1
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Graham SV. HPV and RNA Binding Proteins: What We Know and What Remains to Be Discovered. Viruses 2024; 16:783. [PMID: 38793664 PMCID: PMC11126060 DOI: 10.3390/v16050783] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2024] [Revised: 05/08/2024] [Accepted: 05/12/2024] [Indexed: 05/26/2024] Open
Abstract
Papillomavirus gene regulation is largely post-transcriptional due to overlapping open reading frames and the use of alternative polyadenylation and alternative splicing to produce the full suite of viral mRNAs. These processes are controlled by a wide range of cellular RNA binding proteins (RPBs), including constitutive splicing factors and cleavage and polyadenylation machinery, but also factors that regulate these processes, for example, SR and hnRNP proteins. Like cellular RNAs, papillomavirus RNAs have been shown to bind many such proteins. The life cycle of papillomaviruses is intimately linked to differentiation of the epithelial tissues the virus infects. For example, viral late mRNAs and proteins are expressed only in the most differentiated epithelial layers to avoid recognition by the host immune response. Papillomavirus genome replication is linked to the DNA damage response and viral chromatin conformation, processes which also link to RNA processing. Challenges with respect to elucidating how RBPs regulate the viral life cycle include consideration of the orchestrated spatial aspect of viral gene expression in an infected epithelium and the epigenetic nature of the viral episomal genome. This review discusses RBPs that control viral gene expression, and how the connectivity of various nuclear processes might contribute to viral mRNA production.
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Affiliation(s)
- Sheila V Graham
- MRC-University of Glasgow Centre for Virus Research, School of Infection and Immunity, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow G61 1QH, UK
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2
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Trammel J, Amusan O, Hultgren A, Raikhy G, Bodily JM. Epidermal growth factor receptor-dependent stimulation of differentiation by human papillomavirus type 16 E5. Virology 2024; 590:109952. [PMID: 38103269 PMCID: PMC10842332 DOI: 10.1016/j.virol.2023.109952] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Revised: 11/14/2023] [Accepted: 11/22/2023] [Indexed: 12/19/2023]
Abstract
Human papillomaviruses (HPVs) infect keratinocytes of stratified squamous epithelia, and persistent infection with high-risk HPV types, such as HPV16, may lead to the development of malignancies. HPV evades host immunity in part by linking its gene expression to the host differentiation program, and therefore relies on differentiation to complete its life cycle. Based on previous reports indicating that the HPV16 protein E5 is important in the late stages of the differentiation-dependent life cycle, we found that organotypic cultures harboring HPV16 genomes lacking E5 showed reduced markers of terminal differentiation compared to wild type HPV16-containing cultures. We found that epidermal growth factor receptor (EGFR) levels and activation were increased in an E5-depdendent manner in these tissues, and that EGFR promoted terminal differentiation and expression of the HPV16 L1 gene. These findings suggest a function for E5 in preserving the ability of HPV16 containing keratinocytes to differentiate, thus facilitating the production of new virus progeny.
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Affiliation(s)
- Jessica Trammel
- Department of Microbiology and Immunology, Louisiana State University Health Sciences Center - Shreveport, Shreveport, LA, 71103, USA
| | - Oluwamuyiwa Amusan
- Department of Microbiology and Immunology, Louisiana State University Health Sciences Center - Shreveport, Shreveport, LA, 71103, USA
| | - Allison Hultgren
- Department of Microbiology and Immunology, Louisiana State University Health Sciences Center - Shreveport, Shreveport, LA, 71103, USA; School of Medicine, Louisiana State University Health Sciences Center - Shreveport, Shreveport, LA, 71103, USA
| | - Gaurav Raikhy
- Department of Microbiology and Immunology, Louisiana State University Health Sciences Center - Shreveport, Shreveport, LA, 71103, USA
| | - Jason M Bodily
- Department of Microbiology and Immunology, Louisiana State University Health Sciences Center - Shreveport, Shreveport, LA, 71103, USA.
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3
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Kirk A, Graham SV. The human papillomavirus late life cycle and links to keratinocyte differentiation. J Med Virol 2024; 96:e29461. [PMID: 38345171 DOI: 10.1002/jmv.29461] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2023] [Revised: 12/21/2023] [Accepted: 01/25/2024] [Indexed: 02/15/2024]
Abstract
Regulation of human papillomavirus (HPV) gene expression is tightly linked to differentiation of the keratinocytes the virus infects. HPV late gene expression is confined to the cells in the upper layers of the epithelium where the virus capsid proteins are synthesized. As these proteins are highly immunogenic, and the upper epithelium is an immune-privileged site, this spatial restriction aids immune evasion. Many decades of work have contributed to the current understanding of how this restriction occurs at a molecular level. This review will examine what is known about late gene expression in HPV-infected lesions and will dissect the intricacies of late gene regulation. Future directions for novel antiviral approaches will be highlighted.
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Affiliation(s)
- Anna Kirk
- Centre for Virus Research, University of Glasgow, Glasgow, UK
| | - Sheila V Graham
- Centre for Virus Research, University of Glasgow, Glasgow, UK
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4
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Kajitani N, Schwartz S. The role of RNA-binding proteins in the processing of mRNAs produced by carcinogenic papillomaviruses. Semin Cancer Biol 2022; 86:482-496. [PMID: 35181475 DOI: 10.1016/j.semcancer.2022.02.014] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2021] [Revised: 02/10/2022] [Accepted: 02/11/2022] [Indexed: 02/08/2023]
Abstract
Human papillomaviruses (HPV) are epitheliotropic DNA tumor viruses that are prevalent in the human population. A subset of the HPVs termed high-risk HPVs (HR-HPVs) are causative agents of anogenital cancers and head-and-neck cancers. Cancer is the result of persistent high-risk HPV infections that have not been cleared by the immune system of the host. These infections are characterized by dysregulated HPV gene expression, in particular constitutive high expression of the HPV E6 and E7 oncogenes and absence of the highly immunogenic viral L1 and L2 capsid proteins. HPVs make extensive use of alternative mRNA splicing to express its genes and are therefore highly dependent on cellular RNA-binding proteins for proper gene expression. Levels of RNA-binding proteins are altered in HPV-containing premalignant cervical lesions and in cervical cancer. Here we review our current knowledge of RNA-binding proteins that control HPV gene expression. We focus on RNA-binding proteins that control expression of the E6 and E7 oncogenes since they initiate and drive development of cancer and on the immunogenic L1 and L2 proteins as there silencing may contribute to immune evasion during carcinogenesis. Furthermore, cellular RNA-binding proteins are essential for HPV gene expression and as such may be targets for therapy to HPV infections and HPV-driven cancers.
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Affiliation(s)
- Naoko Kajitani
- Department of Medical Biochemistry and Microbiology (IMBIM), Uppsala University, BMC-B9, 751 23, Uppsala, Sweden; Department of Laboratory Medicine, Lund University, BMC-B13, 221 84, Lund, Sweden
| | - Stefan Schwartz
- Department of Medical Biochemistry and Microbiology (IMBIM), Uppsala University, BMC-B9, 751 23, Uppsala, Sweden; Department of Laboratory Medicine, Lund University, BMC-B13, 221 84, Lund, Sweden.
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5
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Gusho E, Laimins L. Human Papillomaviruses Target the DNA Damage Repair and Innate Immune Response Pathways to Allow for Persistent Infection. Viruses 2021; 13:1390. [PMID: 34372596 PMCID: PMC8310235 DOI: 10.3390/v13071390] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 07/12/2021] [Accepted: 07/15/2021] [Indexed: 12/18/2022] Open
Abstract
Persistent infection with high-risk human papillomaviruses (HPVs) is the major risk factor associated with development of anogenital and oropharyngeal cancers. Initial infection by HPVs occurs into basal epithelial cells where viral genomes are established as nuclear episomes and persist until cleared by the immune response. Productive replication or amplification occurs upon differentiation and is dependent upon activation of the ataxia-telangiectasia mutated (ATM), ataxia telangiectasia and RAD3-related (ATR) DNA damage repair (DDR) pathways. In addition to activating DDR pathways, HPVs must escape innate immune surveillance mechanisms by antagonizing sensors, adaptors, interferons and antiviral gene expression. Both DDR and innate immune pathways are key host mechanisms that crosstalk with each other to maintain homeostasis of cells persistently infected with HPVs. Interestingly, it is still not fully understood why some HPV infections get cleared while others do not. Targeting of these two processes with antiviral therapies may provide opportunities for treatment of cancers caused by high-risk HPVs.
