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Lou H, Boland JF, Li H, Burk R, Yeager M, Anderson SK, Wentzensen N, Schiffman M, Mirabello L, Dean M. HPV16 E7 Nucleotide Variants Found in Cancer-Free Subjects Affect E7 Protein Expression and Transformation. Cancers (Basel) 2022; 14:4895. [PMID: 36230818 PMCID: PMC9562847 DOI: 10.3390/cancers14194895] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Revised: 09/23/2022] [Accepted: 09/30/2022] [Indexed: 11/17/2022] Open
Abstract
The human papillomavirus (HPV) type 16 E7 oncogene is critical to carcinogenesis and highly conserved. Previous studies identified a preponderance of non-synonymous E7 variants amongst HPV16-positive cancer-free controls compared to those with cervical cancer. To investigate the function of E7 variants, we constructed full-length HPV16 E7 genes and tested variants at positions H9R, D21N, N29S, E33K, T56I, D62N, S63F, S63P, T64M, E80K, D81N, P92L, and P92S (found only in controls); D14E, N29H cervical intraepithelial neoplasia (CIN2), and P6L, H51N, R77S (CIN3). We determined the steady-state level of cytoplasmic and nuclear HPV16 E7 protein. All variants from controls showed a reduced level of E7 protein, with 7/13 variants having lower protein levels. In contrast, 2/3 variants from the CIN3 precancer group had near-wild type E7 levels. We assayed the activity of representative variants in stably transfected NIH3T3 cells. The H9R, E33K, P92L, and P92S variants found in control subjects had lower transforming activity than D14E and N29H variants (CIN2), and the R77S (CIN3) had activity only slightly reduced from wild-type E7. In addition, R77S and WT E7 caused increased migration of NIH3T3 cells in a wound-healing assay compared with H9R, E33K, P92L, and P92S (controls) and D14E (CIN2). These data provide evidence that the E7 variants found in HPV16-positive cancer-free women are partially defective for transformation and cell migration, further demonstrating the importance of fully active E7 in cancer development.
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Affiliation(s)
- Hong Lou
- Cancer Genetics Research Laboratory, Division of Cancer Epidemiology and Genetics, Frederick National Laboratory for Cancer Research, Rockville, MD 20850, USA
| | - Joseph F. Boland
- Cancer Genetics Research Laboratory, Division of Cancer Epidemiology and Genetics, Frederick National Laboratory for Cancer Research, Rockville, MD 20850, USA
| | - Hongchuan Li
- Basic Science Program, Frederick National Laboratory for Cancer Research, Frederick, MD 21702, USA
| | - Robert Burk
- Departments of Pediatrics, Microbiology and Immunology, and Obstetrics & Gynecology and Women’s Health, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Meredith Yeager
- Cancer Genetics Research Laboratory, Division of Cancer Epidemiology and Genetics, Frederick National Laboratory for Cancer Research, Rockville, MD 20850, USA
| | - Stephen K. Anderson
- Basic Science Program, Frederick National Laboratory for Cancer Research, Frederick, MD 21702, USA
| | - Nicolas Wentzensen
- Laboratory of Cancer Genetics, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Rockville, MD 20850, USA
| | - Mark Schiffman
- Laboratory of Cancer Genetics, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Rockville, MD 20850, USA
| | - Lisa Mirabello
- Laboratory of Cancer Genetics, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Rockville, MD 20850, USA
| | - Michael Dean
- Laboratory of Translational Genomics, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Rockville, MD 20850, USA
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Basukala O, Banks L. The Not-So-Good, the Bad and the Ugly: HPV E5, E6 and E7 Oncoproteins in the Orchestration of Carcinogenesis. Viruses 2021; 13:1892. [PMID: 34696321 PMCID: PMC8541208 DOI: 10.3390/v13101892] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 09/13/2021] [Accepted: 09/14/2021] [Indexed: 12/15/2022] Open
Abstract
Infection with HPV starts with the access of the viral particles to basal cells in the epidermis, potentially via microtraumas to the skin. The basal cells are able to keep away these pathogens in normal circumstances through a robust immune response from the host, as HPV infections are, in general, cleared within 2 to 3 weeks. However, the rare instances of persistent infection and/or in cases where the host immune system is compromised are major risk factors for the development of lesions potentially leading to malignancy. Evolutionarily, obligatory pathogens such as HPVs would not be expected to risk exposing the host to lethal cancer, as this would entail challenging their own life cycle, but infection with these viruses is highly correlated with cancer and malignancy-as in cancer of the cervix, which is almost always associated with these viruses. Despite this key associative cause and the availability of very effective vaccines against these viruses, therapeutic interventions against HPV-induced cancers are still a challenge, indicating the need for focused translational research. In this review, we will consider the key roles that the viral proteins play in driving the host cells to carcinogenesis, mainly focusing on events orchestrated by early proteins E5, E6 and E7-the not-so-good, the bad and the ugly-and discuss and summarize the major events that lead to these viruses mechanistically corrupting cellular homeostasis, giving rise to cancer and malignancy.
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Affiliation(s)
| | - Lawrence Banks
- Tumour Virology Laboratory, International Centre for Genetic Engineering and Biotechnology, Padriciano 99, I-34149 Trieste, Italy;
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N-Terminal Fatty Acids of NEF MUT Are Required for the CD8 + T-Cell Immunogenicity of In Vivo Engineered Extracellular Vesicles. Vaccines (Basel) 2020; 8:vaccines8020243. [PMID: 32456079 PMCID: PMC7350016 DOI: 10.3390/vaccines8020243] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Revised: 05/15/2020] [Accepted: 05/17/2020] [Indexed: 12/23/2022] Open
Abstract
We recently described a cytotoxic CD8+ T lymphocyte (CTL) vaccine platform based on the intramuscular (i.m.) injection of DNA eukaryotic vectors expressing antigens of interest fused at the C-terminus of HIV-1 Nefmut, i.e., a functionally defective mutant that is incorporated at quite high levels into exosomes/extracellular vesicles (EVs). This system has been proven to elicit strong CTL immunity against a plethora of both viral and tumor antigens, as well as inhibit both transplantable and orthotopic tumors in mice. However, a number of open issues remain regarding the underlying mechanism. Here we provide evidence that hindering the uploading into EVs of Nefmut-derived products by removing the Nefmut N-terminal fatty acids leads to a dramatic reduction of the downstream antigen-specific CD8+ T-cell activation after i.m. injection of DNA vectors in mice. This result formally demonstrates that the generation of engineered EVs is part of the mechanism underlying the in vivo induced CD8+ T-cell immunogenicity. Gaining new insights on the EV-based vaccine platform can be relevant in view of its possible translation into the clinic to counteract both chronic and acute infections as well as tumors.
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The Subcellular Localisation of the Human Papillomavirus (HPV) 16 E7 Protein in Cervical Cancer Cells and Its Perturbation by RNA Aptamers. Viruses 2015; 7:3443-61. [PMID: 26131956 PMCID: PMC4517109 DOI: 10.3390/v7072780] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Revised: 06/17/2015] [Accepted: 06/17/2015] [Indexed: 02/04/2023] Open
Abstract
Human papillomavirus (HPV) is the most common viral infection of the reproductive tract, affecting both men and women. High-risk oncogenic types are responsible for almost 90% of anogenital and oropharyngeal cancers including cervical cancer. Some of the HPV "early" genes, particularly E6 and E7, are known to act as oncogenes that promote tumour growth and malignant transformation. Most notably, HPV-16 E7 interacts with the tumour suppressor protein pRb, promoting its degradation, leading to cell cycle dysregulation in infected cells. We have previously shown that an RNA aptamer (termed A2) selectively binds to HPV16 E7 and is able to induce apoptosis in HPV16-transformed cervical carcinoma cell lines (SiHa) through reduction of E7 levels. In this study, we investigated the effects of the A2 aptamer on E7 localisation in order to define its effects on E7 activity. We demonstrate for the first time that E7 localised to the plasma membrane. In addition, we show that A2 enhanced E7 localisation in the ER and that the A2-mediated reduction of E7 was not associated with proteasomal degradation. These data suggest that A2 perturbs normal E7 trafficking through promoting E7 ER retention.
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Abstract
Human papillomavirus (HPV) infection is a major cause of cervical cancer, the second most common cancer in women worldwide. Currently, a HPV L1-based virus-like particle has been approved as a prophylactic vaccine against HPV infection, which will probably lead to a reduction in cervical cancer incidence within a few decades. Therapeutic vaccines, however, are expected to have an impact on cervical cancer or its precursor lesions, by taking advantage of the fact that the regulatory proteins (E6 and E7) of HPV are expressed constantly in HPV-associated cervical cancer cells. Vaccine types targeting these regulatory proteins include the recombinant protein and DNA vaccines, peptide vaccines, dendritic-cell vaccines, and viral and bacterial vector deliveries of vaccines, and these may provide an opportunity to control cervical cancer. Further approaches incorporating these vaccine types with either conventional therapy modalities or the modulation of CD4(+) regulatory T cells appear to be more promising in achieving increased therapeutic efficacy. In this review, we summarize current and future therapeutic vaccine strategies against HPV-associated malignancies at the animal and clinical levels.
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Affiliation(s)
- Jeong-Im Sin
- Catholic University of Daegu, Department of Microbiology, School of Medicine, 3056-6, Daemyung-4-Dong, Namgu, Daegu, 705-718, Korea.
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Abstract
E7 is an accessory protein that is not encoded by all papillomaviruses. The E7 amino terminus contains two regions of similarity to conserved regions 1 and 2 of the adenovirus E1A protein, which are also conserved in the simian vacuolating virus 40 large tumor antigen. The E7 carboxyl terminus consists of a zinc-binding motif, which is related to similar motifs in E6 proteins. E7 proteins play a central role in the human papillomavirus life cycle, reprogramming the cellular environment to be conducive to viral replication. E7 proteins encoded by the cancer-associated alpha human papillomaviruses have potent transforming activities, which together with E6, are necessary but not sufficient to render their host squamous epithelial cell tumorigenic. This article strives to provide a comprehensive summary of the published research studies on human papillomavirus E7 proteins.
