Identification of a second transforming region in bovine papillomavirus DNA.

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Abstract
Bovine papillomavirus type 1 (BPV-1) was used as a model for studying papillomavirus genetics because BPV-1 virions or BPV-1 genomic viral DNA efficiently induce morphologic transformation of certain cultured cells. Previous studies of BPV-1-induced transformation have found that a cloned 5.4-kilobase (kb) fragment (69T) of the genome is transforming and that a 2.3-kb segment from the 3'' end of this fragment is also transforming if activated by a retroviral regulatory element (the long terminal repeat). 69T contains another transforming segment near its 5'' end that can also be activated by a long terminal repeat. Since this 2nd segment does not overlap the 3'' transforming segment, it was concluded that BPV-1 encodes at least 2 genes that can independently transform cultured cells. Mutational analysis of the 5'' transforming segment suggests that the transforming gene of this segment lies within the E6 open reading frame. The 2 transforming segments differ in their biological activity in that the E6-containing fragment can transform C127 mouse cells but not NIH3T3 mouse cells; the 3'' fragment can transform both cell lines.