Saintopin, a dual inhibitor of DNA topoisomerases I and II, as a probe for drug-enzyme interactions.
Stabilization of the topoisomerase-cleavable complexes is the common initial event leading to the cytotoxicity of topoisomerase I and II (top1 and top2) inhibitors. Using saintopin (STP), a poison of both topoisomerases, we studied top1- and top2-cleavable complexes (Yamashita, Y., Kawada, S.-Z., Fujii, N., and Nakano, H. (1991) Biochemistry 30, 5838-5845). top1 and top2 sites induced in the presence of STP showed the same preferences for the base located 3' to the topoisomerase-induced DNA break (position +1): preference for G and not C. A camptothecin-resistant top1 with a mutation (Asn722-->Ser) next to the catalytic tyrosine (Tyr723) was cross-resistant to STP, suggesting that both STP and camptothecin interact with the protein near the catalytic tyrosine. These results are consistent with a dual interaction of the drug with the enzyme and the DNA and provide further evidence for the "drug-stacking" model. This model proposes that topoisomerase inhibitors bind, possibly through hydrogen bonding and/or stacking, with one of the bases flanking the DNA termini (guanine at position +1 in the case of STP) and within the enzyme catalytic pocket, most likely by stacking with the catalytic tyrosine.
Leteurtre
F
F
Division of Cancer Treatment, NCI, National Institutes of Health, Bethesda, Maryland 20892.
Fujimori
A
A
Tanizawa
A
A
Chhabra
A
A
Mazumder
A
A
Kohlhagen
G
G
Nakano
H
H
Pommier
Y
Y
D001483:Base Sequence; D001551:Benz(a)Anthracenes / Q000378:metabolism / Q000494:pharmacology; D002384:Catalysis; D017931:DNA Primers; D004264:DNA Topoisomerases, Type I / Q000378:metabolism; D004250:DNA Topoisomerases, Type II / Q000378:metabolism; D006801:Humans; D006868:Hydrolysis; D015335:Molecular Probes; D008969:Molecular Sequence Data; D059004:Topoisomerase I Inhibitors; D059005:Topoisomerase II Inhibitors; D014443:Tyrosine / Q000378:metabolism
D001551:Benz(a)Anthracenes; D017931:DNA Primers; D015335:Molecular Probes; D059004:Topoisomerase I Inhibitors; D059005:Topoisomerase II Inhibitors; C066552:saintopin; D014443:Tyrosine; D004264:DNA Topoisomerases, Type I; D004250:DNA Topoisomerases, Type II