1971] [Citation(s) in RCA: 295] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Papillomaviruses are a group of small non-enveloped DNA tumor viruses whose infection usually causes benign epithelial lesions (warts). Certain types of HPVs, such as HPV-16, HPV-18, and HPV-31, have been recognized as causative agents of cervical cancer and anal cancer and their infections, which arise via sexual transmission, are associated with more than 95% of cervical cancer. Papillomaviruses infect keratinocytes in the basal layer of stratified squamous epithelia and replicate in the nucleus of infected keratinocytes in a differentiation-dependent manner. Viral gene expression in infected cells depends on cell differentiation and is tightly regulated at the transcriptional and post-transcriptional levels. A noteworthy feature of all papillomavirus transcripts is that they are transcribed as a bicistronic or polycistronic form containing two or more ORFs and are polyadenylated at either an early or late poly(A) site. In the past ten years, remarkable progress has been made in understanding how this complex viral gene expression is regulated at the level of transcription (such as via DNA methylation) and particularly post-transcription (including RNA splicing, polyadenylation, and translation). Current knowledge of papillomavirus mRNA structure and RNA processing has provided some clues on how to control viral oncogene expression. However, we still have little knowledge about which mRNAs are used to translate each viral protein. Continuing research on post-transcriptional regulation of papillomavirus infection will remain as a future focus to provide more insights into papillomavirus-host interactions, the virus life-cycle, and viral oncogenesis.
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Affiliation(s)
- Zhi-Ming Zheng
- HIV and AIDS Malignancy Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA.
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17
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Rush M, Zhao X, Schwartz S. A splicing enhancer in the E4 coding region of human papillomavirus type 16 is required for early mRNA splicing and polyadenylation as well as inhibition of premature late gene expression. J Virol 2005; 79:12002-15. [PMID: 16140776 PMCID: PMC1212645 DOI: 10.1128/jvi.79.18.12002-12015.2005] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Successful inhibition of human papillomavirus type 16 (HPV-16) late gene expression early in the life cycle is essential for persistence of infection, the highest risk factor for cervical cancer. Our study aimed to locate regulatory RNA elements in the early region of HPV-16 that influence late gene expression. For this purpose, subgenomic HPV-16 expression plasmids under control of the strong human cytomegalovirus immediate early promoter were used. An exonic splicing enhancer that firmly supported the use of the E4 3' splice site at position 3358 in the early region of the HPV-16 genome was identified. The enhancer was mapped to a 65-nucleotide AC-rich sequence located approximately 100 nucleotides downstream of the position 3358 3' splice site. Deletion of the enhancer caused loss of both splicing at the upstream position 3358 3' splice site and polyadenylation at the early polyadenylation signal, pAE. Direct splicing occurred at the competing L1 3' splice site at position 5639 in the late region. Optimization of the position 3358 3' splice site restored splicing to that site and polyadenylation at pAE. Additionally, a sequence of 40 nucleotides with a negative effect on late mRNA production was located immediately downstream of the enhancer. As the E4 3' splice site is employed by both early and late mRNAs, the enhancer constitutes a key regulator of temporal HPV-16 gene expression, which is required for early mRNA production as well as for the inhibition of premature late gene expression.
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Affiliation(s)
- Margaret Rush
- Department of Medical Biochemistry and Microbiology, Uppsala University, Biomedical Centre, Husargatan 3, Box 582, 75123 Uppsala, Sweden
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Deng W, Lin BY, Jin G, Wheeler CG, Ma T, Harper JW, Broker TR, Chow LT. Cyclin/CDK regulates the nucleocytoplasmic localization of the human papillomavirus E1 DNA helicase. J Virol 2004; 78:13954-65. [PMID: 15564503 PMCID: PMC533924 DOI: 10.1128/jvi.78.24.13954-13965.2004] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2004] [Accepted: 08/03/2004] [Indexed: 12/17/2022] Open
Abstract
Cyclin-dependent kinases (CDKs) play key roles in eukaryotic DNA replication and cell cycle progression. Phosphorylation of components of the preinitiation complex activates replication and prevents reinitiation. One mechanism is mediated by nuclear export of critical proteins. Human papillomavirus (HPV) DNA replication requires cellular machinery in addition to the viral replicative DNA helicase E1 and origin recognition protein E2. E1 phosphorylation by cyclin/CDK is critical for efficient viral DNA replication. We now show that E1 is phosphorylated by CDKs in vivo and that phosphorylation regulates its nucleocytoplasmic localization. We identified a conserved regulatory region for localization which contains a dominant leucine-rich nuclear export sequence (NES), the previously defined cyclin binding motif, three serine residues that are CDK substrates, and a putative bipartite nuclear localization sequence. We show that E1 is exported from the nucleus by a CRM1-dependent mechanism unless the NES is inactivated by CDK phosphorylation. Replication activities of E1 phosphorylation site mutations are reduced and correlate inversely with their increased cytoplasmic localization. Nuclear localization and replication activities of most of these mutations are enhanced or restored by mutations in the NES. Collectively, our data demonstrate that CDK phosphorylation controls E1 nuclear localization to support viral DNA amplification. Thus, HPV adopts and adapts the cellular regulatory mechanism to complete its reproductive program.
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Affiliation(s)
- Wentao Deng
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, 510 McCallum Basic Health Sciences Building, 1918 University Blvd., Birmingham, AL 35294-0005, USA
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Longworth MS, Laimins LA. Pathogenesis of human papillomaviruses in differentiating epithelia. Microbiol Mol Biol Rev 2004; 68:362-72. [PMID: 15187189 PMCID: PMC419925 DOI: 10.1128/mmbr.68.2.362-372.2004] [Citation(s) in RCA: 406] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Human papillomaviruses (HPV) are the etiological agents of cervical and other anogenital malignancies. Over 100 different types of HPVs have been identified to date, and all target epithelial tissues for infection. One-third of HPV types specifically infect the genital tract, and a subset of these are the causative agents of anogenital cancers. Other HPV types that infect the genital tract induce benign hyperproliferative lesions or genital warts. The productive life cycle of HPVs is linked to epithelial differentiation. Papillomaviruses are thought to infect cells in the basal layer of stratified epithelia and establish their genomes as multicopy nuclear episomes. In these cells, viral DNA is replicated along with cellular chromosomes. Following cell division, one of the daughter cells migrates away from the basal layer and undergoes differentiation. In highly differentiated suprabasal cells, vegetative viral replication and late-gene expression are activated, resulting in the generation of progeny virions. Since virion production is restricted to differentiated cells, infected basal cells can persist for up to several decades or until the immune system clears the infection. The E6 and E7 genes encode viral oncoproteins that target Rb and p53, respectively. During the viral life cycle, these proteins facilitate stable maintenance of episomes and stimulate differentiated cells to reenter the S phase. The E1 and E2 proteins act as origin recognition factors as well as regulators of early viral transcription. The functions of the E5 and E1--E4 proteins are still largely unknown, but these proteins have been implicated in modulating late viral functions. The L1 and L2 proteins form icosahedral capsids for progeny virion generation. The characterization of the cellular targets of these viral proteins and the mechanisms regulating the differentiation-dependent viral life cycle remain active areas for the study of these important human pathogens.
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Affiliation(s)
- Michelle S Longworth
- Department of Microbiology-Immunology, The Fineberg Medical School, Northwestern University, 303 E. Chicago Ave., Chicago, IL 60611, USA
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