RPA and RAD51 ChIP-seq from B6 and B6xCAST F1 PRDM9-Humanized/CAST mouse testes

Meiotic recombination is initiated by programmed DNA double-strand breaks (DSBs) and proceeds via binding of RPA, RAD51 and DMC1 to single-stranded DNA (ssDNA) substrates created after the formation of DSBs. Here, we report high-resolution in vivo maps of RPA and RAD51 binding in meiosis, mapping their binding locations and lifespans in a B6 and a genetically modified B6xCAST F1 mouse. We ascribe signals separately to the individual homologous chromosomes in the hybrid mouse, thereby separating the signal of binding to the chromosome where DSBs occurred and the chromosome that was used as template for repair. Together with super-resolution microscopy and DMC1 binding maps, we show that DMC1 and RAD51 have distinct spatial localization on ssDNA: whereas DMC1 binds near the break-site, RAD51 binds away from it. We characterize the D-loop, a critical intermediate bound by RPA, in vivo. These data show that DMC1, not RAD51, performs strand exchange in mammalian meiosis. We find that the localisation of D-loop intermediates is similar in crossover and non-crossover pathways, with a longer lifespan for crossover-destined intermediates. These findings answer long-standing questions about the molecular intermediates of recombination.