The checkpoint protein MAD2 and the mitotic regulator CDC20 form a ternary complex with the anaphase-promoting complex to control anaphase initiation
The checkpoint protein MAD2 and the mitotic regulator CDC20 form a ternary complex with the anaphase-promoting complex to control anaphase initiation
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DOI：
10.1101/gad.12.12.1871
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发表时间：
1998-06-15
影响因子：
10.5
通讯作者：
Kirschner, MW
中科院分区：
文献类型：
--
作者：
Fang, GW;Yu, HT;Kirschner, MW
纺锤体组装检查点机制延迟后期启动，直到所有染色体在中期板对齐。退出有丝分裂需要通过结合 CDC20 和 CDH1 来激活后期促进复合物 (APC)，并且 APC 已被认为是检查点干预的目标。我们发现人类检查点蛋白 hlMAD2 通过形成 hMAD2-CDC20-APC 复合物来防止 APC 的激活。当注射到非洲爪蟾胚胎中时，hMAD2 使用非活性 APC 将细胞阻滞在有丝分裂中。重组 hMAD2 蛋白以两种折叠状态存在：四聚体和单体。四聚体和单体均与 CDC20 结合，但只有四聚体抑制 APC 的激活并阻断细胞周期进程。因此，hMAD2 结合不足以抑制，hMAD2 结构的变化可能在转导检查点信号中发挥作用。体内至少可以检测到三种不同形式的有丝分裂 APC：存在于中期的无活性 hMAD2-CDC20-APC 三元复合物、在后期具有降解特定底物活性的 CDC20-APC 二元复合物以及在有丝分裂后期和 G(1) 中具有活性的 CDH1-APC 复合物。我们得出结论，检查点介导的细胞周期停滞涉及 hMAD2 接收上游信号以抑制 APC 的激活。
The spindle assembly checkpoint mechanism delays anaphase initiation until all chromosomes are aligned at the metaphase plate. Activation of the anaphase-promoting complex (APC) by binding of CDC20 and CDH1 is required for exit from mitosis, and APC has been implicated as a target for the checkpoint intervention. We show that the human checkpoint protein hlMAD2 prevents activation of APC by forming a hMAD2-CDC20-APC complex. When injected into Xenopus embryos, hMAD2 arrests cells at mitosis with an inactive APC. The recombinant hMAD2 protein exists in two-folded states: a tetramer and a monomer. Both the tetramer and the monomer bind to CDC20, but only the tetramer inhibits activation of APC and blocks cell cycle progression. Thus, hMAD2 binding is not sufficient for inhibition, and a change in hMAD2 structure may play a role in transducing the checkpoint signal. There are at least three different forms of mitotic APC that can be detected in vivo: an inactive hMAD2-CDC20-APC ternary complex present at metaphase, a CDC20-APC binary complex active in degrading specific substrates at anaphase, and a CDH1-APC complex active later in mitosis and in G(1). We conclude that the checkpoint-mediated cell cycle arrest involves hMAD2 receiving an upstream signal to inhibit activation of APC.