Multiple factors insulate Msh2-Msh6 mismatch repair activity from defects in Msh2 domain I

J Mol Biol. 2011 Aug 26;411(4):765-80. doi: 10.1016/j.jmb.2011.06.030. Epub 2011 Jun 25.

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.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Base Sequence
  • Blotting, Western
  • DNA Footprinting
  • DNA Mismatch Repair*
  • DNA, Fungal / genetics
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Deoxyribonuclease I / metabolism
  • Electrophoretic Mobility Shift Assay
  • Molecular Sequence Data
  • MutS Homolog 2 Protein / genetics
  • MutS Homolog 2 Protein / metabolism*
  • Mutation
  • Protein Structure, Tertiary
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Sequence Homology, Nucleic Acid

Substances

  • DNA, Fungal
  • DNA-Binding Proteins
  • MSH6 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Deoxyribonuclease I
  • MSH2 protein, S cerevisiae
  • MutS Homolog 2 Protein