DNA strand cleavage is required for replication fork arrest by a frozen topoisomerase-quinolone-DNA ternary complex

Hiroshi Hiasa, Diana O. Yousef, Kenneth J. Marians

Research output: Contribution to journalArticlepeer-review

102 Scopus citations

Abstract

The formation of a topoisomerase-quinolone-DNA ternary complex leads to cell death. We show here that an active strand breakage and reunion activity is required for formation of a norfloxacin-topoisomerase IV-DNA ternary complex that can arrest the progression of replication forks in vitro. Mutant topoisomerases containing either an active site mutation, a quinolone resistance-conferring mutation, or both, could all bind DNA as well as the wild-type, but unlike the wild-type, could not halt replication fork progression. The collision between the replication fork and the frozen topoisomerase converted the cleavable complex to a nonreversible form but did not generate a double-stranded break. Thus, the cytotoxicity of this class of topoisomerase inhibitors likely results from a two-step process: (i) conversion of the frozen topoisomerase-quinolone-DNA ternary complex to an unreversible form; and (ii) generation of a double-strand break by subsequent denaturation of the topoisomerase, perhaps by an aborted repair attempt.

Original languageEnglish (US)
Pages (from-to)26424-26429
Number of pages6
JournalJournal of Biological Chemistry
Volume271
Issue number42
DOIs
StatePublished - 1996

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