The S. cerevisiae protein Slk19 has been shown to localize to kinetochores throughout mitosis and to the spindle midzone in anaphase. However, Slk19 clearly also has an important role for spindle formation and stabilization in prometaphase and metaphase. Albeit this role is unresolved. Here we show that Slk19’s localization to metaphase spindles in vivo and to microtubules in vitro depends on the microtubule crosslinking protein Ase1 and the MT crosslinking and stabilizing protein Stu1. By analyzing a slk19 mutant that specifically fails to localize to spindles and microtubules, we surprisingly found that the presence of Slk19 amplified the amount of Ase1 strongly and that of Stu1 moderately at the metaphase spindle in vivo and at microtubules in vitro. Furthermore, Slk19 markedly enhanced the crosslinking of microtubules in vitro, when added together with Ase1 or Stu1. We therefore suggest that Slk19 recruits additional Ase1 and Stu1 to the interpolar microtubules of metaphase spindles and thus increases their crosslinking and stabilization. This is in agreement with our observation that cells with defective Slk19 localization exhibit shorter metaphase spindles, an increased number of unaligned nuclear microtubules and most likely reduced interpolar microtubule overlaps.

已显示酿酒酵母蛋白 Slk19 在有丝分裂过程中定位于动粒，并在后期定位于纺锤体中区。然而，Slk19 显然在前中期和中期的纺锤体形成和稳定中也具有重要作用。虽然这个角色还没有确定。在这里，我们表明 Slk19在体内对中期纺锤体和体外对微管的定位取决于微管交联蛋白 Ase1 和 MT 交联和稳定蛋白 Stu1。通过分析一个无法定位到纺锤体和微管的slk19突变体，我们惊奇地发现，在中期纺锤体中，Slk19 的存在强烈地放大了 Ase1 的数量，而 Stu1 的数量则适度增加。体内和体外微管. 此外，当与 Ase1 或 Stu1 一起添加时，Slk19在体外显着增强了微管的交联。因此，我们建议 Slk19 将额外的 Ase1 和 Stu1 募集到中期纺锤体的极间微管中，从而增加它们的交联和稳定性。这与我们的观察结果一致，即具有缺陷 Slk19 定位的细胞表现出较短的中期纺锤体，未对齐的核微管数量增加，并且极有可能减少了极间微管重叠。