HDGFRP3 interaction with 53BP1 promotes DNA double-strand break repair

Area of Science:

• Molecular Biology
• DNA Repair Mechanisms
• Chromatin Biology

Background:

• 53BP1 is crucial for DNA double-strand break (DSB) repair via the end-joining pathway.
• Regulators of 53BP1 in chromatin are not fully understood.

Purpose of the Study:

• To identify novel regulators of 53BP1 in DNA repair.
• To elucidate the role of HDGFRP3 in 53BP1-mediated DNA repair.

Main Methods:

• Protein-protein interaction studies (HDGFRP3-53BP1).
• Immunofluorescence to observe co-localization at DSB sites.
• CRISPR/Cas9 gene editing to create HDGFRP3 knockout cells.
• Assessment of DNA repair pathway activity (NHEJ, end-resection).
• Analysis of drug sensitivity in BRCA1-deficient cells.

Main Results:

• HDGFRP3 interacts with 53BP1 via its PWWP and 53BP1's Tudor domains.
• HDGFRP3 and 53BP1 co-localize at DSB sites and are vital for DNA damage response.
• Loss of HDGFRP3 impairs NHEJ, reduces 53BP1 accumulation, and increases DNA end-resection.
• HDGFRP3 is essential for 53BP1 recruitment and inhibition of end-resection.
• HDGFRP3 loss confers PARP inhibitor resistance in BRCA1-deficient cells by promoting end-resection.
• HDGFRP3 interaction with H4K20 decreases post-IR, while 53BP1 interaction increases, suggesting phosphorylation-dependent regulation.

Conclusions:

• HDGFRP3 is a novel regulator of 53BP1 in DNA DSB repair.
• The HDGFRP3-53BP1 complex dynamically regulates 53BP1 recruitment and DNA repair.
• This study provides new insights into the 53BP1-mediated DNA repair pathway.