Abstract 1500: Exonuclease 1 recruitment in human DNA mismatch repair

Abstract DNA repair is the process by which cells identify and correct mutations present within the genome. These correction mechanisms maintain genomic stability and prevent the development of cancer. The DNA mismatch repair (MMR) pathway identifies and corrects small insertions, deletions, and misincorporations that arise within the genome as a result of errors during DNA replication. The process by which MMR corrects these mispairs includes recognition of the mispair by the MutS complex, recruitment of the MutL complex to the mutation site, excision of the mispair, and gap filling by DNA polymerase. MMR is also critical for inducing apoptosis after chemically induced mispairs, such as those from alkylating agents. Exonuclease 1 is the protein responsible for the excision step of MMR. However, MMR can occur in the absence of Exo-1. Thus, MMR can be separated into two subpathways: Exo1-dependent MMR and Exo1-independent MMR. In Exo1-dependent MMR Exo-1 binds to both the MutS complex and MutL complex. The MutL interaction is facilitated by an MLH1 interaction peptide (MIP) box. We recently identified a Msh2 interaction peptide (SHIP) box in yeast Exo1. This project aims to understand how MIP and putative human SHIP box motifs influence human Exo1 recruitment to MMR processes. We have created mutations within the predicted binding domains of human Exo1. We observe changes in localization of Exo1-mutant proteins within the cell, suggesting that changes in the overall MMR process may be present. We also observe changes in MMR-mediated apoptotic response when a subset of Exo1-mutations are expressed in the presence of endogenous wildtype Exo1, indicating a potential for a dominant negative interaction. Our ongoing studies are expected to shed more light upon how the changes in these interactions may affect the human MMR process and overall genomic stability. Citation Format: Breanna Knicely. Exonuclease 1 recruitment in human DNA mismatch repair [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1500.