Mutational analysis of Mei5, a subunit of Mei5-Sae3 complex, in Dmc1-mediated recombination during yeast meiosis.

Interhomolog recombination in meiosis is mediated by the Dmc1 recombinase. The Mei5-Sae3 complex of Saccharomyces cerevisiae promotes Dmc1 assembly and functions with Dmc1 for homology-mediated repair of meiotic DNA double-strand breaks. How Mei5-Sae3 facilitates Dmc1 assembly remains poorly understood. In this study, we created and characterized several mei5 mutants featuring the amino acid substitutions of basic residues. We found that Arg97 of Mei5, conserved in its ortholog, SFR1 (complex with SWI5), RAD51 mediator, in humans and other organisms, is critical for complex formation with Sae3 for Dmc1 assembly. Moreover, the substitution of either Arg117 or Lys133 with Ala in Mei5 resulted in the production of a C-terminal truncated Mei5 protein during yeast meiosis. Notably, the shorter Mei5-R117A protein was observed in meiotic cells but not in mitotic cells when expressed, suggesting a unique regulation of Dmc1-mediated recombination by posttranslational processing of Mei5-Sae3.