title: Interactions between eukaryotic DNA topoisomerase I and a specific binding sequence.
abstract: The interaction between eukaryotic DNA topoisomerase I and a high affinity binding sequence was investigated. Quantitative footprint analysis demonstrated that the substrate preference results from strong specific binding of topoisomerase I to the sequence. The specificity was conferred by a tight noncovalent association between the enzyme and its target DNA, whereas the transient formation of a covalently bound enzyme.nicked DNA intermediate contributed insignificantly to the overall affinity. Topoisomerase I protected both strands over a 20-base pair region in which the cleavage site was centrally located. DNA modification interference analysis revealed a 16-base pair interference region on the scissile strand. Essential bases were confined to the 5' side of the cleavage site. The 6-base pair interference region observed on the complementary strand did not contain essential bases.
authors.affiliation: Department of Molecular Biology and Plant Physiology, University of Arhus, Denmark.
authors.forename: T
authors.initials: T
authors.lastname: Stevnsner
authors.forename: U H
authors.initials: UH
authors.lastname: Mortensen
authors.forename: O
authors.initials: O
authors.lastname: Westergaard
authors.forename: B J
authors.initials: BJ
authors.lastname: Bonven
mesh_terms: D000818:Animals; D001483:Base Sequence; D004247:DNA / Q000378:metabolism; D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D007700:Kinetics; D008745:Methylation; D015183:Restriction Mapping; D013379:Substrate Specificity; D013768:Tetrahymena / Q000201:enzymology
chemical_list: D004247:DNA; D004264:DNA Topoisomerases, Type I