title: Ubiquitin charging of human class III ubiquitin-conjugating enzymes triggers their nuclear import.
abstract: Ubiquitin is a small polypeptide that is conjugated to proteins and commonly serves as a degradation signal. The attachment of ubiquitin (Ub) to a substrate proceeds through a multi-enzyme cascade involving an activating enzyme (E1), a conjugating enzyme (E2), and a protein ligase (E3). We previously demonstrated that a murine E2, UbcM2, is imported into nuclei by the transport receptor importin-11. We now show that the import mechanism for UbcM2 and two other human class III E2s (UbcH6 and UBE2E2) uniquely requires the covalent attachment of Ub to the active site cysteine of these enzymes. This coupling of E2 activation and transport arises from the selective interaction of importin-11 with the Ub-loaded forms of these enzymes. Together, these findings reveal that Ub charging can function as a nuclear import trigger, and identify a novel link between E2 regulation and karyopherin-mediated transport.
authors.affiliation: Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA. scott-plafker@ouhsc.edu
authors.forename: Scott M
authors.initials: SM
authors.lastname: Plafker
authors.forename: Kendra S
authors.initials: KS
authors.lastname: Plafker
authors.forename: Allan M
authors.initials: AM
authors.lastname: Weissman
authors.forename: Ian G
authors.initials: IG
authors.lastname: Macara
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000818:Animals; D001665:Binding Sites / Q000502:physiology; D002460:Cell Line; D002467:Cell Nucleus / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D006224:Cricetinae; D003545:Cysteine / Q000378:metabolism; D018014:Gene Transfer Techniques; D006801:Humans; D028884:Karyopherins / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D011485:Protein Binding / Q000502:physiology; D025801:Ubiquitin / Q000378:metabolism*; D044763:Ubiquitin-Conjugating Enzymes / Q000235:genetics / Q000378:metabolism*; D028961:beta Karyopherins
chemical_list: C475690:IPO11 protein, human; D028884:Karyopherins; D026901:Membrane Transport Proteins; D025801:Ubiquitin; D028961:beta Karyopherins; C489963:UBE2E1 protein, human; C106347:UBE2E2 protein, human; C495210:Ube2e1 protein, mouse; D044763:Ubiquitin-Conjugating Enzymes; D003545:Cysteine