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7
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Smal C, Alonso LG, Wetzler DE, Heer A, de Prat Gay G. Ordered self-assembly mechanism of a spherical oncoprotein oligomer triggered by zinc removal and stabilized by an intrinsically disordered domain. PLoS One 2012; 7:e36457. [PMID: 22590549 PMCID: PMC3348928 DOI: 10.1371/journal.pone.0036457] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2012] [Accepted: 04/06/2012] [Indexed: 12/21/2022] Open
Abstract
Background Self-assembly is a common theme in proteins of unrelated sequences or functions. The human papillomavirus E7 oncoprotein is an extended dimer with an intrinsically disordered domain, that can form large spherical oligomers. These are the major species in the cytosol of HPV transformed and cancerous cells. E7 binds to a large number of targets, some of which lead to cell transformation. Thus, the assembly process not only is of biological relevance, but represents a model system to investigate a widely distributed mechanism. Methodology/Principal Findings Using various techniques, we monitored changes in secondary, tertiary and quaternary structure in a time course manner. By applying a robust kinetic model developed by Zlotnik, we determined the slow formation of a monomeric “Z-nucleus” after zinc removal, followed by an elongation phase consisting of sequential second-order events whereby one monomer is added at a time. This elongation process takes place at a strikingly slow overall average rate of one monomer added every 28 seconds at 20 µM protein concentration, strongly suggesting either a rearrangement of the growing complex after binding of each monomer or the existence of a “conformation editing” mechanism through which the monomer binds and releases until the appropriate conformation is adopted. The oligomerization determinant lies within its small 5 kDa C-terminal globular domain and, remarkably, the E7 N-terminal intrinsically disordered domain stabilizes the oligomer, preventing an insoluble amyloid route. Conclusion We described a controlled ordered mechanism with features in common with soluble amyloid precursors, chaperones, and other spherical oligomers, thus sharing determining factors for symmetry, size and shape. In addition, such a controlled and discrete polymerization reaction provides a valuable tool for nanotechnological applications. Finally, its increased immunogenicity related to its supramolecular structure is the basis for the development of a promising therapeutic vaccine candidate for treating HPV cancerous lesions.
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Affiliation(s)
- Clara Smal
- Fundación Instituto Leloir and Instituto de Investigaciones Bioquímicas-Conicet, Buenos Aires, Argentina
| | | | - Diana E. Wetzler
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Buenos Aires, Argentina
| | - Angeles Heer
- Fundación Instituto Leloir and Instituto de Investigaciones Bioquímicas-Conicet, Buenos Aires, Argentina
| | - Gonzalo de Prat Gay
- Fundación Instituto Leloir and Instituto de Investigaciones Bioquímicas-Conicet, Buenos Aires, Argentina
- * E-mail:
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Detection of human papillomavirus type 18 E7 oncoprotein in cervical smears: a feasibility study. J Clin Microbiol 2011; 50:246-57. [PMID: 22135254 DOI: 10.1128/jcm.01108-11] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Persistent infections by high-risk human papillomaviruses (HPVs) are the main etiological factor for cervical cancer, and expression of HPV E7 oncoproteins was suggested to be a potential marker for tumor progression. The objective of this study was to generate new reagents for the detection of the HPV18 E7 oncoprotein in cervical smears. Rabbit monoclonal antibodies against recombinant E7 protein of HPV type 18 (HPV18) were generated and characterized using Western blotting, epitope mapping, indirect immunofluorescence, and immunohistochemistry. One clone specifically recognizing HPV18 E7 was used for the development of a sandwich enzyme-linked immunosorbent assay (ELISA). The assay was validated using recombinant E7 proteins of various HPV types and lysates from E7-positive cervical carcinoma cells. A total of 14 HPV18 DNA-positive cervical swab specimens and 24 HPV DNA-negative-control specimens were used for the determination of E7 protein levels by the newly established sandwich ELISA. On the basis of the average absorbance values obtained from all 24 negative controls, a cutoff above which a clinical sample can be judged E7 positive was established. Significant E7 signals 6- to 30-fold over background were found in 7 out of 14 abnormal HPV18 DNA-positive cervical smear specimens. This feasibility study demonstrates for the first time that HPV18 E7 oncoprotein can be detected in cervical smears.
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Laurson J, Raj K. Localisation of human papillomavirus 16 E7 oncoprotein changes with cell confluence. PLoS One 2011; 6:e21501. [PMID: 21738683 PMCID: PMC3126820 DOI: 10.1371/journal.pone.0021501] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2011] [Accepted: 05/30/2011] [Indexed: 01/19/2023] Open
Abstract
E7 is one of the best studied proteins of human papillomavirus type 16, largely because of its oncogenic potential linked to cervical cancer. Yet the sub-cellular location of E7 remains confounding, even though it has been shown to be able to shuttle between the nucleus and the cytoplasm. Here we show with immunocytochemistry that E7 proteins are located in the nucleus and cytoplasm in sub-confluent cells, but becomes cytoplasmic in confluent cells. The change in E7's location is independent of time in culture, cell division, cell cycle phase or cellular differentiation. Levels of E7 are also increased in confluent cells as determined by Western blotting. Our investigations have also uncovered how different analytical techniques influence the observation of where E7 is localised, highlighting the importance of technical choice in such analysis. Understanding the localisation of E7 will help us to better comprehend the function of E7 on its target proteins.
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Affiliation(s)
- Joanna Laurson
- Division of Virology, National Institute for Medical Research, Medical Research Council, London, United Kingdom.
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10
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Heller C, Weisser T, Mueller-Schickert A, Rufer E, Hoh A, Leonhardt RM, Knittler MR. Identification of key amino acid residues that determine the ability of high risk HPV16-E7 to dysregulate major histocompatibility complex class I expression. J Biol Chem 2011; 286:10983-97. [PMID: 21321113 DOI: 10.1074/jbc.m110.199190] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
High risk human Papillomavirus (HPV) types are the major causative agents of cervical cancer. Reduced expression of major histocompatibility complex class I (MHC I) on HPV-infected cells might be responsible for insufficient T cell response and contribute to HPV-associated malignancy. The viral gene product required for subversion of MHC I synthesis is the E7 oncoprotein. Although it has been suggested that high and low risk HPVs diverge in their ability to dysregulate MHC I expression, it is not known what sequence determinants of HPV-E7 are responsible for this important functional difference. To investigate this, we analyzed the capability to affect MHC I of a set of chimeric E7 variants containing sequence elements from either high risk HPV16 or low risk HPV11. HPV16-E7, but not HPV11-E7, causes significant diminution of mRNA synthesis and surface presentation of MHC I, which depend on histone deacetylase activity. Our experiments demonstrate that the C-terminal region within the zinc finger domain of HPV-E7 is responsible for the contrasting effects of HPV11- and HPV16-E7 on MHC I. By using different loss- and gain-of-function mutants of HPV11- and HPV16-E7, we identify for the first time a residue variation at position 88 that is highly critical for HPV16-E7-mediated suppression of MHC I. Furthermore, our studies suggest that residues at position 78, 80, and 88 build a minimal functional unit within HPV16-E7 required for binding and histone deacetylase recruitment to the MHC I promoter. Taken together, our data provide new insights into how high risk HPV16-E7 dysregulates MHC I for immune evasion.
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Affiliation(s)
- Corina Heller
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Immunology, Tuebingen, Germany
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11
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Dreier K, Scheiden R, Lener B, Ehehalt D, Pircher H, Müller-Holzner E, Rostek U, Kaiser A, Fiedler M, Ressler S, Lechner S, Widschwendter A, Even J, Capesius C, Jansen-Dürr P, Zwerschke W. Subcellular localization of the human papillomavirus 16 E7 oncoprotein in CaSki cells and its detection in cervical adenocarcinoma and adenocarcinoma in situ. Virology 2010; 409:54-68. [PMID: 20970819 PMCID: PMC3003157 DOI: 10.1016/j.virol.2010.09.024] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2010] [Revised: 06/17/2010] [Accepted: 09/22/2010] [Indexed: 11/18/2022]
Abstract
E7 is the major oncoprotein of high-risk human papillomaviruses (HPV) which causes cervical cancer. To date E7 oncoproteins have not been investigated in cervical adenocarcinoma. In this study we generated a rabbit monoclonal anti-HPV-16 E7 antibody, RabMab42-3, which recognizes a conformational epitope in the E7 carboxy-terminal zinc-finger resulting in a strong increase in the sensitivity for the detection of cell-associated HPV-16 E7 protein relative to conventional polyclonal anti-HPV-16 E7 antibodies. Using RabMab42-3, we show that the subcellular localization of endogenous HPV-16 E7 oncoprotein varies during the cell cycle in cervical cancer cells. Moreover, we demonstrate for the first time that the HPV-16 E7 oncoprotein is abundantly expressed in cervical adenocarcinoma in situ and adenocarcinoma, suggesting an important role of HPV-16 E7 for the development of these tumors. Our findings suggest that the HPV-16 E7 oncoprotein could be a useful marker for the detection of cervical adenocarcinoma and their precursors.
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Affiliation(s)
- Kerstin Dreier
- Institute for Biomedical Aging Research of the Austrian Academy of Sciences, Innsbruck, Austria
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12
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The alphaherpesvirus US3/ORF66 protein kinases direct phosphorylation of the nuclear matrix protein matrin 3. J Virol 2010; 85:568-81. [PMID: 20962082 DOI: 10.1128/jvi.01611-10] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The protein kinase found in the short region of alphaherpesviruses, termed US3 in herpes simplex virus type 1 (HSV-1) and pseudorabies virus (PRV) and ORF66 in varicella-zoster virus (VZV), affects several viral and host cell processes, and its specific targets remain an area of active investigation. Reports suggesting that HSV-1 US3 substrates overlap with those of cellular protein kinase A (PKA) prompted the use of an antibody specific for phosphorylated PKA substrates to identify US3/ORF66 targets. HSV-1, VZV, and PRV induced very different substrate profiles that were US3/ORF66 kinase dependent. The predominant VZV-phosphorylated 125-kDa species was identified as matrin 3, one of the major nuclear matrix proteins. Matrin 3 was also phosphorylated by HSV-1 and PRV in a US3 kinase-dependent manner and by VZV ORF66 kinase at a novel residue (KRRRT150EE). Since VZV-directed T150 phosphorylation was not blocked by PKA inhibitors and was not induced by PKA activation, and since PKA predominantly targeted matrin 3 S188, it was concluded that phosphorylation by VZV was PKA independent. However, purified VZV ORF66 kinase did not phosphorylate matrin 3 in vitro, suggesting that additional cellular factors were required. In VZV-infected cells in the absence of the ORF66 kinase, matrin 3 displayed intranuclear changes, while matrin 3 showed a pronounced cytoplasmic distribution in late-stage cells infected with US3-negative HSV-1 or PRV. This work identifies phosphorylation of the nuclear matrix protein matrin 3 as a new conserved target of this kinase group.
