Interaction with CBP/p300 enables the bovine papillomavirus type 1 E6 oncoprotein to downregulate CBP/p300-mediated transactivation by p53

The E6 oncoprotein of bovine papillomavirus type 1 (BPV-1) can transform ce lls independently of p53 degradation. The precise mechanisms underlying thi s transformation are not yet completely understood. Here it is shown that B PV-1 E6 interacts with CBP/p300 in the same way as described for the E6 pro teins of oncogenic human papillomaviruses. This interaction results in an i nhibition of the transcriptional coactivator function of CBP/p300 required by p53 and probably by other transcription factors. The comparison of the C BP/p300-binding properties of BPV-1 E6 mutants previously characterized in transcription and transformation studies suggests (i) that the E6-CBP/p300 interaction may be necessary, but not sufficient, for cell transformation, and (ii) that the transcriptional activator function, inherent to the E6 pr otein, is not derived from forming a complex with CBP/p300.