PRMT5 promotes DNA repair through methylation of 53BP1 and is regulated by Src-mediated phosphorylation

Area of Science:

• Molecular Biology
• Cellular Biology
• Biochemistry

Background:

• Protein arginine methyltransferase 5 (PRMT5) is involved in critical cellular functions like transcription, signaling, mRNA splicing, and DNA repair.
• The precise regulatory mechanisms governing PRMT5 activity remain largely unelucidated.

Purpose of the Study:

• To investigate the regulation of PRMT5 activity, particularly its role in DNA repair.
• To identify the specific kinase and phosphorylation site involved in PRMT5 regulation.

Main Methods:

• Phosphorylation assays using Src kinase and PRMT5.
• Site-directed mutagenesis to substitute the Y324 residue.
• Assessment of PRMT5 binding to S-adenosyl-L-methionine.
• Analysis of PRMT5's role in non-homologous end joining (NHEJ) repair by evaluating p53-binding protein 1 (53BP1) methylation and stabilization.
• Cell viability assays following DNA damage.

Main Results:

• PRMT5 is phosphorylated at residue Y324 by Src kinase, which acts as a negative regulator of PRMT5.
• Phosphorylation or substitution of Y324 impairs PRMT5 activity by hindering its interaction with the methyl donor S-adenosyl-L-methionine.
• PRMT5 promotes DNA repair via non-homologous end joining (NHEJ) by methylating and stabilizing 53BP1, thereby enhancing cell survival post-DNA damage.
• Src-mediated PRMT5 phosphorylation inhibits NHEJ repair during DNA damage, leading to apoptosis.

Conclusions:

• Src kinase negatively regulates PRMT5 activity through phosphorylation at Y324.
• PRMT5 plays a crucial role in DNA repair and cell survival via the NHEJ pathway.
• Src-mediated inhibition of PRMT5 is a key mechanism controlling DNA repair responses and cell fate determination under DNA damage conditions.