Top3-Rmi1 DNA Single-Strand Decatenase Is Integral to the Formation and Resolution of Meiotic Recombination Intermediates

The topoisomerase III (Top3)-Rmi1 heterodimer, which catalyzes DNA single-strand passage, forms a conserved complex with the Bloom’s helicase (BLM, Sgs1 in budding yeast). This complex has been proposed to regulate recombination by disassembling double Holliday junctions in a process called dissolution. Top3-Rmi1 has been suggested to act at the end of this process, resolving hemicatenanes produced by earlier BLM/Sgs1 activity. We show here that, to the contrary, Top3-Rmi1 acts in all meiotic recombination functions previously associated with Sgs1, most notably as an early recombination intermediate chaperone, promoting regulated crossover and noncrossover recombination and preventing aberrant recombination intermediate accumulation. In addition, we show that Top3-Rmi1 has important Sgs1-independent functions that ensure complete recombination intermediate resolution and chromosome segregation. These findings indicate that Top3-Rmi1 activity is important throughout recombination to resolve strand crossings that would otherwise impede progression through both early steps of pathway choice and late steps of intermediate resolution. [Display omitted] •The Sgs1-Top3-Rmi1 complex promotes early noncrossover formation during meiosis•The Sgs1-Top3-Rmi1 complex limits aberrant recombination intermediate formation•Top3-Rmi1 are required for complete recombination intermediate resolution•Top3-catalyzed decatenation is critical to successful meiotic recombination Homologous recombination is critical for genome separation during meiosis. Kaur et al. show that topoisomerase III, Rmi1, and the helicase Sgs1 act together to prevent formation of aberrant recombination intermediates and to ensure that recombination intermediates are completely resolved during meiosis.