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Naturally Occurring Variations Modulate the Activity of the HPV33 Early Promoter and its Affinity for the E2 Transcription Factor. Sci Rep 2018; 8:15015. [PMID: 30301935 PMCID: PMC6177462 DOI: 10.1038/s41598-018-33243-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Accepted: 09/25/2018] [Indexed: 12/15/2022] Open
Abstract
The human papillomavirus (HPV) Long Control Region (LCR) encompasses the early promoter (EP) that drives transcription of the E6 and E7 oncogenes in keratinocytes and HPV-associated cancers. In this study, the transcriptional activities of the HPV33 EP from the prototype LCR and from eight variants representative of the worldwide diversity of the virus were examined in primary human keratinocytes (PHK) and in the HeLa cervical carcinoma cell line by luciferase reporter-gene assays. Remarkably, the two variations with the greatest effect on the EP in PHK were C7732G and a 79-bp deletion that were associated with high-grade cervical lesions and persistent infections, respectively, in epidemiological studies. In contrast, the three variations most active in HeLa cells were C7537A, A7874C and A7879G. A7874C, which lies within an E2-binding sequence, is also shown to increase the activity and binding of E2 at this site. Collectively, these results indicate that naturally-occurring variations affect the HPV33 EP differentially in PHK than in cancer cells and, furthermore, that they can also alter its regulation by E2. These findings provide a molecular basis for rationalizing the results of previous epidemiological studies and for understanding the contribution of LCR polymorphisms to the oncogenicity and persistence of HPV33 infections.
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Delcuratolo M, Fertey J, Schneider M, Schuetz J, Leiprecht N, Hudjetz B, Brodbeck S, Corall S, Dreer M, Schwab RM, Grimm M, Wu SY, Stubenrauch F, Chiang CM, Iftner T. Papillomavirus-Associated Tumor Formation Critically Depends on c-Fos Expression Induced by Viral Protein E2 and Bromodomain Protein Brd4. PLoS Pathog 2016; 12:e1005366. [PMID: 26727473 PMCID: PMC4699637 DOI: 10.1371/journal.ppat.1005366] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Accepted: 12/04/2015] [Indexed: 12/27/2022] Open
Abstract
We investigated the mechanism of how the papillomavirus E2 transcription factor can activate promoters through activator protein (AP)1 binding sites. Using an unbiased approach with an inducible cell line expressing the viral transcription factor E2 and transcriptome analysis, we found that E2 induces the expression of the two AP1 components c-Fos and FosB in a Brd4-dependent manner. In vitro RNA interference confirmed that c-Fos is one of the AP1 members driving the expression of viral oncogenes E6/E7. Mutation analysis and in vivo RNA interference identified an essential role for c-Fos/AP1 and also for the bromodomain protein Brd4 for papillomavirus-induced tumorigenesis. Lastly, chromatin immunoprecipitation analysis demonstrated that E2 binds together with Brd4 to a canonical E2 binding site (E2BS) in the promoter of c-Fos, thus activating c-Fos expression. Thus, we identified a novel way how E2 activates the viral oncogene promoter and show that E2 may act as a viral oncogene by direct activation of c-Fos involved in skin tumorigenesis. Human Papillomaviruses (HPV) are the etiological agents of cervical cancer and of skin cancer in individuals with the inherited disease epidermodysplasia verruciformis (EV). While the role of the viral oncogenes E6/E7 as drivers of tumorigenesis in cervical cancer has been firmly established, the contribution of the early viral genes in skin cancer is less clear. For EV-associated HPV8 and for the skin cancer model system using cottontail rabbit PV, an important role of the viral E2 protein in tumorigenesis was suggested earlier and regulation of cellular genes by E2 through different mechanisms was demonstrated. We show now that the viral E2 and cellular Brd4 act together to induce the cellular gene c-Fos, which as a member of the AP-1 complex, is involved in the regulation of cellular genes and the viral promoter driving the expression of viral oncogenes. As c-Fos has also been shown to be essential for skin cancer, E2 contributes to tumorigenesis via expression of E6/E7 as well as by increasing c-Fos.
