MutSγ-Induced DNA Conformational Changes Provide Insights into Its Role in Meiotic Recombination

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• MutSγ is essential for meiotic recombination and proper chromosome segregation.
• Defects in MutSγ function can lead to aneuploidy, infertility, and birth defects in humans.

Purpose of the Study:

• To investigate the binding affinities and structural interactions of yeast MutSγ (Sc Msh4-Msh5) with DNA substrates modeling recombination intermediates.
• To elucidate the role of Sc Msh4-Msh5 in stabilizing DNA structures during meiosis.

Main Methods:

• Overexpression and isolation of Saccharomyces cerevisiae (Sc) Msh4-Msh5 from Escherichia coli.
• Binding affinity measurements using various DNA substrates (Holliday junctions, overhangs, forks, D-loops).
• Energy-transfer experiments to study DNA structural changes upon protein binding.

Main Results:

• Sc Msh4-Msh5 binds multiple recombination intermediates with nanomolar affinity, showing highest affinity for Holliday junctions (K_d < 0.4 nM).
• Binding modulates DNA structure, displacing single-stranded DNA and stabilizing stacked conformations of junctions.
• Msh4-Msh5 stabilizes open-junction constructs similarly to standard junctions, potentially preventing branch migration.

Conclusions:

• Sc Msh4-Msh5 plays a critical role in stabilizing key DNA structures during meiotic recombination, including pre-junction intermediates.
• This stabilization function is crucial for preventing errors in chromosome segregation and may involve preventing premature branch migration of Holliday junctions.
• The findings provide insights into MutSγ's mechanism in ensuring accurate meiotic recombination and preventing associated genetic disorders.