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Dantur K, Alonso L, Castaño E, Morelli L, Centeno-Crowley JM, Vighi S, de Prat-Gay G. Cytosolic accumulation of HPV16 E7 oligomers supports different transformation routes for the prototypic viral oncoprotein: the amyloid-cancer connection. Int J Cancer 2009; 125:1902-11. [PMID: 19598264 DOI: 10.1002/ijc.24579] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
E7 is the major transforming activity in human papillomaviruses, a causal agent for cervical cancer. HPV16 E7 is a small protein with a natively unfolded domain for which dozens of specific cellular targets were described, and represents a prototypical oncoprotein among small DNA tumor viruses. The protein can form spherical oligomers with amyloid-like properties and chaperone activity. Conformation specific antibodies locate endogenous oligomeric E7 species in the cytosol of 3 model cell lines, strongly co-localizing with amyloid structures and dimeric E7 localizes to the nucleus. The cytosolic oligomeric E7 appear as the most abundant species in all cell systems tested. We show that nuclear E7 levels are replenished dynamically from the cytosolic pool and do not result from protein synthesis. Our results suggest that long-term events related to de-repression of E7 would cause accumulation of excess E7 into oligomeric species in the cytosol. These, together with the known target promiscuity of E7, may allow interactions with many of the non-pRb dependent targets described. This hypothesis is further supported by the detection of E7 oligomers in the cytosol of cancerous cells from tissue biopsies.
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Affiliation(s)
- Karina Dantur
- Instituto Leloir and Instituto de Investigaciones Bioquímicas Buenos Aires, Conicet, Patricias Argentinas 435, (C1405BWE) Ciudad Autonoma de Buenos Aires, Argentina
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Mirecka EA, Hey T, Fiedler U, Rudolph R, Hatzfeld M. Affilin Molecules Selected against the Human Papillomavirus E7 Protein Inhibit the Proliferation of Target Cells. J Mol Biol 2009; 390:710-21. [DOI: 10.1016/j.jmb.2009.05.027] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2009] [Revised: 05/10/2009] [Accepted: 05/15/2009] [Indexed: 01/18/2023]
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McLaughlin-Drubin ME, Münger K. The human papillomavirus E7 oncoprotein. Virology 2008; 384:335-44. [PMID: 19007963 DOI: 10.1016/j.virol.2008.10.006] [Citation(s) in RCA: 289] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2008] [Accepted: 10/03/2008] [Indexed: 01/01/2023]
Abstract
The human papillomavirus (HPV) E7 oncoprotein shares functional similarities with such proteins as adenovirus E1A and SV40 large tumor antigen. As one of only two viral proteins always expressed in HPV-associated cancers, E7 plays a central role in both the viral life cycle and carcinogenic transformation. In the HPV viral life cycle, E7 disrupts the intimate association between cellular differentiation and proliferation in normal epithelium, allowing for viral replication in cells that would no longer be in the dividing population. This function is directly reflected in the transforming activities of E7, including tumor initiation and induction of genomic instability.
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16
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Immune response to human papillomavirus after prophylactic vaccination with AS04-adjuvanted HPV-16/18 vaccine: Improving upon nature. Gynecol Oncol 2008; 110:S1-10. [DOI: 10.1016/j.ygyno.2008.05.036] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2008] [Revised: 05/29/2008] [Accepted: 05/29/2008] [Indexed: 11/20/2022]
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17
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Morandell D, Rostek U, Bouvard V, Campo-Fernández B, Fiedler M, Jansen-Dürr P, Zwerschke W. Human papillomavirus type 45 E7 is a transforming protein inducing retinoblastoma protein degradation and anchorage-independent cell cycle progression. Virology 2008; 379:20-9. [PMID: 18649911 DOI: 10.1016/j.virol.2008.06.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2008] [Revised: 03/27/2008] [Accepted: 06/06/2008] [Indexed: 10/21/2022]
Abstract
High-risk human papillomaviruses (HPV) cause cervical cancer. The biological properties of HPV-45, the third most prevalent high-risk HPV-genotype, are unknown. We demonstrate here that the HPV-45 E7 protein transforms immortalized NIH3T3 fibroblasts, while mutations in either the conserved LXCXE sequence (C28G) or the carboxyl-terminus (Delta87LQQLF91) significantly abolish this activity. To address the mechanisms underlying cell transformation by HPV-45 E7, we investigated its impact on the cell cycle. We show that HPV-45 E7 associates with the hypophosphorylated form of the retinoblastoma protein (pRb) and induces a significant reduction in the pRb half-life which can be blocked by epoxomicin. Moreover, HPV-45 E7 induces anchorage-independent cell cycle progression of NIH3T3 cells and extends the lifespan of primary human keratinocytes. HPV-45 E7C28G did not bind pRb and could neither induce pRb-proteolysis nor promote cell cycle progression. HPV-45 E7Delta87LQQLF91 had intermediate pRb-binding affinity and retained a residual activity to induce the degradation of pRb but lost the capability to promote cell cycle progression in suspension. Another carboxyl-terminal mutant, HPV-45 E7Delta81AEDL84, showed a trend to reduced transforming activity, had reduced pRb-binding activity and lost the capability to induce pRb-degradation; however, this mutant could induce anchorage-independent cell cycle progression with the same efficiency as HPV-45 E7 wild type. In summary, these data suggest that HPV-45 E7 is a transforming protein and that abrogation of cell cycle control contributes to its oncogenic potential.
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Affiliation(s)
- Dieter Morandell
- Cell Metabolism and Differentiation Research Group, Institute for Biomedical Aging Research of the Austrian Academy of Sciences, Rennweg 10, A-6020 Innsbruck, Austria
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Kaposi's sarcoma-associated herpesvirus-encoded LANA can interact with the nuclear mitotic apparatus protein to regulate genome maintenance and segregation. J Virol 2008; 82:6734-46. [PMID: 18417561 DOI: 10.1128/jvi.00342-08] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Kaposi's sarcoma-associated herpesvirus (KSHV) genomes are tethered to the host chromosomes and partitioned faithfully into daughter cells with the host chromosomes. The latency-associated nuclear antigen (LANA) is important for segregation of the newly synthesized viral genomes to the daughter nuclei. Here, we report that the nuclear mitotic apparatus protein (NuMA) and LANA can associate in KSHV-infected cells. In synchronized cells, NuMA and LANA are colocalized in interphase cells and separate during mitosis at the beginning of prophase, reassociating again at the end of telophase and cytokinesis. Silencing of NuMA expression by small interfering RNA and expression of LGN and a dominant-negative of dynactin (P150-CC1), which disrupts the association of NuMA with microtubules, resulted in the loss of KSHV terminal-repeat plasmids containing the major latent origin. Thus, NuMA is required for persistence of the KSHV episomes in daughter cells. This interaction between NuMA and LANA is critical for segregation and maintenance of the KSHV episomes through a temporally controlled mechanism of binding and release during specific phases of mitosis.
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19
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Lin CH, Chang HS, Yu WCY. USP11 stabilizes HPV-16E7 and further modulates the E7 biological activity. J Biol Chem 2008; 283:15681-8. [PMID: 18408009 DOI: 10.1074/jbc.m708278200] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
HPV-16E7 is a major transforming protein, which has been implicated in the development of cervical cancer. The stability of E7 is thus important to ensure its fully functional status. Using the yeast two-hybrid system, we found that USP11 (ubiquitin-specific protease 11), a member of a protein family that cleaves polyubiquitin chains and/or ubiquitin precursors, interacts and forms a specific complex with HPV-16E7. Our results indicate that the USP11 can greatly increase the steady state level of HPV-16E7 by reducing ubiquitination and attenuating E7 degradation. In contrast, a catalytically inactive mutant of USP11 abolished the deubiquitinating ability and returned E7 to a normal rate of degradation. Moreover, USP11 not only protected E7 from ubiquitination but also influenced E7 function as a modulator of cell growth status. These results suggest that USP11 plays an important role in regulating the levels of E7 protein and subsequently affects the biological function of E7 as well as its contribution to cell transformation by HPV-16E7.
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Affiliation(s)
- Ching-Hui Lin
- National Health Research Institutes, 35 Keyan Rd., Zhunan Town, Miaoli County 350, Taiwan
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20
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Valdovinos-Torres H, Orozco-Morales M, Pedroza-Saavedra A, Padilla-Noriega L, Esquivel-Guadarrama F, Gutierrez-Xicotencatl L. Different Isoforms of HPV-16 E7 Protein are Present in Cytoplasm and Nucleus. Open Virol J 2008; 2:15-23. [PMID: 19440460 PMCID: PMC2678815 DOI: 10.2174/1874357900802010015] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2008] [Revised: 02/14/2008] [Accepted: 03/05/2008] [Indexed: 11/22/2022] Open
Abstract
The E7 protein of high risk HPV types has been found with different molecular weights, mainly because of phosphorylation, an event that changes protein charge and mobility in SDS-PAGE. Distribution of E7 protein in the cellular compartments has also been subject of debate as some groups report the protein in nucleus and others in cytoplasm. The different subcellular distribution and molecular weights reported for the E7 protein suggest the presence of isoforms. We examined this possibility by using several antibodies that recognize different epitopes on the HPV-16 E7 protein. We showed that E7 is processed in 3 isoforms with different molecular weights and isoelectric points (IEP), and described as E7a1 (17.5 kDa, IEP 4.68), E7a (17 kDa, IEP 6.18) and E7b (16 kDa, IEP 6.96). The immunofluorescense results also showed that E7 is distributed into different compartments (ER, Golgi and nucleus), which suggest the presence of other posttranslational modifications, besides phosphorylation.
