ATP hydrolysis Promotes Duplex DNA Release by the RecA Presynaptic Complex

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Homologous recombination is crucial for DNA repair and genome stability.
• Escherichia coli RecA protein is central to this process, forming filaments on DNA.
• The role of ATP in RecA's function remains incompletely understood.

Purpose of the Study:

• To investigate the influence of ATP on RecA presynaptic complex interactions with homologous double-stranded DNA (dsDNA).
• To elucidate the specific mechanisms by which ATP affects DNA strand exchange in homologous recombination.

Main Methods:

• Utilized single-molecule studies to observe RecA presynaptic complex behavior.
• Compared RecA interactions with dsDNA in the presence of ATP versus a non-hydrolyzable ATP analog (ATPγS).
• Analyzed initial DNA sampling, stabilization of pairing intermediates, and dissociation rates.

Main Results:

• Initial sampling of heterologous dsDNA by RecA complexes is independent of ATP hydrolysis.
• RecA stabilizes DNA pairing intermediates in discrete three-base steps, with similar energetics in ATP and ATPγS.
• Dissociation rates of paired intermediates are approximately fourfold higher with ATP compared to ATPγS.

Conclusions:

• ATP plays a critical, previously unrecognized role in promoting the turnover of captured dsDNA intermediates during homologous recombination.
• This ATP-dependent turnover facilitates RecA's progression in aligning homologous sequences in the early stages of recombination.
• Understanding ATP's role provides new insights into the regulation of DNA repair pathways.