Proliferating cell nuclear antigen and Msh2p-Msh6p interact to form an active mispair recognition complex

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H Flores-Rozas1, D Clark, R D Kolodner

  • 1Ludwig Institute for Cancer Research, University of California-San Diego School of Medicine, La Jolla, California, USA.

Nature Genetics
|November 4, 2000
PubMed

Insights

Proliferating cell nuclear antigen (PCNA) interacts with Msh2p-Msh6p, aiding DNA mismatch repair (MMR). This interaction is crucial for recognizing DNA base mispairs, suggesting PCNA

Area of Science:

  • Molecular biology
  • Genetics
  • Biochemistry

Background:

  • Proliferating cell nuclear antigen (PCNA) is essential for DNA mismatch repair (MMR).
  • The precise role of PCNA in the early stages of MMR remains biochemically undefined.
  • PCNA is known to interact with key MMR proteins like Msh2p and MLH1.

Purpose of the Study:

  • To elucidate the biochemical mechanism of PCNA's involvement in DNA mismatch repair.
  • To investigate the interaction between PCNA and the Msh2p-Msh6p complex.
  • To determine if PCNA directly participates in DNA mispair recognition.

Main Methods:

  • Investigated the interaction between PCNA and Msh2p-Msh6p using specific binding sites.
  • Utilized mutations in Msh6p to disrupt the PCNA-binding site and observed the phenotypic consequences.
  • Employed mutant PCNA proteins (pol30 alleles) defective in MMR to assess their interaction with Msh2p-Msh6p and impact on mispair binding.

Main Results:

  • Identified a specific PCNA-binding site in Msh6p that mediates the interaction with PCNA.
  • A mutation eliminating this binding site in Msh6p resulted in a mutator phenotype and impaired PCNA interaction.
  • PCNA association with Msh2p-Msh6p enhanced the binding of this complex to mismatched DNA.
  • MMR-defective mutant PCNA proteins failed to interact with Msh2p-Msh6p and did not stimulate mispair binding.

Conclusions:

  • PCNA directly functions in the recognition of DNA base mispairs during MMR.
  • The interaction between PCNA and Msh2p-Msh6p is critical for efficient mispair recognition.
  • Mispair recognition likely involves a higher-order complex including Msh2p-Msh6p and PCNA.

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