부산대학교 도서관

Common cancer treatments, such as radiotherapy, primarily involve the induction of DNA damage. Like healthy cells, the cancer cells rely on the highly conserved DNA damage response (DDR) checkpoints for survival, leading to therapeutic resistance. There are established DDR checkpoints in each interphase stage of the cell cycle, which impede the cell cycle until the damage has been sufficiently repaired. However, there is limited evidence of a specific DDR checkpoint in mitosis. The spindle assembly checkpoint (SAC) is a protective mechanism that regulates mitotic spindle attachment to the centromere, regulating metaphase-anaphase transition. There is emerging evidence to suggest crosstalk between the DDR and SAC pathways in damaged conditions. I have consistently observed a delay in mitotic transit time following the induction of DNA damage by various agents including irradiation, chemotherapeutics and H2O2. Overall, this indicates the existence of a mitotic DNA damage checkpoint (MDDC), which may contribute to treatment resistance. This thesis aims to identify proteins involved and begin to establish a pathway for this novel checkpoint. Firstly, an examination into the antioxidant enzyme superoxide dismutase 1 (SOD1), which was highlighted in a preliminary siRNA DNA damage screen of potential proteins involved in the checkpoint. I observed the MDDC was dependent on SOD1 and revealed SOD1 regulates phosphatase PP2A activity to activate the MDDC. Furthermore, a role of SOD1 in DNA damage repair was also identified. Then a mass spectrometry screen was performed to reveal novel interactors of SAC protein BubR1, identifying the nonsense mediated decay (NMD) factor, Upstream frameshift 1's (UPF1) involvement in the MDDC. Overall, an initial pathway for the MDDC has been established and future direction determined, which will provide potential drug targets to reduce therapeutic resistance of cancer cells to conventional treatments.