Molecular Cell
Volume 57, Issue 4, 19 February 2015, Pages 607-621
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Article
Pervasive and Essential Roles of the Top3-Rmi1 Decatenase Orchestrate Recombination and Facilitate Chromosome Segregation in Meiosis

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Highlights

  • DNA strand passage by Top3-Rmi1 is pivotal for meiotic recombination

  • Conditional alleles define temporally and functionally distinct roles of Top3-Rmi1

  • Top3-Rmi1 partners with RecQ helicase BLM/Sgs1 to prevent abnormal recombination

  • Top3-Rmi1 is essential for disentangling chromosomes enabling complete separation

Summary

The Bloom’s helicase ortholog, Sgs1, plays central roles to coordinate the formation and resolution of joint molecule intermediates (JMs) during meiotic recombination in budding yeast. Sgs1 can associate with type-I topoisomerase Top3 and its accessory factor Rmi1 to form a conserved complex best known for its unique ability to decatenate double-Holliday junctions. Contrary to expectations, we show that the strand-passage activity of Top3-Rmi1 is required for all known functions of Sgs1 in meiotic recombination, including channeling JMs into physiological crossover and noncrossover pathways, and suppression of non-allelic recombination. We infer that Sgs1 always functions in the context of the Sgs1-Top3-Rmi1 complex to regulate meiotic recombination. In addition, we reveal a distinct late role for Top3-Rmi1 in resolving recombination-dependent chromosome entanglements to allow segregation at anaphase. Surprisingly, Sgs1 does not share this essential role of Top3-Rmi1. These data reveal an essential and pervasive role for the Top3-Rmi1 decatenase during meiosis.

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