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Mismatch repair protein hMSH2-hMSH6 recognizes mismatches and forms sliding clamps within a D-loop recombination

Masayoshi Honda1, Yusuke Okuno, Sarah R Hengel

  • 1Department of Biochemistry, University of Iowa, Iowa City, IA 52242.

Proceedings of the National Academy of Sciences of the United States of America
|January 8, 2014
PubMed

Insights

The mismatch repair (MMR) complex hMSH2-hMSH6 recognizes DNA mismatches in recombination intermediates. This recognition is unaffected by other proteins, revealing insights into DNA repair and recombination mechanisms.

Area of Science:

  • Molecular Biology
  • Genetics
  • DNA Repair Mechanisms

Background:

  • Homologous DNA recombination requires high fidelity, involving mismatch repair (MMR) to prevent recombination between divergent sequences.
  • The hMSH2-hMSH6 heterodimer is crucial for postreplicative MMR and heteroduplex DNA rejection, but its mechanism in recombination intermediates was unclear.

Purpose of the Study:

  • To investigate the molecular mechanism of hMSH2-hMSH6 in recognizing mismatches within a D-loop recombination intermediate.
  • To determine if MMR protein interactions differ between D-loop intermediates and linear DNA.

Main Methods:

  • Biochemical assays to study hMSH2-hMSH6 interaction with D-loop structures.
  • Investigated the effect of human replication protein A (HsRPA) and HsRAD51 on mismatch recognition.
  • Analyzed the formation and stability of hMSH2-hMSH6 sliding clamps on D-loops.

Main Results:

  • hMSH2-hMSH6 efficiently recognizes mismatches within D-loop recombination intermediates.
  • HsRPA and HsRAD51 do not inhibit hMSH2-hMSH6 mismatch recognition.
  • ATP-bound hMSH2-hMSH6 sliding clamps form and are stabilized on the D-loop by HsRPA.

Conclusions:

  • hMSH2-hMSH6 exhibits both similarities and differences in mismatch recognition and clamp formation between D-loop intermediates and linear DNA.
  • Findings elucidate the role of MMR proteins in maintaining genome stability during recombination.
Keywords:
homeologous recombinationhomologous recombinationmismatch DNA repairsingle-moleculetotal internal reflection fluorescence microscopy

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