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Updated: Nov 4, 2025
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Published on: June 26, 2020
p97/VCP inhibition causes excessive MRE11-dependent DNA end resection promoting cell killing after ionizing radiation
Susan Kilgas1, Abhay Narayan Singh1, Salome Paillas1
1MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford OX3 7DQ, UK.
Abstract:
The ATPase p97 is a central component of the ubiquitin-proteasome degradation system. p97 uses its ATPase activity and co-factors to extract ubiquitinated substrates from different cellular locations, including DNA lesions, thereby regulating DNA repair pathway choice. Here, we find that p97 physically and functionally interacts with the MRE11-RAD50-NBS1 (MRN) complex on chromatin and that inactivation of p97 blocks the disassembly of the MRN complex from the sites of DNA damage upon ionizing radiation (IR). The inhibition of p97 function results in excessive 5'-DNA end resection mediated by MRE11 that leads to defective DNA repair and radiosensitivity. In addition, p97 inhibition by the specific small-molecule inhibitor CB-5083 increases tumor cell killing following IR both in vitro and in vivo. Mechanistically, this is mediated via increased MRE11 nuclease accumulation. This suggests that p97 inhibitors might be exploited to improve outcomes for radiotherapy patients.
Insights
ATPase p97 regulates DNA repair by interacting with the MRN complex. Inhibiting p97 causes excessive DNA resection, leading to defective repair and increased tumor cell killing after radiation therapy.
Area of Science:
- Molecular Biology
- DNA Repair Mechanisms
- Cancer Therapeutics
Background:
- The ATPase p97 is crucial for the ubiquitin-proteasome system.
- p97 extracts ubiquitinated substrates, influencing DNA repair pathway choice.
- The MRE11-RAD50-NBS1 (MRN) complex plays a key role in DNA damage response.
Purpose of the Study:
- To investigate the interaction between p97 and the MRN complex in DNA repair.
- To determine the effect of p97 inhibition on DNA damage response and radiosensitivity.
- To evaluate the therapeutic potential of p97 inhibitors in cancer treatment.
Main Methods:
- Studied the physical and functional interaction of p97 with the MRN complex on chromatin.
- Inactivated p97 and observed its effect on MRN complex disassembly at DNA damage sites after ionizing radiation (IR).
- Utilized the small-molecule inhibitor CB-5083 to assess p97 inhibition's impact on tumor cells in vitro and in vivo.
Main Results:
- p97 inactivation blocked MRN complex disassembly from DNA damage sites following IR.
- p97 inhibition led to excessive 5'-DNA end resection mediated by MRE11.
- CB-5083 treatment increased tumor cell killing post-IR via enhanced MRE11 nuclease accumulation.
Conclusions:
- p97 is essential for regulating MRN complex dynamics at DNA damage sites.
- Inhibition of p97 disrupts DNA repair, causing radiosensitivity.
- p97 inhibitors like CB-5083 show promise for improving radiotherapy outcomes.
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