Division of Molecular Biology, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia.
Department of Physics, Faculty of Science, University of Zagreb, Bijenička cesta 32, 10000 Zagreb, Croatia.
Curr Biol. 2021 May 24;31(10):R574-R585. doi: 10.1016/j.cub.2021.03.082.
During metaphase, chromosomes are aligned in a lineup at the equatorial plane of the spindle to ensure synchronous poleward movement of chromatids in anaphase and proper nuclear reformation at the end of mitosis. Chromosome alignment relies on microtubules, several types of motor protein and numerous other microtubule-associated and regulatory proteins. Because of the multitude of players involved, the mechanisms of chromosome alignment are still under debate. Here, we discuss the current models of alignment based on poleward pulling forces exerted onto sister kinetochores by kinetochore microtubules, which show length-dependent dynamics and undergo poleward flux, and polar ejection forces that push the chromosome arms away from the pole. We link these models with the recent ideas based on mechanical coupling between bridging and kinetochore microtubules, where sliding of bridging microtubules promotes overlap length-dependent sliding of kinetochore fibers and thus the alignment of sister kinetochores at the spindle equator. Finally, we discuss theoretical models of forces acting on chromosomes during metaphase.
在中期，染色体排列在纺锤体赤道平面的一条线上，以确保后期姐妹染色单体向两极的同步运动以及有丝分裂末期核的正确重建。染色体的排列依赖于微管、几种类型的马达蛋白以及许多其他与微管相关的调节蛋白。由于涉及的参与者众多，染色体排列的机制仍存在争议。在这里，我们根据姐妹动粒微管对动粒施加的向极牵拉力讨论当前的排列模型，这些牵拉力表现出长度依赖性动力学并发生向极流动，以及将染色体臂推向两极的极逐出力。我们将这些模型与基于桥连微管和动粒微管之间机械耦合的最新想法联系起来，其中桥连微管的滑动促进了动粒纤维的重叠长度依赖性滑动，从而在纺锤体赤道处使姐妹动粒对齐。最后，我们讨论有丝分裂中期作用于染色体的力的理论模型。