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Affiliation(s)
| | - Laimonis Laimins
- Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA;
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6
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Kajitani N, Schwartz S. Role of Viral Ribonucleoproteins in Human Papillomavirus Type 16 Gene Expression. Viruses 2020; 12:E1110. [PMID: 33007936 PMCID: PMC7600041 DOI: 10.3390/v12101110] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2020] [Revised: 09/25/2020] [Accepted: 09/26/2020] [Indexed: 02/06/2023] Open
Abstract
Human papillomaviruses (HPVs) depend on the cellular RNA-processing machineries including alternative RNA splicing and polyadenylation to coordinate HPV gene expression. HPV RNA processing is controlled by cis-regulatory RNA elements and trans-regulatory factors since the HPV splice sites are suboptimal. The definition of HPV exons and introns may differ between individual HPV mRNA species and is complicated by the fact that many HPV protein-coding sequences overlap. The formation of HPV ribonucleoproteins consisting of HPV pre-mRNAs and multiple cellular RNA-binding proteins may result in the different outcomes of HPV gene expression, which contributes to the HPV life cycle progression and HPV-associated cancer development. In this review, we summarize the regulation of HPV16 gene expression at the level of RNA processing with focus on the interactions between HPV16 pre-mRNAs and cellular RNA-binding factors.
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Affiliation(s)
- Naoko Kajitani
- Department of Laboratory Medicine, Lund University, 22184 Lund, Sweden;
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7
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Aguayo F, Muñoz JP, Perez-Dominguez F, Carrillo-Beltrán D, Oliva C, Calaf GM, Blanco R, Nuñez-Acurio D. High-Risk Human Papillomavirus and Tobacco Smoke Interactions in Epithelial Carcinogenesis. Cancers (Basel) 2020; 12:E2201. [PMID: 32781676 PMCID: PMC7465661 DOI: 10.3390/cancers12082201] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Revised: 08/04/2020] [Accepted: 08/04/2020] [Indexed: 02/06/2023] Open
Abstract
Cervical, anogenital, and some head and neck cancers (HNC) are etiologically associated with high-risk human papillomavirus (HR-HPV) infection, even though additional cofactors are necessary. Epidemiological studies have established that tobacco smoke (TS) is a cofactor for cervical carcinogenesis because women who smoke are more susceptible to cervical cancer when compared to non-smokers. Even though such a relationship has not been established in HPV-related HNC, a group of HPV positive patients with this malignancy are smokers. TS is a complex mixture of more than 4500 chemical compounds and approximately 60 of them show oncogenic properties such as benzo[α]pyrene (BaP) and nitrosamines, among others. Some of these compounds have been evaluated for carcinogenesis through experimental settings in collaboration with HR-HPV. Here, we conducted a comprehensive review of the suggested molecular mechanisms involved in cooperation with both HR-HPV and TS for epithelial carcinogenesis. Furthermore, we propose interaction models in which TS collaborates with HR-HPV to promote epithelial cancer initiation, promotion, and progression. More studies are warranted to clarify interactions between oncogenic viruses and chemical or physical environmental factors for epithelial carcinogenesis.
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Affiliation(s)
- Francisco Aguayo
- Universidad de Tarapacá, Arica 1000000, Chile
- Advanced Center for Chronic Diseases (ACCDiS), Facultad de Medicina, Universidad de Chile, Santiago 8330024, Chile
| | - Juan P. Muñoz
- Instituto de Alta Investigación, Universidad de Tarapacá, Arica 1000000, Chile; (J.P.M.); (G.M.C.)
| | - Francisco Perez-Dominguez
- Laboratorio Oncovirología, Programa de Virología, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago 8380000, Chile; (F.P.-D.); (D.C.-B.); (C.O.); (R.B.); (D.N.-A.)
| | - Diego Carrillo-Beltrán
- Laboratorio Oncovirología, Programa de Virología, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago 8380000, Chile; (F.P.-D.); (D.C.-B.); (C.O.); (R.B.); (D.N.-A.)
| | - Carolina Oliva
- Laboratorio Oncovirología, Programa de Virología, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago 8380000, Chile; (F.P.-D.); (D.C.-B.); (C.O.); (R.B.); (D.N.-A.)
| | - Gloria M. Calaf
- Instituto de Alta Investigación, Universidad de Tarapacá, Arica 1000000, Chile; (J.P.M.); (G.M.C.)
- Center for Radiological Research, Columbia University Medical Center, New York, NY 10032, USA
| | - Rances Blanco
- Laboratorio Oncovirología, Programa de Virología, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago 8380000, Chile; (F.P.-D.); (D.C.-B.); (C.O.); (R.B.); (D.N.-A.)
| | - Daniela Nuñez-Acurio
- Laboratorio Oncovirología, Programa de Virología, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago 8380000, Chile; (F.P.-D.); (D.C.-B.); (C.O.); (R.B.); (D.N.-A.)
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8
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Kajitani N, Glahder J, Wu C, Yu H, Nilsson K, Schwartz S. hnRNP L controls HPV16 RNA polyadenylation and splicing in an Akt kinase-dependent manner. Nucleic Acids Res 2017; 45:9654-9678. [PMID: 28934469 PMCID: PMC5766200 DOI: 10.1093/nar/gkx606] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Accepted: 07/04/2017] [Indexed: 11/14/2022] Open
Abstract
Inhibition of the Akt kinase activates HPV16 late gene expression by reducing HPV16 early polyadenylation and by activating HPV16 late L1 mRNA splicing. We identified ‘hot spots’ for RNA binding proteins at the early polyA signal and at splice sites on HPV16 late mRNAs. We observed that hnRNP L was associated with sequences at all HPV16 late splice sites and at the early polyA signal. Akt kinase inhibition resulted in hnRNP L dephosphorylation and reduced association of hnRNP L with HPV16 mRNAs. This was accompanied by an increased binding of U2AF65 and Sam68 to HPV16 mRNAs. Furthermore, siRNA knock-down of hnRNP L or Akt induced HPV16 gene expression. Treatment of HPV16 immortalized keratinocytes with Akt kinase inhibitor reduced hnRNP L binding to HPV16 mRNAs and induced HPV16 L1 mRNA production. Finally, deletion of the hnRNP L binding sites in HPV16 subgenomic expression plasmids resulted in activation of HPV16 late gene expression. In conclusion, the Akt kinase inhibits HPV16 late gene expression at the level of RNA processing by controlling the RNA-binding protein hnRNP L. We speculate that Akt kinase activity upholds an intracellular milieu that favours HPV16 early gene expression and suppresses HPV16 late gene expression.
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Affiliation(s)
- Naoko Kajitani
- Department of Laboratory Medicine, Lund University, BMC-B13, 223 62 Lund, Sweden
| | - Jacob Glahder
- Department of Laboratory Medicine, Lund University, BMC-B13, 223 62 Lund, Sweden
| | - Chengjun Wu
- Department of Laboratory Medicine, Lund University, BMC-B13, 223 62 Lund, Sweden
| | - Haoran Yu
- Department of Laboratory Medicine, Lund University, BMC-B13, 223 62 Lund, Sweden
| | - Kersti Nilsson
- Department of Laboratory Medicine, Lund University, BMC-B13, 223 62 Lund, Sweden
| | - Stefan Schwartz
- Department of Laboratory Medicine, Lund University, BMC-B13, 223 62 Lund, Sweden
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9
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Graham SV. Keratinocyte Differentiation-Dependent Human Papillomavirus Gene Regulation. Viruses 2017; 9:E245. [PMID: 28867768 PMCID: PMC5618011 DOI: 10.3390/v9090245] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Revised: 08/24/2017] [Accepted: 08/25/2017] [Indexed: 12/29/2022] Open
Abstract
Human papillomaviruses (HPVs) cause diseases ranging from benign warts to invasive cancers. HPVs infect epithelial cells and their replication cycle is tightly linked with the differentiation process of the infected keratinocyte. The normal replication cycle involves an early and a late phase. The early phase encompasses viral entry and initial genome replication, stimulation of cell division and inhibition of apoptosis in the infected cell. Late events in the HPV life cycle include viral genome amplification, virion formation, and release into the environment from the surface of the epithelium. The main proteins required at the late stage of infection for viral genome amplification include E1, E2, E4 and E5. The late proteins L1 and L2 are structural proteins that form the viral capsid. Regulation of these late events involves both cellular and viral proteins. The late viral mRNAs are expressed from a specific late promoter but final late mRNA levels in the infected cell are controlled by splicing, polyadenylation, nuclear export and RNA stability. Viral late protein expression is also controlled at the level of translation. This review will discuss current knowledge of how HPV late gene expression is regulated.
