| Abstract: |
Meiotic recombination is essential for fertility and allelic shuffling. Canonical recombination models fail to capture the observed complexity of meiotic recombinants. Here, by combining genome-wide meiotic heteroduplex DNA patterns with meiotic DNA double-strand break (DSB) sites, we show that part of this complexity results from frequent template switching during synthesis-dependent strand annealing that yields noncrossovers and from branch migration of double Holliday junction (dHJ)-containing intermediates that mainly yield crossovers. This complexity also results from asymmetric positioning of crossover intermediates relative to the initiating DSB and Msh2-independent conversions promoted by the suspected dHJ resolvase Mlh1-3 as well as Exo1 and Sgs1. Finally, we show that dHJ resolution is biased toward cleavage of the pair of strands containing newly synthesized DNA near the junctions and that this bias can be decoupled from the crossover-biased dHJ resolution. These properties are likely conserved in eukaryotes containing ZMM proteins, which includes mammals. Marsolier-Kergoat et al. analyzed meiotic heteroduplex DNA genome-wide relative to double-strand break sites. They found that meiotic DNA transactions are highly dynamic with template switching and Holliday junction branch migration and that Mlh1-3, Exo1, and Sgs1 promote Msh2-independent conversions. Finally, they observed a strong Holliday junction resolution bias decoupled from the crossover bias. © 2018 Elsevier Inc. |
