title: DNA sequence selectivity of human topoisomerase I-mediated DNA cleavage induced by camptothecin.
abstract: In probing the mechanism of inhibition of hypoxia inducible factor (HIF-1) by campothecins, we investigated the ability of human topoisomerase I to bind and cleave HIF-1 response element (HRE), which contains the known camptothecin-mediated topoisomerase I cleavage site 5'-TG. We observed that the selection of 5'-TG by human topoisomerase I and topotecan depends to a large extent on the specific flanking sequences, and that the presence of a G at the -2 position (where cleavage occurs between -1 and +1) prevents the HRE site from being a preferred site for such cleavage. Furthermore, the presence of -2 T/A can induce the cleavage at a less preferred TC or TA site. However, in the absence of a more preferred site, the HRE site is shown to be cleaved by human topoisomerase I in the presence of topotecan. Thus, it is implied that the -2 base has a significant influence on the selection of the camptothecin-mediated Topo I cleavage site, which can overcome the preference for +1G. While the cleavage site recognition has been known to be based on the concerted effect of several bases spanning the cleavage site, such a determining effect of an individual base has not been previously recognized. A possible base-specific interaction between DNA and topoisomerase I may be responsible for this sequence selectivity.
authors.affiliation: College of Pharmacy, The University of Arizona, 1703 E. Mabel Street, Tucson, AZ 85721, USA.
authors.forename: Chandanamali
authors.initials: C
authors.lastname: Punchihewa
authors.forename: Megan
authors.initials: M
authors.lastname: Carver
authors.forename: Danzhou
authors.initials: D
authors.lastname: Yang
mesh_terms: D001483:Base Sequence; D002166:Camptothecin / Q000494:pharmacology*; D053837:DNA Cleavage; D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D051793:Hypoxia-Inducible Factor 1 / Q000235:genetics; D009841:Oligonucleotides / Q000378:metabolism; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D020218:Response Elements; D059004:Topoisomerase I Inhibitors
chemical_list: D004791:Enzyme Inhibitors; D051793:Hypoxia-Inducible Factor 1; D009841:Oligonucleotides; D011994:Recombinant Proteins; D059004:Topoisomerase I Inhibitors; D004264:DNA Topoisomerases, Type I; D002166:Camptothecin