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Affiliation(s)
- Sheila V Graham
- MRC-University of Glasgow Centre for Virus Research, Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Garscube Estate, Glasgow G61 1QH, UK.
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10
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Splicing and Polyadenylation of Human Papillomavirus Type 16 mRNAs. Int J Mol Sci 2017; 18:ijms18020366. [PMID: 28208770 PMCID: PMC5343901 DOI: 10.3390/ijms18020366] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Revised: 01/29/2017] [Accepted: 02/03/2017] [Indexed: 12/24/2022] Open
Abstract
The human papillomavirus type 16 (HPV16) life cycle can be divided into an early stage in which the HPV16 genomic DNA is replicated, and a late stage in which the HPV16 structural proteins are synthesized and virions are produced. A strong coupling between the viral life cycle and the differentiation state of the infected cell is highly characteristic of all HPVs. The switch from the HPV16 early gene expression program to the late requires a promoter switch, a polyadenylation signal switch and a shift in alternative splicing. A number of cis-acting RNA elements on the HPV16 mRNAs and cellular and viral factors interacting with these elements are involved in the control of HPV16 gene expression. This review summarizes our knowledge of HPV16 cis-acting RNA elements and cellular and viral trans-acting factors that regulate HPV16 gene expression at the level of splicing and polyadenylation.
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11
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RNA Binding Proteins that Control Human Papillomavirus Gene Expression. Biomolecules 2015; 5:758-74. [PMID: 25950509 PMCID: PMC4496695 DOI: 10.3390/biom5020758] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Revised: 04/15/2015] [Accepted: 04/21/2015] [Indexed: 12/23/2022] Open
Abstract
The human papillomavirus (HPV) life cycle is strictly linked to the differentiation program of the infected mucosal epithelial cell. In the basal and lower levels of the epithelium, early genes coding for pro-mitotic proteins and viral replication factors are expressed, while terminal cell differentiation is required for activation of late gene expression and production of viral particles at the very top of the epithelium. Such productive infections are normally cleared within 18–24 months. In rare cases, the HPV infection is stuck in the early stage of the infection. Such infections may give rise to cervical lesions that can progress to cancer, primarily cancer of the uterine cervix. Since cancer progression is strictly linked to HPV gene expression, it is of interest to understand how HPV gene expression is regulated. Cis-acting HPV RNA elements and cellular RNA-binding proteins control HPV mRNA splicing and polyadenylation. These interactions are believed to play a particularly important role in the switch from early to late gene expression, thereby contributing to the pathogenesis of HPV. Indeed, it has been shown that the levels of various RNA binding proteins change in response to differentiation and in response to HPV induced cervical lesions and cancer. Here we have compiled published data on RNA binding proteins involved in the regulation of HPV gene expression.
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12
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Schwartz S. Papillomavirus transcripts and posttranscriptional regulation. Virology 2013; 445:187-96. [PMID: 23706315 DOI: 10.1016/j.virol.2013.04.034] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Revised: 04/26/2013] [Accepted: 04/29/2013] [Indexed: 11/19/2022]
Abstract
Papillomavirus gene expression is strictly linked to the differentiation state of the infected cell and is highly regulated at the level of transcription and RNA processing. All papillomaviruses make extensive use of alternative mRNA polyadenylation and splicing to control gene expression. This chapter contains a compilation of all known alternatively spliced papillomavirus mRNAs and it summarizes our current knowledge of viral RNA elements, and viral and cellular factors that control papillomavirus mRNA processing.
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Affiliation(s)
- Stefan Schwartz
- Department of Laboratory Medicine, Section of Medical Microbiology, Lund University, BMC-B13, Sölvegatan 19, 223 62 Lund, Sweden.
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13
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Regulation of human papillomavirus gene expression by splicing and polyadenylation. Nat Rev Microbiol 2013; 11:239-51. [DOI: 10.1038/nrmicro2984] [Citation(s) in RCA: 115] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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14
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Wilson AD, Armstrong ELR, Gofton RG, Mason J, De Toit N, Day MJ. Characterisation of early and late bovine papillomavirus protein expression in equine sarcoids. Vet Microbiol 2012; 162:369-380. [PMID: 23123175 DOI: 10.1016/j.vetmic.2012.10.010] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2012] [Revised: 10/03/2012] [Accepted: 10/05/2012] [Indexed: 10/27/2022]
Abstract
Sarcoids are common skin tumours of horses and donkeys that are characterised by persistent proliferation of dermal fibroblasts associated with the presence of bovine papillomavirus (BPV) DNA. Some early BPV proteins have been demonstrated within sarcoids and RNA containing both early and late transcripts is present, yet it remains unclear whether late replication of BPV, culminating in the production of infectious virus particles, can occur in equids. Here we report that BPV1 RNA isolated from equine sarcoids encodes a unique deletion of four residues within the L2 protein suggesting a novel variant of virus has evolved in equines. Such viral evolution would require the production and transmission of virus particles among horses with sarcoids. Quantitative RT-PCR demonstrated the presence of mRNA transcripts containing early gene message in sarcoid tissues and BPV-E2 early virus antigen was detected by immunofluorescence in the nuclei of dermal fibroblasts, but no E2 expression could be detected within the overlying epidermis where productive virus replication would be expected to occur. Although immunohistochemistry clearly detected late virus proteins in the nuclei of dermal cells from samples of bovine papillomas, no late protein expression was detected in formalin-fixed tissue from equine sarcoids; either in the dermis or epidermis. Moreover, quantitative RT-PCR demonstrated that late gene mRNA represented <0.3% of the transcribed BPV RNA. We conclude that BPV does not undergo productive infection in the epidermis overlying equine sarcoids at levels comparable with that occurring in its natural bovine host.
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Affiliation(s)
- A D Wilson
- University of Bristol, School of Veterinary Sciences, Langford, Bristol BS40 7DU, UK.
| | - E L R Armstrong
- University of Bristol, School of Veterinary Sciences, Langford, Bristol BS40 7DU, UK
| | - R G Gofton
- University of Bristol, School of Veterinary Sciences, Langford, Bristol BS40 7DU, UK
| | - J Mason
- University of Bristol, School of Veterinary Sciences, Langford, Bristol BS40 7DU, UK
| | - N De Toit
- University of Bristol, School of Veterinary Sciences, Langford, Bristol BS40 7DU, UK; Veterinary Laboratory, The Donkey Sanctuary, Sidmouth, Devon EX10 0NU, UK
| | - M J Day
- University of Bristol, School of Veterinary Sciences, Langford, Bristol BS40 7DU, UK
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15
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Development and validation of a novel reporter assay for human papillomavirus type 16 late gene expression. J Virol Methods 2012; 183:106-16. [DOI: 10.1016/j.jviromet.2012.03.023] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2011] [Revised: 03/13/2012] [Accepted: 03/21/2012] [Indexed: 11/23/2022]
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16
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HPV-16 E2 contributes to induction of HPV-16 late gene expression by inhibiting early polyadenylation. EMBO J 2012; 31:3212-27. [PMID: 22617423 DOI: 10.1038/emboj.2012.147] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2011] [Accepted: 04/24/2012] [Indexed: 11/08/2022] Open
Abstract
We provide evidence that the human papillomavirus (HPV) E2 protein regulates HPV late gene expression. High levels of E2 caused a read-through at the early polyadenylation signal pAE into the late region of the HPV genome, thereby inducing expression of L1 and L2 mRNAs. This is a conserved property of E2 of both mucosal and cutaneous HPV types. Induction could be reversed by high levels of HPV-16 E1 protein, or by the polyadenylation factor CPSF30. HPV-16 E2 inhibited polyadenylation in vitro by preventing the assembly of the CPSF complex. Both the N-terminal and hinge domains of E2 were required for induction of HPV late gene expression in transfected cells as well as for inhibition of polyadenylation in vitro. Finally, overexpression of HPV-16 E2 induced late gene expression from a full-length genomic clone of HPV-16. We speculate that the accumulation of high levels of E2 during the viral life cycle, not only turns off the expression of the pro-mitotic viral E6 and E7 genes, but also induces the expression of the late HPV genes L1 and L2.
