Identification of novel E2 binding sites within the HPV genome and their function in the regulation of viral gene expression

[摘要] The human papillomavirus (HPV) E2 protein regulates the virus life cycle by modulating viral transcription and replication. To execute these functions, E2 binds to consensus sequences within the long control region (LCR). The possibility of novel E2 binding sites outside the LCR is the primary focus of this study. Moreover, the cellular protein CCCTC binding factor (CTCF), is known to regulate viral gene expression, therefore viral genome was screened for the presence of CTCF binding sites to see if they overlap the E2 binding sites. A comparison of CTCF expression within patient tonsil sections comprising normal (non-cancerous), HPV positive and HPV negative cancers may provide valuable information on the viral life cycle as well as disease progression. Chromatin Immunoprecipitation assays using primary human tonsil keratinocytes containing episomal HPV16 genomes revealed novel E2 binding sites within the viral genome. Peak binding at base pairs 4400, 4500, 5600 and 6000 was detected, however consensus E2 binding sites do not exist in this region. CTCF was observed to bind to the same regions as HPV16 E2. Further investigation revealed a physical association between E2 and CTCF suggesting that CTCF could recruit E2 to the late region of the HPV genome. In patient tumour samples high levels of CTCF expression were observed throughout the epithelium; in contrast, the pattern of CTCF expression in the normal tonsil epithelium showed high expression in the lower layers that was dramatically reduced in the differentiated layers. Interestingly increased CTCF expression was observed in all areas of HPV positive tonsil sections in comparison to HPV negative sections. This difference in CTCF expression may be associated with HPV infection and important for the viral life cycle.

[发布机构] University:University of Birmingham;Department:Institute of Cancer Studies

[关键词] R Medicine;RC Internal medicine;RC0254 Neoplasms. Tumors. Oncology (including Cancer)