Protein Determinants of Meiotic DNA Break Hotspots (dataset 1)

Meiotic recombination, crucial for proper chromosome segregation and genome evolution, is initiated by programmed DNA double-strand breaks (DSBs) in budding and fission yeasts and likely all sexually reproducing species. In fission yeast, DSBs occur up to several hundred times more frequently at special sites, called hotspots, than in other regions of the genome. What distinguishes hotspots from cold regions is a major unsolved problem, although transcription factors determine some hotspots. We report here the discovery that three coiled-coil proteins -- Rec25, Rec27, and Mug20 -- bind essentially all hotspots with unprecedented, high specificity even without DSB formation. These small proteins are components of linear elements, are related to synaptonemal complex proteins, and are essential for nearly all DSBs at most hotspots. Our results indicate that these hotspot determinants activate or stabilize the DSB-forming protein Rec12 (Spo11 homolog) rather than promote its binding to hotspots. We propose here a new paradigm for hotspot determination and crossover control by linear element proteins. Meiotic DSB analysis by immunoprecipitation of Rec12 covalently linked to DNA (no exogenous crosslinking agent used) in WT and various mutants; one mutant repeated.