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KMID : 0578319940040010045
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Molecules and Cells
1994 Volume.4 No. 1 p.45 ~ p.50
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Interaction of Escherichia coli DNA Topoisomerase I with B/Z DNA Junctions
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Shim Jae-Kyung
Koo Hyeon-Sook
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Abstract
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The interaction of Escherichia coli DNA topoisomerase I with a plasmid DNA containing a CG-alternating DNA stretch was measured by inducing the topoisomerase I-mediated DNA cleavage. The DNA stretch underwent a local transition of B-DNA into Z-DNA under the conformational strain associated with negative DNA superhelicity. DNA cleavages were enhanced in the supercoiled plasmid DNA compared with the linearized plasmid DNA, especially at a number of DNA sites including the sites juxtaposing the CG-alternating DNA segment. The stabilization of Z-DNA by cytosine CS-methylation affected DNA cleavages at the boundaries between the two different DNA structures. The results suggested that the favorable interaction of the topoisomerase I with DNA regions contiguous to the Z-DNA segment may be due to single-strandedness at the WZ junctions. E colt DNA topoisomerase I-cleavage sites in the plasmid DNA were correlated with S1 nuclease-sensitive sites to analyze DNA structural factors affecting the interaction of E. coli DNA topoisomerase I with DNA.
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