Role of ubiquitylation of components of mitotic checkpoint complex in their dissociation from anaphase-promoting complex/cyclosome
Role of ubiquitylation of components of mitotic checkpoint complex in their dissociation from anaphase-promoting complex/cyclosome
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有丝分裂检查点复合体成分泛素化在其从后期促进复合体/环体解离中的作用
DOI：
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发表时间：
2018
影响因子：
11.1
通讯作者：
A. Hershko
中科院分区：
文献类型：
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作者：
Danielle Sitry;S. Kaisari;Adar Teichner;Shirly Miniowitz;A. Hershko
有丝分裂检查点系统对保证有丝分裂中染色体的正确分离具有重要意义。当染色体不正确地附着在有丝分裂纺锤体上时，形成一个有丝分裂检查点复合体（MCC），通过抑制后期促进复合体/环体（APC/C）泛素连接酶的作用来阻止染色体分离。当检查点关闭时，MCC被拆卸。已知APC/ c结合的MCC的拆卸需要泛素化，但这一过程的机制尚不清楚。本研究表明MCC的两种不同组分可能被泛素化，并表明这些泛素化事件导致它们彼此分离并与APC/C分离。因此，这项研究为有丝分裂检查点失活的分子事件提供了见解。有丝分裂检查点系统确保有丝分裂中染色体分离的保真度，防止后期过早开始，直到染色体正确的双极性附着到有丝分裂纺锤体上。它促进由BubR1、Bub3、Cdc20和Mad2组成的有丝分裂检查点复合体（MCC）的组装，从而抑制后期促进复合体/环体（APC/C）泛素连接酶的活性。当检查点满足时，后期由MCC的拆卸启动。以往的研究表明，APC/ c结合的MCC的解离需要泛素化，并提示泛素化的靶点是MCC的Cdc20组分。然而，目前尚不清楚泛素化如何导致MCC从APC/C中释放及其分解，以及其他蛋白质的泛素化是否参与这一过程。我们发现泛素化导致MCC中BubR1与Cdc20解离，并提示这可能导致APC/C中MCC成分的释放。BubR1在MCC中被APC/C泛素化，尽管程度低于Cdc20。在含有Cdc20赖氨酸缺失突变体的重组MCC中，BubR1泛素化程度显著增加。BubR1 n端赖氨酸残基突变为精氨酸部分抑制了其泛素化，减缓了APC/C中MCC的释放，前提是Cdc20泛素化也被阻断。这表明Cdc20和BubR1的泛素化可能参与了它们相互分离和从APC/C中释放MCC成分的过程。
Significance The mitotic checkpoint system is important for ensuring the correct segregation of chromosomes in mitosis. When chromosomes are not attached correctly to the mitotic spindle, a mitotic checkpoint complex (MCC) is formed that prevents chromosome separation by inhibiting the action of the anaphase-promoting complex/cyclosome (APC/C) ubiquitin ligase. MCC is disassembled when the checkpoint is turned off. The disassembly of APC/C-bound MCC was known to require ubiquitylation, but the mechanisms of this process remained unknown. Here we show that two different components of MCC may be ubiquitylated and suggest that these ubiquitylation events lead to their dissociation from each other and from APC/C. Thus, this investigation provides insight into the molecular events responsible for the inactivation of the mitotic checkpoint. The mitotic checkpoint system ensures the fidelity of chromosome segregation in mitosis by preventing premature initiation of anaphase until correct bipolar attachment of chromosomes to the mitotic spindle is reached. It promotes the assembly of a mitotic checkpoint complex (MCC), composed of BubR1, Bub3, Cdc20, and Mad2, which inhibits the activity of the anaphase-promoting complex/cyclosome (APC/C) ubiquitin ligase. When the checkpoint is satisfied, anaphase is initiated by the disassembly of MCC. Previous studies indicated that the dissociation of APC/C-bound MCC requires ubiquitylation and suggested that the target of ubiquitylation is the Cdc20 component of MCC. However, it remained unknown how ubiquitylation causes the release of MCC from APC/C and its disassembly and whether ubiquitylation of additional proteins is involved in this process. We find that ubiquitylation causes the dissociation of BubR1 from Cdc20 in MCC and suggest that this may lead to the release of MCC components from APC/C. BubR1 in MCC is ubiquitylated by APC/C, although to a lesser degree than Cdc20. The extent of BubR1 ubiquitylation was markedly increased in recombinant MCC that contained a lysine-less mutant of Cdc20. Mutation of lysine residues to arginines in the N-terminal region of BubR1 partially inhibited its ubiquitylation and slowed down the release of MCC from APC/C, provided that Cdc20 ubiquitylation was also blocked. It is suggested that ubiquitylation of both Cdc20 and BubR1 may be involved in their dissociation from each other and in the release of MCC components from APC/C.