Concerted action of the MutLb heterodimer and Mer3 helicase regulates the global extent of meiotic gene conversion

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Duroc, Yann | Kumar, Rajeev | Ranjha, Lepakshi | Adam, Céline | Guérois, Raphaël | Md Muntaz, Khan | Marsolier-Kergoat, Marie-Claude | Dingli, Florent | Laureau, Raphaëlle | Loew, Damarys | Llorente, Bertrand | Charbonnier, Jean-Baptiste | Cejka, Petr | Borde, Valérie

Edité par CCSD ; eLife Sciences Publication -

Correction du nom : Céline Adam et non pas Cécile Adam. International audience. Gene conversions resulting from meiotic recombination are critical in shaping genome diversification and evolution. How the extent of gene conversions is regulated is unknown. Here we show that the budding yeast mismatch repair related MutLb complex, Mlh1-Mlh2, specifically interacts with the conserved meiotic Mer3 helicase, which recruits it to recombination hotspots, independently of mismatch recognition. This recruitment is essential to limit gene conversion tract lengths genome-wide, without affecting crossover formation. Contrary to expectations, Mer3 helicase activity, proposed to extend the displacement loop (D-loop) recombination intermediate, does not influence the length of gene conversion events, revealing non-catalytical roles of Mer3. In addition, both purified Mer3 and MutLb preferentially recognize D-loops, providing a mechanism for limiting gene conversion in vivo. These findings show that MutLb is an integral part of a new regulatory step of meiotic recombination, which has implications to prevent rapid allele fixation and hotspot erosion in populations.

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