m⁵C modification of mRNA serves a DNA damage code to promote homologous recombination

Area of Science:

• Molecular Biology
• Biochemistry
• Genetics

Background:

• DNA repair protein recruitment to DNA damage sites is essential for maintaining genomic stability.
• Post-translational protein modifications at DNA damage sites act as signals to recruit specific repair factors.
• The role of RNA modifications in DNA damage response pathways remains largely unexplored.

Purpose of the Study:

• To investigate the role of RNA modifications in the DNA damage response.
• To determine if messenger RNA (mRNA) is modified at DNA damage sites.
• To elucidate the function of the RNA methyltransferase TRDMT1 in DNA repair.

Main Methods:

• Investigated mRNA modifications at DNA damage sites using m⁵C detection.
• Assessed the recruitment of TRDMT1 to DNA damage sites.
• Utilized cell-based assays to evaluate homologous recombination (HR) efficiency and sensitivity to DNA double-strand breaks (DSBs) in TRDMT1-deficient cells.
• Examined the localization of DNA repair proteins RAD51 and RAD52.
• Performed in vitro binding assays with RAD52 and m⁵C-modified RNA:DNA hybrids.
• Assessed the sensitivity of cancer cells lacking TRDMT1 to PARP inhibitors in vitro and in vivo.

Main Results:

• Messenger RNA (mRNA) is locally modified by N¹-methyladenosine (m⁵C) at sites of DNA damage.
• The RNA methyltransferase TRDMT1 is recruited to DNA damage sites and promotes m⁵C induction.
• Loss of TRDMT1 impairs homologous recombination (HR) and increases sensitivity to DNA double-strand breaks (DSBs).
• TRDMT1 deficiency leads to failed localization of RAD51 and RAD52 to DNA damage sites.
• RAD52 exhibits enhanced binding to m⁵C-modified RNA:DNA hybrids in vitro.
• TRDMT1-deficient cancer cells show increased sensitivity to PARP inhibitors both in vitro and in vivo.

Conclusions:

• An unexpected TRDMT1-m⁵C axis in RNA promotes homologous recombination (HR) DNA repair.
• Post-transcriptional RNA modifications can function as DNA damage codes, regulating DNA repair pathways.
• TRDMT1-mediated m⁵C RNA modification is a novel regulator of the DNA damage response and a potential therapeutic target in cancer.