MEC-17 is an α-tubulin acetyltransferase

MEC1-7 is long-sought α-tubulin acetyltransferase It has long been known that in a subset of microtubules, α-tubulin is modified post-translationally by acetylation of lysine-40. There is growing evidence that this highly conserved microtubule modification is a key event during cell polarization, especially in the nervous system. The enzyme responsible for this reaction has now been identified as MEC-17, a protein related to the Gcn5 histone receptor acetyltransferase and required for the function of touch receptor neurons in Caenorhabditis elegans . In eukaryotic cells, a subset of microtubules undergo post-translational modifications such as acetylation, which alters microtubule dynamics and trafficking of motors. These authors identify MEC-17 as the enzyme that directly acetylates α-tubulin in vitro and in vivo and in both invertebrates and vertebrates. This is the identification of the long-sought enzyme that acetylates microtubules. In most eukaryotic cells, subsets of microtubules are adapted for specific functions by post-translational modifications (PTMs) of tubulin subunits. Acetylation of the ε-amino group of K40 on α-tubulin is a conserved PTM on the luminal side of microtubules 1 that was discovered in the flagella of Chlamydomonas reinhardtii 2 , 3 . Studies on the significance of microtubule acetylation have been limited by the undefined status of the α-tubulin acetyltransferase. Here we show that MEC-17, a protein related to the Gcn5 histone acetyltransferases 4 and required for the function of touch receptor neurons in Caenorhabditis elegans 5 , 6 , acts as a K40-specific acetyltransferase for α-tubulin. In vitro , MEC-17 exclusively acetylates K40 of α-tubulin. Disruption of the Tetrahymena MEC-17 gene phenocopies the K40R α-tubulin mutation and makes microtubules more labile. Depletion of MEC-17 in zebrafish produces phenotypes consistent with neuromuscular defects. In C. elegans , MEC-17 and its paralogue W06B11.1 are redundantly required for acetylation of MEC-12 α-tubulin, and contribute to the function of touch receptor neurons partly via MEC-12 acetylation and partly via another function, possibly by acetylating another protein. In summary, we identify MEC-17 as an enzyme that acetylates the K40 residue of α-tubulin, the only PTM known to occur on the luminal surface of microtubules.