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17
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Graham SV. Human papillomavirus: gene expression, regulation and prospects for novel diagnostic methods and antiviral therapies. Future Microbiol 2011; 5:1493-506. [PMID: 21073310 DOI: 10.2217/fmb.10.107] [Citation(s) in RCA: 108] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Human papillomaviruses (HPVs) cause diseases ranging from benign warts to invasive tumors. A subset of these viruses termed 'high risk' infect the cervix where persistent infection can lead to cervical cancer. Although many HPV genomes have been sequenced, knowledge of virus gene expression and its regulation is still incomplete. This is due in part to the lack, until recently, of suitable systems for virus propagation in the laboratory. HPV gene expression is polycistronic initiating from multiple promoters. Gene regulation occurs at transcriptional, but particularly post-transcriptional levels, including RNA processing, nuclear export, mRNA stability and translation. A close association between the virus replication cycle and epithelial differentiation adds a further layer of complexity. Understanding HPV mRNA expression and its regulation in the different diseases associated with infection may lead to development of novel diagnostic approaches and will reveal key viral and cellular targets for development of novel antiviral therapies.
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Affiliation(s)
- Sheila V Graham
- MRC-University of Glasgow Centre for Virus Research, Institute of Infection Immunity & Inflammation, College of Medicine, Veterinary Medicine and Life Sciences, University of Glasgow G12 8TT, Scotland, UK.
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Somberg M, Rush M, Fay J, Ryan F, Lambkin H, Akusjärvi G, Schwartz S. Adenovirus E4orf4 induces HPV-16 late L1 mRNA production. Virology 2008; 383:279-90. [PMID: 19026433 DOI: 10.1016/j.virol.2008.09.041] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2008] [Revised: 08/29/2008] [Accepted: 09/25/2008] [Indexed: 10/21/2022]
Abstract
The adenovirus E4orf4 protein regulates the switch from early to late gene expression during the adenoviral replication cycle. Here we report that overexpression of adenovirus E4orf4 induces human papillomavirus type 16 (HPV-16) late gene expression from subgenomic expression plasmids. E4orf4 specifically overcomes the negative effects of two splicing silencers at the two late HPV-16 splice sites SD3632 and SA5639. This results in the production of HPV-16 spliced L1 mRNAs. We show that the interaction of E4orf4 with protein phosphatase 2A (PP2A) is necessary for induction of HPV-16 late gene expression. Also an E4orf4 mutant that fails to bind the cellular splicing factor ASF/SF2 fails to induce L1 mRNA production. Collectively, these results suggest that dephosphorylation of SR proteins by E4orf4 activates HPV-16 late gene expression. Indeed, a mutant ASF/SF2 protein in which the RS-domain had been deleted could itself induce HPV-16 late gene expression, whereas wild type ASF/SF2 could not.
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Affiliation(s)
- Monika Somberg
- Department of Medical Biochemistry and Microbiology, BMC, Uppsala University, Sweden
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19
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Polypyrimidine tract binding protein induces human papillomavirus type 16 late gene expression by interfering with splicing inhibitory elements at the major late 5' splice site, SD3632. J Virol 2008; 82:3665-78. [PMID: 18216120 DOI: 10.1128/jvi.02140-07] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
We have initiated a screen for cellular factors that can induce human papillomavirus type 16 (HPV-16) late gene expression in human cancer cells. We report that the overexpression of polypyrimidine tract binding protein (PTB), also known as heterologous nuclear ribonucleoprotein I (hnRNP I), induces HPV-16 late gene expression in cells transfected with subgenomic HPV-16 plasmids or with full-length HPV-16 genomes and in persistently HPV-16-infected cells. In contrast, other hnRNPs such as hnRNP B1/A2, hnRNP F, and hnRNP Q do not induce HPV-16 late gene expression. PTB activates SD3632, the only 5' splice site on the HPV-16 genome that is used exclusively by late mRNAs. PTB interferes with splicing inhibitory sequences located immediately upstream and downstream of SD3632, thereby activating late gene expression. One AU-rich PTB-responsive element was mapped to a 198-nucleotide sequence located downstream of SD3632. The deletion of this element induced HPV-16 late gene expression in the absence of PTB. Our results suggest that the overexpression of PTB interferes with cellular factors that interact with the inhibitory sequences. One may speculate that an increase in PTB levels or a reduction in the concentration of a PTB antagonist is required for the activation of HPV-16 late gene expression during the viral life cycle.
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20
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Zhao X, Fay J, Lambkin H, Schwartz S. Identification of a 17-nucleotide splicing enhancer in HPV-16 L1 that counteracts the effect of multiple hnRNP A1-binding splicing silencers. Virology 2007; 369:351-63. [PMID: 17869320 DOI: 10.1016/j.virol.2007.08.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2007] [Revised: 07/13/2007] [Accepted: 08/01/2007] [Indexed: 11/26/2022]
Abstract
Human papillomavirus type 16 (HPV-16) infections can in rare cases persist and cause lesions that may progress to cervical cancer. Cells in the lesions are not permissive for virus production, nor are cervical cancer cells. The intracellular environment is such that it prevents production of the highly immunogenic, viral structural proteins L1 and L2. One may speculate that inhibition of L1 and L2 expression is a prerequisite for persistence and cancer progression. We have therefore investigated how expression of HPV-16 L1 is regulated. We found that the only splice site in the HPV-16 late region, which is used to produce L1 mRNAs, is under control of a splicing enhancer located in the 17 nucleotides immediately downstream of the splice site. However, the function of this enhancer in cervical cancer cells is largely overshadowed by multiple splicing silencers in the late region which bind to hnRNP A1. High levels of hnRNP A1 therefore inhibit HPV-16 L1 expression. Immunohistological analysis of cervical epithelia revealed that hnRNP A1 is expressed primarily in the lower layers of the epithelium. hnRNP A1 is undetectable in terminally differentiated cells that can express HPV-16 late genes, which supports the conclusion that high levels of hnRNP A1 inhibit HPV-16 L1 expression.
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Affiliation(s)
- Xiaomin Zhao
- Department of Medical Biochemistry and Microbiology, Uppsala University, Biomedical Center, Husargatan 3, Box 582, 751 23 Uppsala, Sweden
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21
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Kung CM, King CC, Lee CN, Huang LM, Lee PI, Kao CL. Differences in replication capacity between enterovirus 71 isolates obtained from patients with encephalitis and those obtained from patients with herpangina in Taiwan. J Med Virol 2007; 79:60-8. [PMID: 17133556 DOI: 10.1002/jmv.20761] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The cellular-tropism and biological characteristics of enterovirus 71 (EV71) isolates in Taiwan (TW) were studied. Growth curve experiments were conducted using cell lines that were possibly exhibited pathogenesis, and RT-PCR and sequencing tests were undertaken to amplify the 5' non-coding region (5'-NCR). The encephalitis isolate EV71 TW98NTU2078 was PBMC-tropic, temperature-resistant (Tr) at 40 degrees C, and easier to replicate in HTB-14 (astrocytoma) than the herpangina isolate EV71 TW98NTU1186 (The viral yields were 100-fold higher than those of the herpangina isolate EV71 TW98NTU1186 at 96 hr post infection.). The herpangina isolate EV71 TW98NTU1186 was non-PBMC-tropic, and temperature-sensitive (Ts) at 40 degrees C. The replication of EV71 TW98NTU1186 in HTB-14 was lower. No EV71 isolate infected HTB-37 (human colon adenocarcinoma cells). The encephalitis EV71 isolate exhibited better replication and transmission in PBMCs and astrocytes than did the EV71 isolate without CNS involvement.
