title: Visualization of eukaryotic DNA mismatch repair reveals distinct recognition and repair intermediates.
abstract: DNA mismatch repair (MMR) increases replication fidelity by eliminating mispaired bases resulting from replication errors. In Saccharomyces cerevisiae, mispairs are primarily detected by the Msh2-Msh6 complex and corrected following recruitment of the Mlh1-Pms1 complex. Here, we visualized functional fluorescent versions of Msh2-Msh6 and Mlh1-Pms1 in living cells. We found that the Msh2-Msh6 complex is an S phase component of replication centers independent of mispaired bases; this localized pool accounted for 10%-15% of MMR in wild-type cells but was essential for MMR in the absence of Exo1. Unexpectedly, Mlh1-Pms1 formed nuclear foci that, although dependent on Msh2-Msh6 for formation, rarely colocalized with Msh2-Msh6 replication-associated foci. Mlh1-Pms1 foci increased when the number of mispaired bases was increased; in contrast, Msh2-Msh6 foci were unaffected. These findings suggest the presence of replication machinery-coupled and -independent pathways for mispair recognition by Msh2-Msh6, which direct formation of superstoichiometric Mlh1-Pms1 foci that represent sites of active MMR.
authors: Ludwig Institute for Cancer Research, University of California School of Medicine, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0669, USA.
authors: Hans
authors: H
authors: Hombauer
authors: Christopher S
authors: CS
authors: Campbell
authors: Catherine E
authors: CE
authors: Smith
authors: Arshad
authors: A
authors: Desai
authors: Richard D
authors: RD
authors: Kolodner
mesh_terms: D000818:Animals; D053843:DNA Mismatch Repair; D045643:DNA Repair Enzymes / Q000378:metabolism; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000378:metabolism; D005090:Exodeoxyribonucleases / Q000378:metabolism; D006801:Humans; D051718:MutS Homolog 2 Protein / Q000378:metabolism; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; C094443:G-T mismatch-binding protein; D018809:Proliferating Cell Nuclear Antigen; D005090:Exodeoxyribonucleases; C028450:exodeoxyribonuclease I; D051718:MutS Homolog 2 Protein; D045643:DNA Repair Enzymes