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Causes and Consequences of Microtubule Acetylation

International audienceAmong the different types of cytoskeletal components, microtubules arguably accumulate the greatest diversity of post-translational modifications (PTMs). Acetylation of lysine 40 (K40) of atubulin has received a particular attention because it is the only tubulin PTM to be found in the lumen of microtubules - most other tubulin PTMs are found at their outer surface. As a consequence, the enzyme catalyzing K40 acetylation needs to penetrate the narrow microtubules lumen to find its substrate. Acetylated microtubules have been considered as stable, long-lived microtubules, however until recently there was little information about whether the longevity of these microtubules is the cause or the consequence of acetylation. Current advances suggest that this PTM helps the microtubule lattice to cope with mechanical stress, thus facilitating microtubule self-repair. These observations now shed a new light on the structural integrity of microtubules, as well as on mechanisms and biological functions of tubulin acetylation. Here we discuss the recentunderstanding on how acetylation is generated in the lumen of microtubules, and how this ‘hidden’PTM can control microtubule properties and functions

SnapShot: Functions of Tubulin Posttranslational Modifications

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Tubulin Posttranslational Modifications and Emerging Links to Human Disease

International audienceTubulin posttranslational modifications are currently emerging as important regulators of the microtubule cytoskeleton and thus have a strong potential to be implicated in a number of disorders. Here, we review the latest advances in understanding the physiological roles of tubulin modifications and their links to a variety of pathologies

The tubulin code at a glance

International audienceMicrotubules are key cytoskeletal elements of all eukaryotic cells and are assembled of evolutionarily conserved α-tubulin-β-tubulin heterodimers. Despite their uniform structure, microtubules fulfill a large diversity of functions. A regulatory mechanism to control the specialization of the microtubule cytoskeleton is the 'tubulin code', which is generated by (i) expression of different α-and β-tubulin isotypes, and by (ii) post-translational modifications of tubulin. In this Cell Science at a Glance article and the accompanying poster, we provide a comprehensive overview of the molecular components of the tubulin code, and discuss the mechanisms by which these components contribute to the generation of functionally specialized microtubules

Molecular interactions between tubulin tails and glutamylases reveal determinants of glutamylation patterns

International audiencePosttranslational modifications of tubulin currently emerge as key regulators of microtubule functions. Polyglutamylation generates a variety of modification patterns that are essential for controlling microtubule functions in different cell types and organelles, and deregulation of these patterns has been linked to ciliopathies, cancer and neurodegeneration. How the different glutamylating enzymes determine precise modification patterns has so far remained elusive. Using computational modelling, molecular dynamics simulations and mutational analyses we now show how the carboxy-terminal tails of tubulin bind into the active sites of glutamylases. Our models suggest that the glutamylation sites on a-and b-tubulins are determined by the positioning of the tails within the catalytic pocket. Moreover, we found that the binding modes of a-and b-tubulin tails are highly similar, implying that most enzymes could potentially modify both, a-and b-tubulin. This supports a model in which the binding of the enzymes to the entire microtubule lattice, but not the specificity of the C-terminal tubulin tails to their active sites, determines the catalytic speci-ficities of glutamylases

Establishing species-specific sexing markers suitable for non-invasive samples of species lacking genomic resources: an example using the highly endangered common hamster Cricetus cricetus

Here we present an approach to establish species-specific genetic markers for sex identification suitable for non-invasive samples. Such markers are not yet available for the endangered common hamster (Cricetus cricetus) because of the lack of genomic resources. Using Y chromosome conserved anchored tagged sequences (YCATS) exonic primers, we obtained Y-chromosomal sequences from hamsters and sympatric rodent species. From this, we designed hamster-specific primers targeting two short Y-chromosomal intron fragments and included them in microsatellite multiplex reactions, using autosomal loci also as amplification controls. The method yielded highly consistent results. The approach can be easily applied to development of sex markers in species for which there are no genome sequences available and thus aid conservation genetics efforts

Microtubule-associated proteins: structuring the cytoskeleton

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Tubulin glycylation controls primary cilia length

International audienc

CLIP-170 tracks growing microtubule ends by dynamically recognizing composite EB1/tubulin-binding sites

The microtubule cytoskeleton is crucial for the internal organization of eukaryotic cells. Several microtubule-associated proteins link microtubules to subcellular structures. A subclass of these proteins, the plus end–binding proteins (+TIPs), selectively binds to the growing plus ends of microtubules. Here, we reconstitute a vertebrate plus end tracking system composed of the most prominent +TIPs, end-binding protein 1 (EB1) and CLIP-170, in vitro and dissect their end-tracking mechanism. We find that EB1 autonomously recognizes specific binding sites present at growing microtubule ends. In contrast, CLIP-170 does not end-track by itself but requires EB1. CLIP-170 recognizes and turns over rapidly on composite binding sites constituted by end-accumulated EB1 and tyrosinated α-tubulin. In contrast to its fission yeast orthologue Tip1, dynamic end tracking of CLIP-170 does not require the activity of a molecular motor. Our results demonstrate evolutionary diversity of the plus end recognition mechanism of CLIP-170 family members, whereas the autonomous end-tracking mechanism of EB family members is conserved