Mechanism of Polyubiquitination by Human Anaphase-Promoting Complex: RING Repurposing for Ubiquitin Chain Assembly

• Published in: Molecular cell Vol. 56; no. 2; pp. 246 - 260
• Main Authors: Brown, Nicholas G., Watson, Edmond R., Weissmann, Florian, Jarvis, Marc A., VanderLinden, Ryan, Grace, Christy R.R., Frye, Jeremiah J., Qiao, Renping, Dube, Prakash, Petzold, Georg, Cho, Shein Ei, Alsharif, Omar, Bao, Ju, Davidson, Iain F., Zheng, Jie J., Nourse, Amanda, Kurinov, Igor, Peters, Jan-Michael, Stark, Holger, Schulman, Brenda A.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 23-10-2014; Elsevier
• Subjects: Amino Acid Sequence; Apc11 Subunit, Anaphase-Promoting Complex-Cyclosome - metabolism; Apc2 Subunit, Anaphase-Promoting Complex-Cyclosome - metabolism; Apc4 Subunit, Anaphase-Promoting Complex-Cyclosome - metabolism; BASIC BIOLOGICAL SCIENCES; Cell Cycle Checkpoints; HeLa Cells; Humans; Molecular Sequence Data; Peptide Biosynthesis, Nucleic Acid-Independent; Polyubiquitin - biosynthesis; Polyubiquitin - genetics; Protein Structure, Tertiary; Ubiquitin-Conjugating Enzymes - metabolism; Ubiquitination - physiology
• ISSN: 1097-2765; 1097-4164
• DOI: 10.1016/j.molcel.2014.09.009

Polyubiquitination by E2 and E3 enzymes is a predominant mechanism regulating protein function. Some RING E3s, including anaphase-promoting complex/cyclosome (APC), catalyze polyubiquitination by sequential reactions with two different E2s. An initiating E2 ligates ubiquitin to an E3-bound substrate. Another E2 grows a polyubiquitin chain on the ubiquitin-primed substrate through poorly defined mechanisms. Here we show that human APC’s RING domain is repurposed for dual functions in polyubiquitination. The canonical RING surface activates an initiating E2-ubiquitin intermediate for substrate modification. However, APC engages and activates its specialized ubiquitin chain-elongating E2 UBE2S in ways that differ from current paradigms. During chain assembly, a distinct APC11 RING surface helps deliver a substrate-linked ubiquitin to accept another ubiquitin from UBE2S. Our data define mechanisms of APC/UBE2S-mediated polyubiquitination, reveal diverse functions of RING E3s and E2s, and provide a framework for understanding distinctive RING E3 features specifying ubiquitin chain elongation.
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•APC uses canonical RING mechanism for initial substrate ubiquitin (Ub) modification•APC uses unprecedented mechanisms to activate the E2 UBE2S for polyubiquitination•APC drives UBE2S-mediated Ub chain elongation by lowering Kmapp for the acceptor Ub•Noncanonical APC11 RING surface delivers acceptor Ub for chain elongation by UBE2S
Brown et al. show that human APC catalyzes polyubiquitination through two distinct mechanisms. APC’s canonical RING surface activates an initial E2 for ubiquitin ligation to a substrate. Polyubiquitination involves a different APC RING surface, which helps deliver the substrate-linked ubiquitin to a different E2 to assemble polyubiquitin chains.