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Affiliation(s)
- Chien-Min Kung
- Department of Medical Technology, Yuanpei University, Hsinchu, Taiwan, Republic of China
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22
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Zheng ZM, Baker CC. Papillomavirus genome structure, expression, and post-transcriptional regulation. FRONT BIOSCI-LANDMRK 2006; 11:2286-302. [PMID: 16720315 PMCID: PMC1472295 DOI: 10.2741/1971] [Citation(s) in RCA: 295] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Papillomaviruses are a group of small non-enveloped DNA tumor viruses whose infection usually causes benign epithelial lesions (warts). Certain types of HPVs, such as HPV-16, HPV-18, and HPV-31, have been recognized as causative agents of cervical cancer and anal cancer and their infections, which arise via sexual transmission, are associated with more than 95% of cervical cancer. Papillomaviruses infect keratinocytes in the basal layer of stratified squamous epithelia and replicate in the nucleus of infected keratinocytes in a differentiation-dependent manner. Viral gene expression in infected cells depends on cell differentiation and is tightly regulated at the transcriptional and post-transcriptional levels. A noteworthy feature of all papillomavirus transcripts is that they are transcribed as a bicistronic or polycistronic form containing two or more ORFs and are polyadenylated at either an early or late poly(A) site. In the past ten years, remarkable progress has been made in understanding how this complex viral gene expression is regulated at the level of transcription (such as via DNA methylation) and particularly post-transcription (including RNA splicing, polyadenylation, and translation). Current knowledge of papillomavirus mRNA structure and RNA processing has provided some clues on how to control viral oncogene expression. However, we still have little knowledge about which mRNAs are used to translate each viral protein. Continuing research on post-transcriptional regulation of papillomavirus infection will remain as a future focus to provide more insights into papillomavirus-host interactions, the virus life-cycle, and viral oncogenesis.
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Affiliation(s)
- Zhi-Ming Zheng
- HIV and AIDS Malignancy Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA.
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23
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Abstract
Carcinoma of the uterine cervix, a leading cause of cancer death in women worldwide, is initiated by infection with high-risk types of human papillomaviruses (HPVs). This review summarizes laboratory studies over the past 20 years that have elucidated the major features of the HPV life cycle, identified the functions of the viral proteins, and clarified the consequences of HPV infection for their host cells. This information has allowed the development of various strategies to prevent or treat infections, including prophylactic vaccination with virus-like particles, therapeutic vaccination against viral proteins expressed in cancer cells, and antiviral approaches to inhibit virus replication, spread, or pathogenesis. These strategies have the potential to cause a dramatic reduction in the incidence of cervical carcinoma and serve as the prototype for comprehensive efforts to combat virus-induced tumors.
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Affiliation(s)
- Daniel DiMaio
- Department of Genetics, Yale University School of Medicine, New Haven, Connecticut 06510, USA
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24
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Bodily JM, Alam S, Meyers C. Regulation of human papillomavirus type 31 late promoter activation and genome amplification by protein kinase C. Virology 2006; 348:328-40. [PMID: 16500689 DOI: 10.1016/j.virol.2006.01.036] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2005] [Revised: 09/19/2005] [Accepted: 01/26/2006] [Indexed: 10/25/2022]
Abstract
The life cycle of papillomaviruses is tightly linked to differentiation of host keratinocytes, but the mechanisms and cues by which life cycle events are tied to differentiation remain obscure. We have begun a systematic study of the differentiation-dependent life cycle of HPV31. A variety of signaling pathways have been implicated in controlling keratinocyte differentiation, especially the protein kinase C (PKC) pathway. We have used pharmacological inhibitors to determine that genome amplification and late transcription depend on specific PKC isoforms, and that transcription and replication are independently controlled. We found that tyrosine kinases are necessary for viral amplification but not viral transcription. These studies indicate that the PKC pathway is an important regulator of differentiation-dependent HPV31 replication and transcription.
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Affiliation(s)
- Jason M Bodily
- Department of Microbiology and Immunology, The Pennsylvania State University College of Medicine, Hershey, 17033, USA
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25
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Unwalla HJ, Li HT, Bahner I, Li MJ, Kohn D, Rossi JJ. Novel Pol II fusion promoter directs human immunodeficiency virus type 1-inducible coexpression of a short hairpin RNA and protein. J Virol 2006; 80:1863-73. [PMID: 16439542 PMCID: PMC1367144 DOI: 10.1128/jvi.80.4.1863-1873.2006] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
We demonstrate a novel approach for coexpression of a short hairpin RNA (shRNA) with an open reading frame which exploits transcriptional read-through of a minimal polyadenylation signal from a Pol II promoter. We first observed efficient inducible expression of enhanced green fluorescent protein along with an anti-rev shRNA. We took advantage of this observation to test coexpression of the transdominant negative mutant (humanized) of human immunodeficiency type 1 (HIV-1) Rev (huRevM10) along with an anti-rev shRNA via an HIV-1-inducible fusion promoter. The coexpression of the shRNA and transdominant protein resulted in potent, long-term inhibition of HIV-1 gene expression and suppression of shRNA-resistant mutants. This dual expression system has broad-based potential for other shRNA applications, such as cases where simultaneous knockdown of mutant and wild-type transcripts must be accompanied by replacement of the wild-type protein.
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MESH Headings
- Cell Line
- Cloning, Molecular
- DNA Polymerase II/genetics
- Gene Expression
- Gene Expression Regulation, Viral
- Gene Products, rev/biosynthesis
- Gene Products, tat/physiology
- Genes, Dominant
- Genes, Reporter
- Green Fluorescent Proteins/biosynthesis
- Green Fluorescent Proteins/genetics
- HIV Core Protein p24/analysis
- HIV Long Terminal Repeat
- HIV-1/genetics
- HIV-1/physiology
- Humans
- Mutation
- Promoter Regions, Genetic
- RNA Interference
- RNA, Small Interfering/biosynthesis
- Transcription, Genetic
- Transfection
- rev Gene Products, Human Immunodeficiency Virus
- tat Gene Products, Human Immunodeficiency Virus
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Affiliation(s)
- Hoshang J Unwalla
- Department of Molecular Biology, Beckman Research Institute of the City of Hope, 1450 E. Duarte Rd., Duarte, CA 91010, USA.
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26
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Sík A, Coté A, Boldogkõi Z. Selective spread of neurotropic herpesviruses in the rat hippocampus. J Comp Neurol 2006; 496:229-43. [PMID: 16538677 DOI: 10.1002/cne.20921] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Transsynaptically spreading viruses are widely used for tracing neuronal circuits in both the central and peripheral nervous systems. However, viruses are capricious tools with selective spreading properties that can produce false-negative results. Using herpes simplex virus type 1 and two pseudorabies virus strains, we aimed at mapping quantitatively neuronal connections in the rat hippocampus. We found that none of the tested viruses infected CA3 pyramidal neurons across synapses following inoculation into the CA1 area. Combined injections of the viruses with the retrograde tracer cholera toxin B (CTB) resulted in CTB, but not virus labeling of CA3 pyramidal neurons. In contrast, other brain regions known to send inputs to the CA1 (the entorhinal cortex, medial septum and diagonal band of Broca, raphe nuclei) were transsynaptically infected. Our results indicate that Schaffer collaterals of CA3 pyramidal cells lack the appropriate cellular machinery for successful neurotropic herpesvirus infection. After injections of viruses into the dentate gyrus/CA3 area, we found labeling in commissurally projecting mossy cells and their afferent granule cells but not in contralateral CA3 pyramidal cells. Using this unique spreading property, we estimated that single mossy cells receive input from a compact cluster of 30-40 granule cells.
