Tumour necrosis factor (TNF) is a cytokine with important functions in inflammation, immunity and cancer. Signalling processes mediated by ubiquitin are crucial for TNF signalling. The seven lysine (K) residues and the N-terminus of ubiquitin can be used to form ubiquitin chains. Employing a method newly developed in our laboratory we identified the presence of four of these ubiquitin chain linkage types in the native TNF receptor signalling complex (TNF-RSC). Our knowledge of the specific functions of the different ubiquitin linkages is currently very limited. However, their presence in the TNF-RSC, combined with our recent technological advance in dissecting the composition of this protein complex with previously unreached specificity and sensitivity provides a unique opportunity for the proposed research programme: to molecularly and functionally decipher the ubiquitin code. We will aim to achieve this by studying the different ubiquitin chain linkages at the molecular level within the TNF-RSC and by determining how perturbation of specific ubiquitin linkage events impacts the physiological role of TNF in immunity to infection and its pathological function in inflammation-induced cancer.The specific objectives of this project are:• to molecularly decipher the ubiquitin code of the TNF-RSC (objective 1),• to link this code to physiological functions of TNF in immunity to infection (objective 2)• and to test its pathological impact on cancer-related inflammation (objective 3).