Vitre Benjamin, Coquelle Frédéric M, Heichette Claire, Garnier Cyrille, Chrétien Denis, Arnal Isabelle
Université de Rennes 1, Centre Nationale de la Recherche Scientifique, Unité Mixte de Recherche 6026, Institut Fédératif de Recherche 140, Génétique Fonctionnelle Agronomie et Santé, Campus de Beaulieu, 263, Avenue du Général Leclerc, 35042 Rennes, France.
Nat Cell Biol. 2008 Apr;10(4):415-21. doi: 10.1038/ncb1703. Epub 2008 Mar 23.
End binding 1 (EB1) is a plus-end-tracking protein (+TIP) that localizes to microtubule plus ends where it modulates their dynamics and interactions with intracellular organelles. Although the regulating activity of EB1 on microtubule dynamics has been studied in cells and purified systems, the molecular mechanisms involved in its specific activity are still unclear. Here, we describe how EB1 regulates the dynamics and structure of microtubules assembled from pure tubulin. We found that EB1 stimulates spontaneous nucleation and growth of microtubules, and promotes both catastrophes (transitions from growth to shrinkage) and rescues (reverse events). Electron cryomicroscopy showed that EB1 induces the initial formation of tubulin sheets, which rapidly close into the common 13-protofilament-microtubule architecture. Our results suggest that EB1 favours the lateral association of free tubulin at microtubule-sheet edges, thereby stimulating nucleation, sheet growth and closure. The reduction of sheet length at microtubule growing-ends together with the elimination of stressed microtubule lattices may account for catastrophes. Conversely, occasional binding of EB1 to the microtubule lattice may induce rescues.
末端结合蛋白1（EB1）是一种正端追踪蛋白（+TIP），定位于微管正端，在那里它调节微管的动力学以及与细胞内细胞器的相互作用。尽管EB1对微管动力学的调节活性已在细胞和纯化系统中进行了研究，但其特定活性所涉及的分子机制仍不清楚。在这里，我们描述了EB1如何调节由纯微管蛋白组装而成的微管的动力学和结构。我们发现EB1刺激微管的自发成核和生长，并促进微管的解聚（从生长到收缩的转变）和挽救（反向事件）。电子冷冻显微镜显示，EB1诱导微管蛋白片层的初始形成，这些片层迅速闭合形成常见的13原纤维微管结构。我们的结果表明，EB1有利于游离微管蛋白在微管片层边缘的侧向结合，从而刺激成核、片层生长和闭合。微管生长末端片层长度的减少以及应力微管晶格的消除可能是导致微管解聚的原因。相反，EB1偶尔与微管晶格结合可能会引发挽救。
