Department of Bioengineering & Therapeutic Sciences, UCSF, 600 16th Street, San Francisco, CA 94158, USA.
Department of Bioengineering & Therapeutic Sciences, UCSF, 600 16th Street, San Francisco, CA 94158, USA.
Curr Biol. 2022 Jun 20;32(12):2621-2631.e3. doi: 10.1016/j.cub.2022.04.061. Epub 2022 May 16.
The kinetochore links chromosomes to spindle microtubules to drive chromosome segregation at cell division. While we know nearly all mammalian kinetochore proteins, how these give rise to the strong yet dynamic microtubule attachments required for function remains poorly understood. Here, we focus on the Astrin-SKAP complex, which localizes to bioriented kinetochores and is essential for chromosome segregation but whose mechanical role is unclear. Live imaging reveals that SKAP depletion dampens the movement and decreases the coordination of metaphase sister kinetochores and increases the tension between them. Using laser ablation to isolate kinetochores bound to polymerizing versus depolymerizing microtubules, we show that without SKAP, kinetochores move slower on both polymerizing and depolymerizing microtubules and that more force is needed to rescue microtubules to polymerize. Thus, in contrast to the previously described kinetochore proteins that increase the grip on microtubules under force, Astrin-SKAP reduces the grip, increasing attachment dynamics and force responsiveness and reducing friction. Together, our findings suggest a model where the Astrin-SKAP complex effectively "lubricates" correct, bioriented attachments to help preserve them.
着丝粒将染色体与纺锤体微管连接起来，以在细胞分裂时驱动染色体分离。虽然我们几乎了解所有哺乳动物的着丝粒蛋白，但这些蛋白如何产生功能所需的强而动态的微管附着仍知之甚少。在这里，我们专注于 Astrin-SKAP 复合物，它定位于双定向着丝粒，对于染色体分离是必不可少的，但它的机械作用尚不清楚。实时成像显示，SKAP 耗竭会抑制中期姐妹着丝粒的运动和协调，并增加它们之间的张力。使用激光消融来分离结合在聚合和去聚合微管上的着丝粒，我们表明，没有 SKAP，着丝粒在聚合和去聚合微管上的运动速度更慢，需要更大的力才能恢复微管聚合。因此，与之前描述的在力的作用下增加微管抓握力的着丝粒蛋白不同，Astrin-SKAP 降低了抓握力，增加了附着动力学和力响应性，并减少了摩擦力。总之，我们的研究结果表明，Astrin-SKAP 复合物的有效“润滑”有助于正确的双定向附着的保持。
