hMSH2 recruits ATR to DNA damage sites for activation during DNA damage-induced apoptosis

Area of Science:

• Molecular Biology
• Cellular Biology
• Genetics

Background:

• DNA damage response (DDR) is essential for maintaining genomic stability.
• ATM and ATR protein kinases are master regulators of DDR.
• Cisplatin chemotherapy induces apoptosis via ATR-dependent DDR, but ATR activation mechanisms remain unclear.

Purpose of the Study:

• To identify key regulators of ATR activation after DNA damage.
• To investigate the role of hMSH2 in ATR signaling.

Main Methods:

• Proteomic analysis using blue native-PAGE and co-immunoprecipitation to identify ATR-binding proteins.
• Functional assays in hMSH2-deficient cells to assess ATR activation and downstream signaling.
• Treatment with cisplatin and N-methyl-N-nitrosourea to induce DNA damage.

Main Results:

• The mismatch repair protein hMSH2 was identified as a major ATR-binding protein.
• hMSH2 deficiency attenuated ATR activation, nuclear foci recruitment, and downstream DNA damage signaling (Chk2, p53, PUMA-α).
• hMSH2-dependent ATR activation was observed for both cisplatin and N-methyl-N-nitrosourea treatments.

Conclusions:

• A novel hMSH2-dependent pathway for ATR activation and downstream signaling is proposed.
• hMSH2 plays a critical role in ATR recruitment and activation, independent of RPA, Rad17, and the 9-1-1 complex.
• This finding elucidates a new mechanism in the DNA damage response pathway.