Regulation of the BH3-only protein PUMA by growth factor signalling.

Abstract

P53 Upregulated Modifier of Apoptosis (PUMA), a pro-apoptotic member of the Bcl-2 family, is transcriptionally activated by p53 and is a key effector of p53-dependent apoptosis. We show that PUMA protein is subject to rapid post-translational regulation by phosphorylation at a conserved residue, serine 10, following serum or Interleukin-3 (IL-3) stimulation. Serine 10 is not within the BH3 domain and PUMA phosphorylated at serine 10 retained the ability to co-immunoprecipitate with anti-apoptotic Bcl-2 family members. However, phosphorylated PUMA was targeted for proteasomal degradation indicating that it is less stable than unphosphorylated PUMA. Importantly, we identified NEMO/IKK1/IKK2 as the kinase complex that interacts with and phosphorylates PUMA thereby also demonstrating that IL-3 activates NFκB signalling. This thesis therefore identified and characterised a novel survival pathway with important implications for IL-3 signalling and haemopoietic cell development.