Dehydroaltenusin, a mammalian DNA polymerase alpha inhibitor

Dehydroaltenusin was found to be an inhibitor of mammalian DNA polymerase a lpha (pol alpha) in vitro. Surprisingly, among the polymerases and DNA meta bolic enzymes tested, dehydroaltenusin inhibited only mammalian pol alpha. Dehydroaltenusin did not influence the activities of the other replicative DNA polymerases, such as delta and epsilon; it also showed no effect even o n the pol alpha activity from another vertebrate (fish) or plant species. T he inhibitory effect of dehydroaltenusin on mammalian pol alpha was dose-de pendent, and 50% inhibition was observed at a concentration of 0.5 muM. Deh ydroaltenusin-induced inhibition of mammalian pol alpha activity was compet itive with the template-primer and non-competitive with the dNTP substrate. BIAcore analysis demonstrated that dehydroaltenusin bound to the core doma in of the largest subunit, p180, of mouse pol alpha, which has catalytic ac tivity, but did not bind to the smallest subunit or the DNA primase p46 of mouse pol alpha. These results suggest that the dehydroaltenusin molecule c ompetes with the template primer molecule on its binding site of the cataly tic domain of mammalian pol alpha, binds to the site, and simultaneously di sturbs dNTP substrate incorporation into the template-primer.