Ricerc@Sapienza

Meiotic recombination initiates following the formation of DNA double strand breaks (DSBs) by the Spo11 endonuclease early in prophase I at discrete regions in the genome coined hotspots. In mammals, meiotic DSB site selection is directed in part by sequence specific binding of PRDM9, a polymorphic histone H3 (H3K4Me3) methyltransferase. However, other chromatin features needed for meiotic hotspot specification are largely unknown. Here, we show that the recombinogenic cores of active hotspots in mice harbor several histone H3 and H4 acetylation and methylation marks that are typical of open, active chromatin. Further, deposition of these open chromatin-associated histone marks is dynamic and is manifest at spermatogonia and/or pre-leptotene meiotic stage cells, which would facilitate PRDM9 binding and access for Spo11 to direct the formation of DSBs, which are initiated at leptotene. Importantly, manipulating histone acetylase and deacetylase activity established that histone acetylation marks are necessary for both hotspot activity and crossover resolution. We conclude there are functional roles for histone acetylation marks at mammalian meiotic recombination hotspots.