αTAT1 controls longitudinal spreading of acetylation marks from open microtubules extremities OPEN - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Scientific Reports Année : 2016

αTAT1 controls longitudinal spreading of acetylation marks from open microtubules extremities OPEN

Résumé

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. Results and Discussion Microtubules (MTs) are dynamic polymers composed of α β-tubulin dimers that assembled into hollow tubes. In most eukaryotic cells, MTs can undergo post-translational modifications (PTMs) that modify their properties and functions 1. Acetylation of the lysine 40 of α-tubulin (K40) is a common PTM that is catalysed by the α-tubulin acetyl-transferase α TAT1 and is associated with stable, long-lived MTs 2-4. Remarkably, K40 acetylation occurs in the lumen of MTs 5,6 and is the only such PTM that we know of ref. 1. Supporting this, Szyk et al. recently used in vitro approaches to demonstrate that α TAT1 enters into and diffuses within the MT lumen 7. However, Szyk et al. also suggested that fast diffusivity of α TAT1 leads to stochastic acetylation that occurs uniformly along the length of MTs. This was in marked contrast with earlier in vivo observations of discrete acetylated segments along MTs 8-10 progressively elongating with time 11. More recently, several groups have reported that the acetylated segments were predominately associated with the ends of MTs in vivo 3,12. Thus, reported observations in vivo do not match the proposed model of uniformly distributed acetylated K40 marks based on experiments performed with in vitro MTs 7. To understand how acetylated K40 marks spreading occurs in vivo, we first analyzed acetylation dynamics in HeLa cells. In order to synchronize acetylation events, HeLa cells were subjected to complete MT depolymeri-sation by a prolonged treatment with Nocodazole before being allowed to reassemble MTs after washing out the
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hal-02376384 , version 1 (22-11-2019)

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Nathalie Ly, Nadia Elkhatib, Enzo Bresteau, Olivier Pietrement, Mehdi Khaled, et al.. αTAT1 controls longitudinal spreading of acetylation marks from open microtubules extremities OPEN. Scientific Reports, 2016, ⟨10.1038/srep35624⟩. ⟨hal-02376384⟩
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