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Affiliation(s)
- H Valdovinos-Torres
- Research Center of Infectious Diseases, National Institute of Public Health, Cuernavaca, Morelos, Mexico
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21
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Tindle RW, Frazer IH. Section Review: Biologicals & Immunologicals: Human papillomavirus infection, genital warts and cervical cancer: prospects for prophylactic and therapeutic vaccines. Expert Opin Investig Drugs 2008. [DOI: 10.1517/13543784.4.9.783] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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22
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Kim MS, Sin JI. Both antigen optimization and lysosomal targeting are required for enhanced anti-tumour protective immunity in a human papillomavirus E7-expressing animal tumour model. Immunology 2005; 116:255-66. [PMID: 16162274 PMCID: PMC1817814 DOI: 10.1111/j.1365-2567.2005.02219.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
DNA immunization is a new approach for cancer immune therapy. In this study, we constructed human papillomavirus (HPV) 16 E7 expression vector cassettes and then compared the abilities of these constructs to induce antitumour protection. Lysosome-targeted E7 antigens, and to a lesser degree signal sequence-conjugated and transmembrane region sequence-conjugated E7 antigens in a DNA form, displayed tumour protection significantly higher than wild-type E7 antigens. This enhanced tumour protection was mediated by CD8+ cytotoxic T lymphocytes (CTL), as determined by in vivo T-cell depletion and in vitro interferon-gamma (IFN-gamma) production. Subsequent co-injection with interleukin-12-expressing cDNA showed insignificantly enhanced antitumour protection. However, E7 codon optimization plus lysosomal targeting resulted in a dramatic enhancement in antitumour protection both prophylactically and therapeutically through augmentation of the E7-specific CTL population, compared to either one of them alone. However, wild-type or codonoptimized E7 antigens without intracellular targeting displayed no protection against tumour challenge. Thus, these data suggest that antigen codon optimization plus lysosomal targeting strategy could be important in crafting more efficacious E7 DNA vaccines for tumour protection.
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Affiliation(s)
- Mi Suk Kim
- Department of Obstetrics and Gynaecology, School of Medicine, Catholic Universit of Daegu, Namgu, Daegu, Korea
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23
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Longworth MS, Wilson R, Laimins LA. HPV31 E7 facilitates replication by activating E2F2 transcription through its interaction with HDACs. EMBO J 2005; 24:1821-30. [PMID: 15861133 PMCID: PMC1142589 DOI: 10.1038/sj.emboj.7600651] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2004] [Accepted: 03/24/2005] [Indexed: 02/04/2023] Open
Abstract
The E7 proteins of human papillomaviruses (HPVs) contribute to oncogenesis by associating with Rb family members as well class I histone deacetylases (HDACs). The binding of HDACs is also important for the maintenance of viral episomes during the differentiation-dependent productive life cycle. The effects of E7 and other viral proteins on E2F family members were examined in differentiating keratinocytes. E7 was found to specifically activate E2F2 transcription in suprabasal keratinocytes through its ability to bind HDACs. Chromatin immunoprecipitation assays demonstrated that, in differentiating cells, E7 acts to inhibit HDAC binding to the E2F2 promoter resulting in activation of expression. Reduction of E2F2 levels through the use of siRNA confirmed that E2F2 expression facilitated HPV replication but its loss did not affect cell proliferation. Our study demonstrates a mechanism by which binding of HDACs to E7 directly modulates viral replication and identifies E2F2 as a possible target for antiviral therapies.
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Affiliation(s)
- Michelle S Longworth
- Department of Microbiology and Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Regina Wilson
- Department of Microbiology and Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Laimonis A Laimins
- Department of Microbiology and Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
- Department of Microbiology and Immunology, Northwestern University, Morton 6-693, 303 E Chicago Ave, Chicago, IL 60611, USA. Tel.: +1 312 503 0648; Fax: +1 312 503 0649; E-mail:
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24
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Qin Y, Wang XH, Cui HL, Cheung YK, Hu MH, Zhu SG, Xie Y. Human papillomavirus type 16 E7 peptide(38-61) linked with an immunoglobulin G fragment provides protective immunity in mice. Gynecol Oncol 2005; 96:475-83. [PMID: 15661238 DOI: 10.1016/j.ygyno.2004.10.028] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2004] [Indexed: 11/23/2022]
Abstract
OBJECTIVE To explore whether the recombinant protein (Human papillomavirus (HPV) type16 E7 peptide(38-61) linked with an immunoglobulin G fragment) will generate protective immunity in mouse model. METHODS In our study, we combined the HPV16 E7 peptide(38-61) with a murine IgG heavy chain constant region to construct a chimeric protein compound, which was highly expressed as inclusion bodies in a bacterial expression system with Escherichia coli. The purified chimeric protein was injected into C57BL/6 mice and the efficiency of the chimeric vaccine candidate was evaluated by antibody response assay, T cell proliferation assay, CTL assay, tumor challenge assay and therapeutic experiment. RESULTS The chimeric vaccine candidate was able to induce anti-HPV antibodies as well as to elicit HPV16 E7-specific CTLs and T cell proliferation in a pre-clinical mouse model. It was also able to effectively protect mice against the challenge of HPV16-positive tumor cells, and to eradicate HPV16-expressing tumors in mice. CONCLUSIONS The chimeric protein vaccine can induce E7-specific immune responses and protect mice against challenge of HPV16-positive tumor, even eradicate developed tumor. The results indicated a possibility to use the chimeric protein vaccine to protect human against HPV infection.
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Affiliation(s)
- Y Qin
- College of Life Science, Peking University, Beijing, PR China
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25
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Majewski S, Jablonska S. Possible involvement of epidermodysplasia verruciformis human papillomaviruses in the immunopathogenesis of psoriasis: a proposed hypothesis. Exp Dermatol 2004; 12:721-8. [PMID: 14714550 DOI: 10.1111/j.0906-6705.2003.00125.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
We have shown previously in psoriasis a very high prevalence of epidermodysplasia verruciforms-associated human papillomavirus 5 (EVHPV5) DNA and antibodies to human papillomavirus 5 (HPV5) virus-like particle (VLP) L1, and we suggested that this benign hyperproliferative disorder could be a reservoir for EVHPVs. Here we provide new data confirming the expression of EVHPVs in psoriasis and present our hypothesis on their possible involvement in the immunopathogenesis of the disorder. The new important finding was detection by radioimmunoprecipitation assay of a very high prevalence of antibodies to E6/E7 HPV5 oncoproteins, known to enhance keratinocyte proliferation. More recently, EV genes were identified, EVER1 and EVER2, whose mutations are responsible for epidermodysplasia verruciformis. Eidermodysplasia verruciforms-associated human papillomaviruses are harmless to the general population as a result of genetic restriction, which in psoriasis appears to be partly alleviated, and this may allow the viral gene expression. We hypothesize that induction of keratinocyte proliferation in psoriasis by various stimuli initiates the EVHPV life cycle with expression of early (E6/E7) and late (L1) viral proteins. The early proteins may, in turn, enhance the keratinocyte proliferation, and the late proteins could serve as target for specific-B- and T-cell-mediated responses. Immune responses against the viral antigens in the epidermis may result in the chemoattraction of leukocytes and Munro abscess formation, as well as in production of the psoriatic process. The novel immunomodulatory therapies could also inhibit immune responses against EVHPV proteins, leading to decreased cytokine production, keratinocyte proliferation and EVHPV expression. Thus the beneficial effect of these therapies is not discordant with the propose hypothesis of possible involvement of EVHPVs in the immunopathogenesis of psoriasis.
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Affiliation(s)
- Slawomir Majewski
- Department of Medicine and Venereology, Warsaw School of Medicine, Poland
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26
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Oh KJ, Kalinina A, Wang J, Nakayama K, Nakayama KI, Bagchi S. The papillomavirus E7 oncoprotein is ubiquitinated by UbcH7 and Cullin 1- and Skp2-containing E3 ligase. J Virol 2004; 78:5338-46. [PMID: 15113913 PMCID: PMC400333 DOI: 10.1128/jvi.78.10.5338-5346.2004] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Recurrent infections with high-risk human papillomaviruses (HPVs) are associated with human cervical cancers. All HPV-associated cancer tissues express the viral oncoproteins E6 and E7, which stimulate cell growth. The expression of E7 is crucial for both the initiation and the maintenance of HPV-associated cancer. Recent studies showed that the level of E7 in cancer cells is regulated by ubiquitin-dependent proteolysis through the 26S proteasome. In this study, we characterized the enzymes involved in the ubiquitin-dependent proteolysis of E7. We show that UbcH7, an E2 ubiquitin-conjugating enzyme, is specifically involved in the ubiquitination of E7. Furthermore, we show that E7 interacts with the SCF (Skp-Cullin-F box) ubiquitin ligase complex containing Cullin 1 (Cul1) and Skp2 and can be ubiquitinated by the Cul1-containing ubiquitin ligase in vitro. Coimmunoprecipitation analyses revealed that E7 interacts with Skp2 and Cul1 in vivo. Finally, the half-life of E7 was found to be significantly longer in Skp2(-/-) mouse embryo fibroblasts (MEFs) than in wild-type MEFs. Taken together, these results suggest that the Cul1- and Skp2-containing ubiquitin ligase plays a role in the ubiquitination and proteolysis of E7. In HPV type 16-containing cervical carcinoma cell line Caski, E7 localizes to both the cytoplasm and the nucleus. Brief treatment of Caski cells with MG132 (a proteasome inhibitor) causes the accumulation of E7 in discrete nuclear bodies. These nuclear bodies are detergent insoluble and contain polyubiquitinated E7. We suggest that E7 relocates to specific nuclear bodies for proteolysis in HPV-containing epithelial cells.
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Affiliation(s)
- Kwang-Jin Oh
- Center for Molecular Biology of Oral Diseases, College of Dentistry, University of Illinois at Chicago, 801 South Paulina Street, Chicago, IL 60612, USA
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27
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Fiedler M, Müller-Holzner E, Viertler HP, Widschwendter A, Laich A, Pfister G, Spoden GA, Jansen-Dürr P, Zwerschke W. High level HPV-16 E7 oncoprotein expression correlates with reduced pRb-levels in cervical biopsies. FASEB J 2004; 18:1120-2. [PMID: 15155561 DOI: 10.1096/fj.03-1332fje] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
High-risk human papillomaviruses (HPVs) are major etiological agents of cervical cancer. Despite excellent epidemiological evidence for a direct role of HPV-16 in cervical carcinogenesis, molecular pathways underlying carcinogenesis in vivo remain obscure. The E7 gene is required for immortalization and maintenance of the transformed phenotype in vitro; however, little is known about its role for tumorigenesis in vivo. The E7 gene codes for an unstable protein the abundance of which in cervical biopsies is unknown. We show here that E7 protein levels strongly increase during cervical carcinogenesis, underlining its fundamental role in cervical cancer. The E7 protein was found predominantly in the nucleus and to a minor extent in the cytoplasm in the cervical cancer cell line Ca Ski in vitro and in invasive cervical carcinoma in situ, suggesting that nuclear resident E7 plays a major role in cervical carcinogenesis in humans. The retinoblastoma protein (pRb) is a major E7-target in vitro. We show here that pRb expression is initially upregulated in LSIL and disappears in later stages concomitant with increased E7 levels, suggesting that E7-driven degradation of pRb is involved in cervical tumorigenesis in humans.
