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 h ydrophobic polypeptide that contributes to primary cell transformation by c onferring 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 junc tions, and this binding is accompanied by a loss of gap junction intercellu lar communication in transformed bovine fibroblasts, However, through the a nalysis 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 th at there is no absolute correlation between down-regulation of gap junction communication and the transformed phenotype.