Topoisomerase III can serve as the cellular decatenase in Escherichia coli.
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.
Nurse
Pearl
P
Molecular Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.
Levine
Cindy
C
Hassing
Heide
H
Marians
Kenneth J
KJ
D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D004269:DNA, Bacterial / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology*; D008856:Microscopy, Fluorescence; D013379:Substrate Specificity
D004269:DNA, Bacterial; D004264:DNA Topoisomerases, Type I