Department of Cell Biology, Institute for Virus Research, Kyoto University, Kyoto 606-8507, Japan.
Nat Commun. 2012 Jan 17;3:626. doi: 10.1038/ncomms1634.
Despite the growing evidence for the regulated spindle orientation in mammals, a systematic approach for identifying the responsible genes in mammalian cells has not been established. Here we perform a kinase-targeting RNAi screen in HeLa cells and identify ABL1 as a novel regulator of spindle orientation. Knockdown of ABL1 causes the cortical accumulation of Leu-Gly-Asn repeat-enriched-protein (LGN), an evolutionarily conserved regulator of spindle orientation. This results in the LGN-dependent spindle rotation and spindle misorientation. In vivo inactivation of ABL1 by a pharmacological inhibitor or by ablation of the abl1 gene causes spindle misorientation and LGN mislocalization in mouse epidermis. Furthermore, ABL1 directly phosphorylates NuMA, a binding partner of LGN, on tyrosine 1774. This phosphorylation maintains the cortical localization of NuMA during metaphase, and ensures the LGN/NuMA-dependent spindle orientation control. This study provides a novel approach to identify genes regulating spindle orientation in mammals and uncovers new signalling pathways for this mechanism.
尽管越来越多的证据表明哺乳动物的纺锤体定向受到调控，但尚未建立一种系统的方法来鉴定哺乳动物细胞中负责的基因。在这里，我们在 HeLa 细胞中进行了激酶靶向 RNAi 筛选，并鉴定出 ABL1 是纺锤体定向的一个新的调控因子。ABL1 的敲低导致富含亮氨酸-甘氨酸-天冬氨酸重复序列的蛋白（LGN）在皮质的积累，LGN 是一种进化上保守的纺锤体定向调控因子。这导致 LGN 依赖性的纺锤体旋转和纺锤体定向错误。用药理学抑制剂或 abl1 基因敲除体内失活 ABL1 会导致小鼠表皮中的纺锤体定向错误和 LGN 定位错误。此外，ABL1 直接在酪氨酸 1774 处磷酸化 LGN 的结合伴侣 NuMA。这种磷酸化在中期维持 NuMA 的皮质定位，并确保 LGN/NuMA 依赖性的纺锤体定向控制。这项研究为鉴定调控哺乳动物纺锤体定向的基因提供了一种新方法，并揭示了该机制的新信号通路。
