Programmed formation of DNA double strand breaks (DSBs) initiates the meiotic homologous recombination pathway. This pathway allows homologous chromosomes to find each other and the formation of crossing overs, the products of reciprocal exchanges, which are required for proper chromosome segregation at the first meiotic division. Meiotic DSBs are catalyzed by Spo11 that forms a complex with a second subunit, TopoVIBL, and mediates a DNA type II topoisomerase-like cleavage. Several other

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... s are essential for meiotic DSB formation, including three evolutionarily conserved proteins first identified in Saccharomyces cerevisiae (Mer2, Mei4 and Rec114). These three S. cerevisiae proteins and their mouse orthologs (IHO1, MEI4 and REC114) co-localize on the axes of meiotic chromosomes, and mouse IHO1 and MEI4 are essential for meiotic DSB formation. Here, we show that mouse Rec114 is required for meiotic DSB formation. Moreover, MEI4 forms a complex with REC114 and IHO1 in mouse spermatocytes, consistent with cytological observations. We then demonstrated in vitro the formation of a stable complex between REC114 C-terminal domain and MEI4 N-terminal domain. We further determine the structure of REC114 N-terminal domain that revealed similarity with Pleckstrin Homology domains and its property to dimerize. These analyses provide direct insights into the architecture of these essential components of the meiotic DSB machinery.