The Effect of Hydroxycamptothecin in the Activity of RNA and DNA Polymerases Prepared from Murine Hepatoma Cells

Hydroxycamptothecin (HCPT) is an antitumor alkaloid isolated from Camptotheca acuminata indigenous to China. It could reduce the activity of nuclear RNA polymerase II and I(III) of hepatoma cells. HCPT at 25-100 μ M caused a remarkable inhibition on DNA polymerase α whilst only a slight inhibition on β. The inhibitory action on α was restored by increasing amounts of enzyme or DNA template, but unchanged by varying amounts of substrate. It is suggested that HCPT may exert a stronger inhibition on DNA replication process.