Inserm U1170, Gustave Roussy Institute, Université Paris-Saclay, Villejuif, France.
CNRS UMR8126, Gustave Roussy Institute, Université Paris-Saclay, Villejuif, France.
Sci Rep. 2016 Oct 18;6:35624. doi: 10.1038/srep35624.
Acetylation of the lysine 40 of α-tubulin (K40) is a post-translational modification occurring in the lumen of microtubules (MTs) and is controlled by the α-tubulin acetyl-transferase αTAT1. How αTAT1 accesses the lumen and acetylates α-tubulin there has been an open question. Here, we report that acetylation starts at open ends of MTs and progressively spreads longitudinally from there. We observed acetylation marks at the open ends of in vivo MTs re-growing after a Nocodazole block, and acetylated segments growing in length with time. Bias for MTs extremities was even more pronounced when using non-dynamic MTs extracted from HeLa cells. In contrast, K40 acetylation was mostly uniform along the length of MTs reconstituted from purified tubulin in vitro. Quantitative modelling of luminal diffusion of αTAT1 suggested that the uniform acetylation pattern observed in vitro is consistent with defects in the MT lattice providing lateral access to the lumen. Indeed, we observed that in vitro MTs are permeable to macromolecules along their shaft while cellular MTs are not. Our results demonstrate αTAT1 enters the lumen from open extremities and spreads K40 acetylation marks longitudinally along cellular MTs. This mode of tip-directed microtubule acetylation may allow for selective acetylation of subsets of microtubules.
α-微管蛋白赖氨酸 40 乙酰化（K40）是一种发生在微管（MTs）腔中的翻译后修饰，由 α-微管乙酰转移酶 αTAT1 控制。αTAT1 如何进入腔并在那里乙酰化 α-微管一直是一个悬而未决的问题。在这里，我们报告说乙酰化从 MT 的开口端开始，并从那里纵向逐渐扩散。我们观察到在用诺考达唑阻断后重新生长的体内 MT 的开口端有乙酰化标记，并且乙酰化片段随时间增长。当使用从 HeLa 细胞中提取的非动态 MT 时，对 MT 末端的偏向更为明显。相比之下，从纯化的微管蛋白体外重构的 MT 中，K40 乙酰化在长度上基本均匀。对 αTAT1 腔扩散的定量建模表明，在体外观察到的均匀乙酰化模式与 MT 晶格中的缺陷一致，这些缺陷为腔提供了横向进入的途径。事实上，我们观察到体外 MT 可沿其轴贯穿大分子，而细胞 MT 则不行。我们的结果表明，αTAT1 从开口端进入腔，并沿细胞 MT 纵向扩散 K40 乙酰化标记。这种尖端导向的微管乙酰化模式可能允许对微管的亚群进行选择性乙酰化。
