Omer Safia, Brock Katia, Beckford John, Lee Wei-Lih
Department of Biological Sciences, Dartmouth College, 78 College Street, Hanover, NH 03755, USA.
Department of Biological Sciences, Dartmouth College, 78 College Street, Hanover, NH 03755, USA
J Cell Sci. 2020 Oct 15;133(20):jcs246363. doi: 10.1242/jcs.246363.
The current model for spindle positioning requires attachment of the microtubule (MT) motor cytoplasmic dynein to the cell cortex, where it generates pulling force on astral MTs to effect spindle displacement. How dynein is anchored by cortical attachment machinery to generate large spindle-pulling forces remains unclear. Here, we show that cortical clustering of Num1, the yeast dynein attachment molecule, is limited by its assembly factor Mdm36. Overexpression of Mdm36 results in an overall enhancement of Num1 clustering but reveals a population of dim Num1 clusters that mediate dynein anchoring at the cell cortex. Direct imaging shows that bud-localized, dim Num1 clusters containing around only six Num1 molecules mediate dynein-dependent spindle pulling via a lateral MT sliding mechanism. Mutations affecting Num1 clustering interfere with mitochondrial tethering but do not interfere with the dynein-based spindle-pulling function of Num1. We propose that formation of small ensembles of attachment molecules is sufficient for dynein anchorage and cortical generation of large spindle-pulling forces.This article has an associated First Person interview with the first author of the paper.
目前的纺锤体定位模型要求微管（MT）马达胞质动力蛋白附着在细胞皮层上，在那里它对星状微管产生拉力以实现纺锤体位移。动力蛋白如何通过皮层附着机制锚定以产生大的纺锤体拉力仍不清楚。在这里，我们表明酵母动力蛋白附着分子Num1的皮层聚集受其组装因子Mdm36的限制。Mdm36的过表达导致Num1聚集的总体增强，但揭示了一群介导动力蛋白锚定在细胞皮层的二聚体Num1簇。直接成像显示，芽定位的、仅包含约六个Num1分子的二聚体Num1簇通过横向微管滑动机制介导依赖动力蛋白的纺锤体拉动。影响Num1聚集的突变会干扰线粒体的系留，但不会干扰Num1基于动力蛋白的纺锤体拉动功能。我们提出，附着分子小集合的形成足以实现动力蛋白的锚定和在皮层产生大的纺锤体拉力。本文有对该论文第一作者的相关第一人称访谈。
