Meiotic recombination is initiated by programmed DNA double strand breaks (DSBs) catalysed by the evolutionary conserved Spo11 protein and associated factors. In the yeast S. cerevisiae, the DSB sites are non-randomly distributed along the chromosomes: certain genomic regions have higher propensity to form DSBs than others, explaining the expansion and contraction of the genetic versus physical maps. The cis- and trans-acting factors that select the DSB sites in the chromatin architecture and make a particular region 'hot' or ‘cold’ are not elucidated. The aim of this project is to decipher the role of histone modifications and other types of chromatin structural elements that orchestrate the recruitment and/or the cleavage activity of the DSB-forming machinery along the chromosomes. In wild type and a panel of mutant strains defective in histone modifying and remodeling activities, we will assess the spatial and temporal dynamics of the histone modification landscape upon DSB formation on the genome-wide scale using the ChIP-Chip, ChIP-Seq, Re-ChIP and FAIRE techniques. The chromatin-state of hot and cold regions will be mapped both at natural and ectopic hot/cold spots using the Gal4BD-Spo11 protein that is suitable for the targeted stimulation of recombination at naturally cold but permissive (warmable) regions but not at other cold (refractory) regions located near centromeres and telomeres. Successful completion of these studies will (1) include the construction of complete, genome-wide maps of meiotic chromatin-state in wild type and mutant yeast strains, and (2) improve our knowledge on how Spo11-dependent DSB formation is differentially controlled in relation to the chromatin context and coupled to homologous recombination, and differ from other sources of DNA lesions (in particular replication fork collapse) also leading to genomic rearrangements by homologous recombination.
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