Human AP endonuclease inefficiently removes abasic sites within G4 structures compared to duplex DNA

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Genome stability is crucial for preventing diseases.
• Non-canonical DNA structures can impede DNA repair.
• G-quadruplex (G4) DNA is a non-canonical structure formed by guanine-rich sequences.

Purpose of the Study:

• To develop a FRET-based method to detect G4 DNA in damaged DNA.
• To investigate the impact of abasic sites within G4 structures on DNA repair enzyme activity.

Main Methods:

• Development of a Förster Resonance Energy Transfer (FRET)-based assay.
• Monitoring G4 DNA presence in single-stranded and double-stranded DNA containing lesions.
• Assessing human AP endonuclease activity on damaged DNA within G4 structures.

Main Results:

• The study successfully developed a FRET-based approach to monitor G4 DNA.
• Abasic sites within G4 structures significantly reduce human AP endonuclease efficiency.
• This reduction is primarily due to decreased enzyme activity, not binding affinity.

Conclusions:

• The FRET-based method provides a novel tool for studying DNA repair at non-canonical structures.
• G4 structures containing abasic sites pose a challenge to DNA repair pathways.
• Impaired repair at these sites may contribute to mutagenesis and disease.