Protein-lysine methyltransferases G9a and GLP1 promote responses to DNA damage

Area of Science:

• Molecular Biology
• Epigenetics
• DNA Damage Response

Background:

• DNA breaks trigger ATM activation, initiating chromatin modifications for DNA repair protein recruitment.
• Defects in DNA repair pathways are linked to genomic instability and cancer.
• The roles of protein lysine methyltransferases in DNA repair are not fully understood.

Purpose of the Study:

• To investigate the role of G9a (EHMT2) and GLP1 (EHMT1) in the DNA repair pathway.
• To determine the mechanism by which G9a and GLP1 are recruited to DNA breaks.
• To assess the functional significance of G9a catalytic activity in DNA repair.

Main Methods:

• Immunofluorescence to track protein localization to DNA breaks.
• Western blotting to assess protein phosphorylation.
• Enzyme activity assays to evaluate G9a's catalytic function.
• Cellular assays measuring DNA repair factor recruitment and sensitivity to ionizing radiation.

Main Results:

• G9a and GLP1 rapidly localize to DNA breaks, with GLP1 recruitment dependent on G9a.
• ATM-mediated phosphorylation of G9a at serine 569 is essential for its DNA break localization.
• G9a's catalytic activity is required for the timely recruitment of 53BP1 and BRCA1 to DNA breaks.
• G9a inhibition impairs DNA repair and sensitizes cells to ionizing radiation.

Conclusions:

• G9a and GLP1 are critical components of the DNA repair machinery.
• G9a acts as a key regulator in the early stages of DNA break repair.
• G9a's catalytic activity and localization are vital for efficient DNA repair, positioning it as a potential therapeutic target.