Overexpression of yeast homologs of the mammalian checkpoint gene RCC1 suppresses the class of alpha-tubulin mutations that arrest with excess microtubules.
Microtubules in eukaryotic cells participate in a variety of nuclear and cytoplasmic structures, reflecting functional requirements and cell cycle position. We are studying the cellular regulation of microtubule assembly and organization in the yeast Saccharomyces cerevisiae. We screened for genes that when overexpressed suppress the growth phenotype of conditional mutants in alpha-tubulin that arrest with excess microtubules at the nonpermissive temperature (class 2 mutations). Here we describe one such suppressing element, called ATS1 (for Alpha Tubulin Suppressor). Overexpression of this gene rescues both the growth and microtubule phenotypes of all class 2 mutations, but not the cold-sensitive mutations that arrest with no microtubules (class 1 mutations). Deletion of ATS1 confers a modest slow growth phenotype which is slightly enhanced in strains containing both a deletion of ATS1 and a class 2 tub 1 mutation. The predicted ATS1 protein contains 333 amino acids and has considerable structural homology to the products of both the mammalian mitotic control gene RCC1 and the S. cerevisiae gene SRM1/PRP20. Overexpression of SRM1/PRP20 also suppresses class 2 mutants. The results suggest that this family of genes may participate in regulatory interactions between microtubules and the cell cycle.
Kirkpatrick
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Department of Biology, Massachusetts Institute of Technology, Cambridge 02139.
Solomon
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F
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002453:Cell Cycle; D018797:Cell Cycle Proteins; D017124:Conserved Sequence; D004268:DNA-Binding Proteins / Q000235:genetics*; D005656:Fungal Proteins / Q000235:genetics*; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D005838:Genotype; D020662:Guanine Nucleotide Exchange Factors; D008322:Mammals; D008870:Microtubules / Q000502:physiology*; D008969:Molecular Sequence Data; D005810:Multigene Family; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics; D009838:Oligodeoxyribonucleotides; D016366:Open Reading Frames; D010957:Plasmids; D012097:Repressor Proteins / Q000235:genetics*; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics* / Q000254:growth & development; D029701:Saccharomyces cerevisiae Proteins; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D013489:Suppression, Genetic; D014404:Tubulin / Q000235:genetics*
C089099:ATS1 protein, S cerevisiae; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D020662:Guanine Nucleotide Exchange Factors; D009687:Nuclear Proteins; D009838:Oligodeoxyribonucleotides; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D014404:Tubulin