Functional Interplay between Recombinases during Meiosis – FIReMe

DNA double-strand breaks (DSBs) are the most dangerous lesions for genome integrity and at risk of generating mutations and chromosome rearrangements. However, during meiosis, DSB are deliberately inflicted as part of a developmental program, and are repaired by error-free homologous recombination, which is tightly regulated. Understanding the mechanisms at work in meiosis is of utmost importance to detect, analyze and cure human diseases such as sterility and aneuploidy and to improve the genetic pool of crops in agriculture. Moreover, meiotic recombination genes when ectopically re-expressed in cancer cells confer genome instability. Around 200 DSB per cell are formed during meiosis, and must find a remote homologous DNA sequence for repair. Meiotic cells employ two recombinases, Rad51 (also used for somatic recombination) and Dmc1 (specific to meiotic cells), instead of one, which form filaments on the DSB ends and cooperate to promote homology search. This project aims to decipher their respective role in this process: how the Rad51 and/or Dmc1 filaments move in the nucleus to find their homologous sequence, what Dmc1 brings to this process, how and if the recombinases interact together as well as how they arrange in vivo on a single ssDNA tail is still not clear. A major obstacle so far has been the impossibility to tag the recombinases while keeping them functional in vivo. Our labs have generated functionally tagged versions of the two recombinases, allowing their fine live imaging and molecular characterization. The aims of this project will be to follow the dynamics of these proteins by live imaging, in wild-type and several mutants, to establish their respective binding profile at DSBs, and to extensively decipher their interactome during meiotic DSB repair. Our multidisciplinary project will combine advanced super resolution microscopy, genomics, proteomics and computational biology to answer a question at the heart of genome stability and transmission.