An unconventional regulatory circuitry involving Aurora B controls anaphase onset and error-free chromosome segregation in trypanosomes.
An unconventional regulatory circuitry involving Aurora B controls anaphase onset and error-free chromosome segregation in trypanosomes.
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涉及 Aurora B 的非常规调控电路控制着锥虫的后期开始和无差错染色体分离。
DOI：
10.1101/2024.01.20.576407
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发表时间：
2024
期刊：
影响因子：
--
通讯作者：
Akiyoshi,Bungo
中科院分区：
文献类型：
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作者：
Ballmer,Daniel;Lou,HuaJane;Ishii,Midori;Turk,BenjaminE;Akiyoshi,Bungo
在有丝分裂过程中染色体的精确分离要求所有的染色体与纺锤体建立稳定的双向连接。动粒形成染色体和纺锤体微管之间的界面，因此受到复杂的调控电路的严格控制。作为染色体乘客复合体（CPC）的一部分，极光B激酶在该回路中起着核心作用，它通过使不适当的着丝粒-微管附着不稳定并将附着状态传递给纺锤体组装检查点，纺锤体组装检查点是一种反馈控制系统，通过抑制后期促进复合体/细胞周期体来延迟后期的开始。有趣的是，极光B甚至在动质体中也是保守的，动质体是一个进化上不同的真核生物群体，其动粒由一组独特的结构和调节蛋白组成。动质体没有一个典型的纺锤体检查点，目前还不清楚它们的动粒是如何调节的，以确保染色体分离的保真度和时间。在这里，我们表明，在布氏锥虫，动质体寄生虫，导致非洲昏睡病，抑制极光B使用类似物敏感的方法逮捕细胞中期，减少正确的双向动粒。Aurora B在体外磷酸化几种动粒蛋白，包括趋异Bub 1样蛋白KKT 14的N-末端区域。耗尽KKT 14部分覆盖极光B抑制引起的细胞周期停滞，而非磷酸化KKT 14蛋白的过度表达导致中期到后期过渡的显著延迟。最后，我们证明了使用基于纳米抗体的系统，将CPC的催化模块重新靶向到外部动粒足以促进有丝分裂退出，但会导致后期大量染色体错误分离。我们的研究结果表明，CPC和KKT 14参与了一个非常规的途径控制有丝分裂出口和错误的染色体分离锥虫。
Accurate chromosome segregation during mitosis requires that all chromosomes establish stable bi-oriented attachments with the spindle apparatus. Kinetochores form the interface between chromosomes and spindle microtubules and as such are under tight control by complex regulatory circuitry. As part of the chromosomal passenger complex (CPC), the Aurora B kinase plays a central role within this circuitry by destabilizing improper kinetochore-microtubule attachments and relaying the attachment status to the spindle assembly checkpoint, a feedback control system that delays the onset of anaphase by inhibiting the anaphase-promoting complex/cyclosome. Intriguingly, Aurora B is conserved even in kinetoplastids, an evolutionarily divergent group of eukaryotes, whose kinetochores are composed of a unique set of structural and regulatory proteins. Kinetoplastids do not have a canonical spindle checkpoint and it remains unclear how their kinetochores are regulated to ensure the fidelity and timing of chromosome segregation. Here, we show in Trypanosoma brucei, the kinetoplastid parasite that causes African sleeping sickness, that inhibition of Aurora B using an analogue-sensitive approach arrests cells in metaphase, with a reduction in properly bi-oriented kinetochores. Aurora B phosphorylates several kinetochore proteins in vitro, including the N-terminal region of the divergent Bub1-like protein KKT14. Depletion of KKT14 partially overrides the cell cycle arrest caused by Aurora B inhibition, while overexpression of a non-phosphorylatable KKT14 protein results in a prominent delay in the metaphase-to-anaphase transition. Finally, we demonstrate using a nanobody-based system that re-targeting the catalytic module of the CPC to the outer kinetochore is sufficient to promote mitotic exit but causes massive chromosome mis-segregation in anaphase. Our results indicate that the CPC and KKT14 are involved in an unconventional pathway controlling mitotic exit and error-free chromosome segregation in trypanosomes.