Hop2-Mnd1 functions as a DNA sequence fidelity switch in Dmc1-mediated DNA recombination.

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• Homologous recombination is essential for meiosis, ensuring proper chromosome segregation and genetic diversity.
• The recombinase Dmc1 mediates genetic exchange between homologous chromosomes, capable of processing mismatched DNA.
• The Hop2-Mnd1 complex is known to facilitate Dmc1 activity.

Purpose of the Study:

• To elucidate the regulatory role of the Hop2-Mnd1 complex in controlling substrate selection during meiotic recombination.
• To understand the mechanistic basis by which Hop2-Mnd1 maintains recombination fidelity.

Main Methods:

• Isolation and characterization of Hop2-Mnd1 separation-of-function variants.
• Biochemical assays to examine Dmc1 activity with various DNA substrates in the presence of Hop2-Mnd1.
• Analysis of Dmc1 filament formation and DNA binding activities of Hop2-Mnd1 variants.

Main Results:

• Hop2-Mnd1 upregulates Dmc1 activity on fully homologous and mismatched DNA substrates.
• Hop2-Mnd1 inhibits DNA strand exchange between substrates with only microhomology.
• Suppression of illegitimate recombination by Hop2-Mnd1 depends on its interaction with Dmc1 filaments, not its DNA binding capability.

Conclusions:

• Hop2-Mnd1 plays a crucial regulatory role in restricting Dmc1's substrate specificity during meiosis.
• The interaction of Hop2-Mnd1 with Dmc1 filaments is critical for preventing aberrant recombination events.
• This study provides key mechanistic insights into how Hop2-Mnd1 ensures the fidelity of meiotic recombination.