A tumor promoting phorbol ester, TPA, enhances polyomavirus DNA replication by activating the function of the viral enhancer.

The effect of tumor promoter, 12-O-tetradecanoylphorbol 13-acetate (TPA) on enhancer dependent polyomavirus (Py) DNA replication was examined in cells expressing Py large T antigen. The results showed that TPA enhanced Py DNA replication by stimulating the activity of the A element, one of the two cores of Py enhancer. Of the three subdomains of the A element, the biding sites of PEBP1 (PEA1), a member of AP1 family, and of PEBP5 were by themselves able to activate Py DNA replication. Furthermore, each binding site of PEBP1 and PEBP5 responded to TPA to enhance Py DNA replication. The results suggest that growth promoting signals could activate DNA replication directly via enhancer binding proteins.