Recovery from spindle checkpoint-mediated arrest requires a novel Dnt1-dependent APC/C activation mechanism.
Recovery from spindle checkpoint-mediated arrest requires a novel Dnt1-dependent APC/C activation mechanism.
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从纺锤体检查点介导的停滞中恢复需要一种新型的 Dnt1 依赖性 APC/C 激活机制。
DOI：
10.1371/journal.pgen.1010397
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发表时间：
2022-09
期刊：
影响因子：
4.5
通讯作者：
中科院分区：
文献类型：
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作者：
激活的纺锤体组装检查点（SAC）有效地抑制后期促进复合物/环体（APC/C），以确保在后期准确的染色体分离。早期的研究已经认识到，SAC应该在几分钟内沉默，以便在所有动粒正确附着后快速激活APC/C和同步分离染色体，但潜在的沉默剂仍在阐明中。在这里，我们报告说，及时沉默的SAC在裂殖酵母需要dnt 1+，这会导致严重的噻苯咪唑（TBZ）的敏感性和增加率落后染色体删除时。Dnt 1的缺失导致有丝分裂检查点复合物（MCC）与APC/C的抑制性结合延长，Slp 1 Cdc 20蛋白水平降低，从而减缓细胞周期蛋白B和securin的降解，最终延迟SAC激活释放的细胞进入后期。有趣的是，Dnt 1在SAC激活后与APC/C物理结合。我们建议，这种协会可能会抵御过度和长期MCC结合APC/C，并有助于保持Slp 1Cdc 20的稳定性。这可能允许APC/C的一个子集保留活性，从而确保一旦SAC失活，后期快速开始和有丝分裂退出。因此，我们的研究发现了一个新的球员在决定APC/C激活的时间和功效，这是积极需要从纺锤体检查点抑制APC/C恢复后保持细胞活力。在真核细胞有丝分裂周期中，后期促进复合物/细胞周期体（APC/C）泛素连接酶受到严格的调控，以确保securin和cyclin B的程序化泛素化和蛋白水解，从而启动后期进入和有丝分裂退出。APC/C活性的多方面负调控主要通过其有效抑制剂有丝分裂检查点复合物（MCC）的直接结合来介导。在这项研究中，我们已经确定了一个意想不到的作用，为分裂酵母核仁蛋白Dnt 1在维持足够水平的APC/C共激活剂，Slp 1Cdc 20，进入后期，并抑制过度抑制作用MCC对APC/C激活。有趣的是，Dnt 1在纺锤体组装检查点（SAC）激活后与APC/C物理相互作用，这可能使其能够主动微调MCC与APC/C的缔合，特别是在SAC失活和有丝分裂退出过程中。我们的研究还表明，当酵母细胞从纺锤体检查点对APC/C的抑制中释放出来时，Dnt 1积极参与维持细胞活力。
The activated spindle assembly checkpoint (SAC) potently inhibits the anaphase-promoting complex/cyclosome (APC/C) to ensure accurate chromosome segregation at anaphase. Early studies have recognized that the SAC should be silenced within minutes to enable rapid APC/C activation and synchronous segregation of chromosomes once all kinetochores are properly attached, but the underlying silencers are still being elucidated. Here, we report that the timely silencing of SAC in fission yeast requires dnt1+, which causes severe thiabendazole (TBZ) sensitivity and increased rate of lagging chromosomes when deleted. The absence of Dnt1 results in prolonged inhibitory binding of mitotic checkpoint complex (MCC) to APC/C and attenuated protein levels of Slp1Cdc20, consequently slows the degradation of cyclin B and securin, and eventually delays anaphase entry in cells released from SAC activation. Interestingly, Dnt1 physically associates with APC/C upon SAC activation. We propose that this association may fend off excessive and prolonged MCC binding to APC/C and help to maintain Slp1Cdc20 stability. This may allow a subset of APC/C to retain activity, which ensures rapid anaphase onset and mitotic exit once SAC is inactivated. Therefore, our study uncovered a new player in dictating the timing and efficacy of APC/C activation, which is actively required for maintaining cell viability upon recovery from the inhibition of APC/C by spindle checkpoint. During eukaryotic mitotic cycle, the anaphase-promoting complex/cyclosome (APC/C) ubiquitin ligase is tightly regulated to ensure programmed ubiquitination and proteolysis of securin and cyclin B to consequently initiate anaphase entry and mitotic exit. Multifaceted negative regulation of the APC/C activity is mediated primarily through direct binding by its potent inhibitor, the mitotic checkpoint complex (MCC). Here in this study, we have identified an unexpected role for the fission yeast nucleolar protein Dnt1 in maintaining a sufficient level of APC/C co-activator, Slp1Cdc20, for anaphase entry, and restraining overly inhibitory action of MCC on APC/C activation. Interestingly, Dnt1 physically interacts with APC/C upon spindle assembly checkpoint (SAC) activation, this possibly allows it to actively fine tune the association of MCC with APC/C, especially during the process of SAC inactivation and mitotic exit. Our study also revealed that Dnt1 is actively involved in maintaining cell viability when yeast cells are released from the inhibition of APC/C by spindle checkpoint.
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