title: The recognition of ubiquitinated proteins by the proteasome.
abstract: The ability of ubiquitin to form up to eight different polyubiquitin chain linkages generates complexity within the ubiquitin proteasome system, and accounts for the diverse roles of ubiquitination within the cell. Understanding how each type of ubiquitin linkage is correctly interpreted by ubiquitin binding proteins provides important insights into the link between chain recognition and cellular fate. A major function of ubiquitination is to signal degradation of intracellular proteins by the 26S proteasome. Lysine-48 (K48) linked polyubiquitin chains are well established as the canonical signal for proteasomal degradation, but recent studies show a role for other ubiquitin linked chains in facilitating degradation by the 26S proteasome. Here, we review how different types of polyubiquitin linkage bind to ubiquitin receptors on the 26S proteasome, how they signal degradation and discuss the implications of ubiquitin chain linkage in regulating protein breakdown by the proteasome.
authors.affiliation: Department of Medicine, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, CB2 0XY, UK.
authors.forename: Guinevere L
authors.initials: GL
authors.lastname: Grice
authors.affiliation: Department of Medicine, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, CB2 0XY, UK. jan33@cam.ac.uk.
authors.forename: James A
authors.initials: JA
authors.lastname: Nathan
mesh_terms: D006801:Humans; D025821:Polyubiquitin / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D025801:Ubiquitin / Q000378:metabolism; D057149:Ubiquitinated Proteins / Q000737:chemistry / Q000378:metabolism*
chemical_list: D025801:Ubiquitin; D057149:Ubiquitinated Proteins; D025821:Polyubiquitin; D046988:Proteasome Endopeptidase Complex
keywords: Polyubiquitin chains; Proteasome; Ubiquitin; Ubiquitin binding domain; Ubiquitin binding protein; Ubiquitin receptors