The Configuration of RPA, RAD51, and DMC1 Binding in Meiosis Reveals the Nature of Critical Recombination Intermediates

Summary

Meiotic recombination proceeds via binding of RPA, RAD51, and DMC1 to single-stranded DNA (ssDNA) substrates created after formation of programmed DNA double-strand breaks. Here we report high-resolution in vivo maps of RPA and RAD51 in meiosis, mapping their binding locations and lifespans to individual homologous chromosomes using a genetically engineered hybrid mouse. Together with high-resolution microscopy and DMC1 binding maps, we show that DMC1 and RAD51 have distinct spatial localization on ssDNA: DMC1 binds near the break site, and RAD51 binds away from it. We characterize inter-homolog recombination intermediates bound by RPA in vivo, with properties expected for the critical displacement loop (D-loop) intermediates. These data support the hypothesis that DMC1, not RAD51, performs strand exchange in mammalian meiosis. RPA-bound D-loops can be resolved as crossovers or non-crossovers, but crossover-destined D-loops may have longer lifespans. D-loops resemble crossover gene conversions in size, but their extent is similar in both repair pathways.

Graphical Abstract

Highlights

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  DMC1 binds near and RAD51 away from DNA break sites on homology search filaments

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  RPA binds the repair template chromosome in mammalian meiotic D-loops in vivo

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  DMC1, not RAD51, performs strand exchange in mammalian meiotic DNA break repair

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  D-loops resemble crossover gene conversion tracts in size and localization

Abstract

Hinch et al. show that DMC1 and RAD51 bind substrates created after formation of DNA breaks with distinct localization in mouse meiosis. DMC1 binds near break sites and performs strand exchange with the homologous chromosome. RPA binds the template chromosome in D-loop intermediates, which resemble crossover gene conversions in size and localization, in multiple repair pathways.