Recombination protein Tid1p controls local resolution of cohesion in meiosis

Sister chromatid cohesion and interhomolog recombination are coordinated to promote segregation of homologous chromosomes instead of sister chromatids at the first meiotic division. During meiotic prophase in S. cerevisiae , the meiosis-specific cohesin Rec8p localizes along chromosome axes and mediates most of the cohesion. The mitotic cohesin Mcd1p/Scc1p localizes to discrete spots along chromosome arms and its function is not clear. In cells lacking Tid1p, a member of the SWI2/SNF2 family of helicase-like proteins involved in chromatin remodeling, Mcd1p and Rec8p persist abnormally through both meiotic divisions and chromosome segregation fails in the majority of cells. Genetic results indicate that the primary defect in these cells is failure to resolve Mcd1p-mediated connections. Another protein required for maintenance of cohesion, Pds5p, also contributes to failure of chromosome segregation in tid1Delta. Tid1p interacts with recombination enzymes Dmc1p and Rad51p and has an established role in recombination repair. Tid1p may remodel Mcd1p-mediated cohesion early in meiotic prophase to facilitate interhomolog recombination and the subsequent segregation of homologous chromosomes. Persistent connections lead to anaphase arrest in tid1Delta by invoking a previously unknown meiotic anaphase checkpoint that depends on Rad9p function. Several suppressors of the tid1Delta sporulation defect have been identified in a high-copy screen that may act through a function of Tid1p in cohesion remodeling or through a new anaphase checkpoint.