Elucidating EXO1’s Key Interactions with MutS in DNA Mismatch Repair Via Atomic Force Microscopy

<span style="font-weight: 400;">DNA mismatch repair (MMR) is a highly conserved pathway that ensures genomic stability by correcting errors and excising mismatched base pairs in newly synthesized DNA. Even after proofreading by DNA polymerases, errors occur in DNA replication at a rate of 1 in 100,000 nucleotides. In a genome of six billion base pairs, this error rate leads to ~120,000 replication errors per cell division. Uncorrected replication errors can lead to harmful mutations that drive cancer and other genetic disorders. These errors are exemplified in Lynch Syndrome, a hereditary cancer predisposition caused by mutations in core MMR proteins. Two key proteins in the MMR pathway are MutS, which recognizes the site of the mismatch, and EXO1, an exonuclease that excises the erroneous base pair. This work will specifically characterize EXO1's interactions with MutS in the MMR pathway using atomic force microscopy (AFM), which will elucidate novel conformational information about EXO1-MutS complexes through quantitative analyses involving volumes and heights of complexes. These findings will contribute to a deeper understanding of EXOI's mechanistic role in MMR, which may have implications for therapeutic strategies targeting MMR-deficient cancers.</span>