The ubiquitin proteasome system is a fundamental actor for the proteolysis of cellular proteins. My results demonstrated that the E3 ligase Mdm2 and its substrate p53 might be implied in the formation of the fully-assembled proteasome. Mdm2 promotes also the ubiquitination of some 19S subunits of the proteasome via a non-conventional chain and it is not a signal for self-degradation. Moreover, this ubiqitination seemed to play a role in the formation of the proteasome
