Two distinct modes of strand unlinking during θ-type DNA replication

Hiroshi Hiasa, Kenneth J. Marians

Research output: Contribution to journalArticlepeer-review

93 Scopus citations


DNA gyrase and topoisomerase IV (Topo IV) are type II bacterial DNA topoisomerases that show a high degree of similarity to each other yet appear to have different functions during DNA replication. We show here that the torsional stress generated during θ-type DNA replication in vitro can take the form of either positive supercoils ahead of the replication fork or catenane-like right-handed windings (precatenanes) of the two partially replicated duplexes behind the fork. Gyrase prefers to act on the former, whereas Topo IV prefers the latter. Removal of either form of positive winding can support nascent chain elongation, but only precatenane removal can support the final stages of DNA replication: processing of the late intermediate and daughter chromosome decatenation.

Original languageEnglish (US)
Pages (from-to)21529-21535
Number of pages7
JournalJournal of Biological Chemistry
Issue number35
StatePublished - 1996

Bibliographical note

Copyright 2007 Elsevier B.V., All rights reserved.


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