Redox-driven ADAR1 activation promotes Okazaki fragment maturation and DNA replication integrity.

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Okazaki fragment maturation is crucial for DNA replication fidelity.
• Error-prone primase can introduce mismatched RNA primers during lagging strand synthesis.
• Mechanisms for correcting these mismatched primers remain largely unknown.

Purpose of the Study:

• To elucidate the mechanism by which mismatched RNA primers are corrected during Okazaki fragment maturation.
• To investigate the role of reactive oxygen species (ROS) and ADAR1 in this process.

Main Methods:

• In vitro biochemical assays to study ADAR1 activity and dimerization.
• Cellular assays to assess Okazaki fragment maturation and DNA damage.
• Analysis of RNA editing and primer degradation in response to ROS levels.

Main Results:

• Physiological ROS levels induce ADAR1 dimerization and adenosine-to-inosine (A-to-I) RNA editing at replication forks.
• A-to-I editing enhances the degradation of mismatched primers by RNase H2, particularly on d(T+C)-rich centromeric DNA.
• Disruption of ADAR1 oxidation leads to increased DNA damage, including unligated Okazaki fragments and double-strand breaks.

Conclusions:

• ROS-mediated ADAR1 oxidation and subsequent A-to-I RNA editing safeguard lagging-strand synthesis.
• This pathway ensures efficient Okazaki fragment maturation and maintains replication fork stability.
• The findings reveal a novel link between redox signaling, RNA editing, and DNA replication integrity.