부산대학교 도서관

The ubiquitin-proteasome system (UPS) is responsible for most of the protein degradation in mammalian cells which represents a particular challenge in cancer cells that commonly have heightened protein stress. The AAA+ ATPase p97 is a central component of the UPS, where it functions in concert with its co-factors to bind and unfold ubiquitinated substrates from various cellular locations, including DNA break sites. The work in this thesis demonstrates that p97 functionally interacts with one of the main DNA double-strand break (DSB) repair complexes, MRE11-RAD50-NBS1 (MRN), and influences DSB repair pathway choice by disassembling MRN from chromatin after ionising radiation (IR). Inactivation of p97 blocks MRN complex disassembly from chromatin and sites of DNA damage upon IR, which results in excessive MRE11-mediated DNA end resection, leading to defective error-free homologous recombination (HR) and upregulation of the mutagenic single-strand annealing (SSA) pathway, resulting in cancer cell radiosensitivity. Mechanistically, p97 inhibition causes radiosensitivity through MRE11 nuclease accumulation, and cancer cell survival after IR is rescued when MRE11 is inactivated in combination with p97 inhibition. Furthermore, the small molecule ATPase inhibitor of p97, CB-5083, is well-tolerated and causes tumour cell killing after IR in vivo. These results suggest that p97 inhibitors might be used to improve cancer radiotherapy outcomes.