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MESH Headings
- Animals
- Antibodies, Viral/immunology
- Biopsy
- Bone Neoplasms/pathology
- Bone Neoplasms/virology
- Carcinoma, Squamous Cell/etiology
- Carcinoma, Squamous Cell/genetics
- Carcinoma, Squamous Cell/pathology
- Carcinoma, Squamous Cell/virology
- Cell Differentiation
- Cell Line, Tumor/metabolism
- Cell Line, Tumor/virology
- Cell Nucleus/virology
- Cell Transformation, Neoplastic/genetics
- Cell Transformation, Viral/genetics
- Cervix Uteri/pathology
- Cervix Uteri/virology
- Disease Progression
- Epithelial Cells/ultrastructure
- Epithelial Cells/virology
- Female
- Gene Expression Regulation, Neoplastic
- Gene Expression Regulation, Viral
- Genes, Retinoblastoma
- Humans
- Oncogene Proteins, Viral/biosynthesis
- Oncogene Proteins, Viral/genetics
- Oncogene Proteins, Viral/immunology
- Oncogene Proteins, Viral/physiology
- Osteosarcoma/pathology
- Osteosarcoma/virology
- Papillomaviridae/genetics
- Papillomaviridae/pathogenicity
- Papillomavirus E7 Proteins
- Papillomavirus Infections/genetics
- Rabbits
- Retinoblastoma Protein/metabolism
- Transfection
- Tumor Virus Infections/genetics
- Uterine Cervical Neoplasms/etiology
- Uterine Cervical Neoplasms/genetics
- Uterine Cervical Neoplasms/pathology
- Uterine Cervical Neoplasms/virology
- Uterine Cervical Dysplasia/etiology
- Uterine Cervical Dysplasia/genetics
- Uterine Cervical Dysplasia/pathology
- Uterine Cervical Dysplasia/virology
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Affiliation(s)
- Marc Fiedler
- Tyrolean Cancer Research Institute at the University of Innsbruck, 6020 Innsbruck, Austria
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28
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Angeline M, Merle E, Moroianu J. The E7 oncoprotein of high-risk human papillomavirus type 16 enters the nucleus via a nonclassical Ran-dependent pathway. Virology 2004; 317:13-23. [PMID: 14675621 DOI: 10.1016/j.virol.2003.08.024] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
E7, the major transforming protein of high-risk human papillomavirus (HPV), type 16, binds and inactivates the retinoblastoma protein (pRb), and the Rb-related proteins p107 and p130. HPV16 E7 is a nuclear protein lacking a classical basic nuclear localization signal. In this study we investigated the nuclear import of HPV16 E7 oncoprotein in digitonin-permeabilized HeLa cells. HPV16 E7 nuclear import was independent of pRb, as an E7(DeltaDLYC) variant defective in pRb binding was imported into the nuclei of digitonin-permeabilized cells as efficiently as wild-type E7 in the presence of exogenous cytosol. Interestingly, we discovered that HPV16 E7 is imported into the nuclei via a novel pathway different from those mediated by Kap alpha2beta1 heterodimers, Kap beta1, or Kap beta2. Nuclear accumulation of E7 required Ran and was not inhibited by the RanG19V-GTP variant, an inhibitor of Kap beta mediated import pathways. Together the data suggest that HPV16 E7 translocates through the nuclear pores via a nonclassical Ran-dependent pathway, independent of the main cytosolic Kap beta import receptors.
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Affiliation(s)
- Michael Angeline
- Biology Department, Boston College, Chestnut Hill, MA 02467, USA
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29
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Tao M, Kruhlak M, Xia S, Androphy E, Zheng ZM. Signals that dictate nuclear localization of human papillomavirus type 16 oncoprotein E6 in living cells. J Virol 2004; 77:13232-47. [PMID: 14645580 PMCID: PMC296047 DOI: 10.1128/jvi.77.24.13232-13247.2003] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Human papillomavirus (HPV) type 16 E6 (16E6) is an oncogenic, multifunctional nuclear protein that induces p53 degradation and perturbs normal cell cycle control, leading to immortalization and transformation of infected keratinocytes and epithelial cells. Although it is unclear how 16E6 disrupts the epigenetic profile of host genes, its presence in the nucleus is a key feature. The present report describes intrinsic properties of 16E6 that influence its nuclear import in living cells. When the coding region of full-length 16E6 was inserted in frame into the C terminus of green fluorescent protein (GFP), it effectively prevented the 16E6 pre-mRNA from being spliced and led to the expression of a GFP-E6 fusion which localized predominantly to the nucleus. Further studies identified three novel nuclear localization signals (NLSs) in 16E6 that drive the protein to accumulate in the nucleus. We found that all three NLS sequences are rich in positively charged basic residues and that point mutations in these key residues could abolish the retention of 16E6 in the nucleus as well as the p53 degradation and cell immortalization activities of the protein. When inserted into corresponding regions of low-risk HPV type 6 E6, the three NLS sequences described for 16E6 functioned actively in converting the normally cytoplasmic HPV type 6 E6 into a nuclear protein. The separate NLS sequences, however, appear to play different roles in nuclear import and retention of HPV E6. The discovery of three unique NLS sequences in 16E6 provides new insights into the nuclear association of 16E6 which may reveal other novel activities of this important oncogenic protein.
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Affiliation(s)
- Mingfang Tao
- HIV and AIDS Malignancy Branch. Experimental Immunology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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30
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Stachowiak MK, Fang X, Myers JM, Dunham SM, Berezney R, Maher PA, Stachowiak EK. Integrative nuclear FGFR1 signaling (INFS) as a part of a universal ?feed-forward-and-gate? signaling module that controls cell growth and differentiation. J Cell Biochem 2003; 90:662-91. [PMID: 14587025 DOI: 10.1002/jcb.10606] [Citation(s) in RCA: 108] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
A novel signaling mechanism is described through which extracellular signals and intracellular signaling pathways regulate proliferation, growth, differentiation, and other functions of cells in the nervous system. Upon cell stimulation, fibroblast growth factor receptor-1 (FGFR1), a typically plasma membrane-associated protein, is released from ER membranes into the cytosol and translocates to the cell nucleus by an importin-beta-mediated transport pathway along with its ligand, FGF-2. The nuclear accumulation of FGFR1 is activated by changes in cell contacts and by stimulation of cells with growth factors, neurotransmitters and hormones as well as by a variety of different second messengers and thus was named integrative nuclear FGFR1 signaling (INFS). In the nucleus, FGFR1 localizes specifically within nuclear matrix-attached speckle-domains, which are known to be sites for RNA Pol II-mediated transcription and co-transcriptional pre-mRNA processing. In these domains, nuclear FGFR1 colocalizes with RNA transcription sites, splicing factors, modified histones, phosphorylated RNA Pol II, and signaling kinases. Within the nucleus, FGFR1 serves as a general transcriptional regulator, as indicated by its association with the majority of active nuclear centers of RNA synthesis and processing, by the ability of nuclear FGFR1 to activate structurally distinct genes located on different chromosomes and by its stimulation of multi-gene programs for cell growth and differentiation. We propose that FGFR1 is part of a universal "feed-forward-and-gate" signaling module in which classical signaling cascades initiated by specific membrane receptors transmit signals to sequence specific transcription factors (ssTFs), while INFS elicited by the same stimuli feeds the signal forward to the common coactivator, CREB-binding protein (CBP). Activation of CBP by INFS, along with the activation of ssTFs by classical signaling cascades brings about coordinated responses from structurally different genes located at different genomic loci.
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Affiliation(s)
- Michal K Stachowiak
- Molecular and Structural Neurobiology and Gene Therapy Program, Department of Pathology and Anatomical Sciences, State University of New York at Buffalo, New York 14214, USA.
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31
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Nilges K, Höhn H, Pilch H, Neukirch C, Freitag K, Talbot PJ, Maeurer MJ. Human papillomavirus type 16 E7 peptide-directed CD8+ T cells from patients with cervical cancer are cross-reactive with the coronavirus NS2 protein. J Virol 2003; 77:5464-74. [PMID: 12692247 PMCID: PMC153943 DOI: 10.1128/jvi.77.9.5464-5474.2003] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Human papillomavirus type 16 (HPV16) E6 and E7 oncoproteins are required for cellular transformation and represent candidate targets for HPV-specific and major histocompatibility complex class I-restricted CD8(+)-T-cell responses in patients with cervical cancer. Recent evidence suggests that cross-reactivity represents the inherent nature of the T-cell repertoire. We identified HLA-A2 binding HPV16 E7 variant peptides from human, bacterial, or viral origin which are able to drive CD8(+)-T-cell responses directed against wild-type HPV16 E7 amino acid 11 to 19/20 (E7(11-19/20)) epitope YMLDLQPET(T) in vitro. CD8(+) T cells reacting to the HLA-A2-presented peptide from HPV16 E7(11-19(20)) recognized also the HLA-A2 binding peptide TMLDIQPED (amino acids 52 to 60) from the human coronavirus OC43 NS2 gene product. Establishment of coronavirus NS2-specific, HLA-A2-restricted CD8(+)-T-cell clones and ex vivo analysis of HPV16 E7 specific T cells obtained by HLA-A2 tetramer-guided sorting from PBL or tumor-infiltrating lymphocytes obtained from patients with cervical cancer showed that cross-reactivity with HPV16 E7(11-19(20)) and coronavirus NS2(52-60) represents a common feature of this antiviral immune response defined by cytokine production. Zero of 10 patients with carcinoma in situ neoplasia and 3 of 18 patients with cervical cancer showed > or =0.1% HPV16 E7-reactive T cells in CD8(+) peripheral blood lymphocytes. In vivo priming with HPV16 was confirmed in patients with cervical cancer or preinvasive HPV16-positive lesions using HLA-A2 tetramer complexes loaded with the E6-derived epitope KLPQLCTEL. In contrast, we could not detect E6-reactive T cells in healthy individuals. These data imply that the measurement of the HPV16 E7(11-19(20)) CD8(+)-T-cell response may reflect cross-reactivity with a common pathogen and that variant peptides may be employed to drive an effective cellular immune response against HPV.
