Division of Molecular Biology, Ruđer Bošković Institute, Zagreb, Croatia.
Elife. 2021 Jan 22;10:e61170. doi: 10.7554/eLife.61170.
During metaphase, chromosome position at the spindle equator is regulated by the forces exerted by kinetochore microtubules and polar ejection forces. However, the role of forces arising from mechanical coupling of sister kinetochore fibers with bridging fibers in chromosome alignment is unknown. Here, we develop an optogenetic approach for acute removal of PRC1 to partially disassemble bridging fibers and show that they promote chromosome alignment. Tracking of the plus-end protein EB3 revealed longer antiparallel overlaps of bridging microtubules upon PRC1 removal, which was accompanied by misaligned and lagging kinetochores. Kif4A/kinesin-4 and Kif18A/kinesin-8 were found within the bridging fiber and largely lost upon PRC1 removal, suggesting that these proteins regulate the overlap length of bridging microtubules. We propose that PRC1-mediated crosslinking of bridging microtubules and recruitment of kinesins to the bridging fiber promote chromosome alignment by overlap length-dependent forces transmitted to the associated kinetochore fibers.
在中期，染色体在纺锤体赤道处的位置由动粒微管和极性逐出力产生的力来调节。然而，姐妹动粒纤维与桥接纤维的机械耦合产生的力在染色体排列中的作用尚不清楚。在这里，我们开发了一种光遗传学方法来急性去除 PRC1，部分解聚桥接纤维，并表明它们促进染色体排列。EB3 加端蛋白的追踪显示，PRC1 去除后桥接微管的反平行重叠更长，随之而来的是动粒未对齐和滞后。Kif4A/驱动蛋白-4 和 Kif18A/驱动蛋白-8 存在于桥接纤维中，并且在 PRC1 去除后大量丢失，这表明这些蛋白质调节桥接微管的重叠长度。我们提出 PRC1 介导的桥接微管交联和向桥接纤维募集驱动蛋白通过传递给相关动粒纤维的重叠长度依赖性力来促进染色体排列。
