title: Camptothecin-sensitive relaxation of supercoiled DNA by the topoisomerase I-like activity associated with poly(ADP-ribose) polymerase-1.
abstract: Poly(ADP-ribose) polymerase-1 is a highly abundant nuclear enzyme implicated in transcription, DNA replication, and DNA repair through binding of nascent RNA and interactions with various factors. We found that purified fractions of recombinant human poly(ADP-ribose) polymerase-1 expressed in Escherichia coli possess yet another activity, a Mg(2+)-dependent DNA supercoil relaxation activity. Cleavage of recombinant poly(ADP-ribose) polymerase-1 by caspase-3, an apoptotic protease, reduced this activity, as did the removal of either of the two zinc finger motifs located in the N-terminal DNA-binding domain of poly(ADP-ribose) polymerase-1. In addition, this activity was separated from E. coli topoisomerase I by gel-filtration column chromatography, suggesting that this activity is specifically associated with poly(ADP-ribose) polymerase-1. Because this relaxation activity did not require ATP and was resistant to VP16, a topoisomerase II inhibitor, this activity is closer to that of topoisomerase I. However, the supercoiled DNA relaxation activity associated with poly(ADP-ribose) polymerase-1 is distinct from that of human or E. coli topoisomerase I, as this activity could not completely remove superhelical tensions from plasmid DNA. Thus, we referred to this activity as topoisomerase I-like activity. This Mg(2+)-dependent DNA supercoil relaxation activity was found to be sensitive to camptothecin, a mammalian topoisomerase I inhibitor.
authors.affiliation: DNA Repair Group, Health and Environment Unit, Laval University Medical Center, Centre Hospitalier Universitaire de Québec, Faculty of Medicine, Laval University, Ste-Foy, Quebec G1V 4G2, Canada.
authors.forename: Tetsu M C
authors.initials: TM
authors.lastname: Yung
authors.forename: Marianne
authors.initials: M
authors.lastname: Parent
authors.forename: Erick L Y
authors.initials: EL
authors.lastname: Ho
authors.forename: Masahiko S
authors.initials: MS
authors.lastname: Satoh
mesh_terms: D002166:Camptothecin / Q000494:pharmacology*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D004278:DNA, Superhelical / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D016297:Mutagenesis, Site-Directed; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism
chemical_list: D004278:DNA, Superhelical; D011994:Recombinant Proteins; D011065:Poly(ADP-ribose) Polymerases; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D004264:DNA Topoisomerases, Type I; D002166:Camptothecin