Myosins are ATP‐dependent actin‐based molecular motors critical for diverse cellular processes like intracellular trafficking, cell motility, and cell invasion. During cell division, myosin MYO10 is important for proper mitotic spindle assembly, the anchoring of the spindle to the cortex, and positioning of the spindle to the cell mid‐plane. However, myosins are regulated by myosin regulatory light chains (RLCs), and whether RLCs are important for cell division has remained unexplored. Here, we have determined that the previously uncharacterized myosin RLC Myl5 associates with the mitotic spindle and is required for cell division. We show that Myl5 localizes to the leading edge and filopodia during interphase and to mitotic spindle poles and spindle microtubules during early mitosis. Importantly, depletion of Myl5 led to defects in mitotic spindle assembly, chromosome congression, and chromosome segregation and to a slower transition through mitosis. Furthermore, Myl5 bound to MYO10 in vitro and co‐localized with MYO10 at the spindle poles. These results suggest that Myl5 is important for cell division and that it may be performing its function through MYO10.

中文翻译：

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肌球蛋白调节轻链 Myl5 定位于有丝分裂纺锤体极，是正常细胞分裂所必需的

肌球蛋白是依赖于 ATP 的基于肌动蛋白的分子马达，对于细胞内运输、细胞运动和细胞侵袭等多种细胞过程至关重要。在细胞分裂过程中，肌球蛋白 MYO10 对正确的有丝分裂纺锤体组装、纺锤体与皮层的锚定以及纺锤体与细胞中平面的定位非常重要。然而，肌球蛋白受肌球蛋白调节轻链 (RLC) 的调节，而 RLC 是否对细胞分裂很重要尚未探索。在这里，我们已经确定以前未表征的肌球蛋白 RLC Myl5 与有丝分裂纺锤体相关，并且是细胞分裂所必需的。我们显示Myl5 在间期定位于前缘和丝状伪足，在早期有丝分裂期间定位于有丝分裂纺锤体极和纺锤体微管。重要的，Myl5 的缺失导致有丝分裂纺锤体组装、染色体聚集和染色体分离的缺陷，并导致有丝分裂的过渡变慢。此外，Myl5 在体外与 MYO10 结合，并与 MYO10 在纺锤体两极共定位。这些结果表明 Myl5 对细胞分裂很重要，它可能通过 MYO10 发挥其功能。