Highly conserved mismatch repair (MMR) systems have been identified in organisms ranging from bacteria to humans that recognize and repair base pair and small insertion/deletion mismatches that arise as the result of DNA replication errors, DNA damage, and genetic recombination. In humans, mutations in MMR genes have been correlated to both an increased mutation rate and a predisposition to a hereditary form of colorectal cancer (HNPCC). HNPCC has a high cure rate if detected early, underscoring the importance of obtaining new mechanistic understandings of mismatch repair and new diagnostic tools.
My current work is focused on understanding how MMR proteins identify mismatches and signal downstream factors during DNA replication and repair, and the role of genetic background in determining the penetrance of MMR mutations. 1. We are currently analyzing the behavior of single MSH and MLH complexes interacting with DNA using total internal fluorescence microscopy. These studies are aimed at distinguishing between competing models for how MSH and MLH proteins signal downstream steps in MMR. In addition, my lab is using genetic and biochemical approaches to test interactions between MMR components and the SGS1 helicase to prevent recombination between divergent DNA sequences. 2. My group is using deep sequencing technologies to examine genome-wide mutation accumulation in wild-type and MMR mutants. This work will allow us to identify mutational hotspots in yeast and humans and provide information that should help cancer researchers distinguish mutations critical for transformation to a cancer state from those that occur after transformation. 3. We are using molecular evolution approaches to study incompatibilities in MMR. This work offers new tools to identify genetic interactions in DNA repair pathways, with the overall goal of understanding the effect of genetic background on cancer susceptibility.
My laboratory has been funded since 1995 by GM53085. A nice aspect of our current work is that it involves long-term collaborations with a single molecule biophysicist (Eric Greene, Ilya Finkelstein), and population geneticists (Charles Aquadro). The result of these efforts is a novel set of interdisciplinary approaches to study the roles of MMR in maintaining genome stability.