title: Multiple factors insulate Msh2-Msh6 mismatch repair activity from defects in Msh2 domain I.
abstract: DNA mismatch repair (MMR) is a highly conserved mutation avoidance mechanism that corrects DNA polymerase misincorporation errors. In initial steps in MMR, Msh2-Msh6 binds mispairs and small insertion/deletion loops, and Msh2-Msh3 binds larger insertion/deletion loops. The msh2Δ1 mutation, which deletes the conserved DNA-binding domain I of Msh2, does not dramatically affect Msh2-Msh6-dependent repair. In contrast, msh2Δ1 mutants show strong defects in Msh2-Msh3 functions. Interestingly, several mutations identified in patients with hereditary non-polyposis colorectal cancer map to domain I of Msh2; none have been found in MSH3. To understand the role of Msh2 domain I in MMR, we examined the consequences of combining the msh2Δ1 mutation with mutations in two distinct regions of MSH6 and those that increase cellular mutational load (pol3-01 and rad27). These experiments reveal msh2Δ1-specific phenotypes in Msh2-Msh6 repair, with significant effects on mutation rates. In vitro assays demonstrate that msh2Δ1-Msh6 DNA binding is less specific for DNA mismatches and produces an altered footprint on a mismatch DNA substrate. Together, these results provide evidence that, in vivo, multiple factors insulate MMR from defects in domain I of Msh2 and provide insights into how mutations in Msh2 domain I may cause hereditary non-polyposis colorectal cancer.
authors: Department of Biochemistry, School of Medical and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY 14214, USA.
authors: Charanya
authors: C
authors: Kumar
authors: Sarah C
authors: SC
authors: Piacente
authors: Justin
authors: J
authors: Sibert
authors: Andrew R
authors: AR
authors: Bukata
authors: Jaime
authors: J
authors: O'Connor
authors: Eric
authors: E
authors: Alani
authors: Jennifer A
authors: JA
authors: Surtees
mesh_terms: D001483:Base Sequence; D015153:Blotting, Western; D018983:DNA Footprinting; D053843:DNA Mismatch Repair; D004271:DNA, Fungal / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D003850:Deoxyribonuclease I / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D008969:Molecular Sequence Data; D051718:MutS Homolog 2 Protein / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D017434:Protein Structure, Tertiary; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D012689:Sequence Homology, Nucleic Acid
chemical_list: D004271:DNA, Fungal; D004268:DNA-Binding Proteins; C098790:MSH6 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D003850:Deoxyribonuclease I; C489751:MSH2 protein, S cerevisiae; D051718:MutS Homolog 2 Protein