title: Acidic phospholipids directly inhibit DNA binding of mammalian DNA topoisomerase I.
abstract: Inhibition of mammalian DNA topoisomerase I by phospholipids was investigated using purified enzyme. Acidic phospholipids inhibited the DNA relaxation activity of topoisomerase I whereas neutral phospholipid, phosphatidylethanolamine, did not. Accumulation of a protein-DNA cleavable complex, an intermediate which is known to accumulate upon inhibition by a specific inhibitor camptothecin, did not occur. The filter binding assay revealed that the DNA binding activity of the enzyme was inhibited by acidic phospholipids. Moreover, direct binding of phosphatidylglycerol to topoisomerase I was demonstrated. These results indicated that the inhibitory effect of acidic phospholipids on topoisomerase I was due to the loss of the DNA binding of the enzyme as a result of direct interaction between phospholipids and the enzyme.
authors.affiliation: Department of Hygienic Chemistry, Meiji College of Pharmacy, Tokyo, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Tamura
authors.forename: Y
authors.initials: Y
authors.lastname: Ikegami
authors.forename: K
authors.initials: K
authors.lastname: Ono
authors.forename: K
authors.initials: K
authors.lastname: Sekimizu
authors.forename: T
authors.initials: T
authors.lastname: Andoh
mesh_terms: D000818:Animals; D002166:Camptothecin / Q000494:pharmacology; D002286:Carcinoma, Ehrlich Tumor / Q000201:enzymology; D004247:DNA / Q000378:metabolism*; D004264:DNA Topoisomerases, Type I / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D006863:Hydrogen-Ion Concentration; D051379:Mice; D010714:Phosphatidylethanolamines / Q000494:pharmacology; D010715:Phosphatidylglycerols / Q000494:pharmacology; D010716:Phosphatidylinositols / Q000494:pharmacology; D010718:Phosphatidylserines / Q000494:pharmacology; D010743:Phospholipids / Q000494:pharmacology*; D059004:Topoisomerase I Inhibitors; D014407:Tumor Cells, Cultured
chemical_list: D010714:Phosphatidylethanolamines; D010715:Phosphatidylglycerols; D010716:Phosphatidylinositols; D010718:Phosphatidylserines; D010743:Phospholipids; D059004:Topoisomerase I Inhibitors; D004247:DNA; D004264:DNA Topoisomerases, Type I; D002166:Camptothecin