High-risk human papillomavirus (HPV) infection is the primary risk factor for cervical cancer, which is the second most prevalent cancer in women worldwide causing 15% of female cancer mortality. Papillomaviruses establish persistent infection by maintaining their genomes as episomes in infected cells. In the HPV life cycle that is tightly linked to the differentiation program of host epithelium, E2 ensures that the viral genome is established, replicated and maintained in the early-infected basal epithelial cells. During epithelium differentiation, E2 also contributes to the tight regulation of the viral oncogene transcription to create a conducive environment for successful completion of the viral life cycle. Loss of E2 expression leads to dysregulated viral oncogene expression and has been mechanistically linked to malignant progression of HPV positive lesions. Our previous work identified the cellular protein Brd4 (bromodomain-containing protein 4) as a novel receptor for E2. Brd4-E2 interaction functions in viral episome maintenance, viral transcriptional activation and repression of the viral oncogenes. Our studies established that Brd4 is highly expressed in the basal epithelial layer, supporting its role in E2 functions during the early phase of the viral life cycle. However, little is known about how Brd4 regulates the multiple functions of E2, nor is it clear how this virus-host interaction contributes to the differentiation- dependent HPV life cycle. This grant application aims to identify and characterize additional cellular components that regulate the E2-Brd4 functions, to determine how Brd4 contributes to E2 transcriptional regulation, and to investigate the functional impact of E2-Brd4 interactions in the HPV life cycle during epithelium differentiation. Infection by the HPV is the most common sexually transmitted agent, afflicting 50-80% of the population. This research will provide greater understanding of the molecular mechanisms that regulate the HPV life cycle and malignant progression. The new mechanisms identified in this study will provide a point of departure for developing new compounds to abrogate the virus-host interaction and cure HPV persistent infections. Mechanistic insights into how E2-Brd4 interactions repress the viral oncogenes that account for the tumorigenic nature of HPV-associated diseases will offer promising leads for novel therapeutic strategies. This study will provide a paradigm for other episomal DNA tumor viruses, including Kaposi's sarcoma-associated herpesvirus and Epstein-Barr virus, both of which also target Brd4.

Public Health Relevance

High-risk human papillomaviruses (HPVs) are strongly associated with cervical cancer, which is the second most common cancer in women worldwide causing 15% of female cancer mortality. This proposal will investigate the molecular mechanisms that regulate the papillomavirus and host interactions during the HPV life cycle and malignant progression. Our study will identify novel targets for developing therapeutic approaches to cure HPV persistent infection and associated human cancers.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA142723-03
Application #
8209261
Study Section
Special Emphasis Panel (ZRG1-IDM-Q (02))
Program Officer
Read-Connole, Elizabeth Lee
Project Start
2010-02-18
Project End
2014-12-31
Budget Start
2012-01-01
Budget End
2012-12-31
Support Year
3
Fiscal Year
2012
Total Cost
$322,040
Indirect Cost
$120,765
Name
University of Pennsylvania
Department
Microbiology/Immun/Virology
Type
Schools of Medicine
DUNS #
042250712
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
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Wang, Ranran; Liu, Wei; Helfer, Christine M et al. (2014) Activation of SOX2 expression by BRD4-NUT oncogenic fusion drives neoplastic transformation in NUT midline carcinoma. Cancer Res 74:3332-43
Li, Jing; Li, Qing; Diaz, Jason et al. (2014) Brd4-mediated nuclear retention of the papillomavirus E2 protein contributes to its stabilization in host cells. Viruses 6:319-35
Helfer, Christine M; Yan, Junpeng; You, Jianxin (2014) The cellular bromodomain protein Brd4 has multiple functions in E2-mediated papillomavirus transcription activation. Viruses 6:3228-49
Liu, W; Stein, P; Cheng, X et al. (2014) BRD4 regulates Nanog expression in mouse embryonic stem cells and preimplantation embryos. Cell Death Differ 21:1950-60
Wang, Xin; Helfer, Christine M; Pancholi, Neha et al. (2013) Recruitment of Brd4 to the human papillomavirus type 16 DNA replication complex is essential for replication of viral DNA. J Virol 87:3871-84
Li, Jing; Wang, Xin; Diaz, Jason et al. (2013) Merkel cell polyomavirus large T antigen disrupts host genomic integrity and inhibits cellular proliferation. J Virol 87:9173-88
Helfer, Christine M; Wang, Ranran; You, Jianxin (2013) Analysis of the papillomavirus E2 and bromodomain protein Brd4 interaction using bimolecular fluorescence complementation. PLoS One 8:e77994
Wang, Ranran; Li, Qing; Helfer, Christine M et al. (2012) Bromodomain protein Brd4 associated with acetylated chromatin is important for maintenance of higher-order chromatin structure. J Biol Chem 287:10738-52
Yan, Junpeng; Diaz, Jason; Jiao, Jing et al. (2011) Perturbation of BRD4 protein function by BRD4-NUT protein abrogates cellular differentiation in NUT midline carcinoma. J Biol Chem 286:27663-75

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