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Meiosis is the unique process in which diploid cells undergo two consecutive divisions to produce haploid daughter cells. It is indispensable for sexual reproduction in all eukaryotic organisms and maintains proper chromosome number through generations. An integral step in the meiotic program is genetic recombination; recombination is required for a successful reductional division. In the yeast Saccharomyces cerevisiae, recombination is initiated by DNA double strand breaks (DSBs) that are created by ten recombination initiation proteins. Similar phenotypes are observed when any of these genes is mutated. This has made the mechanism by which these proteins function to initiate recombination difficult to unravel. One hypothesis is that these proteins form a functional complex for activity, in which all (or most) of them physically interact. The work described in Chapter 2 contributes to understanding the putative DSB-producing recombination initiation complex, suggesting there is substantial flexibility among initiation protein interactions. The results are also consistent with the view that the proteins assemble on the DNA. Studies in Chapter 3 examined the recombination initiation protein interactions during DSB formation in more detail using a novel experimental approach. While the initial experiments using this approach produced unexpected results, the assay is a promising tool for the future.
In addition to creating DSBs, a subset of the initiation proteins perform a second function during early meiosis; they create a recombination initiation signal (RIS) to delay the onset of the reductional division in wild-type cells. Although the signal and the downstream target are well-defined, less is known about how the RIS is transduced to the downstream target. The work in Chapter 4 contributes to defining this transduction, and therefore enhances our understanding of the relationship between the recombination initiation proteins and the reductional division.