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Dissociation of mismatch recognition and ATPase activity by hMSH2-hMSH3

T Wilson1, S Guerrette, R Fishel

  • 1Genetics and Molecular Biology Program, Department of Microbiology and Immunology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.

The Journal of Biological Chemistry
|July 27, 1999
PubMed

Insights

The human MutS homolog 2-MutS homolog 3 (hMSH2-hMSH3) complex repairs DNA insertion/deletion loops. Mismatch recognition is necessary but not sufficient to activate its ATPase for repair.

Area of Science:

  • Molecular Biology
  • DNA Repair Mechanisms
  • Protein Biochemistry

Background:

  • The MSH2-MSH3 complex plays a crucial role in DNA mismatch repair, specifically targeting insertion/deletion loops.
  • Understanding the biochemical mechanisms governing MSH2-MSH3's specificity and activity is vital for comprehending genome stability.

Purpose of the Study:

  • To investigate the biochemical basis of hMSH2-hMSH3's specificity in repairing insertion/deletion loops.
  • To characterize the mispair binding and ATPase activity of the hMSH2-hMSH3 complex.

Main Methods:

  • Biochemical assays to characterize protein-DNA interactions.
  • ATPase activity assays to measure ADP/ATP exchange.
  • Analysis of hMSH2-hMSH3 binding to varying lengths of insertion/deletion loops.

Main Results:

  • hMSH2-hMSH3 efficiently repairs insertion/deletion loops up to 13 nucleotides.
  • ATPase activity is regulated by mismatch-stimulated ADP to ATP exchange, inducing conformational changes.
  • Strong binding to a 24-nucleotide loop occurred without triggering ADP/ATP exchange, indicating mismatch recognition alone is insufficient for activation.

Conclusions:

  • hMSH2-hMSH3 acts as an adenosine nucleotide-regulated molecular switch for DNA mismatch repair.
  • Activation of the hMSH2-hMSH3 ATPase requires specific nucleotide mismatches, not just binding.
  • These findings elucidate the regulatory mechanism controlling MSH2-MSH3's function in maintaining genomic integrity.

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