Binding of bovine papillomavirus type 4 E8 to ductin (16K proteolipid), down-regulation of gap junction intercellular communication and full cell transformation are independent events.

The E8 open reading frame of bovine papillomavirus type 4 encodes a small hydrophobic polypeptide that contributes to primary cell transformation by conferring to cells the ability to form foci and to grow in low serum and in suspension. Wild-type E8 binds in vitro to ductin, a component of gap junctions, and this binding is accompanied by a loss of gap junction intercellular communication in transformed bovine fibroblasts. However, through the analysis of a panel of E8 mutants, we show here that binding of E8 to ductin is not sufficient for down-regulation of gap junction communication and that there is no absolute correlation between down-regulation of gap junction communication and the transformed phenotype.