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Affiliation(s)
- Katja Nilges
- Department of Medical Microbiology, University of Mainz, Germany
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32
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Cid-Arregui A, Juárez V, zur Hausen H. A synthetic E7 gene of human papillomavirus type 16 that yields enhanced expression of the protein in mammalian cells and is useful for DNA immunization studies. J Virol 2003; 77:4928-37. [PMID: 12663798 PMCID: PMC152128 DOI: 10.1128/jvi.77.8.4928-4937.2003] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A synthetic E7 gene of human papillomavirus (HPV) type 16 was generated that consists entirely of preferred human codons. Expression analysis of the synthetic E7 gene in human and animal cells showed levels of E7 protein 20- to 100-fold higher than those obtained with wild-type E7. Enhanced expression of E7 protein resulted from highly efficient translation, as well as increased stability of the E7 mRNA due to its codon optimization. Higher levels of E7 protein in cells transfected with synthetic E7 correlated with significant loss of cell viability in various human cell lines. In contrast, lower E7 protein expression driven by the wild-type gene resulted in a slight induction of cell proliferation. Furthermore, mice inoculated with plasmids expressing the synthetic E7 gene produced significantly higher levels of E7 antibodies than littermates injected with wild-type E7, suggesting that synthetic E7 may be useful for DNA immunization studies and the development of genetic vaccines against HPV-16. In view of these results, we hypothesize that HPVs may have retained a pattern of G + C content and codon usage distinct from that of their host cells in response to selective pressure. Thus, the nonhuman codon bias may have been conserved by HPVs to prevent compromising viability of the host cells by excessive viral early protein expression, as well as to evade the immune system.
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Affiliation(s)
- Angel Cid-Arregui
- Angewandte Tumorvirologie, Deutsches Krebsforschungszentrum, D-69120 Heidelberg, Germany.
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33
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Du J, Chen GG, Vlantis AC, Xu H, Tsang RKY, van Hasselt AC. The nuclear localization of NFkappaB and p53 is positively correlated with HPV16 E7 level in laryngeal squamous cell carcinoma. J Histochem Cytochem 2003; 51:533-9. [PMID: 12642632 DOI: 10.1177/002215540305100415] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The interaction between the HPV (human papilloma virus) 16 E7 and other cell growth factors, such as p53 and NFkappaB in laryngeal cancer is not clearly understood. The aim of this study was to examine the expression of these three proteins in tumor and non-tumor laryngeal tissues from patients with laryngeal squamous cell carcinoma. These three proteins were dominantly expressed in the nucleus and their levels were higher in the tumor tissue than in the non-tumor tissue, although the comparison between the tumor and non-tumor tissues of p53 staining did not reach significance. The intensity of the nuclear stain of E7 and p53 was stronger than that of p65, a subunit of NFkappaB. Correlation analysis revealed that there was a positive relationship between the level of HPV16 E7 and the expression of p65. The correlation between E7 and p53 was also significant, although to a lesser degree. The finding of nuclear localization of p65 suggests that NFkappaB is constantly activated in the laryngeal cancer cells, whereas the sequestration of p53 in the nucleus may represent a mutated form of p53, which is probably inactivated by HPV16 oncoproteins. In conclusion, this study suggests that the nuclear localization of NFkappaB and p53 may play a role in the development of human laryngeal squamous cell carcinoma infected with HPV16.
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Affiliation(s)
- Jing Du
- Department of Surgery, Prince of Wales Hospital, the Chinese University of Hong Kong, Shatin, N.T. Hong Kong.
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34
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Chen HB, Chen L, Zhang JK, Shen ZY, Su ZJ, Cheng SB, Chew EC. Human papillomavirus 16 E6 is associated with the nuclear matrix of esophageal carcinoma cells. World J Gastroenterol 2001; 7:788-91. [PMID: 11854902 PMCID: PMC4695595 DOI: 10.3748/wjg.v7.i6.788] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To explore the etiologic role of HPV infection in esophageal carcinoma, and the association of HPV-16 E6 with the nuclear matrix of carcinoma cells.
METHODS: Two esophageal carcinoma cell lines, EC/CUHK1 and EC/CUHK2, were tested for HPV-16 E6 subgenetic fragment by polymer a se chain reaction amplification of virus DNA associated nuclear matrix. RT-PCR and immunocytochemistry were also used to visualize the expression of E6 subgene in the cells.
RESULTS: The HPV-16 E6 subgenetic fragment was found to be present in nuclear matrix-associated DNA, E6 oncoprotein localized in the nucleus where it is tightly associated with nuclear matrix after sequential extraction in EC/CUHK2 cells. It was not detected, however, in EC/CUHK1 cells.
CONCLUSION: The interaction between HPV-16 E6 and nuclear matrix may contribute to the virus induced carcinogenesis in esophageal carcinoma.
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Affiliation(s)
- H B Chen
- Department of Histology and Embryology, Shantou University Medical College, Guangdong Province, China.
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35
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Münger K, Basile JR, Duensing S, Eichten A, Gonzalez SL, Grace M, Zacny VL. Biological activities and molecular targets of the human papillomavirus E7 oncoprotein. Oncogene 2001; 20:7888-98. [PMID: 11753671 DOI: 10.1038/sj.onc.1204860] [Citation(s) in RCA: 412] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The human papillomavirus (HPV) E7 protein is one of only two viral proteins that remain expressed in HPV-associated human cancers. HPV E7 proteins share structural and functional similarities with oncoproteins encoded by other small DNA tumor viruses such as adenovirus E1A and SV40 large tumor antigen. The HPV E7 protein plays an important role in the viral life cycle by subverting the tight link between cellular differentiation and proliferation in normal epithelium, thus allowing the virus to replicate in differentiating epithelial cells that would have normally withdrawn from the cell division cycle. The transforming activities of E7 largely reflect this important function.
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Affiliation(s)
- K Münger
- Department of Pathology and Harvard Center for Cancer Biology, Harvard Medical School, Boston, MA 02115, USA.
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36
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Daemen T, Pries F, Bungener L, Kraak M, Regts J, Wilschut J. Genetic immunization against cervical carcinoma: induction of cytotoxic T lymphocyte activity with a recombinant alphavirus vector expressing human papillomavirus type 16 E6 and E7. Gene Ther 2000; 7:1859-66. [PMID: 11110419 DOI: 10.1038/sj.gt.3301257] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Infection of genital epithelial cells with human papillomavirus (HPV) types 16 and 18 is closely associated with the development of cervical carcinoma. The transforming potential of these high-risk HPVs depends on the expression of the E6 and E7 early viral gene products. Since the expression of E6 and E7 is selectively maintained in premalignant and malignant cervical lesions these proteins are attractive candidates for immunotherapeutic and prophylactic strategies. This report describes the construction, characterization and the in vivo immunotherapeutic potential of recombinant Semliki Forest virus (SFV) expressing the HPV16 E6 and E7 proteins (SFV-E6E7). Western blot analysis and immunofluorescence staining demonstrated expression of E6 and E7 in BHK cells infected with SFV-E6E7. Immunization of mice with SFV-E6E7 resulted in an efficient in vivo priming of HPV-specific CTL activity. The induced CTL lysed murine tumor cells transformed with the HPV16 genome and EL4 cells loaded with an immunodominant class I-binding HPV E7 peptide. CTLs could reproducibly be induced by immunization with three injections of as few as 10(5) infectious units of SFV-E6E7. Protection from tumor challenge was studied using the tumor cell line TC-1. Immunization with 5 x 10(6) SFV-E6E7 particles protected 40% of the mice from tumor challenge. These results indicate that E6E7 expression by the efficient and safe recombinant SFV system represents a promising strategy for immunotherapy or immunoprophylaxis of cervical carcinoma.
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Affiliation(s)
- T Daemen
- Department of Medical Microbiology, University of Groningen, The Netherlands
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37
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Therrien JP, Drouin R, Baril C, Drobetsky EA. Human cells compromised for p53 function exhibit defective global and transcription-coupled nucleotide excision repair, whereas cells compromised for pRb function are defective only in global repair. Proc Natl Acad Sci U S A 1999; 96:15038-43. [PMID: 10611334 PMCID: PMC24769 DOI: 10.1073/pnas.96.26.15038] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
After exposure to DNA-damaging agents, the p53 tumor suppressor protects against neoplastic transformation by inducing growth arrest and apoptosis. A series of investigations has also demonstrated that, in UV-exposed cells, p53 regulates the removal of DNA photoproducts from the genome overall (global nucleotide excision repair), but does not participate in an overlapping pathway that removes damage specifically from the transcribed strand of active genes (transcription-coupled nucleotide excision repair). Here, the highly sensitive ligation-mediated PCR was employed to quantify, at nucleotide resolution, the repair of UVB-induced cyclobutane pyrimidine dimers (CPDs) in genetically p53-deficient Li-Fraumeni skin fibroblasts, as well as in human lung fibroblasts expressing the human papillomavirus (HPV) E6 oncoprotein that functionally inactivates p53. Lung fibroblasts expressing the HPV E7 gene product, which similarly inactivates the retinoblastoma tumor-suppressor protein (pRb), were also investigated. pRb acts downstream of p53 to mediate G(1) arrest, but has no demonstrated role in DNA repair. Relative to normal cells, HPV E6-expressing lung fibroblasts and Li-Fraumeni skin fibroblasts each manifested defective CPD repair along both the transcribed and nontranscribed strands of the p53 and/or c-jun loci. HPV E7-expressing lung fibroblasts also exhibited reduced CPD removal, but only along the nontranscribed strand. Our results provide striking evidence that transcription-coupled repair, in addition to global repair, are p53-dependent in UV-exposed human fibroblasts. Moreover, the observed DNA-repair defect in HPV E7-expressing cells reveals a function for this oncoprotein in HPV-mediated carcinogenesis, and may suggest a role for pRb in global nucleotide excision repair.
