title: Induction of mammalian DNA topoisomerase I and II mediated DNA cleavage by saintopin, a new antitumor agent from fungus.
abstract: Saintopin is an antitumor antibiotic recently discovered in mechanistically oriented screening using purified calf thymus DNA topoisomerases. Saintopin induced topoisomerase I mediated DNA cleavage comparable to that of camptothecin, and topoisomerase II mediated DNA cleavage equipotent to those of 4'-(9-acridinylamino)methanesulfon-m-anisidide (m-AMSA) or 4'-demethylepipodophyllotoxin 9-(4,6-O-ethylidene-beta-D-glucopyranoside) (VP-16). Treatment of a reaction mixture containing saintopin and topoisomerase I or II with either elevated temperature (65 degrees C) or higher salt concentration (0.5 M NaCl) resulted in a substantial reduction in DNA cleavage, suggesting that the topoisomerase I and II mediated DNA cleavage induced by saintopin is through the mechanism of stabilizing the reversible enzyme-DNA "cleavable complex". Consistent with the cleavable complex formation with both topoisomerases, saintopin inhibited catalytic activities of both topoisomerase I and topoisomerase II. The DNA cleavage intensity pattern induced by saintopin with topoisomerase I was different from that by camptothecin. A difference in cleavage pattern was also detected between saintopin and m-AMSA or VP-16 in topoisomerase II mediated DNA cleavage. DNA unwinding assay using T4 DNA ligase showed that saintopin is a weak DNA intercalator like m-AMSA. Thus, saintopin represents a new class of antitumor agent that can induce both mammalian DNA topoisomerase I and mammalian DNA topisomerase II mediated DNA cleavage.
authors.affiliation: Tokyo Research Laboratories, Kyowa Hakko Kogyo Co. Ltd., Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Yamashita
authors.forename: S
authors.initials: S
authors.lastname: Kawada
authors.forename: N
authors.initials: N
authors.lastname: Fujii
authors.forename: H
authors.initials: H
authors.lastname: Nakano
mesh_terms: D000677:Amsacrine / Q000494:pharmacology; D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D001551:Benz(a)Anthracenes / Q000494:pharmacology; D002166:Camptothecin / Q000494:pharmacology; D002417:Cattle; D004264:DNA Topoisomerases, Type I / Q000302:isolation & purification / Q000378:metabolism*; D004250:DNA Topoisomerases, Type II / Q000302:isolation & purification / Q000378:metabolism*; D004269:DNA, Bacterial / Q000187:drug effects* / Q000302:isolation & purification / Q000378:metabolism; D004317:Doxorubicin / Q000494:pharmacology; D004926:Escherichia coli / Q000235:genetics; D007700:Kinetics; D010957:Plasmids / Q000187:drug effects*; D013950:Thymus Gland / Q000201:enzymology*
chemical_list: D000903:Antibiotics, Antineoplastic; D001551:Benz(a)Anthracenes; D004269:DNA, Bacterial; D000677:Amsacrine; C066552:saintopin; D004317:Doxorubicin; D004264:DNA Topoisomerases, Type I; D004250:DNA Topoisomerases, Type II; D002166:Camptothecin