Resolution of Holliday junctions by eukaryotic DNA topoisomerase I

Jo Ann Sekiguchi, Nadrian C. Seeman, Stewart Shuman

Research output: Contribution to journalArticlepeer-review


The Holliday junction, a key intermediate in both homologous and site- specific recombination, is generated by the reciprocal exchange of single strands between two DNA duplexes. Resolution of the junctions can occur in two directions with respect to flanking markers, either restoring the parental DNA configuration or generating a genetic crossover. Recombination can he regulated, in principle, by factors that influence the directionality of the resolution step. We demonstrate that the vaccinia virus DNA topoisomerase, a eukaryotic type I enzyme, catalyzes resolution of synthetic Holliday junctions in vitro. The mechanism entails concerted transesterifications at two recognition sites, 5'-CCCTT↓, that are opposed within a partially mobile four-way junction. Cruciforms are resolved unidirectionally and with high efficiency into two linear duplexes. These findings suggest a model whereby type I topoisomerases may either promote or suppress genetic recombination in vivo.

Original languageEnglish (US)
Pages (from-to)785-789
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number2
StatePublished - Jan 23 1996

ASJC Scopus subject areas

  • General


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