Mechanism of polyubiquitination by human anaphase-promoting complex: RING repurposing for ubiquitin chain assembly.
Publication Type:Journal Article
Source:Mol Cell, Volume 56, Issue 2, p.246-260 (2014)
Keywords:Amino Acid Sequence, Apc11 Subunit, Anaphase-Promoting Complex-Cyclosome, Apc2 Subunit, Anaphase-Promoting Complex-Cyclosome, Apc4 Subunit, Anaphase-Promoting Complex-Cyclosome, Cell Cycle Checkpoints, HeLa Cells, Humans, Molecular Sequence Data, Peptide Biosynthesis, Nucleic Acid-Independent, Polyubiquitin, Protein Structure, Tertiary, Ubiquitin-Conjugating Enzymes, Ubiquitination
<p>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.</p>