Phosphorylated hMSH6: DNA mismatch versus DNA damage recognition.

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• DNA mismatch repair (MMR) is crucial for maintaining genomic integrity.
• The MMR pathway also mediates DNA damage responses to lesions like O(6)-methylguanine (O(6)meG).
• Regulation of these distinct MMR pathways is not fully understood.

Purpose of the Study:

• To investigate the cellular regulation of DNA mismatch repair (MMR) and DNA damage response pathways.
• To elucidate the role of hMSH6 phosphorylation in hMutSα binding and cellular signaling.

Main Methods:

• Utilized kinase activators (TPA) and inhibitors (UCN-01) to study hMSH6 phosphorylation and hMutSα binding.
• Examined cell cycle progression in HeLa MR cells treated with UCN-01 and MNNG.
• Investigated recombinant hMutSα with mutated phosphoserines.

Main Results:

• Phosphorylated hMSH6 concentration increases with G:T mismatches more than O(6)meG:T lesions.
• TPA enhances hMSH6 phosphorylation and hMutSα binding to G:T mismatches.
• UCN-01 inhibits hMSH6 phosphorylation and hMutSα binding to both mismatches and O(6)meG:T lesions.
• UCN-01 treatment in MNNG-exposed cells bypasses Cdc25c-mediated cell cycle arrest.
• Mutated hMSH6 shows reduced phosphorylation and hMutSα binding.

Conclusions:

• hMSH6 phosphorylation is modulated by DNA mismatches and alkylation damage.
• The level of phosphorylated hMSH6 bound to DNA influences MMR and damage recognition signaling.
• These findings suggest a regulatory mechanism involving hMSH6 phosphorylation in MMR pathway signaling.