An Msh3 ATPase domain mutation has no effect on MMR function

Yasmin Edwards

doi:10.1186/s13104-017-2939-4

Abstract

ObjectiveTo demonstrate that the Msh3 ATPase domain is required for DNA mismatch repair and tumor suppression in a murine model.ResultsThe DNA mismatch repair proteins are members of the ABC family of ATPases. ATP binding and hydrolysis regulates their mismatch repair function. In the current study, a mouse model was generated harboring a glycine to aspartic acid residue change in the Walker A motif of the ATPase domain of Msh3. Impaired ATP mediated release of the Msh2-Msh3GD/GD complex from it’s DNA substrate in vitro confirmed the presence of an ATPase defect. However, the mismatch repair function of the protein was not significantly affected. Therefore, mutation of a critical residue within the ATPase domain of Msh3 did not preclude mismatch repair at the genomic sequences tested. Indicating that Msh3 mediated mismatch function is retained the absence of a functional ATPase domain.

Highlights

ResultsThe DNA mismatch repair proteins are members of the ABC family of ATPases
DNA mismatch repair (MMR) proteins target and mediate repair of DNA polymerase errors of replication and signal the DNA damage response [1]
Msh2‐Msh3GD/GD impaired ATP mediated DNA substrate release Dissociation of the Msh2-MutS homologue 3 (Msh3)+/+ and Msh2-Msh3GD/GD complexes from the DNA substrate was observed upon addition of increasing concentrations of cold competitor to the binding reactions, confirming the specificity of binding (Fig. 1a)

Summary

Results

Msh2‐Msh3GD/GD impaired ATP mediated DNA substrate release Dissociation of the Msh2-Msh3+/+ (positive control) and Msh2-Msh3GD/GD complexes from the DNA substrate was observed upon addition of increasing concentrations of cold competitor to the binding reactions, confirming the specificity of binding (Fig. 1a). TG27 and D7Mit dinucleotide markers, the highest instability was observed in the Msh2-Msh3−/− animals, 15 and 9% respectively, with p values of 0.03 and 0.02 compared to wild type (Table 1). Comparison of MSI negative tumors from wild type animals to the tumor numbers in the Msh2-Msh3GD/GD animals proved significant using the Fisher exact test, p value = 0.03. MSI in tumors was similar to the somatic MSI, with greater instability at the mononucleotide marker in the Msh2-Msh3GD/GD tumors and at the dinucleotide marker in the Msh2-Msh3−/− tumors. These numbers were not significant (Table 1). Wild type animals began to succumb later, at 16th months (Fig. 2c)

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