Valosin-containing protein mediates DNA-dependent protein kinase activation in response to DNA topoisomerase II-associated DNA double-strand breaks

Area of Science:

• Molecular Biology
• DNA Repair Mechanisms
• Cancer Therapeutics

Background:

• DNA topoisomerase II (Top2) manages DNA torsional stress by inducing double-strand breaks (DSBs).
• Etoposide (ETP), an anticancer drug, traps Top2, causing DSBs and Top2-DNA protein crosslinks (Top2-DPC).
• Proteasome-mediated processing of trapped Top2 is crucial for cellular responses to ETP, but its role in DSB repair is unclear.

Purpose of the Study:

• To investigate the role of valosin-containing protein (VCP), a proteasome mediator, in resolving Top2-DNA protein crosslinks (Top2-DPC).
• To analyze the impact of suppressed Top2-DPC resolution on the repair of etoposide (ETP)-induced DNA double-strand breaks (DSBs).

Main Methods:

• Utilized VCP inhibitors to suppress Top2-DPC resolution.
• Assessed the activation of DNA-dependent protein kinase (DNA-PK), a key factor in non-homologous end-joining (NHEJ).
• Quantified the repair activity in response to ETP-induced DSBs under VCP inhibition.

Main Results:

• VCP inhibition suppressed the activation of DNA-dependent protein kinase (DNA-PK) following ETP treatment.
• Suppression of VCP led to reduced repair activity of ETP-induced DSBs.
• VCP inhibition delayed the resolution of ETP-induced Top2-DPC, indicating impaired Top2 removal.

Conclusions:

• The VCP-proteasome pathway is essential for efficient processing of trapped Top2.
• Efficient Top2 removal by VCP is critical for DNA-PK activation and subsequent DNA double-strand break repair.
• Targeting VCP may represent a strategy to modulate DNA repair in cancer therapy.