A Meiosis-Specific Factor MRM/C19orf57 Modulates Localization of RAD51 and DMC1 Recombinases To DSBs in Mouse Meiotic Recombination

Meiotic recombination is critical for genetic exchange and generation of chiasmata that ensures faithful chromosome segregation during meiosis I. Meiotic recombination is initiated by DNA double-strand break (DSB) followed by multiple processes of DNA repair. The exact mechanisms how recombinases localize to DSB remained elusive.  Here we show that MRM/C19orf57 is a new player for meiotic recombination in mice. MRM/C19orf57 associates with ssDNA binding proteins, BRCA2 and MEILB2/HSF2BP, critical recruiters of recombinases onto DSB sites. Disruption of MRM/C19orf57 shows severe impact on DSB repair and male fertility. Remarkably, removal of single stranded DNA (ssDNA) binding proteins from DSB sites is delayed, and reciprocally the loading of RAD51 and DMC1 onto resected ssDNA is impaired in Mrm KO spermatocytes. We propose that MRM/C19orf57 modulates localization of  recombinases to meiotic DSB sites through the interaction with the BRCA2-MEILB2/HSF2BP complex during meiotic recombination.