title: Ubiquitin chain elongation requires E3-dependent tracking of the emerging conjugate.
abstract: Protein modification with ubiquitin chains is an essential signaling event catalyzed by E3 ubiquitin ligases. Most human E3s contain a signature RING domain that recruits a ubiquitin-charged E2 and a separate domain for substrate recognition. How RING-E3s can build polymeric ubiquitin chains while binding substrates and E2s at defined interfaces remains poorly understood. Here, we show that the RING-E3 APC/C catalyzes chain elongation by strongly increasing the affinity of its E2 for the distal acceptor ubiquitin in a growing conjugate. This function of the APC/C requires its coactivator as well as conserved residues of the E2 and ubiquitin. APC/C's ability to track the tip of an emerging conjugate is required for APC/C-substrate degradation and accurate cell division. Our results suggest that RING-E3s tether the distal ubiquitin of a growing chain in proximity to the active site of their E2s, allowing them to assemble polymeric conjugates without altering their binding to substrate or E2.
authors.affiliation: Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA 94720, USA.
authors.forename: Aileen
authors.initials: A
authors.lastname: Kelly
authors.affiliation: Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA 94720, USA.
authors.forename: Katherine E
authors.initials: KE
authors.lastname: Wickliffe
authors.affiliation: Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA 94720, USA.
authors.forename: Ling
authors.initials: L
authors.lastname: Song
authors.affiliation: Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA 94720, USA.
authors.forename: Indro
authors.initials: I
authors.lastname: Fedrigo
authors.affiliation: Howard Hughes Medical Institute, University of California at Berkeley, Berkeley, CA 94720, USA; Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA 94720, USA. Electronic address: mrape@berkeley.edu.
authors.forename: Michael
authors.initials: M
authors.lastname: Rape
mesh_terms: D064198:Apc11 Subunit, Anaphase-Promoting Complex-Cyclosome / Q000378:metabolism*; D064190:Apc2 Subunit, Anaphase-Promoting Complex-Cyclosome / Q000378:metabolism*; D020134:Catalytic Domain; D064199:Cdc20 Proteins / Q000235:genetics / Q000378:metabolism*; D059447:Cell Cycle Checkpoints / Q000235:genetics; D045744:Cell Line, Tumor; D004789:Enzyme Activation; D006367:HeLa Cells; D006801:Humans; D046908:Peptide Biosynthesis, Nucleic Acid-Independent / Q000235:genetics*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D034622:RNA Interference; D034741:RNA, Small Interfering; D025801:Ubiquitin / Q000096:biosynthesis / Q000235:genetics*; D044763:Ubiquitin-Conjugating Enzymes / Q000378:metabolism*; D054875:Ubiquitination
chemical_list: D064199:Cdc20 Proteins; D034741:RNA, Small Interfering; D025801:Ubiquitin; C544962:Ube2S protein, human; D044763:Ubiquitin-Conjugating Enzymes; C577351:ANAPC11 protein, human; D064198:Apc11 Subunit, Anaphase-Promoting Complex-Cyclosome; D064190:Apc2 Subunit, Anaphase-Promoting Complex-Cyclosome