Investigating the spatial regulation of meiotic recombination in S. cerevisiae

In order for a species to engage in and reap the evolutionary benefits of sexual reproduction, a subset of cells in each individual must undergo a complex ordeal known as meiosis—a specialised cell division. By halving the genome content and “shuffling the deck”, meiosis generates genetically diverse haploid gametes (eggs, sperm) or spores from diploid cells. Such a monumental task is by no means easy or risk free: during the meiotic programme, cells intentionally damage their own genomes through widespread induction of DNA double-strand breaks (DSBs) in order to initiate homologous recombination—a DNA-repair process—and subsequent crossover (CO) formation. The success of meiosis is, however, not left up to chance. Rather, a complicated web of regulation acts at multiple stages to ensure this dangerous tradeoff pays dividends. Notably, the spatial pattern of meiotic recombination across the genome is complex and non-random. Whilst ultimately stochastic in nature, recombination events within any given meiotic cell display relatively even distributions along each chromosome—a phenomenon mediate by processes of “interference” acting at two key stages in meiosis: DSB and CO formation. Despite wide ranging historical observation, relatively little is known about how either form of interference is accomplished. Genome-wide mapping of recombination within S. cerevisiae has, however, provided a unique opportunity to investigate the underlying mechanisms. By computationally and mathematically analysing genome-wide data, work presented throughout this thesis seeks to: (i) investigate CO distribution and CO interference within various DNA damage response and DNA repair mutants (Tel1ATM, Mec1ATR, Rad24, Msh2) (Chapter 2) (ii) develop novel approaches to DSB mapping (Chapter 3) (iii) characterise the hyperlocal regulation of DSB formation (Chapter 3) and (iv) examine the mechanics of DSB interference (Chapter 4). Moreover, widely applicable simulation platforms for investigating DSB and CO formation have been developed (Chapter 2, 4). Collectively, this thesis further elucidates the mechanisms that underpin the spatial regulation of meiotic recombination in S. cerevisiae.