Microtubules growing and shortening under constant force

Kinetochores are macromolecular machines that couple chromosomes to dynamic microtubule tips during cell division, thereby generating force to segregate the chromosomes. Accurate segregation depends on selective stabilization of correct 'bi-oriented' kinetochore-microtubule attachments, which come under tension as the result of opposing forces exerted by microtubules. Tension is thought to stabilize these bi-oriented attachments indirectly, by suppressing the destabilizing activity of a kinase, Aurora B. However, a complete mechanistic understanding of the role of tension requires reconstitution of kinetochore-microtubule attachments for biochemical and biophysical analyses in vitro. Here we show that native kinetochore particles retaining the majority of kinetochore proteins can be purified from budding yeast and used to reconstitute dynamic microtubule attachments. Individual kinetochore particles maintain load-bearing associations with assembling and disassembling ends of single mi...动粒（kinetochore）是一类大分子机器，在细胞分裂过程中介导染色体与动态微管末端的耦联，进而产生拉力以实现染色体分离。精准的染色体分离依赖于对正确“双定向（bi-oriented）”动粒-微管附着的选择性稳定：此类附着会因微管施加的反向拉力而承受张力。目前学界认为，张力可通过抑制奥罗拉B（Aurora B）激酶的去稳定活性，间接稳定这类双定向附着。然而，要完整阐明张力的作用机制，需在体外重构动粒-微管附着体系以开展生化与生物物理分析。本研究证实，可从出芽酵母中纯化得到保留绝大多数动粒蛋白的天然动粒颗粒，并利用其重构动态微管附着。单个动粒颗粒可与单根微管的组装/去组装末端维持承重关联……