RecQ Helicase Stimulates Both DNA Catenation and Changes in DNA Topology by Topoisomerase III

Together, RecQ helicase and topoisomerase III (Topo III) of Escherichia coli comprise a potent DNA strand passage activity that can catenate covalently closed DNA (Harmon, F. G., DiGate, R. J., and Kowalczykowski, S. C. (1999) Mol. Cell 3, 611-620). Here we directly assessed the structure of the cat...

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Bibliographic Details
Published in:The Journal of biological chemistry 2003-10, Vol.278 (43), p.42668-42678
Main Authors: Harmon, Frank G., Brockman, Joel P., Kowalczykowski, Stephen C.
Format: Article
Language:English
Subjects:
Adenosine Triphosphatases - physiology
DNA - chemistry
DNA - metabolism
DNA Helicases - physiology
DNA Topoisomerases, Type I - physiology
DNA, Catenated - biosynthesis
DNA, Catenated - chemistry
DNA-Binding Proteins - physiology
Escherichia coli Proteins - physiology
Kinetics
Microscopy, Atomic Force
Nucleic Acid Conformation
Polyethylene Glycols - pharmacology
RecQ Helicases
Titrimetry
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Summary:Together, RecQ helicase and topoisomerase III (Topo III) of Escherichia coli comprise a potent DNA strand passage activity that can catenate covalently closed DNA (Harmon, F. G., DiGate, R. J., and Kowalczykowski, S. C. (1999) Mol. Cell 3, 611-620). Here we directly assessed the structure of the catenated DNA species formed by RecQ helicase and Topo III using atomic force microscopy. The images show complex catenated DNA species involving crossovers between multiple double-stranded DNA molecules that are consistent with full catenanes. E. coli single-stranded DNA-binding protein significantly stimulated both the topoisomerase activity of Topo III alone and the DNA strand passage activity of RecQ helicase and Topo III. Titration data suggest that an intermediate of the RecQ helicase unwinding process, perhaps a RecQ helicase-DNA fork, is the target for Topo III action. Catenated DNA is the predominant product under conditions of molecular crowding; however, we also discovered that RecQ helicase and single-stranded DNA-binding protein greatly stimulated the intramolecular strand passage (“supercoiling”) activity of Topo III, as revealed by changes in the linking number of uncatenated DNA. Together our results demonstrate that RecQ helicase and Topo III function together to comprise a potent and concerted single-strand DNA passage activity that can mediate both catenation-decatenation processes and changes in DNA topology.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M302994200