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Affiliation(s)
- Attila Sík
- Department of Psychiatry, Faculty of Medicine, Centre de recherche Université Laval Robert-Giffard, Québec City G1J 2G3, Canada
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27
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Vinther J, Rosenstierne MW, Kristiansen K, Norrild B. The 3' region of human papillomavirus type 16 early mRNAs decrease expression. BMC Infect Dis 2005; 5:83. [PMID: 16225671 PMCID: PMC1266366 DOI: 10.1186/1471-2334-5-83] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2005] [Accepted: 10/14/2005] [Indexed: 11/27/2022] Open
Abstract
Background High risk human papillomavirus (HR-HPV) infects mucosal surfaces and HR-HPV infection is required for development of cervical cancer. Accordingly, enforced expression of the early HR-HPV proteins can induce immortalisation of human cells. In most cervical cancers and cervical cancer cell lines the HR-HPV double stranded DNA genome has been integrated into the host cell genome. Methods We have used a retroviral GUS reporter system to generate pools of stably transfected HaCaT and SiHa cells. The HPV-16 early sequences that are deleted upon integration of the HPV-16 genome was inserted into the 3' UTR of the reporter mRNA. Pools containing thousands of independent integrations were tested for the steady state levels of the reporter mRNA by Real Time PCR and reporter protein by a GUS enzymatic activity assays. In addition, we tested the cellular distribution and half lives of the reporter mRNAs. The integrity of the reporter mRNAs were tested by northern blotting. Results We show that the 3' region of the HPV-16 early mRNAs (HPV-16 nucleotide (nt.) 2582–4214) act in cis to decrease both mRNA and protein levels. This region seems to affect transcription from the exogenous minimal CMV promoter or processing of the reporter mRNA. The observed repression was most pronounced at the protein level, suggesting that this sequence may also affect translation. For the HPV types: 2, 6, 11, 13, 18, 30, 31, and 35 we have investigated the regulatory effect of the regions corresponding to the HPV-16 nt. 3358–4214. For all types, except HPV-18, the region was found to repress expression by posttranscriptional mechanisms. Conclusion We find that the 3' region of HPV-16 early mRNAs interfere with gene expression. It is therefore possible that the deletion of the 3' part of early HPV-16 mRNAs occurring during cervical oncogenesis could contribute to transformation of cells through deregulation of the viral oncogene synthesis. Moreover, we find that the corresponding region from several other HPV types also repress expression, suggesting that the repression by this region may be a general feature of the HPV life cycle.
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Affiliation(s)
- Jeppe Vinther
- Institute of Molecular Pathology, University of Copenhagen, Blegdamsvej 3C, Bldg. 6.2, DK-2200 Copenhagen N, Denmark
- Institute of Molecular Biology, University of Copenhagen, Universitetsparken 15, Bldg. 10, DK-2100 Copenhagen Ø, Denmark
| | - Maiken W Rosenstierne
- Institute of Molecular Pathology, University of Copenhagen, Blegdamsvej 3C, Bldg. 6.2, DK-2200 Copenhagen N, Denmark
| | - Karen Kristiansen
- Institute of Molecular Pathology, University of Copenhagen, Blegdamsvej 3C, Bldg. 6.2, DK-2200 Copenhagen N, Denmark
- BioCentrum-DTU, Technical University of Denmark, Building 208, DK-2800 Lyngby, Denmark
| | - Bodil Norrild
- Institute of Molecular Pathology, University of Copenhagen, Blegdamsvej 3C, Bldg. 6.2, DK-2200 Copenhagen N, Denmark
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28
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Oberg D, Fay J, Lambkin H, Schwartz S. A downstream polyadenylation element in human papillomavirus type 16 L2 encodes multiple GGG motifs and interacts with hnRNP H. J Virol 2005; 79:9254-69. [PMID: 15994820 PMCID: PMC1168734 DOI: 10.1128/jvi.79.14.9254-9269.2005] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Production of human papillomavirus type 16 (HPV-16) virus particles is totally dependent on the differentiation-dependent induction of viral L1 and L2 late gene expression. The early polyadenylation signal in HPV-16 plays a major role in the switch from the early to the late, productive stage of the viral life cycle. Here, we show that the L2 coding region of HPV-16 contains RNA elements that are necessary for polyadenylation at the early polyadenylation signal. Consecutive mutations in six GGG motifs located 174 nucleotides downstream of the polyadenylation signal resulted in a gradual decrease in polyadenylation at the early polyadenylation signal. This caused read-through into the late region, followed by production of the late mRNAs encoding L1 and L2. Binding of hnRNP H to the various triple-G mutants correlated with functional activity of the HPV-16 early polyadenylation signal. In addition, the polyadenylation factor CStF-64 was also found to interact specifically with the region in L2 located 174 nucleotides downstream of the early polyadenylation signal. Staining of cervix epithelium with anti-hnRNP H-specific antiserum revealed high expression levels of hnRNP H in the lower layers of cervical epithelium and a loss of hnRNP H production in the superficial layers, supporting a model in which a differentiation-dependent down regulation of hnRNP H causes a decrease in HPV-16 early polyadenylation and an induction of late gene expression.
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Affiliation(s)
- Daniel Oberg
- Department of Medical Biochemistry and Microbiology, Uppsala University, BMC, Box 582, Husargatan 3, 751 23 Uppsala, Sweden
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29
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Zhao X, Oberg D, Rush M, Fay J, Lambkin H, Schwartz S. A 57-nucleotide upstream early polyadenylation element in human papillomavirus type 16 interacts with hFip1, CstF-64, hnRNP C1/C2, and polypyrimidine tract binding protein. J Virol 2005; 79:4270-88. [PMID: 15767428 PMCID: PMC1061554 DOI: 10.1128/jvi.79.7.4270-4288.2005] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
We have investigated the role of the human papillomavirus type 16 (HPV-16) early untranslated region (3' UTR) in HPV-16 gene expression. We found that deletion of the early 3' UTR reduced the utilization of the early polyadenylation signal and, as a consequence, resulted in read-through into the late region and production of late L1 and L2 mRNAs. Deletion of the U-rich 3' half of the early 3' UTR had a similar effect, demonstrating that the 57-nucleotide U-rich region acted as an enhancing upstream element on the early polyadenylation signal. In accordance with this, the newly identified hFip1 protein, which has been shown to enhance polyadenylation through U-rich upstream elements, interacted specifically with the HPV-16 upstream element. This upstream element also interacted specifically with CstF-64, hnRNP C1/C2, and polypyrimidine tract binding protein, suggesting that these factors were either enhancing or regulating polyadenylation at the HPV-16 early polyadenylation signal. Mutational inactivation of the early polyadenylation signal also resulted in increased late mRNA production. However, the effect was reduced by the activation of upstream cryptic polyadenylation signals, demonstrating the presence of additional strong RNA elements downstream of the early polyadenylation signal that direct cleavage and polyadenylation to this region of the HPV-16 genome. In addition, we identified a 3' splice site at genomic position 742 in the early region with the potential to produce E1 and E4 mRNAs on which the E1 and E4 open reading frames are preceded only by the suboptimal E6 AUG. These mRNAs would therefore be more efficiently translated into E1 and E4 than previously described HPV-16 E1 and E4 mRNAs on which E1 and E4 are preceded by both E6 and E7 AUGs.
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Affiliation(s)
- Xiaomin Zhao
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
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30
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Bodily JM, Meyers C. Genetic analysis of the human papillomavirus type 31 differentiation-dependent late promoter. J Virol 2005; 79:3309-21. [PMID: 15731225 PMCID: PMC1075705 DOI: 10.1128/jvi.79.6.3309-3321.2005] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Human papillomaviruses infect stratifying squamous epithelia, causing benign and malignant lesions. Upon differentiation of the host keratinocyte, the virus undergoes a dramatic increase in both DNA replication and transcription from the late promoter, leading to expression of late genes and virion morphogenesis. In human papillomavirus type 31 (HPV31), the late promoter is designated p742 and includes multiple start sites embedded within the E7 gene. In this report, we mapped viral DNA elements that control transcriptional activity from p742. Enhancer elements in the viral upstream regulatory region positively regulate this promoter. The region containing the transcriptional start sites is dispensable for activity, and at least two separate elements in the E6/E7 region are capable of supporting transcription. Of these, we mapped one to a 150-bp region of the E7 open reading frame and designate it the core p742 promoter. Using GF109203X, an inhibitor of protein kinase C signaling, we show that p742 activation is independent of viral genome amplification. Finally, we mapped elements in the region of p742 that confer responsiveness to differentiation and show that the upstream regulatory region does not contribute to the differentiation response of p742. These studies are an important step toward understanding the functioning and regulation of this multiple-start promoter.