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Affiliation(s)
- Maria Delcuratolo
- Division of Experimental Virology, Institute of Medical Virology, University Hospital Tübingen, Tübingen, Germany
| | - Jasmin Fertey
- Division of Experimental Virology, Institute of Medical Virology, University Hospital Tübingen, Tübingen, Germany
| | - Markus Schneider
- Division of Experimental Virology, Institute of Medical Virology, University Hospital Tübingen, Tübingen, Germany
| | - Johanna Schuetz
- Division of Experimental Virology, Institute of Medical Virology, University Hospital Tübingen, Tübingen, Germany
| | - Natalie Leiprecht
- Division of Experimental Virology, Institute of Medical Virology, University Hospital Tübingen, Tübingen, Germany
| | - Benjamin Hudjetz
- Division of Experimental Virology, Institute of Medical Virology, University Hospital Tübingen, Tübingen, Germany
| | - Stephan Brodbeck
- Division of Experimental Virology, Institute of Medical Virology, University Hospital Tübingen, Tübingen, Germany
| | - Silke Corall
- Division of Experimental Virology, Institute of Medical Virology, University Hospital Tübingen, Tübingen, Germany
| | - Marcel Dreer
- Division of Experimental Virology, Institute of Medical Virology, University Hospital Tübingen, Tübingen, Germany
| | - Roxana Michaela Schwab
- Division of Experimental Virology, Institute of Medical Virology, University Hospital Tübingen, Tübingen, Germany
| | - Martin Grimm
- Department of Oral and Maxillofacial Surgery, University Hospital Tübingen, Tübingen, Germany
| | - Shwu-Yuan Wu
- University of Texas Southwestern Medical Center, Simmons Comprehensive Cancer Center, Department of Biochemistry, Department of Pharmacology, Dallas, Texas, United States of America
| | - Frank Stubenrauch
- Division of Experimental Virology, Institute of Medical Virology, University Hospital Tübingen, Tübingen, Germany
| | - Cheng-Ming Chiang
- University of Texas Southwestern Medical Center, Simmons Comprehensive Cancer Center, Department of Biochemistry, Department of Pharmacology, Dallas, Texas, United States of America
| | - Thomas Iftner
- Division of Experimental Virology, Institute of Medical Virology, University Hospital Tübingen, Tübingen, Germany
- * E-mail:
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Chang R, Wei L, Lu Y, Cui X, Lu C, Liu L, Jiang D, Xiong Y, Wang G, Wan C, Qian H. Upregulated expression of ubiquitin-conjugating enzyme E2Q1 (UBE2Q1) is associated with enhanced cell proliferation and poor prognosis in human hapatocellular carcinoma. J Mol Histol 2014; 46:45-56. [PMID: 25311764 DOI: 10.1007/s10735-014-9596-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Accepted: 09/30/2014] [Indexed: 02/07/2023]
Abstract
Hepatocellular carcinoma (HCC) is the fifth most common cancer in the world. Ubiquitin-proteasome system has been shown to play a pivotal role in the pathophysiology of HCC and other malignancies. UBE2Q1 is a putative E2 ubiquitin conjugating enzyme, and may be involved in the regulation of cancer-related proteins. In this study, we investigated the expression pattern of UBE2Q1 in HCC cell lines and human HCC specimens, and its potential clinical and biological significance in HCC. Western blot and immunohistochemical analyses revealed that UBE2Q1 was significantly upregulated in HCC tumorous tissues compared with the adjacent noncancerous ones. Next, univariate and multivariate survival analyses were performed to determine the prognostic significance of UBE2Q1 in HCC. The results showed that upregulated expression of UBE2Q1 was positively correlated with high histological grades of HCC and predicted poor prognosis. In addition, the expression of UBE2Q1 was progressively increased in serum-refed HCC cells. UBE2Q1 depletion by small interfering RNA inhibited cell proliferation and led to G1 phase arrest in HepG2 and BEL-7404 cells. Furthermore, we showed that cells transfected with UBE2Q1-targeting siRNA resulted in significant increase in the levels of p53, p21 in HepG2 and BEL-7404 cells. These data imply that UBE2Q1 is upregulated in liver cancer cell lines and tumorous samples and may play a role in the development of HCC.
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Affiliation(s)
- Renan Chang
- Department of Hepatobiliary Surgery, The First Affiliated Hospital of Soochow University, Suzhou, 215006, China
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Tang SY, Li L, Liu Y, Liu AY, Yu MJ, Zhang Y, Liu LZ, Wan YP. Interaction of Daxx and human papillomavirus type 16 E2 protein. Mol Biol 2014. [DOI: 10.1134/s0026893314040165] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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The viral E8^E2C repressor limits productive replication of human papillomavirus 16. J Virol 2013; 88:937-47. [PMID: 24198405 DOI: 10.1128/jvi.02296-13] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Productive replication of human papillomavirus type 16 (HPV16) occurs only in differentiated keratinocyte cells. In addition to the viral E2 activator protein, HPV16 and related HPV types express transcripts coding for an E8^E2C fusion protein, which limits genome replication in undifferentiated keratinocytes. To address E8^E2C's role in productive replication of HPV16, stable keratinocyte cell lines containing wild-type (wt), E8^E2C knockout (E8-), or E8 KWK mutant (mt) genomes, in which conserved E8 residues were inactivated, were established. Copy numbers of E8- and E8 KWK mt genomes and amounts of early and late viral transcripts were greatly increased compared to those for the wt in undifferentiated keratinocytes, suggesting that HPV16 E8^E2C activities are highly dependent upon the E8 part. Upon differentiation in organotypic cultures, E8 mt genomes displayed higher early viral transcript levels, but no changes in cellular differentiation or virus-induced cellular DNA replication in suprabasal cells were observed. E8 mt genomes were amplified to higher copy numbers and showed increased L1 transcripts compared to wt genomes. Furthermore, the number of cells expressing the viral late protein E4 or L1 or amplifying viral genomes was greatly increased in E8 mt cell lines. In wild-type cells, E8^E2C transcript levels did not decrease by differentiation. Our data indicate that the E8^E2C repressor limits viral transcription and replication throughout the complete life cycle of HPV16.
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