The Mad2 spindle checkpoint protein has two distinct natively folded states
The Mad2 spindle checkpoint protein has two distinct natively folded states
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DOI：
10.1038/nsmb748
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发表时间：
2004-04-01
影响因子：
16.8
通讯作者：
Yu, HT
中科院分区：
文献类型：
--
作者：
Luo, XL;Tang, ZY;Yu, HT
纺锤体检查点延迟染色体分离，以响应在有丝分裂过程中不对齐的姐妹染色单体，从而确保染色体遗传的保真度。通过与Cdc20结合，Mad2纺锤体检查点蛋白抑制该检查点的靶点，泛素蛋白连接酶APC/C-Cdc20。我们现在表明，在没有辅因子结合或共价修饰的情况下，Mad2在平衡状态下采用两种不同的折叠构象（称为N1-Mad2和N2-Mad2）。用核磁共振光谱法测定了N2-Mad2的结构。N2-Mad2在APC/C抑制中更有效。特异性隔离N2-Mad2的Mad2突变体的过表达部分阻断活细胞中的检查点信号传导。这两种Mad2构象在体外相互转化缓慢，但Mad2的上游调控因子Mad1的一个片段加速了相互转化。我们的研究结果表明，Mad2不寻常的双态行为对纺锤体检查点信号传导至关重要。
The spindle checkpoint delays chromosome segregation in response to misaligned sister chromatids during mitosis, thus ensuring the fidelity of chromosome inheritance. Through binding to Cdc20, the Mad2 spindle checkpoint protein inhibits the target of this checkpoint, the ubiquitin protein ligase APC/C-Cdc20. We now show that without cofactor binding or covalent modification Mad2 adopts two distinct folded conformations at equilibrium ( termed N1-Mad2 and N2-Mad2). The structure of N2-Mad2 has been determined by NMR spectroscopy. N2-Mad2 is much more potent in APC/C inhibition. Overexpression of a Mad2 mutant that specifically sequesters N2-Mad2 partially blocks checkpoint signaling in living cells. The two Mad2 conformers interconvert slowly in vitro, but interconversion is accelerated by a fragment of Mad1, an upstream regulator of Mad2. Our results suggest that the unusual two-state behavior of Mad2 is critical for spindle checkpoint signaling.