Microtubule depolymerases of the kinesin-13 family play important roles in various cellular processes and are frequently overexpressed in different cancer types. Despite the importance of their correct abundance, remarkably little is known about how their levels are regulated in cells. Using comprehensive screening on protein microarrays, we identified 161 candidate substrates of the multi-subunit ubiquitin E3 ligase SCF^Fbxw5, including the kinesin-13 member Kif2c/MCAK. In vitro reconstitution assays demonstrate that MCAK and its closely related orthologs Kif2a and Kif2b become efficiently polyubiquitylated by neddylated SCF^Fbxw5 and Cdc34, without requiring preceding modifications. In cells, SCF^Fbxw5 targets MCAK for proteasomal degradation predominantly during G₂. While this seems largely dispensable for mitotic progression, loss of Fbxw5 leads to increased MCAK levels at basal bodies and impairs ciliogenesis in the following G₁/G₀, which can be rescued by concomitant knockdown of MCAK, Kif2a or Kif2b. We thus propose a novel regulatory event of ciliogenesis that begins already within the G₂ phase of the preceding cell cycle.

中文翻译：

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SCFFbxw5 靶向驱动蛋白 13 蛋白以促进纤毛发生

驱动蛋白 13 家族的微管解聚酶在各种细胞过程中发挥重要作用，并且在不同的癌症类型中经常过度表达。尽管它们的正确丰度很重要，但人们对它们在细胞中的水平如何调节知之甚少。通过对蛋白质微阵列的全面筛选，我们鉴定了多亚基泛素 E3 连接酶 SCF ^Fbxw5的 161 个候选底物，包括驱动蛋白 13 成员 Kif2c/MCAK。体外重构测定表明，MCAK 及其密切相关的直系同源物 Kif2a 和 Kif2b 可以被 neddylated SCF ^Fbxw5和 Cdc34 有效地多泛素化，而无需事先进行修饰。在细胞中，SCF ^Fbxw5 主要在 G ₂期间以 MCAK 为目标进行蛋白酶体降解。_{虽然这对于有丝分裂进展来说似乎是可有可无的，但 Fbxw5 的缺失会导致基体的 MCAK 水平升高，并损害接下来的 G 1} /G ₀中的纤毛发生，这可以通过同时敲低 MCAK、Kif2a 或 Kif2b 来挽救。因此，我们提出了一种新的纤毛发生调控事件，该事件已经在前一细胞周期的G _{2期内开始。}