Novel attributes of Hed1 affect dynamics and activity of the Rad51 presynaptic filament during meiotic recombination.

During meiosis, recombination events that occur between homologous chromosomes help prepare the chromosome pairs for proper disjunction in meiosis I. The concurrent action of the Rad51 and Dmc1 recombinases is necessary for an interhomolog bias. Notably, the activity of Rad51 is tightly controlled, so as to minimize the use of the sister chromatid as recombination partner. We demonstrated recently that Hed1, a meiosis-specific protein in Saccharomyces cerevisiae, restricts the access of the recombinase accessory factor Rad54 to presynaptic filaments of Rad51. We now show that Hed1 undergoes self-association in a Rad51-dependent manner and binds ssDNA. We also find a strong stabilizing effect of Hed1 on the Rad51 presynaptic filament. Biochemical and genetic analyses of mutants indicate that these Hed1 attributes are germane for its recombination regulatory and Rad51 presynaptic filament stabilization functions. Our results shed light on the mechanism of action of Hed1 in meiotic recombination control.

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