MEC-12, an alpha-tubulin required for touch sensitivity in C. elegans.
mec-12 is one of a dozen genes required for touch receptor neuron function in Caenorhabditis elegans. Some mec-12 mutants (mechanosensory-defective) lack the large-diameter microtubules that are characteristic of these neurons (15 protofilaments, as opposed to 11). Mutants of mec-7, a alpha-tubulin encoding gene, have a similar phenotype. We have identified the nature of mec-12 by germline transformation rescue and characterization of a point mutation. Sequence analysis of the mec-12 encoded product (MEC-12) indicates that it corresponds to a novel C. elegans alpha-tubulin. MEC-12 is the only identified C. elegans alpha-tubulin that contains a lysine at position 40, a known site of post-translational acetylation. Some mec-12 mutations eliminate microtubule acetylation as assayed immunocyto-chemically; phenotypic rescue using a MEC-12 variant lacking the lysine-40 showed that acetylation is not required for MEC-12 activity. Although functionally needed only in the touch neurons, mec-12 is expressed in several other neuron types. These results support the notion that tubulin isotype diversity contributes to the formation of distinct classes of microtubules; 15-protofilament microtubule assembly requires MEC-12 alpha-tubulin and MEC-7 beta-tubulin, which are both highly expressed in the touch receptor neurons. MEC-12 is the first reported alpha-tubulin isotype that appears to be required in a single class of neuronal microtubules.
Fukushige
T
T
Toyohashi University of Technology, Laboratory of Molecular Biology, Tempaku-cho, Toyohashi, 441 Japan.
Siddiqui
Z K
ZK
Chou
M
M
Culotti
J G
JG
Gogonea
C B
CB
Siddiqui
S S
SS
Hamelin
M
M
D000107:Acetylation; D000595:Amino Acid Sequence; D000818:Animals; D015152:Blotting, Northern; D017173:Caenorhabditis elegans / Q000033:anatomy & histology / Q000378:metabolism* / Q000502:physiology; D029742:Caenorhabditis elegans Proteins; D019084:Fluorescent Antibody Technique, Indirect; D015801:Helminth Proteins / Q000378:metabolism; D008870:Microtubules / Q000378:metabolism; D008969:Molecular Sequence Data; D017354:Point Mutation; D012150:Polymorphism, Restriction Fragment Length; D014110:Touch / Q000502:physiology*; D014404:Tubulin / Q000378:metabolism*
D029742:Caenorhabditis elegans Proteins; D015801:Helminth Proteins; C118234:MEC-12 protein, C elegans; C115872:Mec-7 protein, C elegans; D014404:Tubulin