The Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, Copenhagen, Denmark.
J Cell Sci. 2012 Jul 1;125(Pt 13):3243-53. doi: 10.1242/jcs.104208. Epub 2012 Mar 27.
The Ndc80 complex establishes end-on attachment of kinetochores to microtubules, which is essential for chromosome segregation. The Ndc80 subunit is characterized by an N-terminal region that binds directly to microtubules, and a long coiled-coil region that interacts with Nuf2. A loop region in Ndc80 that generates a kink in the structure disrupts the long coiled-coil region but the exact function of this loop, has until now, not been clear. Here we show that this loop region is essential for end-on attachment of kinetochores to microtubules in human cells. Cells expressing loop mutants of Ndc80 are unable to align the chromosomes, and stable kinetochore fibers are absent. Through quantitative mass spectrometry and immunofluorescence we found that the binding of the spindle and kinetochore associated (Ska) complex depends on the loop region, explaining why end-on attachment is defective. This underscores the importance of the Ndc80 loop region in coordinating chromosome segregation through the recruitment of specific proteins to the kinetochore.
Ndc80 复合物将动粒与微管建立末端连接，这对于染色体分离至关重要。Ndc80 亚基的特征是具有一个直接结合微管的 N 端区域，和一个与 Nuf2 相互作用的长螺旋卷曲区域。Ndc80 中的一个环区在结构中产生一个扭曲，破坏了长螺旋卷曲区域，但这个环的具体功能直到现在还不清楚。在这里，我们表明，这个环区对于人细胞中动粒与微管的末端连接是必不可少的。表达环突变体的 Ndc80 的细胞无法使染色体排列整齐，并且稳定的动粒纤维也不存在。通过定量质谱和免疫荧光，我们发现纺锤体和着丝粒相关 (Ska) 复合物的结合依赖于环区，这解释了为什么末端连接是有缺陷的。这强调了 Ndc80 环区在通过招募特定蛋白质到动粒来协调染色体分离中的重要性。
