APE2 promotes DNA damage response pathway from a single-strand break

Area of Science:

• Molecular Biology
• Cellular Biology
• Genetics

Background:

• DNA single-strand breaks (SSBs) are a common DNA damage type crucial for genome stability.
• Unrepaired SSBs are linked to cancer and neurodegenerative diseases.
• The mechanism of unrepaired SSB recognition by the DNA damage response (DDR) pathway is not well understood.

Purpose of the Study:

• To investigate the mechanism by which unrepaired SSBs are recognized and trigger DDR.
• To elucidate the role of APE2 protein in SSB signaling and repair.

Main Methods:

• Utilized a Xenopus high-speed supernatant (HSS) system with a plasmid-based site-specific SSB structure.
• Investigated the involvement of ATR, ATRIP, TopBP1, Rad9, Claspin, APE2, and PCNA proteins.
• Analyzed protein-protein interactions, including a novel APE2 Zf-GRF and PCNA C-terminus interaction.

Main Results:

• Demonstrated ATR-dependent checkpoint signaling activation by a defined SSB structure.
• Identified APE2 and canonical checkpoint proteins as essential for SSB signaling.
• Showed that APE2-PCNA interaction via APE2 Zf-GRF facilitates DNA end resection, checkpoint assembly, and DDR.
• Confirmed that ATR DDR is essential for SSB repair.

Conclusions:

• APE2 plays a critical role in promoting the ATR-Chk1 DDR pathway activation from SSBs.
• A novel APE2-PCNA interaction mechanism involving APE2's Zf-GRF domain is identified.
• This interaction is crucial for efficient SSB repair and maintaining genome integrity.