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Affiliation(s)
- J P Therrien
- Division of Pathology, Department of Medical Biology, Faculty of Medicine, Laval University, Quebec, Canada
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38
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Frazer IH, Thomas R, Zhou J, Leggatt GR, Dunn L, McMillan N, Tindle RW, Filgueira L, Manders P, Barnard P, Sharkey M. Potential strategies utilised by papillomavirus to evade host immunity. Immunol Rev 1999; 168:131-42. [PMID: 10399070 DOI: 10.1111/j.1600-065x.1999.tb01288.x] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The co-evolution of papillomaviruses (PV) and their mammalian hosts has produced mechanisms by which PV might avoid specific and non-specific host immune responses. Low level expression of PV proteins in infected basal epithelial cells, together with an absence of inflammation and of virus-induced cell lysis, restricts the opportunity for effective PV protein presentation to immunocytes by dendritic cells. Additionally, PV early proteins, by a range of mechanisms, may restrict the efficacy of antigen presentation by these cells. Should an immune response be induced to PV antigens, resting keratinocytes (KC) appear resistant to interferon-gamma-enhanced mechanisms of cytotoxic T-lymphocyte (CTL)-mediated lysis, and expression of PV antigens by resting KC can tolerise PV-specific CTL. Thus, KC, in the absence of inflammation, may represent an immunologically privileged site for PV infection. Together, these mechanisms play a part in allowing persistence of PV-induced proliferative skin lesions for months to years, even in immunocompetent hosts.
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Affiliation(s)
- I H Frazer
- Centre for Immunology and Cancer Research, University of Queensland Department of Medicine, Princess Alexandra Hospital, Brisbane, Australia.
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39
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Keesee SK, Marchese J, Meneses A, Potz D, Garcia-Cuellar C, Szaro RP, Solorza G, Osornio-Vargas A, Mohar A, de la Garza JG, Wu YJ. Human cervical cancer-associated nuclear matrix proteins. Exp Cell Res 1998; 244:14-25. [PMID: 9770344 DOI: 10.1006/excr.1998.4202] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The nuclear matrix is the nonchromatin protein structural component of the nucleus that governs nuclear shape and also exerts regulatory control over higher order gene organization. Recent studies have documented the presence of tumor-associated nuclear matrix proteins in several human cancers. We used high-resolution two-dimensional gel electrophoresis to compare nuclear matrix protein patterns in cervical carcinomas with those from normal cervical tissue. Tumors obtained from 20 patients undergoing hysterectomy for clinically localized cervical cancer were compared with normal cervical tissue. We have identified five polypeptides (CvC-1: Mr = 69,408 Da, pI = 5. 78; CvC-2: Mr = 53,752 Da, pI = 5.54; CvC-3: Mr = 47,887 Da, pI = 5. 60; CvC-4: Mr = 46,006 Da, pI = 5.07; and CvC-5: Mr = 44,864 Da, pI = 6.61) in the nuclear matrix from cervical carcinomas that were present in 20 of 20 cervical tumors but 0 of 10 normal tissues. These data extend similar findings of cancer-associated nuclear matrix proteins in other human cancers and suggest that nuclear matrix proteins may represent a new class of cancer markers that could aid the diagnosis or management of some types of cancer.
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Affiliation(s)
- S K Keesee
- Matritech, Inc., 330 Nevada Street, Newton, Massachusetts, 02160, USA.
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40
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Braspenning J, Meschede W, Marchini A, Müller M, Gissmann L, Tommasino M. Secretion of heterologous proteins from Schizosaccharomyces pombe using the homologous leader sequence of pho1+ acid phosphatase. Biochem Biophys Res Commun 1998; 245:166-71. [PMID: 9535802 DOI: 10.1006/bbrc.1998.8402] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In this study we report the use of the S. pombe leader sequence of pho1+ acid phosphatase (Elliott et al., J. Biol. Chem. 216, 2916-2941, 1986) for the secretion of heterologous proteins into the medium. The green fluorescent protein (GFP) and the Human Papillomavirus (HPV) type 16 E7 protein are normally not secreted; fusion of the S. pombe pho1 leader peptide (SPL) to GFP and HPV 16 E7 resulted in an efficient secretion of these proteins although the latter contains a nuclear targeting sequence. These data suggest that SPL fused constructs could be applied for the production of other recombinant proteins using the S. pombe expression system. Furthermore, since GFP retains its intrinsic fluorescence during the secretion, this system may be useful to study the secretory pathway of fission yeast in vivo.
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Affiliation(s)
- J Braspenning
- Deutsches Krebsforschungszentrum, Angewandte Tumorvirologie, INF, 242, 69120 Heidelberg, Germany.
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41
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Sanchez V, Angeletti PC, Engler JA, Britt WJ. Localization of human cytomegalovirus structural proteins to the nuclear matrix of infected human fibroblasts. J Virol 1998; 72:3321-9. [PMID: 9525659 PMCID: PMC109810 DOI: 10.1128/jvi.72.4.3321-3329.1998] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The intranuclear assembly of herpesvirus subviral particles remains an incompletely understood process. Previous studies have described the nuclear localization of capsid and tegument proteins as well as intranuclear tegumentation of capsid-like particles. The temporally and spatially regulated replication of viral DNA suggests that assembly may also be regulated by compartmentalization of structural proteins. We have investigated the intranuclear location of several structural and nonstructural proteins of human cytomegalovirus (HCMV). Tegument components including pp65 (ppUL83) and ppUL69 and capsid components including the major capsid protein (pUL86) and the small capsid protein (pUL48/49) were retained within the nuclear matrix (NM), whereas the immediate-early regulatory proteins IE-1 and IE-2 were present in the soluble nuclear fraction. The association of pp65 with the NM resisted washes with 1 M guanidine hydrochloride, and direct binding to the NM could be demonstrated by far-Western blotting. Furthermore, pp65 exhibited accumulation along the nuclear periphery and in far-Western analysis bound to proteins which comigrated with proteins of the size of nuclear lamins. A direct interaction between pp65 and lamins was demonstrated by coprecipitation of lamins in immune complexes containing pp65. Together, our findings provide evidence that major virion structural proteins localized to a nuclear compartment, the NM, during permissive infection of human fibroblasts.
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Affiliation(s)
- V Sanchez
- Department of Microbiology, University of Alabama at Birmingham, 35233, USA
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42
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Angeletti PC, Engler JA. Adenovirus preterminal protein binds to the CAD enzyme at active sites of viral DNA replication on the nuclear matrix. J Virol 1998; 72:2896-904. [PMID: 9525610 PMCID: PMC109735 DOI: 10.1128/jvi.72.4.2896-2904.1998] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/1997] [Accepted: 12/18/1997] [Indexed: 02/06/2023] Open
Abstract
Adenovirus (Ad) replicative complexes form at discrete sites on the nuclear matrix (NM) via an interaction mediated by the precursor of the terminal protein (pTP). The identities of cellular proteins involved in these complexes have remained obscure. We present evidence that pTP binds to a multifunctional pyrimidine biosynthesis enzyme found at replication domains on the NM. Far-Western blotting identified proteins of 150 and 240 kDa that had pTP binding activity. Amino acid sequencing of the 150-kDa band revealed sequence identity to carbamyl phosphate synthetase I (CPS I) and a high degree of homology to the related trifunctional enzyme known as CAD (for carbamyl phosphate synthetase, aspartate transcarbamylase, and dihydroorotase). Western blotting with an antibody directed against CAD detected a 240-kDa band that comigrated with that detected by pTP far-Western blotting. Binding experiments showed that a pTP-CAD complex was immunoprecipitable from cell extracts in which pTP was expressed by a vaccinia virus recombinant. Additionally, in vitro-translated epitope-tagged pTP and CAD were immunoprecipitable as a complex, indicating the occurrence of a protein-protein interaction. Confocal fluorescence microscopy of Ad-infected NM showed that pTP and CAD colocalized in nuclear foci. Both pTP and CAD were confirmed to colocalize with active sites of replication detected by bromodeoxyuridine incorporation. These data support the concept that the pTP-CAD interaction may allow anchorage of Ad replication complexes in the proximity of required cellular factors and may help to segregate replicated and unreplicated viral DNA.
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Affiliation(s)
- P C Angeletti
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Alabama at Birmingham, 35294-0005, USA
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43
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Stachowiak MK, Moffett J, Maher P, Tucholski J, Stachowiak EK. Growth factor regulation of cell growth and proliferation in the nervous system. A new intracrine nuclear mechanism. Mol Neurobiol 1997; 15:257-83. [PMID: 9457702 DOI: 10.1007/bf02740663] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
This article discusses a novel intracrine mechanism of growth-factor action in the nervous system whereby fibroblast growth factor-2 (FGF-2) and its receptor accumulate in the cell nucleus and act as mediators in the control of cell growth and proliferation. In human and rat brain the levels and subcellular localization of FGF-2 differ between quiescent and reactive astrocytes. Quiescent cells express a low level of FGF-2, which is located predominantly within the cytoplasm. In reactive astrocytes, the expression of FGF-2 increases and the proteins are found in both the cytoplasm and nucleus. In glioma tumors, FGF-2 is overexpressed in the nuclei of neoplastic cells. Similar changes in FGF-2 expression and localization are found in vitro. The nuclear accumulation of FGF-2 reflects a transient activation of the FGF-2 gene by potentially novel transactivating factors interacting with an upstream regulatory promoter region. In parallel with FGF-2, the nuclei of astrocytes contain the high-affinity FGF-2 receptor, FGFR1. Nuclear FGFR1 is full length, retains kinase activity, and is localized within the nuclear interior in association with the nuclear matrix. Transfection of either FGF-2 or FGFR1 into cells that do not normally express these proteins results in their nuclear accumulation and concomitant increases in cell proliferation. A similar regulation of nuclear FGF-2 and FGFR1 is observed in neural crestderived adrenal medullary cells and of FGF-2 in the nuclei of cerebellar neurons. Thus, the regulation of the nuclear content of FGF-2 and FGFR1 could serve as a novel mechanism controlling growth and proliferation of glial and neuronal cells.
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Affiliation(s)
- M K Stachowiak
- Laboratory of Molecular Neurobiology, Barrow Neurological Institute, Phoenix, AZ, USA
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44
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Müller M, Zhou J, Reed TD, Rittmüller C, Burger A, Gabelsberger J, Braspenning J, Gissmann L. Chimeric papillomavirus-like particles. Virology 1997; 234:93-111. [PMID: 9234950 DOI: 10.1006/viro.1997.8591] [Citation(s) in RCA: 148] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
We have constructed chimeric papillomavirus-like particles (CVLPs) by replacing the 34-carboxy-terminal amino acids of the HPV 16 L1 protein with various parts of the HPV 16 E7 protein. Chimeric proteins were expressed by recombinant baculoviruses and analyzed by electron microscopy for their ability to assemble into virus capsids. We were able to produce CVLPs in high efficiencies with inserts of up to 60 amino acids. CVLPs are able to induce a neutralizing antibody response, assayed by inhibition of hemagglutination of mouse erythrocytes. CVLPs are interacting with the putative receptor for papillomaviruses as they were shown to hemagglutinate mouse red blood cells and bind to and penetrate cells in vitro. As CVLPs follow a similar intracellular pathway as observed earlier for BPV VLPs, we speculate that CVLPs can be used to deliver peptides into mammalian cells in vitro and in vivo, possibly reaching the pathway for MHC class I presentation.
