"The nucleus contains distinct sub-compartments, the composition and localisation of which change during normal physiological processes, or in response to stress or disease. The molecular stimuli that provoke these changes, and their effects on gene expression are not well characterised. This proposal aims to further define the mechanisms that underlie nuclear organisation, which is fundamentally important to most eukaryotic cell-types. Moreover, as there are many diseases linked with distinct changes in nuclear architecture, a better understanding of these mechanisms will aid in the development of new treatments, and diagnosis/screening procedures. Both these outcomes will reinforce the scientific excellence of Europe. My work will focus on the dynamic behaviour of Cajal bodies (CBs), which are conserved sub-nuclear domains involved in ribonucleoprotein-complex assembly. Recently, it was discovered that upon UV-C irradiation of cells, many CB proteins redistribute into “microfoci”. One of these proteins, coilin, displayed an increase in association with a novel binding partner after UV-C irradiation, Proteasome Activator subunit gamma (PA28g). Several lines of evidence suggest that the UV-C-induced redistribution of CBs occurs via a novel pathway that promotes the formation of PA28g/coilin complexes. I will extend these observations and determine the molecular mechanisms underlying the transduction of stress signals to the nucleus, by using biochemical and proteomic approaches (including a cutting-edge mass spectrometry technique; SILAC-MS) to identify novel proteins that show increased association with coilin/PA28g following UV-C irradiation. I will also determine the role of PA28g phosphorylation in the UV-C-induced redistribution of CBs by applying gene-silencing techniques and cell biological approaches. Finally, advanced fluorescence-microscopy methodologies will be combined with MS to determine if PA28g is functionally associated with the 20S proteasome."