PHRF1 promotes genome integrity by modulating non-homologous end-joining

Area of Science:

• Molecular Biology
• Epigenetics
• DNA Repair

Background:

• Methylated histone readers are crucial for chromatin regulation and DNA repair.
• PHRF1, a human protein with PHD and RING domains, is known as a tumor suppressor involved in TGF-β signaling.
• The role of PHRF1 in the DNA damage response was previously unclear.

Purpose of the Study:

• To investigate the novel function of PHRF1 in modulating non-homologous end-joining (NHEJ).
• To elucidate the molecular mechanisms by which PHRF1 participates in DNA damage response.

Main Methods:

• Investigated PHRF1 localization to DNA damage lesions.
• Assessed NHEJ efficiency using plasmid-based assays and reporter cells.
• Utilized immunoprecipitation and peptide pull-down assays to determine protein interactions.
• Analyzed the role of the PHD domain and SDTE motif in PHRF1 function.
• Examined PHRF1's effect on PARP1 ubiquitination and degradation.

Main Results:

• PHRF1 rapidly localizes to DNA damage sites upon genotoxic insults.
• PHRF1 deficiency impairs NHEJ efficiency, while its overexpression enhances it.
• PHRF1 directly binds to H3K36me2 and H3K36me3 via its PHD domain.
• The PHD domain and SDTE motif are essential for PHRF1's NHEJ-promoting activity.
• PHRF1 mediates polyubiquitination and proteasomal degradation of PARP1.

Conclusions:

• PHRF1 plays a significant role in promoting NHEJ, a key DNA double-strand break repair pathway.
• PHRF1 integrates epigenetic marks (H3K36 methylation) with DNA repair machinery (NBS1).
• PHRF1 contributes to maintaining genomic stability by facilitating DNA repair and degrading PARP1.