Dissociation of transforming and trans-activation functions for bovine papillomavirus type 1.

It has been shown that genetic information encoded by the 3' open reading frames (ORFs), E2, E3, E4 and E5, of bovine papillomavirus type 1 (BPV-1), is sufficient to induce cellular transformation of certain mouse cells. The product of the E2 ORF has further been shown to be responsible for the trans-activation of a transcriptional regulatory element located in the noncoding region (NCR) of the BPV-1 genome. To examine whether or not the E2 trans-activation function is encoded by the same gene that encodes the 3' ORF viral transformation function, we have now analysed the expression of the trans-activation function in series of mouse C127 cells transformed by BPV-1 deletion mutants. In addition, using mutated complementary DNA clones generated by the insertion of a premature translational termination linker into different sites of a BPV-1 cDNA clone containing the 3' ORFs intact, we demonstrate that transformation and transcriptional trans-activation functions can be dissociated and that they map respectively to the E5 and E2 ORFs.