AbstractDNA damage induces MDC1 recruitment and establishes a signalling platform that mediates the DNA damage response (DDR). I show that Bod1L plays a central role in DDR by controlling MDC1 and PP2A-B56 localisation to damaged DNA. Bod1L depletion leads to micronuclei formation in undamaged cells and hypersensitivity to genotoxic stress. Bod1L binds to chromatin and is phosphorylated by ATM at sites of DNA damage. In Bod1L-depleted cells, ATM activity is normal, but there is over-accumulation of MDC1 at damaged sites caused by hyper-phosphorylation of MDC1-T4. I show that PP2A-B56 phosphatase can dephosphorylate MDC1-T4 following DNA damage and that MDC1 accumulation is limited by PP2A-B56. PP2A-B56 binds Bod1L exclusively in damaged cells and requires Bod1L for localisation to damaged DNA.
In addition to mediating repair, DNA damage triggers cell-cycle arrest, allowing adequate time for DNA repair to occur and to prevent transmission of any DNA lesion to daughter cells. The data presented in this thesis provides evidence that Bod1L acts as a regulator of Chk2 activation, acting to release Chk2 from the well-characterised inhibitory Chk2/PP2A-B56 phosphatase complex upon DNA damage, thus allowing the kinase to phosphorylate downstream substrates.
Overall, Bod1L makes three critical contributions to the DNA damage response: it promotes the initial targeting of MDC1, limits MDC1 accumulation by targeting PP2A-B56 to dephosphorylate MDC1-T4 and regulates the phosphorylation and activation of the transducer kinase Chk2.
|Date of Award
|Jason Swedlow (Supervisor)