Activation of meiotic recombination by nuclear import of the DNA break hotspot-determining complex

Meiotic recombination forms crossovers important for proper chromosome segregation and viability of offspring. This process involves many proteins acting at each of the multiple steps of recombination. Recombination is initiated by formation of DNA double-strand breaks (DSBs), which in the several species examined often occur with high frequency at special sites (DSB hotspots). In the fission yeast Schizosaccharomyces pombe DSB hotspots are bound with high specificity and activated by linear element (LinE) proteins Rec25, Rec27, and Mug20 which form co-localized nuclear foci with Rec10, essential for all DSB formation and recombination. Here, we identify Rec10’s nuclear localization signal (NLS) and show it is important for coordinated nuclear entry after complex-formation with other LinE proteins. In NLS mutants, recombination is much reduced but not eliminated; nuclear entry of limited amounts of Rec10 can account for the residual recombination. LinEs are related to synaptonemal complex proteins of other species, suggesting that they also may share an as-yet-unidentified NLS and protein complex-formation before nuclear entry.