title: Minimal DNA duplex requirements for topoisomerase I-mediated cleavage in vitro.
abstract: The minimal DNA duplex requirements for topoisomerase I-mediated cleavage at a specific binding sequence were determined by analyzing the interaction of the enzyme with sets of DNA substrates varying successively by single nucleotides at the 5'- or 3' end of either strand. Topoisomerase I cleavage experiments showed a minimal region of nine nucleotides on the scissile strand and five nucleotides on the noncleaved strand. On the scissile strand, seven of the nine nucleotides were situated upstream to the cleavage site, while all five nucleotides required on the non-cleaved strand were located to this side. The results suggested that topoisomerase I bound tightly to this region, stabilizing the DNA duplex extensively. On minimal substrates which were partially single-stranded downstream to the cleavage site, cleavage was suicidal, that is, the enzyme was able to cleave the substrates, but unable to perform the final religation.
authors.affiliation: Department of Molecular Biology and Plant Physiology, University of Aarhus, Denmark.
authors.forename: J Q
authors.initials: JQ
authors.lastname: Svejstrup
authors.forename: K
authors.initials: K
authors.lastname: Christiansen
authors.forename: A H
authors.initials: AH
authors.lastname: Andersen
authors.forename: K
authors.initials: K
authors.lastname: Lund
authors.forename: O
authors.initials: O
authors.lastname: Westergaard
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000378:metabolism*; D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D013045:Species Specificity; D013379:Substrate Specificity
chemical_list: D004247:DNA; D004264:DNA Topoisomerases, Type I