During cytokinesis, signals from the anaphase spindle direct the formation and position of a contractile ring at the cell cortex [1]. The chromosomal passenger complex (CPC) participates in cytokinesis initiation by signaling from the spindle midzone and equatorial cortex [2], but the mechanisms underlying the anaphase-specific CPC localization are currently unresolved. Accumulation of the CPC at these sites requires the presence of microtubules and the mitotic kinesin-like protein 2, MKLP2 (KIF20A), a member of the kinesin-6 family [2, 3, 4, 5, 6, 7], and this has led to the hypothesis that the CPC is transported along microtubules by MKLP2 [3, 4, 5, 7]. However, the structure of the MKLP2 motor domain with its extended neck-linker region suggests that this kinesin might not be able to drive processive transport [8, 9]. Furthermore, experiments in Xenopus egg extracts indicated that the CPC might be transported by kinesin-4, KIF4A [10]. Finally, CPC-MKLP2 complexes might be directly recruited to the equatorial cortex via association with actin and myosin II, independent of kinesin activity [4, 8]. Using microscopy-based assays with purified proteins, we demonstrate that MKLP2 is a processive plus-end directed motor that can transport the CPC along microtubules in vitro. In cells, strong suppression of MKLP2-dependent CPC motility by expression of an MKLP2 P-loop mutant perturbs CPC accumulation at both the spindle midzone and equatorial cortex, whereas a weaker inhibition of MKLP2 motor using Paprotrain mainly affects CPC localization to the equatorial cortex. Our data indicate that control of cytokinesis initiation by the CPC requires its directional MKLP2-dependent transport.

在胞质分裂期间，来自后期纺锤体的信号指导细胞皮层收缩环的形成和位置 [1]。染色体乘客复合体 (CPC) 通过来自纺锤体中区和赤道皮层的信号参与胞质分裂起始 [2]，但后期特异性 CPC 定位的机制目前尚未解决。CPC 在这些位点的积累需要存在微管和有丝分裂驱动蛋白样蛋白 2，MKLP2 (KIF20A)，驱动蛋白 6 家族的成员 [2, 3, 4, 5, 6, 7]，这导致假设 CPC 由 MKLP2 沿微管运输 [3, 4, 5, 7]。然而，MKLP2 运动域的结构及其扩展的颈部链接器区域表明该驱动蛋白可能无法驱动进行性运输 [8, 9]。此外，爪蟾卵提取物表明 CPC 可能由驱动蛋白 4、KIF4A [10] 运输。最后，CPC-MKLP2 复合物可能通过与肌动蛋白和肌球蛋白 II 的结合而被直接募集到赤道皮层，独立于驱动蛋白活性 [4, 8]。使用基于显微镜的分析纯化蛋白质，我们证明 MKLP2 是一种进行性正端定向马达，可以在体外沿微管运输 CPC. 在细胞中，通过表达 MKLP2 P 环突变体对 MKLP2 依赖性 CPC 运动的强烈抑制扰乱了纺锤体中区和赤道皮层的 CPC 积累，而使用 Paprotrain 对 MKLP2 运动的较弱抑制主要影响 CPC 定位到赤道皮层。我们的数据表明，CPC 对胞质分裂起始的控制需要其定向 MKLP2 依赖性转运。