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Affiliation(s)
- M Müller
- Department of Microbiology and Immunology, Loyola University Chicago, Maywood, Illinois 60153, USA.
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45
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Lukonis CJ, Weller SK. Formation of herpes simplex virus type 1 replication compartments by transfection: requirements and localization to nuclear domain 10. J Virol 1997; 71:2390-9. [PMID: 9032376 PMCID: PMC191349 DOI: 10.1128/jvi.71.3.2390-2399.1997] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
During infection, the seven essential herpes simplex virus type 1 (HSV-1) replication proteins are found in globular nuclear structures called replication compartments. Replication compartments form adjacent to ND10, nuclear matrix-bound domains which are present in most cell types but whose function is unknown (G. G. Maul, I. M. Ishov, and R. D. Everett, Virology 217:67-75, 1996). We now demonstrate that replication compartments can be formed by cotransfecting Vero cells with constructs expressing the seven essential viral replication proteins and a plasmid containing an HSV-1 origin of DNA replication. Like replication compartments in infected cells, replication compartments formed by cotransfection contain all of the essential viral replication proteins, are sites of DNA synthesis, and are found adjacent to ND10. However, neither the viral origin-binding protein nor a plasmid containing an HSV-1 origin of DNA replication is individually required for the formation of transfection replication compartments, although the presence of each increases the efficiency of replication compartment formation. Further, we provide evidence that UL29 independently localizes adjacent to ND10 and so may play a role in directing replication compartments to these preexisting nuclear structures.
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Affiliation(s)
- C J Lukonis
- Department of Microbiology, University of Connecticut Health Center, Farmington 06030, USA
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46
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Panagiotidis CA, Lium EK, Silverstein SJ. Physical and functional interactions between herpes simplex virus immediate-early proteins ICP4 and ICP27. J Virol 1997; 71:1547-57. [PMID: 8995681 PMCID: PMC191212 DOI: 10.1128/jvi.71.2.1547-1557.1997] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The ordered expression of herpes simplex virus type 1 (HSV-1) genes, during the course of a productive infection, requires the action of the virus immediate-early regulatory proteins. Using a protein interaction assay, we demonstrate specific in vitro protein-protein interactions between ICP4 and ICP27, two immediate-early proteins of HSV-1 that are essential for virus replication. We map multiple points of contact between these proteins. Furthermore, by coimmunoprecipitation experiments, we demonstrate the following. (i) ICP4-ICP27 complexes are present in extracts from HSV-1 infected cells. (ii) ICP27 binds preferentially to less modified forms of ICP4, a protein that is extensively modified posttranslationally. We also demonstrate, by performing electrophoretic mobility shift assays and supershifts with monoclonal antibodies to ICP4 or ICP27, that both proteins are present in a DNA-protein complex with a noncanonical ICP4 binding site present in the HSV thymidine kinase (TK) gene. ICP4, in extracts from cells infected with ICP27-deficient viruses, is impaired in its ability to form complexes with the TK site but not with the canonical site from the alpha4 gene. However, ICP4 is able to form complexes with the TK probe, in the absence of ICP27, when overproduced in mammalian cells or expressed in bacteria. These data suggest that the inability of ICP4 from infected cell extracts to bind the TK probe in the absence of ICP27 does not reflect a requirement for the physical presence of ICP27 in the complex. Rather, they imply that ICP27 is likely to modulate the DNA binding activity of ICP4 by affecting its posttranslational modification status. Therefore, we propose that ICP27, in addition to its established role as a posttranscriptional regulator of virus gene expression, may also modulate transcription either through direct or indirect interactions with HSV regulatory regions, or through its ability to modulate the DNA binding activity of ICP4.
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Affiliation(s)
- C A Panagiotidis
- Department of Microbiology, College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA
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47
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Ullman CG, Haris PI, Galloway DA, Emery VC, Perkins SJ. Predicted alpha-helix/beta-sheet secondary structures for the zinc-binding motifs of human papillomavirus E7 and E6 proteins by consensus prediction averaging and spectroscopic studies of E7. Biochem J 1996; 319 ( Pt 1):229-39. [PMID: 8870673 PMCID: PMC1217759 DOI: 10.1042/bj3190229] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The E7 and E6 proteins are the main oncoproteins of human papillomavirus types 16 and 18 (HPV-16 and HPV-18), and possess unknown protein structures. E7 interacts with the cellular tumour-suppressor protein pRB and contains a zinc-binding site with two Cys-Xaa2-Cys motifs spaced 29 or 30 residues apart. E6 interacts with another cellular tumour-suppressor protein p53 and contains two zinc-binding sites, each with two Cys-Xaa2-Cys motifs at a similar spacing of 29 or 30 residues. By using the GOR I/III, Chou-Fasman, SAPIENS and PHD methods, the effectiveness of consensus secondary structure predictions on zinc-finger proteins was first tested with sequences for 160 transcription factors and 72 nuclear hormone receptors. These contain Cys2His2 and Cys2Cys2 zinc-binding regions respectively, and possess known atomic structures. Despite the zinc- and DNA-binding properties of these protein folds, the major alpha-helix structures in both zinc-binding regions were correctly identified. Thus validated, the use of these prediction methods with 47 E7 sequences indicated four well-defined alpha-helix (alpha) and beta-sheet (beta) secondary structure elements in the order beta beta alpha beta in the zinc-binding region of E7 at its C-terminus. The prediction was tested by Fourier transform infrared spectroscopy of recombinant HPV-16 E7 in H2O and 2H2O buffers. Quantitative integration showed that E7 contained similar amounts of alpha-helix and beta-sheet structures, in good agreement with the averaged prediction of alpha-helix and beta-sheet structures in E7 and also with previous circular dichroism studies. Protein fold recognition analyses predicted that the structure of the zinc-binding region in E7 was similar to a beta beta alpha beta motif found in the structure of Protein G. This is consistent with the E7 structure predictions, despite the low sequence similarities with E7. This predicted motif is able to position four Cys residues in proximity to a zinc atom. A model for the zinc-binding motif of E7 was constructed by combining the Protein G coordinates with those for the zinc-binding site in transcription factor TFIIS. Similar analyses for the two zinc-binding motifs in E6 showed that they have different alpha/beta secondary structures from that in E7. When compared with 12 other zinc-binding proteins, these results show that E7 and E6 are predicted to possess novel types of zinc-binding structure.
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Affiliation(s)
- C G Ullman
- Department of Biochemistry and Molecular Biology, Royal Free Hospital School of Medicine, London, U.K
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48
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49
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Abstract
The eukaryotic cell nucleus is a membrane-enclosed compartment containing the genome and associated molecules supported by a highly insoluble filamentous network known as the nucleoskeleton or nuclear matrix. The nuclear matrix is believed to play roles in maintaining nuclear architecture and organizing nuclear metabolism. Recently, advances in microscopic techniques and the availability of new molecular probes have made it possible to localize functional domains within the nuclear matrix and demonstrate dynamic interactions between both soluble and insoluble components involved in the control of multiple nuclear transactions. Like the cytoplasm and its skeleton, the nucleoplasm is highly structured and very crowded with an equally complex skeletal framework. In fact, there is growing evidence that the two skeletal systems are functionally contiguous, providing a dynamic cellular matrix connecting the cell surface with the genome. If we impose cell cycle dynamics upon this skeletal organization, it is obvious that the genome and associated nuclear matrix must undergo a major structural transition during mitosis, being disassembled and/or reorganized in late G2 and reassembled again in daughter nuclei. However, recent evidence from our laboratory and elsewhere suggests that much of the nuclear matrix is used to form the mitotic apparatus (MA). Indeed, both facultative and constitutive matrix-associated proteins such as NuMA, CENP-B, CENP-F, and the retinoblastoma protein (Rb) associate within and around the MA. During mitosis, the nuclear matrix proteins may either become inert "passengers" or assume critical functions in partitioning the genome into newly formed G1 nuclei. Therefore, we support the view that the nuclear matrix exists as a dynamic architectural continuum, embracing the genome and maintaining cellular regulation throughout the cell cycle.
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Affiliation(s)
- M A Mancini
- Department of Cell Biology, Baylor College of Medicine, Houston, Texas 77030, USA
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Stachowiak MK, Maher PA, Joy A, Mordechai E, Stachowiak EK. Nuclear accumulation of fibroblast growth factor receptors is regulated by multiple signals in adrenal medullary cells. Mol Biol Cell 1996; 7:1299-317. [PMID: 8856671 PMCID: PMC275979 DOI: 10.1091/mbc.7.8.1299] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
In an effort to determine the localization of fibroblast growth factor (FGF) receptors (FGFR) that could mediate the intracellular action of FGF-2, we discovered the presence of high-affinity. FGF-2 binding sites in the nuclei of bovine adrenal medullary cells (BAMC). Western blot analysis demonstrated the presence of 103-, 118-, and 145-kDa forms of FGFR1 in nuclei isolated from BAMC. 125I-FGF-2 cross-linking to nuclear extracts followed by FGFR1 immunoprecipitation showed that FGFR1 can account for the nuclear FGF-2 binding sites. Nuclear FGFR1 has kinase activity and undergoes autophosphorylation. Immunocytochemistry with the use of confocal and electron microscopes demonstrated the presence of FGFR1 within the nuclear interior. Nuclear subfractionation followed by Western blot or immunoelectron microscopic analysis showed that the nuclear FGFR1 is contained in the nuclear matrix and the nucleoplasm. Agents that induce translocation of endogenous FGF-2 to the nucleus (forskolin, carbachol, or angiotensin II) increased the intranuclear accumulation of FGFR1. This accumulation was accompanied by an overall increase in FGF-2-inducible tyrosine kinase activity. Our findings suggest a novel mode for growth factor action whereby growth factor receptors translocate to the nucleus in parallel with their ligand and act as direct mediators of nuclear responses to cell stimulation.
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Affiliation(s)
- M K Stachowiak
- Barrow Neurological Institute, Phoenix, Arizona 85013, USA
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