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Saccharomyces cerevisiae MSH2-MSH3 and MSH2-MSH6 complexes display distinct requirements for DNA binding domain I in

Susan D Lee1, Jennifer A Surtees, Eric Alani

  • 1Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853-2703, USA.

Journal of Molecular Biology
|December 13, 2006
PubMed

Insights

A specific mutation in MSH2 (mismatch repair protein) separates functions of MSH2-MSH3 and MSH2-MSH6 complexes. This reveals distinct roles for MSH2 domain I in DNA mismatch repair specificity.

Area of Science:

  • Molecular Biology
  • Genetics
  • DNA Repair Mechanisms

Background:

  • Eukaryotic DNA mismatch repair (MMR) utilizes distinct protein complexes, MSH2-MSH6 and MSH2-MSH3, to address different types of DNA mismatches.
  • MSH2-MSH6 typically repairs base-base and small insertion/deletion mismatches, while MSH2-MSH3 handles larger insertion/deletion mismatches.

Purpose of the Study:

  • To investigate the functional role of Domain I of MSH2 in the distinct MMR activities of MSH2-MSH3 and MSH2-MSH6 complexes.
  • To elucidate the specific contributions of MSH2 and MSH3 Domain I to DNA mismatch recognition and binding specificity.

Main Methods:

  • Utilized a specific msh2Delta1 mutation, lacking MSH2's conserved mismatch recognition Domain I, to assess MMR and recombination functions.
  • Employed genetic assays and biochemical analyses to evaluate the DNA binding specificity and functional impact of Domain I in MSH2-MSH3 and MSH2-MSH6.

Main Results:

  • The msh2Delta1 mutation resulted in near wild-type MMR and recombination activity for MSH2-MSH6 but a complete defect in MSH2-MSH3 functions.
  • Biochemical assays indicated that MSH2 Domain I contributes non-specific DNA binding, whereas MSH3 Domain I is crucial for mismatch binding specificity and suppression of non-specific binding.
  • These findings highlight differential requirements for MSH2 Domain I in MSH2-MSH3 versus MSH2-MSH6-mediated DNA repair.

Conclusions:

  • Domain I of MSH2 plays distinct roles in the MMR pathways mediated by MSH2-MSH3 and MSH2-MSH6.
  • The protein-DNA interactions governing MSH2-MSH3 mismatch binding differ significantly from those of MSH2-MSH6, particularly concerning the involvement of Domain I.

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