Amplification of specific DNA sequences in C127 mouse cells transformed by bovine papillomavirus type 4.

A rearranged bovine papillomavirus type 4 DNA fragment, present in a line of transformed C127 cells, was molecularly cloned into lambda GT 10. The rearranged viral fragment was found to consist of two separate sequences of 3.8 kb each. Clone A comprised 3.3 kb of host DNA linked to 0.5 kb of BPV-4 DNA. Clone B consisted of 2.2 kb of host DNA linked to 1.5 kb of BPV-4 DNA. The AB locus was found to be amplified and rearranged in a number of different BPV-4 transformed C127 cell lines, irrespective of the presence of viral DNA. The rearranged amplified locus was transferred and maintained in second and third round transformants. We propose that the altered AB locus is involved in the maintenance of the transformed phenotype in the absence of the BPV-4 DNA, and may act as an activated oncogene.