Concentration gradients of soluble proteins are believed to be responsible for control of morphogenesis of subcellular systems, but the mechanisms that generate the spatial organization of these subcellular gradients remain poorly understood. Here, we use a newly developed multipoint fluorescence fluctuation spectroscopy technique to study the ras-related nuclear protein (Ran) pathway, which forms soluble gradients around chromosomes in mitosis and is thought to spatially regulate microtubule behaviors during spindle assembly. We found that the distribution of components of the Ran pathway that influence microtubule behaviors is determined by their interactions with microtubules, resulting in microtubule nucleators being localized by the microtubules whose formation they stimulate. Modeling and perturbation experiments show that this feedback makes the length of the spindle insensitive to the length scale of the Ran gradient, allows the spindle to assemble outside the peak of the Ran gradient, and explains the scaling of the spindle with cell size. Such feedback between soluble signaling pathways and the mechanics of the cytoskeleton may be a general feature of subcellular organization.
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机译:可溶性蛋白质的浓度梯度被认为是控制亚细胞系统形态发生的原因,但产生这些亚细胞梯度空间组织的机制仍然知之甚少。在这里,我们使用一种新开发的多点荧光涨落光谱技术来研究 ras 相关核蛋白 (Ran) 通路,该通路在有丝分裂中在染色体周围形成可溶性梯度,并被认为在空间上调节纺锤体组装过程中的微管行为。我们发现,影响微管行为的 Ran 通路组分的分布取决于它们与微管的相互作用,导致微管成核器被它们刺激的微管形成定位。建模和扰动实验表明,这种反馈使得纺锤体的长度对Ran梯度的长度尺度不敏感,允许纺锤体在Ran梯度的峰值之外组装,并解释了纺锤体随细胞大小的变化而变化。可溶性信号通路和细胞骨架力学之间的这种反馈可能是亚细胞组织的一般特征。
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