The genetic regulation of genome stability and the mechanism of mitotic recombination.
The mechanisms by which eukaryotic cells maintain genome stability. Most of our studies are done using the yeast Saccharomyces cerevisiae. We have identified a number of mutants that have elevated levels of genetic instability and we are using DNA microarrays and high-throughput DNA sequencing to characterize the types of genetic alterations observed in these strains. For example, we have shown that yeast strains with low levels of DNA polymerase alpha (one of the replicative DNA polymerases) have very high levels of deletions, duplications, and chromosome losses. Many of the deletions and duplications have retrotransponsons at their breakpoints. Our second area of interest is mitotic recombination. We have developed methods of mapping mitotic exchanges with high resolution (about 1 kb) throughout the genome. Using these methods, we have identified mitotic recombination "hotspots." Two of these hotspots are defined by pairs of inverted retrotransposons. We have thus far mapped spontaneous mitotic recombination events in about 10% of the genome and our goal is to map spontaneous exchanges throughout the genome. We have also done genome-wide mapping of recombination events induced by gamma rays and by ultraviolet light. These experiments represent the first analysis of radiation-induced recombination events throughout the genome.