A remarkable feature of the microtubule cytoskeleton is the coexistence of subpopulations having different dynamic properties. A prominent example is the anaphase spindle, where stable antiparallel bundles exist alongside dynamic microtubules and provide spatial cues for cytokinesis. How are the dynamics of spatially proximal arrays differentially regulated? We reconstitute a minimal system of three midzone proteins: microtubule-crosslinker PRC1 and its interactors CLASP1 and Kif4A, proteins that promote and suppress microtubule elongation, respectively. We find that their collective activity promotes elongation of single microtubules while simultaneously stalling polymerization of crosslinked bundles. This differentiation arises from (1) strong rescue activity of CLASP1, which overcomes the weaker effects of Kif4A on single microtubules, and (2) lower microtubule- and PRC1-binding affinity of CLASP1, which permits the dominance of Kif4A at overlaps. In addition to canonical mechanisms where antagonistic regulators set microtubule length, our findings illuminate design principles by which collective regulator activity creates microenvironments of arrays with distinct dynamic properties.

微管细胞骨架的一个显着特征是具有不同动态特性的亚群共存。一个突出的例子是后期纺锤体，其中稳定的反平行束与动态微管并存，并为胞质分裂提供空间线索。空间近端阵列的动力学是如何进行差异调节的？我们重建了三个中间区域蛋白的最小系统：微管交联剂 PRC1 及其相互作用物 CLASP1 和 Kif4A，分别促进和抑制微管伸长的蛋白质。我们发现它们的集体活动促进了单个微管的伸长，同时阻止了交联束的聚合。这种分化源于 (1) CLASP1 的强拯救活性，它克服了 Kif4A 对单个微管的较弱影响，(2) CLASP1 的微管和 PRC1 结合亲和力较低，这使得 Kif4A 在重叠时占优势。除了拮抗调节剂设定微管长度的典型机制外，我们的研究结果阐明了设计原则，集体调节剂活动通过这些设计原则创造了具有不同动态特性的阵列微环境。