Journal Article

Molecular basis of APC/C regulation by the spindle assembly checkpoint

Chang, Leifu, Zhang, Ziguo, Yang, Jing, Skehel, Mark, Barford, David, Alfieri, Claudio, Maslen, Sarah

2016

Overview

In the dividing eukaryotic cell, the spindle assembly checkpoint (SAC) ensures that each daughter cell inherits an identical set of chromosomes. The SAC coordinates the correct attachment of sister chromatid kinetochores to the mitotic spindle with activation of the anaphase-promoting complex (APC/C), the E3 ubiquitin ligase responsible for initiating chromosome separation. In response to unattached kinetochores, the SAC generates the mitotic checkpoint complex (MCC), which inhibits the APC/C and delays chromosome segregation. By cryo-electron microscopy, here we determine the near-atomic resolution structure of a human APC/C–MCC complex (APC/C MCC ). Degron-like sequences of the MCC subunit BubR1 block degron recognition sites on Cdc20, the APC/C coactivator subunit responsible for substrate interactions. BubR1 also obstructs binding of the initiating E2 enzyme UbcH10 to repress APC/C ubiquitination activity. Conformational variability of the complex enables UbcH10 association, and structural analysis shows how the Cdc20 subunit intrinsic to the MCC (Cdc20 MCC ) is ubiquitinated, a process that results in APC/C reactivation when the SAC is silenced. A high-resolution structure of a complex between the anaphase-promoting complex (APC/C) and the mitotic checkpoint complex (MCC) reveals how MCC interacts with and represses APC/C by obstructing substrate recognition and suppressing E3 ligase activity. Basis of mitotic regulation The spindle assembly checkpoint (SAC) is a surveillance mechanism that detects incorrect chromatid kinetochore attachments and delays chromosome segregation by generating a 'wait anaphase' signal. It is activated via the mitotic checkpoint complex (MCC), which inhibits the anaphase-promoting complex (APC/C), a multimeric E3 ligase. Here, David Barford and colleagues use cryo-electron microscopy to determine near-atomic resolution structures of the APC/C–MCC complex. The structures reveal how MCC interacts with and represses APC/C by obstructing substrate recognition and suppressing E3 ligase activity.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 101/28 / 101/58 / 631/535/1258/1259 / 631/80/641/2187 / Anaphase-Promoting Complex-Cyclosome - antagonists & inhibitors / Anaphase-Promoting Complex-Cyclosome - chemistry / Anaphase-Promoting Complex-Cyclosome - metabolism / Anaphase-Promoting Complex-Cyclosome - ultrastructure / Binding sites / Biocatalysis / Cdc20 Proteins - chemistry / Cdc20 Proteins - metabolism / Cdc20 Proteins - ultrastructure / Cell Cycle Proteins - metabolism / Cell division / Chromosome Segregation / Chromosomes / Cryoelectron Microscopy / Crystal structure / Humanities and Social Sciences / Humans / Kinases / Kinetochores - metabolism / Ligases / M Phase Cell Cycle Checkpoints - physiology / Models, Molecular / Molecular biology / multidisciplinary / Physiological aspects / Protein Binding / Protein Conformation / Protein Serine-Threonine Kinases - chemistry / Protein Serine-Threonine Kinases - metabolism / Protein Serine-Threonine Kinases - ultrastructure / Protein Subunits - chemistry / Protein Subunits - metabolism / Science / Spindle (Cytoplasm) / Spindle Apparatus - chemistry / Spindle Apparatus - metabolism / Spindle Apparatus - ultrastructure / Structural analysis / Structure-Activity Relationship / Ubiquitin-Conjugating Enzymes - chemistry / Ubiquitin-Conjugating Enzymes - metabolism / Ubiquitin-Conjugating Enzymes - ultrastructure / Ubiquitin-Protein Ligases - metabolism / Ubiquitination