The XRCC1 phosphate-binding pocket binds poly (ADP-ribose) and is required for XRCC1 function

Area of Science:

• Molecular Biology
• DNA Repair Mechanisms
• Biochemistry

Background:

• Poly (ADP-ribose) synthesis occurs at DNA single-strand breaks.
• XRCC1 is a scaffold protein involved in DNA repair.
• The precise mechanism and significance of poly (ADP-ribose) binding by XRCC1 have been debated.

Purpose of the Study:

• To elucidate the mechanism of poly (ADP-ribose) binding by XRCC1.
• To investigate the importance of this interaction for XRCC1 function in DNA repair.

Main Methods:

• Characterization of poly (ADP-ribose) binding by XRCC1.
• Analysis of XRCC1 binding to poly (ADP-ribose) at varying ADP-ribosylation levels.
• Assessment of XRCC1 recruitment to DNA damage sites (UVA laser, H2O2, PCNA foci).
• Evaluation of XRCC1-dependent DNA repair (single-strand break repair, base excision repair) and cell survival.

Main Results:

• The phosphate-binding pocket in XRCC1's BRCT1 domain is essential for selective poly (ADP-ribose) binding and PARP1 interaction.
• This pocket is required for XRCC1 recruitment to DNA damage sites, including replication stress foci.
• The phosphate-binding pocket is critical for accelerating DNA single-strand break repair, base excision repair, and enhancing cell survival post-DNA damage.

Conclusions:

• Poly (ADP-ribose) synthesis facilitates XRCC1 recruitment to DNA damage sites.
• The BRCT1 domain's phosphate-binding pocket is vital for poly (ADP-ribose) recognition and subsequent XRCC1 function in DNA repair and cell survival.