Genetics Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA.
PLoS One. 2013 May 30;8(5):e64575. doi: 10.1371/journal.pone.0064575. Print 2013.
Integrity of the microtubule spindle apparatus and intact cell division checkpoints are essential to ensure the fidelity of distributing chromosomes into daughter cells. Cytoskeleton-associated protein 2, CKAP2, is a microtubule-associated protein that localizes to spindle poles and aids in microtubule stabilization, but the exact function and mechanism of action are poorly understood. In the present study, we utilized RNA interference to determine the extent to which the expression of CKAP2 plays a role in chromosome segregation. CKAP2-depleted cells showed a significant increase of multipolar mitoses and other spindle pole defects. Notably, when interrogated for microtubule nucleation capacity, CKAP2-depleted cells showed a very unusual phenotype as early as two minutes after release from mitotic block, consisting of dispersal of newly polymerized microtubule filaments through the entire chromatin region, creating a cage-like structure. Nevertheless, spindle poles were formed after one hour of mitotic release suggesting that centrosome-mediated nucleation remained dominant. Finally, we showed that suppression of CKAP2 resulted in a higher incidence of merotelic attachments, anaphase lagging, and polyploidy. Based on these results, we conclude that CKAP2 is involved in the maintenance of microtubule nucleation sites, focusing microtubule minus ends to the spindle poles in early mitosis, and is implicated in maintaining genome stability.
微管纺锤体装置的完整性和完整的细胞分裂检查点对于确保染色体准确分配到子细胞中至关重要。细胞骨架相关蛋白 2（CKAP2）是一种微管相关蛋白，定位于纺锤体两极，有助于微管的稳定，但确切的功能和作用机制尚不清楚。在本研究中，我们利用 RNA 干扰技术确定 CKAP2 的表达在染色体分离中的作用程度。CKAP2 耗竭的细胞表现出多极有丝分裂和其他纺锤体极缺陷的显著增加。值得注意的是，当检测 CKAP2 耗竭细胞的微管成核能力时，在从有丝分裂阻断中释放后仅两分钟，就观察到一种非常异常的表型，即新聚合的微管丝通过整个染色质区域扩散，形成笼状结构。然而，在有丝分裂释放后一个小时形成了纺锤体极，这表明中心体介导的成核仍然占主导地位。最后，我们表明 CKAP2 的抑制导致更多的桥接连接、后期滞后和多倍体形成。基于这些结果，我们得出结论，CKAP2 参与维持微管成核位点，在早期有丝分裂中将微管的负端聚焦到纺锤体极，并与维持基因组稳定性有关。
