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bioRxiv · 10.1101/2022.06.27.497840

Mer3 helicase protects early crossover intermediates from STR complex disassembly during meiosis

Altmannova, V.·Firlej, M.·Mueller, F.·Janning, P.·Rauleder, R.·Rousova, D.·Schaeffler, A.·Weir, J. R.
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Abstract

During meiosis I it is necessary that homologous chromosomes are linked to one another so that they can be faithfully separated. S. cerevisiae Mer3 (HFM1 in mammals) is a SF2 helicase and member of the ZMM group of proteins, that facilitates the formation of class I crossovers during meiosis. Here we describe the structural organisation of Mer3 and, using AlphaFold modelling and XL-MS, we further characterise the previously described interaction with Mlh1-Mlh2. We find that Mer3 also forms a previously undescribed complex with the recombination regulating factors Top3 and Rmi1 and that this interaction is competitive with Sgs1BLM helicase in a phospho-dependent manner. Using in vitro reconstituted D-loop assays we show that Mer3 inhibits the anti-recombination activity of Sgs1/Top3/Rmi1 (STR) complex. Thus we provide a mechanism whereby Mer3 downregulates the anti-crossover activity of the STR complex, hence promoting the formation of crossovers during meiosis I.

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Altmannova, V., Firlej, M., Mueller, F., Janning, P., Rauleder, R., Rousova, D., Schaeffler, A., Weir, J. R.. 2022-06-27. Mer3 helicase protects early crossover intermediates from STR complex disassembly during meiosis. https://doi.org/10.1101/2022.06.27.497840

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