Laboratory of Biosignaling & Therapeutics, Department of Cellular and Molecular Medicine, University of Leuven, 3000 Leuven, Belgium.
Departament de Biotecnologia, Universitat Politècnica de València, Camino de Vera, 14, 46022 Valencia, Spain.
Mol Cell. 2017 Nov 16;68(4):715-730.e5. doi: 10.1016/j.molcel.2017.10.011. Epub 2017 Nov 9.
The spindle assembly checkpoint (SAC) generates a diffusible protein complex that prevents anaphase until all chromosomes are properly attached to spindle microtubules. A key step in SAC initiation is the recruitment of MAD1 to kinetochores, which is generally thought to be governed by the microtubule-kinetochore (MT-KT) attachment status. However, we demonstrate that the recruitment of MAD1 via BUB1, a conserved kinetochore receptor, is not affected by MT-KT interactions in human cells. Instead, BUB1:MAD1 interaction depends on BUB1 phosphorylation, which is controlled by a biochemical timer that integrates counteracting kinase and phosphatase effects on BUB1 into a pulse-generating incoherent feedforward loop. We propose that this attachment-independent timer serves to rapidly activate the SAC at mitotic entry, before the attachment-sensing MAD1 receptors have become fully operational. The BUB1-centered timer is largely impervious to conventional anti-mitotic drugs, and it is, therefore, a promising therapeutic target to induce cell death through permanent SAC activation.
纺锤体组装检查点 (SAC) 会产生一种可扩散的蛋白质复合物，该复合物可以防止后期进入，直到所有染色体都正确连接到纺锤体微管上。SAC 起始的一个关键步骤是将 MAD1 招募到动粒上，这通常被认为是由微管-动粒 (MT-KT) 连接状态控制的。然而，我们证明，在人类细胞中，通过 BUB1（一种保守的动粒受体）招募 MAD1 不受 MT-KT 相互作用的影响。相反，BUB1:MAD1 相互作用取决于 BUB1 的磷酸化，这是由一个生化定时器控制的，该定时器将对 BUB1 的拮抗激酶和磷酸酶效应整合到一个产生脉冲的非相干前馈回路中。我们提出，这种不依赖于连接的定时器可用于在有丝分裂进入之前快速激活 SAC，此时附着感应 MAD1 受体尚未完全发挥作用。以 BUB1 为中心的定时器对传统的抗有丝分裂药物几乎不敏感，因此，它是一个很有前途的治疗靶点，可以通过永久性 SAC 激活诱导细胞死亡。
