Mei5-Sae3 stabilizes both active and inactive forms of Dmc1 filaments independently of its impact on ATP hydrolysis

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Meiosis involves DNA recombination, crucial for genetic diversity.
• The protein Dmc1 plays a key role in homologous recombination during meiosis.
• Meiosis-specific protein complex Mei5-Sae3 regulates Dmc1 activity.

Purpose of the Study:

• To investigate how Mei5-Sae3 stabilizes Dmc1 filaments.
• To understand the role of nucleotide cofactors in Dmc1 filament formation and stability.
• To elucidate the relationship between Dmc1's ATPase activity and its recombinogenic functions.

Main Methods:

• In vitro biochemical assays to study Dmc1 filament formation and stabilization.
• Analysis of Dmc1's ATPase activity in the presence of Mei5-Sae3 and different nucleotide cofactors.
• Characterization of a gain-of-function Dmc1 mutant (Dmc1-E157D).

Main Results:

• Mei5-Sae3 stabilizes Dmc1 filaments in both active (ATP-bound) and inactive (ADP-bound) conformations.
• Unlike other stabilizers, Mei5-Sae3 does not inhibit ATP hydrolysis in active filaments.
• Mei5-Sae3 can increase Dmc1's ATP hydrolysis rate.
• The Dmc1-E157D mutant stabilizes active filaments but has defective ATPase activity.

Conclusions:

• Mei5-Sae3's filament stabilization mechanism is distinct and does not solely rely on altering the ATP hydrolysis cycle.
• Dmc1's DNA repair functions (homology search and strand exchange) are independent of its ATP hydrolysis activity.
• These findings provide a deeper understanding of the regulation of meiotic recombination.