TY - JOUR
T1 - Roles of topoisomerases in maintaining steady-state DNA supercoiling in Escherichia coli
AU - Zechiedrich, E. Lynn
AU - Khodursky, Arkady B.
AU - Bachellier, Sophie
AU - Schneider, Robert
AU - Chen, Dongrong
AU - Lilley, David M J
AU - Cozzarelli, Nicholas R.
PY - 2000/3/17
Y1 - 2000/3/17
N2 - 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 (σ) 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 σ 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 σ = -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 (σ = -0.09), greatly stimulating transcription from the supercoiling sensitive leu-500 promoter and increasing the number of supercoils trapped by λ integrase site-specific recombination.
AB - 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 (σ) 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 σ 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 σ = -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 (σ = -0.09), greatly stimulating transcription from the supercoiling sensitive leu-500 promoter and increasing the number of supercoils trapped by λ integrase site-specific recombination.
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U2 - 10.1074/jbc.275.11.8103
DO - 10.1074/jbc.275.11.8103
M3 - Article
C2 - 10713132
AN - SCOPUS:0034677898
SN - 0021-9258
VL - 275
SP - 8103
EP - 8113
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 11
ER -