An Analysis of the Transforming Functions of Bovine Papillomavirus Type 4 in an In Vitro Assay System

Virology, Genetics

Pennie, William David

University:University of Glasgow

关键词: Virology, Genetics;   

Others  :  http://theses.gla.ac.uk/78389/1/11011456.pdf

来源: University of Glasgow

【 摘 要 】

The transformation biology of bovine papillomavirus type 4 (BPV-4) was investigated using an in vitro assay system. In vivo the virus cooperates with bracken to cause alimentary canal carcinoma in cattle and transforms via a "hit-and-run" mechanism; viral DNA is observed in papillomas but not in the resulting tumours. Molecularly cloned BPV-4 genome and subgenomic fragments were transfected into primary bovine palate fibroblasts (PalF) and their ability to induce morphological transformation assessed. BPV-4 is incapable of transformation without the introduction of a cooperating activated ras oncogene and the resultant cells are neither immortal nor tumorigenic. The major transforming function was found to be the E7 open reading frame (ORF) with a possible role for the E8 ORF. The majority of BPV-4 transformed lines are found to lose viral DNA on passage, as observed in vivo. BPV-4 and the other BPV subgroup B viruses BPV-3 and BPV-6 lack an E6 ORF, a transforming function in other papillomaviruses. Introducing an E6 from human papillomavirus type 16 in cooperation with BPV-4 E7 leads to immortalisation. Immunocytochemistry was used to determine the cellular localisation of the transforming proteins of the virus. A possible interaction of the E8 protein with a structural component of gap junctions is demonstrated. A bracken mutagen, quercetin, is able to initiate PalF cells, allowing full malignant transformation by BPV-4 and ras.