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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