1] Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), 1030 Vienna, Austria [2] Institute of Biochemistry, ETH Zurich, 8093 Zurich, Switzerland [3] Marine Biological Laboratory, Woods Hole, Massachusetts 02543, USA.
Nat Cell Biol. 2013 Nov;15(11):1370-7. doi: 10.1038/ncb2842. Epub 2013 Oct 6.
The mitotic spindle assembly checkpoint (SAC) delays anaphase onset until all chromosomes have attached to both spindle poles. Here, we investigated SAC signalling kinetics in response to acute detachment of individual chromosomes using laser microsurgery. Most detached chromosomes delayed anaphase until they had realigned to the metaphase plate. A substantial fraction of cells, however, entered anaphase in the presence of unaligned chromosomes. We identify two mechanisms by which cells can bypass the SAC: first, single unattached chromosomes inhibit the anaphase-promoting complex/cyclosome (APC/C) less efficiently than a full complement of unattached chromosomes; second, because of the relatively slow kinetics of re-imposing APC/C inhibition during metaphase, cells were unresponsive to chromosome detachment up to several minutes before anaphase onset. Our study defines when cells irreversibly commit to enter anaphase and shows that the SAC signal strength correlates with the number of unattached chromosomes. Detailed knowledge about SAC signalling kinetics is important for understanding the emergence of aneuploidy and the response of cancer cells to chemotherapeutics targeting the mitotic spindle.
有丝分裂纺锤体组装检查点（SAC）会延迟后期起始，直到所有染色体都连接到两个纺锤极上。在这里，我们使用激光微手术研究了单个染色体急性脱离时 SAC 信号转导的动力学。大多数脱离的染色体会延迟后期，直到它们重新排列到中期板上。然而，相当一部分细胞在未对齐的染色体存在的情况下进入后期。我们确定了细胞可以绕过 SAC 的两种机制：首先，单个未连接的染色体比完整的未连接染色体对促进有丝分裂的复合物/周期蛋白（APC/C）的抑制作用更弱；其次，由于在中期重新施加 APC/C 抑制的动力学相对较慢，因此细胞在后期开始前几分钟对染色体脱离没有反应。我们的研究定义了细胞不可逆地进入后期的时间，并表明 SAC 信号强度与未连接染色体的数量相关。详细了解 SAC 信号转导动力学对于理解非整倍体的出现以及癌细胞对针对有丝分裂纺锤体的化疗药物的反应非常重要。
