Meiotic recombination forms crossovers important for proper chromosome segregation and offspring viability. This complex process involves many proteins acting at each of the multiple steps of recombination. Recombination initiates by formation of DNA double-strand breaks (DSBs), which in the several species examined occur with high frequency at special sites (DSB hotspots). In Schizosaccharomyces pombe DSB hotspots are bound with high specificity and strongly 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 test the hypothesis that Rec10's nuclear localization signal (NLS) is crucial for coordinated nuclear entry after forming a complex with other LinE proteins. In NLS mutants, all LinEs were abundant in the cytoplasm, not the nucleus; DSB-formation and recombination were much reduced but not eliminated. Nuclear entry of limited amounts of Rec10, apparently small enough for passive nuclear entry, can account for residual recombination. LinEs are related to synaptonemal complex proteins of other species, suggesting that they also share an NLS, not yet identified, and protein complex-formation before nuclear entry.
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-yetunidentified NLS and protein complex-formation before nuclear entry.
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