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Affiliation(s)
- Jason M Bodily
- Department of Microbiology and Immunology H107, P. O. Box 850, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
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31
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Qiu J, Nayak R, Pintel DJ. Alternative polyadenylation of adeno-associated virus type 5 RNA within an internal intron is governed by both a downstream element within the intron 3' splice acceptor and an element upstream of the P41 initiation site. J Virol 2004; 78:83-93. [PMID: 14671090 PMCID: PMC303416 DOI: 10.1128/jvi.78.1.83-93.2004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Adeno-associated virus type 5 (AAV5) has a linear, single-stranded DNA genome of ca. 5 kb and an overlapping transcription profile featuring multiple promoters and a single intron in the center of the genome. Unlike the situation for the prototype AAV2, AAV5 RNAs transcribed from upstream promoters at map units 7 (P7) and 19 (P19), which encode the viral Rep proteins, are predominantly polyadenylated at a site within the intron [(pA)p]. RNAs generated from the AAV5 capsid gene promoter P41, which is only 78 nucleotides (nt) upstream of the intron donor, and 281 nt upstream of (pA)p, primarily readthrough (pA)p, are polyadenylated at a more distal site at the 3' end of the genome [(pA)d] and ultimately spliced. The intron contains the core sequences sufficient for polyadenylation at (pA)p, which is governed by a G/U-rich downstream element that overlaps with the intron 3' A2 splice acceptor. In addition, polyadenylation of P7- and P19-generated RNAs at (pA)p is influenced by an upstream element that lies 5' to the start of the P41 transcript. Our results also suggest that splicing and polyadenylation of P41-generated RNA can compete for the same pool of precursor pre-mRNA molecules. The cis-acting signals within the A2 3' splice site that govern polyadenylation and splicing of AAV5 RNAs must be optimized to program both (i) the levels of polyadenylation of P7- and P19-generated RNA at (pA)p required to generate the proper levels of the essential Rep proteins and (ii) the splicing of P41-generated RNAs to generate the proper ratio of capsid proteins during AAV5 infection.
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Affiliation(s)
- Jianming Qiu
- Department of Molecular Microbiology and Immunology, School of Medicine, University of Missouri-Columbia, Columbia, Missouri 65212, USA
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32
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Ozbun MA. Infectious human papillomavirus type 31b: purification and infection of an immortalized human keratinocyte cell line. J Gen Virol 2002; 83:2753-2763. [PMID: 12388811 DOI: 10.1099/0022-1317-83-11-2753] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Human papillomaviruses (HPVs) are aetiological agents of human malignancies, most notably cervical cancers. The life-cycles of HPVs are dependent on epithelial differentiation, and this has impeded many basic studies of HPV biology. The organotypic (raft) culture system supports epithelial differentiation such that infectious virions are synthesized in raft tissues from epithelial cells that replicate extrachromosomal HPV genomes. The CIN-612 9E cell line maintains episomal copies of HPV type 31b (HPV31b), an HPV type associated with cervical cancers. Many previous studies, including our own, have focused on characterizing the later stages of the HPV31b life-cycle in CIN-612 9E raft tissues. In this study, we have used the raft system to generate large numbers of HPV31b viral DNA (vDNA)-containing particles. We found a biologically contained homogenization system to be efficient at virion extraction from raft epithelial tissues. We also determined that vDNA-containing particles could be directly quantified from density-gradient fractions. Using an RT-PCR assay, the presence of newly synthesized, spliced HPV31b transcripts was detected following HPV31b infection of the immortalized HaCaT epithelial cell line. Spliced E6 and E1( wedge )E4 RNAs were detected using a single round of RT-PCR from cells infected with a dose as low as 1.0 vDNA-containing particle per cell. Spliced E1*I,E2 transcripts were found in cells infected with an HPV31b dose as low as 10 vDNA-containing particles per cell. Infectivity was blocked by HPV31 antiserum, but was not affected by DNase I. This work lays a foundation for a detailed analysis of the early events in HPV infection.
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Affiliation(s)
- Michelle A Ozbun
- Department of Molecular Genetics and Microbiology, The University of New Mexico School of Medicine, Albuquerque, New Mexico 87131, USA1
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Ozbun MA. Human papillomavirus type 31b infection of human keratinocytes and the onset of early transcription. J Virol 2002; 76:11291-300. [PMID: 12388689 PMCID: PMC136784 DOI: 10.1128/jvi.76.22.11291-11300.2002] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2002] [Accepted: 08/12/2002] [Indexed: 11/20/2022] Open
Abstract
Human papillomaviruses (HPVs) cause a number of human tumors and malignancies, including cervical cancers. Epithelial differentiation is required for the complete HPV life cycle and can be achieved using the organotypic (raft) culture system. The CIN-612 9E cell line maintains episomal copies of HPV type 31b (HPV31b), an HPV type associated with cervical cancers. When grown in the raft system, CIN-612 9E cells form a differentiated epithelium such that infectious virions can be synthesized. Many aspects of the later stages of the HPV31b life cycle have been investigated in CIN-612 9E raft tissues. We used a biologically contained homogenization system for efficient virion extraction from raft epithelial tissues. Purified HPV31b virions were used to infect low-passage-number human foreskin keratinocytes and a variety of epithelial cell lines. Newly synthesized, spliced HPV31b transcripts were detected by reverse transcription and PCR (RT-PCR) following HPV31b infection. HPV31b infection was most efficient and reproducible in HaCaT cells. The onset of viral transcription following infection was also investigated using RT-PCR techniques. Spliced E1(*)I,E2 RNAs were present as early as 4 h postinfection (p.i.), whereas the other major viral transcripts were detected by 8 to 10 h p.i. Furthermore, we characterized the structures and temporal expression of seven novel spliced early transcripts expressed following infection.
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Affiliation(s)
- Michelle A Ozbun
- Department of Molecular Genetics and Microbiology, The University of New Mexico School of Medicine, Albuquerque, New Mexico 87131, USA.
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Cumming SA, Repellin CE, McPhillips M, Radford JC, Clements JB, Graham SV. The human papillomavirus type 31 late 3' untranslated region contains a complex bipartite negative regulatory element. J Virol 2002; 76:5993-6003. [PMID: 12021332 PMCID: PMC136222 DOI: 10.1128/jvi.76.12.5993-6003.2002] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2001] [Accepted: 03/14/2002] [Indexed: 11/20/2022] Open
Abstract
The papillomavirus life cycle is tightly linked to epithelial cell differentiation. Production of virus capsid proteins is restricted to the most terminally differentiated keratinocytes in the upper layers of the epithelium. However, mRNAs encoding the capsid proteins can be detected in less-differentiated cells, suggesting that late gene expression is controlled posttranscriptionally. Short sequence elements (less than 80 nucleotides in length) that inhibit gene expression in undifferentiated epithelial cells have been identified in the late 3' untranslated regions (UTRs) of several papillomaviruses, including the high-risk mucosal type human papillomavirus type 16 (HPV-16). Here we show that closely related high-risk mucosal type HPV-31 also contains elements that can act to repress gene expression in undifferentiated epithelial cells. However, the HPV-31 negative regulatory element is surprisingly complex, comprising a major inhibitory element of approximately 130 nucleotides upstream of the late polyadenylation site and a minor element of approximately 110 nucleotides mapping downstream. The first 60 nucleotides of the major element have 68% identity to the negative regulatory element of HPV-16, and these elements bind the same cellular proteins, CstF-64, U2AF(65), and HuR. The minor inhibitory element binds some cellular proteins in common with the major inhibitory element, though it also binds certain proteins that do not bind the upstream element.
