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Zechiedrich, E.L.* ; Khodursky, A.B.* ; Bachellier, S.* ; Schneider, R.* ; Chen, D.* ; Lilley, D.M.* ; Cozzarelli, N.R.*

Roles of topoisomerases in maintaining steady-state DNA supercoiling in Escherichia coli.

J. Biol. Chem. 275, 8103-8113 (2000)
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DNA supercoiling is essential for bacterial cell survival. We demonstrated that DNA topoisomerase IV, acting in concert with topoisomerase I and gyrase, makes an important contribution to the steady-state level of supercoiling in Escherichia coli. Following inhibition of gyrase, topoisomerase IV alone relaxed plasmid DNA to a final supercoiling density (sigma) of -0.015 at an initial rate of 0.8 links min(-1). Topoisomerase I relaxed DNA at a faster rate, 5 links min(-1), but only to a sigma of -0.05. Inhibition of topoisomerase IV in wild-type cells increased supercoiling to approximately the same level as in a mutant lacking topoisomerase I activity (to sigma = -0.08). The role of topoisomerase IV was revealed by two functional assays. Removal of both topoisomerase I and topoisomerase IV caused the DNA to become hyper-negatively supercoiled (sigma = -0.09), greatly stimulating transcription from the supercoiling sensitive leu-500 promoter and increasing the number of supercoils trapped by lambda integrase site-specific recombination.
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Publikationstyp Artikel: Journalartikel
Dokumenttyp Wissenschaftlicher Artikel
ISSN (print) / ISBN 0021-9258
e-ISSN 1083-351X
Quellenangaben Band: 275, Heft: 11, Seiten: 8103-8113 Artikelnummer: , Supplement: ,
Verlag American Society for Biochemistry and Molecular Biology
Begutachtungsstatus Peer reviewed