Mismatch-repair protein MSH6 is associated with Ku70 and regulates DNA double-strand break repair

Area of Science:

• Molecular Biology
• DNA Repair Mechanisms
• Cellular Response to Radiation

Background:

• MSH6 is essential for DNA mismatch repair.
• Ku70 is a critical component of the DNA-dependent protein kinase involved in DNA double-strand break (DSB) repair via non-homologous end-joining (NHEJ).

Purpose of the Study:

• To investigate the potential role of MSH6 in DSB repair.
• To identify novel MSH6-interacting proteins involved in DNA damage response.

Main Methods:

• Yeast two-hybrid screening to identify MSH6-interacting proteins.
• Treatment with neocarzinostatin (NCS) or ionizing radiation (IR) to induce DSBs.
• Immunofluorescence staining for MSH6 and γ-H2AX.
• Comet assay and clonogenic cell-survival assay to assess DNA damage and cell viability.
• MSH6 depletion and overexpression studies.

Main Results:

• MSH6 was identified as a novel Ku70-interacting protein.
• Ku70-MSH6 association is enhanced upon NCS or IR treatment.
• MSH6 forms nuclear foci and colocalizes with γ-H2AX at DNA damage sites.
• MSH6 depletion leads to accumulation of persistent DSBs and impaired NHEJ.
• MSH6-deficient cells exhibit hypersensitivity to NCS/IR-induced cell death.

Conclusions:

• MSH6 plays a significant role in DSB repair, potentially by associating with Ku70 to enhance NHEJ.
• MSH6 is critical for maintaining genomic stability and cell survival following exposure to DNA-damaging agents.