THE E5 TRANSFORMING PROTEINS OF THE PAPILLOMAVIRUSES

The E5 proteins are short, hydrophobic transforming proteins encoded b y many of the papillomaviruses. The 44 amino acid E5 protein of bovine papillomavirus efficiently transforms cultured fibroblasts and intera cts with a variety of cellular proteins. Considerable evidence implica tes the PDGF beta receptor as an important mediator of the transformin g activity of the BPV E5 protein in fibroblasts. Other potential targe ts of the BPV E5 protein include the EGF receptor, a subunit of the th e vacuolar H+ - ATPase, and a protein related to alpha-adaplin. The E5 transforming proteins of the human papillomaviruses may interact with similar cellular targets in keratinocytes.