title: Polyubiquitin binding and cross-reactivity in the USP domain deubiquitinase USP21.
abstract: Modification of proteins by ubiquitin (Ub) and Ub-like (Ubl) modifiers regulates a variety of cellular functions. The ability of Ub to form chains of eight structurally and functionally distinct types adds further complexity to the system. Ub-specific proteases (USPs) hydrolyse polyUb chains, and some have been suggested to be cross-reactive with Ubl modifiers, such as neural precursor cell expressed, developmentally downregulated 8 (NEDD8) and interferon-stimulated gene 15 (ISG15). Here, we report that USP21 cleaves Ub polymers, and with reduced activity also targets ISG15, but is inactive against NEDD8. A crystal structure of USP21 in complex with linear diUb aldehyde shows how USP21 interacts with polyUb through a previously unidentified second Ub- and ISG15-binding surface on the USP domain core. We also rationalize the inability of USP21 to target NEDD8 and identify differences that allow USPs to distinguish between structurally related modifications.
authors.affiliation: Protein and Nucleic Acid Chemistry, Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK.
authors.forename: Yu
authors.initials: Y
authors.lastname: Ye
authors.forename: Masato
authors.initials: M
authors.lastname: Akutsu
authors.forename: Francisca
authors.initials: F
authors.lastname: Reyes-Turcu
authors.forename: Radoslav I
authors.initials: RI
authors.lastname: Enchev
authors.forename: Keith D
authors.initials: KD
authors.lastname: Wilkinson
authors.forename: David
authors.initials: D
authors.lastname: Komander
mesh_terms: D001665:Binding Sites / Q000502:physiology; D018360:Crystallography, X-Ray; D016207:Cytokines / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D000075687:NEDD8 Protein; D025821:Polyubiquitin / Q000378:metabolism*; D011485:Protein Binding; D043222:Ubiquitin Thiolesterase / Q000737:chemistry* / Q000378:metabolism*; D014452:Ubiquitins / Q000737:chemistry / Q000378:metabolism
chemical_list: D016207:Cytokines; D000075687:NEDD8 Protein; C082860:NEDD8 protein, human; C408875:USP21 protein, human; D014452:Ubiquitins; D025821:Polyubiquitin; C074034:ISG15 protein, human; D043222:Ubiquitin Thiolesterase