Cancer Cell Biology, Institute of Molecular Genetics, Czech Academy of Sciences, Prague CZ14220, Czech Republic.
Institute for Clinical and Experimental Pharmacology and Toxicology I, Medical Faculty, University of Freiburg, Freiburg 79104, Germany.
Proc Natl Acad Sci U S A. 2024 Jul 16;121(29):e2321647121. doi: 10.1073/pnas.2321647121. Epub 2024 Jul 12.
Precise segregation of chromosomes during mitosis requires assembly of a bipolar mitotic spindle followed by correct attachment of microtubules to the kinetochores. This highly spatiotemporally organized process is controlled by various mitotic kinases and molecular motors. We have recently shown that Casein Kinase 1 (CK1) promotes timely progression through mitosis by phosphorylating FAM110A leading to its enrichment at spindle poles. However, the mechanism by which FAM110A exerts its function in mitosis is unknown. Using structure prediction and a set of deletion mutants, we mapped here the interaction of the N- and C-terminal domains of FAM110A with actin and tubulin, respectively. Next, we found that the FAM110A-Δ40-61 mutant deficient in actin binding failed to rescue defects in chromosomal alignment caused by depletion of endogenous FAM110A. Depletion of FAM110A impaired assembly of F-actin in the proximity of spindle poles and was rescued by expression of the wild-type FAM110A, but not the FAM110A-Δ40-61 mutant. Purified FAM110A promoted binding of F-actin to microtubules as well as bundling of actin filaments in vitro. Finally, we found that the inhibition of CK1 impaired spindle actin formation and delayed progression through mitosis. We propose that CK1 and FAM110A promote timely progression through mitosis by mediating the interaction between spindle microtubules and filamentous actin to ensure proper mitotic spindle formation.
在有丝分裂过程中，染色体的精确分离需要组装一个两极纺锤体，然后微管正确地附着到动粒上。这个高度时空组织的过程受到各种有丝分裂激酶和分子马达的控制。我们最近表明，酪蛋白激酶 1（CK1）通过磷酸化 FAM110A 促进有丝分裂的适时进展，导致其在纺锤体极富集。然而，FAM110A 在有丝分裂中发挥其功能的机制尚不清楚。我们使用结构预测和一系列缺失突变体，在这里分别映射了 FAM110A 的 N 端和 C 端结构域与肌动蛋白和微管蛋白的相互作用。接下来，我们发现缺乏与肌动蛋白结合能力的 FAM110A-Δ40-61 突变体不能挽救内源性 FAM110A 耗竭引起的染色体排列缺陷。FAM110A 的耗竭破坏了纺锤体极附近的 F-肌动蛋白的组装，而野生型 FAM110A 的表达可以挽救这种缺陷，但 FAM110A-Δ40-61 突变体则不能。纯化的 FAM110A 促进了 F-肌动蛋白与微管的结合以及肌动蛋白丝的成束。最后，我们发现 CK1 的抑制破坏了纺锤体肌动蛋白的形成，并延迟了有丝分裂的进程。我们提出，CK1 和 FAM110A 通过介导纺锤体微管和丝状肌动蛋白之间的相互作用，促进有丝分裂的适时进展，以确保有丝分裂纺锤体的正常形成。
