of Work: Rare DNA synthesis errors are corrected by post-replication DNA mismatch repair (MMR). Loss of MMR increases mutation rates and leads to cancer, and mutations in certain MMR genes result in infertility in model organisms. The goals of this project are to understand the biochemistry and genetics of MMR in normal eukaryotic cells, and how mutations in MMR genes lead to environmentally associated human diseases. This year we investigated the properties of the yeast Msh2-Msh6 and Mlh1-Pms1 heterodimers that are essential for the early steps in MMR. Based on the structures of the homologous bacterial proteins, we made a number of mutants to test the importance of ATPase activity and DNA binding to MMR. We provided evidence that all four proteins have intrinsic ATPase activities and hypothesize that they operate in the order Msh6, Msh2, Mlh1 then Pms1. We investigated the contributions of various amino acids in Msh2 and Msh6 to binding to both the mismatched bases and to the DNA backbone. We demonstrated that Mlh1-Pms1 also binds to DNA, with preference for double stranded over single stranded DNA, with very high affinity and in an apparently cooperative manner. The biochemical properties were compared to genetic results indicating that ATPase and DNA binding are essential for MMR activity in vivo. These studies have important implications for the participation of these proteins in MMR, meiotic recombination and transcription-coupled excision repair. They are also important for understanding, the risk posed to individuals in the population by exposure to DNA damaging agents and the molecular basis for the initiating events in cancer and its subsequent treatment.
| Burgers, Peter M J; Kunkel, Thomas A (2017) Eukaryotic DNA Replication Fork. Annu Rev Biochem 86:417-438 |
| Kunkel, Thomas A; Erie, Dorothy A (2015) Eukaryotic Mismatch Repair in Relation to DNA Replication. Annu Rev Genet 49:291-313 |
| St Charles, Jordan A; Liberti, Sascha E; Williams, Jessica S et al. (2015) Quantifying the contributions of base selectivity, proofreading and mismatch repair to nuclear DNA replication in Saccharomyces cerevisiae. DNA Repair (Amst) 31:41-51 |
| Liu, Songbai; Lu, Guojun; Ali, Shafat et al. (2015) Okazaki fragment maturation involves ?-segment error editing by the mammalian FEN1/MutS? functional complex. EMBO J 34:1829-43 |
| Makarova, Alena V; Nick McElhinny, Stephanie A; Watts, Brian E et al. (2014) Ribonucleotide incorporation by yeast DNA polymerase ?. DNA Repair (Amst) 18:63-7 |
| Schaetzlein, Sonja; Chahwan, Richard; Avdievich, Elena et al. (2013) Mammalian Exo1 encodes both structural and catalytic functions that play distinct roles in essential biological processes. Proc Natl Acad Sci U S A 110:E2470-9 |
| Sparks, Justin L; Chon, Hyongi; Cerritelli, Susana M et al. (2012) RNase H2-initiated ribonucleotide excision repair. Mol Cell 47:980-6 |
| Lujan, Scott A; Williams, Jessica S; Pursell, Zachary F et al. (2012) Mismatch repair balances leading and lagging strand DNA replication fidelity. PLoS Genet 8:e1003016 |
| Kunkel, Thomas A (2011) Balancing eukaryotic replication asymmetry with replication fidelity. Curr Opin Chem Biol 15:620-6 |
| Jirawatnotai, Siwanon; Hu, Yiduo; Michowski, Wojciech et al. (2011) A function for cyclin D1 in DNA repair uncovered by protein interactome analyses in human cancers. Nature 474:230-4 |
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