The biochemical mode of inhibition of DNA polymerase beta by alpha-rubromycin

Quinone antibiotics, alpha- and beta -rubromycin, were originally found as inhibitors of retroviral reverse transcriptase. We investigated the effects of these agents on DNA metabolic enzymes including DNA and RNA polymerases as retroviral reverse transcriptase is a kind of the polymerase. As expect ed, we found that alpha- and beta -rubromycin strongly inhibited not only t he retroviral reverse transcriptase activity, but the activities of the mam malian DNA polymerases, telomerase and terminal deoxynucleotidyl transferas e in vitro. These agents should therefore be classified as DNA polymerase i nhibitors. The Ki values of alpha -rubromycin against nucleotide substrate were 0.66 and 0.17 muM for DNA polymerase alpha and beta (pol. alpha and be ta), respectively, and those of beta -rubromycin was 2.40 and 10.5 muM, res pectively, alpha -Rubromycin strongly inhibited the pol. beta activity, and showed the strongest pol. beta inhibitory effect reported to date. At leas t on pol. beta, alpha -rubromycin was suggested to bind to the active regio n competing with the nucleotide substrate, and subsequently inhibit the cat alytic activity. alpha -Rubromycin directly competed with the nucleotide su bstrate, and indirectly but simultaneously and non-competitively disturbed the template-DNA interaction with pol. beta. (C) 2000 Elsevier Science B.V. All rights reserved.