Microtubule stability in budding yeast: characterization and dosage suppression of a benomyl-dependent tubulin mutant.
To better understand the dynamic regulation of microtubule structures in yeast, we studied a conditional-lethal beta-tubulin mutation tub2-150. This mutation is unique among the hundreds of tubulin mutations isolated in Saccharomyces cerevisiae in that it appears to cause an increase in the stability of microtubules. We report here that this allele is a mutation of threonine 238 to alanine, and that tub2-150 prevents the spindle from elongating during anaphase, suggesting a nuclear microtubule defect. To identify regulators of microtubule stability and/or anaphase, yeast genes were selected that, when overexpressed, could suppress the tub2-150 temperature-sensitive phenotype. One of these genes, JSN1, encodes a protein of 125 kDa that has limited similarity to a number of proteins of unknown function. Overexpression of the JSN1 gene in a TUB2 strain causes that strain to become more sensitive to benomyl, a microtubule-destabilizing drug. Of a representative group of microtubule mutants, only one other mutation, tub2-404, could be suppressed by JSN1 overexpression, showing that JSN1 is an allele-specific suppressor. As tub2-404 mutants are also defective for spindle elongation, this provides additional support for a role for JSN1 during anaphase.
Department of Molecular and Cell Biology, University of California, Berkeley 94720, USA.
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Machin
J M
JM
Lee
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Barnes
D000483:Alleles; D000595:Amino Acid Sequence; D000705:Anaphase; D000818:Animals; D001542:Benomyl / Q000494:pharmacology*; D005656:Fungal Proteins / Q000235:genetics* / Q000276:immunology / Q000378:metabolism / Q000502:physiology*; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D008969:Molecular Sequence Data; D016601:RNA-Binding Proteins; D011817:Rabbits; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012100:Reproduction, Asexual; D012441:Saccharomyces cerevisiae / Q000254:growth & development / Q000276:immunology / Q000648:ultrastructure*; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D008941:Spindle Apparatus / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D013489:Suppression, Genetic; D014404:Tubulin / Q000235:genetics* / Q000276:immunology / Q000378:metabolism
D005656:Fungal Proteins; C097438:JSN1 protein, S cerevisiae; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D014404:Tubulin; D001542:Benomyl