Functional Dissection and Hierarchy of Tubulin-folding Cofactor Homologues in Fission Yeast
- 1 September 1999
- journal article
- Published by American Society for Cell Biology (ASCB) in Molecular Biology of the Cell
- Vol. 10 (9), 2987-3001
- https://doi.org/10.1091/mbc.10.9.2987
Abstract
We describe the isolation of fission yeast homologues of tubulin-folding cofactors B (Alp11) and E (Alp21), which are essential for cell viability and the maintenance of microtubules. Alp11Bcontains the glycine-rich motif (the CLIP-170 domain) involved in microtubular functions, whereas, unlike mammalian cofactor E, Alp21Edoes not. Both mammalian and yeast cofactor E, however, do contain leucine-rich repeats. Immunoprecipitation analysis shows that Alp11Binteracts with both α-tubulin and Alp21E, but not with the cofactor D homologue Alp1, whereas Alp21Ealso interacts with Alp1D. The cellular amount of α-tubulin is decreased in both alp1 and alp11 mutants. Overproduction of Alp11Bresults in cell lethality and the disappearance of microtubules, which is rescued by co-overproduction of α-tubulin. Both full-length Alp11Band the C-terminal third containing the CLIP-170 domain localize in the cytoplasm, and this domain is required for efficient binding to α-tubulin. Deletion of alp11 is suppressed by multicopy plasmids containing either alp21+or alp1+, whereas alp21deletion is rescued by overexpression ofalp1+but notalp11+. Finally, the alp1mutant is not complemented by either alp11+or alp21+. The results suggest that cofactors operate in a linear pathway (Alp11B-Alp21E-Alp1D), each with distinct roles.Keywords
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