title: Topoisomerase III can serve as the cellular decatenase in Escherichia coli.
abstract: topB, encoding topoisomerase III, was identified as a high copy suppressor of the temperature-sensitive parC1215 allele, encoding one of the subunits of topoisomerase IV. Overexpression of topoisomerase III at the nonpermissive temperature was shown subsequently to restore timely chromosome decatenation and suppress lethality in strains carrying either temperature-sensitive parE or parC alleles. By developing an assay in vitro for precatenane unlinking, we demonstrated directly that both topoisomerase III and topoisomerase IV were efficient at this task, whereas DNA gyrase was very inefficient at precatenane removal. These observations suggest that precatenane unlinking is sufficient to sustain decatenation of replicating daughter chromosomes in the cell.
authors.affiliation: Molecular Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.
authors.forename: Pearl
authors.initials: P
authors.lastname: Nurse
authors.forename: Cindy
authors.initials: C
authors.lastname: Levine
authors.forename: Heide
authors.initials: H
authors.lastname: Hassing
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Marians
mesh_terms: D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D004269:DNA, Bacterial / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology*; D008856:Microscopy, Fluorescence; D013379:Substrate Specificity
chemical_list: D004269:DNA, Bacterial; D004264:DNA Topoisomerases, Type I