PIF1, RAD54 and RDH54/TID1 promote residual double strand break repair during meiosis in the budding yeast, Saccharomyces cerevisiae

In the budding yeast, Saccharomyces cerevisiae, repair of programmed double strand breaks occurs in two phases during prophase I of meiosis. During Phase 1 interhomolog recombination is mediated by the meiosis-specific Dmc1 recombinase. Crossover-specific recombination intermediates enable synapsis of homologous chromosomes, resulting in a transition to Rad51-mediated recombination in Phase 2 that repairs any residual double strand breaks so that chromosomes are intact when cells progress into the first meiotic division. Studying Phase 2 recombination is challenging because the number of breaks present at pachynema (the prophase I stage when all the homologs are synapsed) is small and a low frequency of new breaks continues to be made. Using a newly developed method for analyzing Phase 2 recombination, this work discovered that RDH54/TID1 can partially compensate for RAD54, while PIF1 functions independently from both RAD54 and RDH54/TID1 in this process. ARTICLE SUMMARYMeiotic recombination involves repair of numerous programmed double strand breaks (DSBs). Failure to repair all the DSBs results in inviable gametes. Meiotic DSB repair occurs in two phases. In Phase 1, recombination occurs between homologs to create crossovers needed for proper chromosome segregation. Subsequently, Phase 2 recombination repairs any remaining DSBs prior to cells progressing through Meiosis I. Using a novel method for studying Phase 2 recombination, this work shows that RDH54/TID1 can partially substitute for the related RAD54 translocase and that the conserved PIF1 helicase functions independently of both RDH54/TID1 and RAD54 in this process.