title: Molecular mechanisms of coupled monoubiquitination.
abstract: Many proteins contain ubiquitin-binding domains or motifs (UBDs), such as the UIM (ubiquitin-interacting motif) and are referred to as ubiquitin receptors. Ubiquitin receptors themselves are frequently monoubiquitinated by a process that requires the presence of a UBD and is referred to as coupled monoubiquitination. Using a UIM-containing protein, eps15, as a model, we show here that coupled monoubiquitination strictly depends on the ability of the UIM to bind to monoubiquitin (mUb). We found that the underlying molecular mechanism is based on interaction between the UIM and a ubiquitin ligase (E3), which has itself been modified by ubiquitination. Furthermore, we demonstrate that the in vivo ubiquitination of members of the Nedd4 family of E3 ligases correlates with their ability to monoubiquitinate eps15. Thus, our results clarify the mechanism of coupled monoubiquitination and identify the ubiquitination of E3 ligases as a critical determinant in this process.
authors.affiliation: IFOM, The FIRC Institute for Molecular Oncology, Via Adamello 16, 20139, Milan, Italy.
authors.forename: Tanja
authors.initials: T
authors.lastname: Woelk
authors.forename: Barbara
authors.initials: B
authors.lastname: Oldrini
authors.forename: Elena
authors.initials: E
authors.lastname: Maspero
authors.forename: Stefano
authors.initials: S
authors.lastname: Confalonieri
authors.forename: Elena
authors.initials: E
authors.lastname: Cavallaro
authors.forename: Pier Paolo
authors.initials: PP
authors.lastname: Di Fiore
authors.forename: Simona
authors.initials: S
authors.lastname: Polo
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D001665:Binding Sites / Q000235:genetics; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D002384:Catalysis; D056827:Endosomal Sorting Complexes Required for Transport; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D000075702:Nedd4 Ubiquitin Protein Ligases; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D014162:Transfection; D025801:Ubiquitin / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002135:Calcium-Binding Proteins; C486206:EPS15 protein, human; D056827:Endosomal Sorting Complexes Required for Transport; D047908:Intracellular Signaling Peptides and Proteins; D010750:Phosphoproteins; D025801:Ubiquitin; D000075702:Nedd4 Ubiquitin Protein Ligases; C000618483:Nedd4 protein, human; C465283:WWP2 protein, human; D044767:Ubiquitin-Protein Ligases