(CAG)(n)-hairpin DNA binds to Msh2-Msh3 and changes properties of mismatch recognition

Nat Struct Mol Biol. 2005 Aug;12(8):663-70. doi: 10.1038/nsmb965. Epub 2005 Jul 17.


Cells have evolved sophisticated DNA repair systems to correct damaged DNA. However, the human DNA mismatch repair protein Msh2-Msh3 is involved in the process of trinucleotide (CNG) DNA expansion rather than repair. Using purified protein and synthetic DNA substrates, we show that Msh2-Msh3 binds to CAG-hairpin DNA, a prime candidate for an expansion intermediate. CAG-hairpin binding inhibits the ATPase activity of Msh2-Msh3 and alters both nucleotide (ADP and ATP) affinity and binding interfaces between protein and DNA. These changes in Msh2-Msh3 function depend on the presence of A.A mispaired bases in the stem of the hairpin and on the hairpin DNA structure per se. These studies identify critical functional defects in the Msh2-Msh3-CAG hairpin complex that could misdirect the DNA repair process.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenosine Diphosphate / metabolism
  • Adenosine Triphosphate / metabolism
  • Animals
  • Base Pair Mismatch / genetics*
  • Base Pairing
  • Base Sequence
  • DNA / metabolism*
  • DNA Repair / genetics*
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Electrophoretic Mobility Shift Assay
  • Mice
  • Mice, Transgenic
  • Models, Genetic*
  • Molecular Sequence Data
  • MutS Homolog 2 Protein
  • MutS Homolog 3 Protein
  • Protein Binding
  • Proteins / genetics
  • Proteins / metabolism*
  • Proto-Oncogene Proteins / genetics
  • Proto-Oncogene Proteins / metabolism*
  • Trinucleotide Repeat Expansion / genetics*


  • DNA-Binding Proteins
  • Msh3 protein, mouse
  • MutS Homolog 3 Protein
  • Proteins
  • Proto-Oncogene Proteins
  • Adenosine Diphosphate
  • Adenosine Triphosphate
  • DNA
  • Msh2 protein, mouse
  • MutS Homolog 2 Protein