We studied the relationship between recombination and segregation in the fission yeast Schizosaccharomyces pombe. In meiosis, chromosomes undergo two rounds of segregation to produce haploid meiotic products. Crossover meiotic ecombination (chiasmata) promotes chromosome segregation during meiosis I; achiasmatic chromosomes often suffer on disjunction in meiosis I. Recl2 protein is a topoisomerase IIortholog that introduces double-strand DNA breaks that nitiate recombination. The red2 null (deletion) and active site (Y98F) mutants lack recombination and crossovers, and onsequently suffer meiosis I nondisjunction. However, null mutants chromosomes segregate to opposite poles more frequently than predicted. Thus, fission yeast has a backup, "distributive segregation" pathway that can function in the absence of Rec 12 and Rec12-dependent chiasmata. Interestingly, presence of catalytically-inactive Rec 12 protein (Y98F) enhances the fidelity of distributive segregation. We hypothesize that Rec 12 protein activates a checkpoint that promotes use of the distributive segregation pathway.
Sharif, Wallace D.; Davidson, Mari K.; and Wahls, Wayne P.
"Rec12 (Spo11) Recominase of Fission Yeast Promotes a Backup, Distributive Pathway for Chromosome Segregation in Meiosis I,"
Journal of the Arkansas Academy of Science: Vol. 57
, Article 21.
Available at: http://scholarworks.uark.edu/jaas/vol57/iss1/21