Chimeric Saccharomyces cerevisiae Msh6 protein with an Msh3 mispair-binding domain combines properties of both...

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• DNA mismatch repair (MMR) is crucial for maintaining genomic stability in eukaryotes.
• The Msh2-Msh3 and Msh2-Msh6 complexes initiate MMR by recognizing DNA mispairs.
• Conserved residues in prokaryotic MutS homolog suggest Msh6's mispair interaction mechanism, but Msh3 lacks these.

Purpose of the Study:

• To investigate the specific requirements for Msh3's interaction with DNA mispairs.
• To elucidate the role of the mispair-binding domain (MBD) in Msh3's function.
• To understand the functional conservation and differences between Msh2-Msh3 and Msh2-Msh6 complexes.

Main Methods:

• Construction and functional analysis of a chimeric protein swapping Msh6's MBD with Msh3's MBD.
• Assessing mismatch repair activity of the chimeric protein.
• Evaluating genetic interactions with MutL homologs and an Msh2 MBD deletion mutant.

Main Results:

• The chimeric protein, containing Msh3's MBD, was functional for mismatch repair.
• This chimera exhibited Msh3's specific mispair-binding properties.
• Communication between the MBD and ATPase domain is conserved in both Msh2-Msh3 and Msh2-Msh6 complexes.

Conclusions:

• The MBD is a key determinant of Msh3's mispair-binding specificity.
• Msh3-specific behaviors, beyond mispair recognition, are not solely controlled by its MBD.
• Functional communication pathways between domains are conserved across related MMR complexes.