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Affiliation(s)
- Sarah A Cumming
- Institute of Virology, University of Glasgow, Glasgow G11 5JR, Scotland
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Terhune SS, Hubert WG, Thomas JT, Laimins LA. Early polyadenylation signals of human papillomavirus type 31 negatively regulate capsid gene expression. J Virol 2001; 75:8147-57. [PMID: 11483760 PMCID: PMC115059 DOI: 10.1128/jvi.75.17.8147-8157.2001] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The L1 and L2 capsid genes of human papillomavirus type 31 (HPV-31) are expressed upon keratinocyte differentiation from a promoter located in the E7 open reading frame (ORF) of the early region. Late transcripts must therefore pass through and ignore the early polyadenylation sequences to use the downstream late AAUAAA element located at the end of the L1 ORF. To identify sequences which modulate downstream capsid gene expression, a variety of substitution mutations were introduced into the early polyadenylation signal and studied first in the context of polycistronic luciferase reporter constructs. Removal of the G/U-rich cleavage stimulation factor (CstF) binding sites and the degenerate cleavage and polyadenylation specificity factor binding sites, UAUAUA, had minimal effect on downstream expression as defined by luciferase activities. This is in contrast to the deletion of the HPV-31 early AAUAAA element, which resulted in a dramatic increase in downstream expression. Additional sequences within the first 800 bp of the L2 ORF were also found to negatively regulate capsid expression in luciferase assays. To determine how these mutations influence gene expression in the context of the complete HPV-31 genome, recombinant genomes were constructed that contained a substitution in the AAUAAA sequence, an inserted strong CstF binding site, an inserted simian virus 40 (SV40) late poly(A) signal, or a substitution of the 5'-most 800 nucleotides of the L2 ORF. Reductions in both transient and stable replication were observed with the recombinant genomes containing the strong CstF site or the late SV40 signal, suggesting that alterations in the strength of the upstream poly(A) signal influence expression of viral replication factors. Similarly, disruption of the L2 ORF resulted in a significant reduction in genome replication and an inability to be maintained stably. In contrast, genomes containing a substitution of the AAUAAA sequence had increased levels of transient and stable replication. Quantitation of late transcripts following keratinocyte differentiation in methylcellulose also showed a reduction in downstream capsid gene expression in lines containing genomes with the strong CstF site or the late SV40 signal mutations, while a significant increase in expression was detected in the lines with genomes lacking the AAUAAA sequence. These studies demonstrate that capsid gene expression in HPV-31 requires an inefficient early poly(A) signal which is defined primarily by the AAUAAA element as well as a major negative regulatory element located within the L2 ORF.
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Affiliation(s)
- S S Terhune
- Department of Microbiology-Immunology, Northwestern University Medical School, Chicago, Illinois 606113, USA
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Thomas JT, Oh ST, Terhune SS, Laimins LA. Cellular changes induced by low-risk human papillomavirus type 11 in keratinocytes that stably maintain viral episomes. J Virol 2001; 75:7564-71. [PMID: 11462028 PMCID: PMC114991 DOI: 10.1128/jvi.75.16.7564-7571.2001] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Infections by low-risk papillomavirus types, such as human papillomavirus (HPV) type 6 (HPV-6) and HPV-11, induce benign genital warts that rarely progress to malignancy. In contrast, lesions induced by high-risk HPV types have the potential to progress to cancer. Considerable information is available concerning the pathogenesis of high-risk HPV types, but little is known about the life cycle of low-risk HPV types. Although functionally distinct, both high- and low-risk virus types infect keratinocytes and induce virion production upon differentiation. This information suggests that they may share common mechanisms for regulating their productive life cycles. Using tissue culture methods developed to study high-risk HPV types, we examined the ability of HPV-11 to be stably maintained as episomes following transfection of normal human keratinocytes with cloned viral DNA. HPV-11 genomes were found to be maintained in keratinocytes for extended passages in cultures in 14 independent experiments involving transfection of cloned HPV-11 DNA. Interestingly, the HPV-11-positive cells exhibited an extended life span that averaged approximately twofold longer than that of control neomycin-transfected cells. In organotypic cultures, HPV-11-positive cells exhibited altered differentiation patterns, but the extent of disruption was less severe than that seen with high-risk HPV types. In addition, the amplification of HPV-11 DNA, as well as the induction of several viral messages, was observed following differentiation of transfected cells in semisolid media. To determine whether global changes in cellular gene expression induced by HPV-11 were similar to those observed with high-risk HPV-31 (Y. E. Chang and L. A. Laimins, J. Virol. 74:4174-4182, 2000), microarray analysis of 7,075 expressed sequences was performed. A spectrum of cellular genes different from that previously reported for HPV-31 was found to be activated or repressed by HPV-11. The expression of only a small set of genes was similarly altered by both high- and low-risk HPV types. This result suggests that different classes of HPVs have distinct effects on global cellular transcription patterns during infection. The methods described allow for a genetic analysis of HPV-11 in the context of its differentiation-dependent life cycle.
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Affiliation(s)
- J T Thomas
- Department of Microbiology-Immunology, Northwestern University Medical School, Chicago, Illinois 60611, USA
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Juge F, Audibert A, Benoit B, Simonelig M. Tissue-specific autoregulation of Drosophila suppressor of forked by alternative poly(A) site utilization leads to accumulation of the suppressor of forked protein in mitotically active cells. RNA (NEW YORK, N.Y.) 2000; 6:1529-1538. [PMID: 11105753 PMCID: PMC1370023 DOI: 10.1017/s1355838200001266] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The Suppressor of forked protein is the Drosophila homolog of the 77K subunit of human cleavage stimulation factor, a complex required for the first step of the mRNA 3'-end-processing reaction. We have shown previously that wild-type su(f) function is required for the accumulation of a truncated su(f) transcript polyadenylated in intron 4 of the gene. This led us to propose a model in which the Su(f) protein would negatively regulate its own accumulation by stimulating 3'-end formation of this truncated su(f) RNA. In this article, we demonstrate this model and show that su(f) autoregulation is tissue specific. The Su(f) protein accumulates at a high level in dividing tissues, but not in nondividing tissues. We show that this distribution of the Su(f) protein results from stimulation by Su(f) of the tissue-specific utilization of the su(f) intronic poly(A) site, leading to the accumulation of the truncated su(f) transcript in nondividing tissues. Utilization of this intronic poly(A) site is affected in a su(f) mutant and restored in the mutant with a transgene encoding wild-type Su(f) protein. These data provide an in vivo example of cell-type-specific regulation of a protein level by poly(A) site choice, and confirm the role of Su(f) in regulation of poly(A) site utilization.
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Affiliation(s)
- F Juge
- Génétique du Développement de la Drosophile, Institut de Génétique Humaine, Montpellier, France
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Koffa MD, Graham SV, Takagaki Y, Manley JL, Clements JB. The human papillomavirus type 16 negative regulatory RNA element interacts with three proteins that act at different posttranscriptional levels. Proc Natl Acad Sci U S A 2000; 97:4677-82. [PMID: 10781073 PMCID: PMC18292 DOI: 10.1073/pnas.070049097] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In human papillomaviruses, expression of the late genes L1 and L2, encoding the capsid proteins, is restricted to the upper layers of the infected epithelium. A 79-nt GU-rich negative regulatory element (NRE) located at the 3' untranslated region of the human papillomavirus 16 L1 gene was identified previously as key to the posttranscriptional control of late gene expression. Here, we demonstrate that in epithelial cells, the NRE can directly bind the U2 auxiliary splicing factor 65-kDa subunit, the cleavage stimulation factor 64-kDa subunit, and the Elav-like HuR protein. On induction of epithelial cell differentiation, levels of the U2 auxiliary splicing factor 65-kDa subunit decrease, levels of the cleavage stimulation factor 64-kDa subunit increase, and the levels of HuR remain unchanged, although redistribution of the HuR from the nucleus to the cytoplasm is observed. Late gene transcripts, which appear to be fully processed, are detected in undifferentiated W12 cells, but are confined in the nucleus. We propose that repression of late gene expression in basal epithelial cells may be caused by nuclear retention or cytoplasmic instability of NRE-containing late gene transcripts.
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Affiliation(s)
- M D Koffa
- Division of Virology, Institute of Biomedical and Life Sciences, University of Glasgow, Church Street, Glasgow, G11 5JR, Scotland, United Kingdom
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Abstract
Productive infection by human papillomaviruses (HPV) is dependent upon the differentiation of the host cell. Following entry into basal epithelial cells, HPV genomes are established as autonomous replicating extrachromosomal elements and a low level of HPV expression occurs. Upon differentiation of infected cells, productive replication and expression of capsid genes is induced resulting in the synthesis of progeny virions. Evidence from immunosuppressed patients as well as individuals with recurring laryngeal papillomatosis suggest that certain HPV types can exist in a latent state. In latently infected cells, HPV DNA may be present but no differentiation-dependent synthesis of virions occurs. The presence of a latent state for HPVs can be a determining factor in the effectiveness of therapeutic methods for treatment of infections.
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Affiliation(s)
- F Stubenrauch
- Universitatsklinikum Tu@a2bingen, Abt. Medizinische Virologie, Sektion Experimentelle Virologie, Calwerstr. 7/6, D72076 Tuebingen, Germany
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