A dimer of BPV-1 E2 containing a protease resistant core interacts with its DNA target.

The E2 proteins encoded by papillomaviruses interact with the viral DNA to regulate its transcription. In the present study, we have constructed bacterial vectors expressing the full-length or N-terminal truncated BPV-1 E2 proteins under the control of an inducible promoter. By UV cross-linking experiments we show that a dimer of the intact or truncated E2 protein interacts with a single palindromic site ACCGNNNNCGGT. The DNA-binding domain of E2 can be reduced to a small protease resistant core. Methylation interference studies show that this C-terminal domain interacts with the major groove of the DNA by contacting two consecutive guanine residues in both halves of the palindrome. Although one binding site is sufficient for high affinity binding in vitro or in vivo, two E2 binding sites are required for transcriptional activation in eukaryotic cells.