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Single-molecule study of DNA unlinking by eukaryotic and prokaryotic type-II topoisomerases.

ABSTRACT: Type-II topoisomerases are responsible for untangling DNA during replication by removing supercoiled and interlinked DNA structures. Using a single-molecule micromanipulation setup, we follow the real-time decatenation of two mechanically braided DNA molecules by Drosophila melanogaster topoisomerase (Topo) II and Escherichia coli Topo IV. Although Topo II relaxes left-handed (L) and right-handed (R-) braids similarly at a rate of approximately 2.9 s-1, Topo IV has a marked preference for L-braids, which it relaxes completely and processively at a rate of approximately 2.4 s-1. However, Topo IV can unlink R-braids at about half that rate when they supercoil to form L-plectonemes. These results imply that the preferred substrate for unlinking by Topo IV has the symmetry of an L-crossing and shed new light on the decatenation of daughter strands during DNA replication, which are usually assumed to be linked in an R-braid.

SUBMITTER: Charvin G

PROVIDER: S-EPMC187850 | biostudies-literature | 2003 Aug

REPOSITORIES: biostudies-literature

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Single-molecule study of DNA unlinking by eukaryotic and prokaryotic type-II topoisomerases.

Charvin G G Bensimon D D Croquette V V

Proceedings of the National Academy of Sciences of the United States of America 20030805 17

Type-II topoisomerases are responsible for untangling DNA during replication by removing supercoiled and interlinked DNA structures. Using a single-molecule micromanipulation setup, we follow the real-time decatenation of two mechanically braided DNA molecules by Drosophila melanogaster topoisomerase (Topo) II and Escherichia coli Topo IV. Although Topo II relaxes left-handed (L) and right-handed (R-) braids similarly at a rate of approximately 2.9 s-1, Topo IV has a marked preference for L-brai ...[more]

PMID: 12902541

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