Abstract
The fission yeast Schizosaccharomyces pombe Rec12 protein, the homolog of Spo11 in other organisms, initiates meiotic recombination by creating DNA double-strand breaks (DSBs) and becoming covalently linked to the DNA ends of the break. This protein–DNA linkage has previously been detected only in mutants such as rad50S in which break repair is impeded and DSBs accumulate. In the budding yeast Saccharomyces cerevisiae, the DSB distribution in a rad50S mutant is markedly different from that in wild-type (RAD50) meiosis, and it was suggested that this might also be true for other organisms. Here, we show that we can detect Rec12-DNA linkages in Sc. pombe rad50+ cells, which are proficient for DSB repair. In contrast to the results from Sa. cerevisiae, genome-wide microarray analysis of Rec12-DNA reveals indistinguishable meiotic DSB distributions in rad50+ and rad50S strains of Sc. pombe. These results confirm our earlier findings describing the occurrence of widely spaced DSBs primarily in large intergenic regions of DNA and demonstrate the relevance and usefulness of fission yeast studies employing rad50S. We propose that the differential behavior of rad50S strains reflects a major difference in DSB regulation between the two species—specifically, the requirement for the Rad50-containing complex for DSB formation in budding yeast but not in fission yeast. Use of rad50S and related mutations may be a useful method for DSB analysis in other species.
Highlights
Sexual reproduction involves the fusion of two gametes to create diploid offspring with equal genetic contributions from each parent
To better understand where recombination occurs and why it occurs there, we investigated in fission yeast the initiating step in recombination—formation of DNA double-strand breaks (DSBs)
Our results show that the genomic distributions of S. pombe meiotic DSBs in these strains are indistinguishable (Figures 1, 3, 4, S2, S5, and [5,12])
Summary
Sexual reproduction involves the fusion of two gametes to create diploid offspring with equal genetic contributions from each parent. To maintain the proper chromosome number (ploidy), it is necessary for the gametes to be haploid. This is achieved via meiosis, where a single round of DNA replication is followed by two nuclear divisions: in the first division, homologous chromosomes (homologs) separate from each other (Meiosis I), followed in the second division by the separation of sister chromatids (Meiosis II). Before the first meiotic division, homologs become aligned and intimately synapsed [1] During this time meiotic recombination is initiated by DNA double-strand breaks (DSBs), introduced by Spo in the budding yeast Saccharomyces cerevisiae or its ortholog Rec in the fission yeast Schizosaccharomyces pombe [2]. Resolution of the joint DNA molecules can result in a reciprocal exchange of genetic information, called a crossover, which aids proper homolog segregation at Meiosis I
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