gamma-Tubulin-like Tub4p of Saccharomyces cerevisiae is associated with the spindle pole body substructures that organize microtubules and is required for mitotic spindle formation.
Tub4p is a novel tubulin in Saccharomyces cerevisiae that most closely resembles gamma-tubulin. We report in this manuscript that the essential Tub4p is associated with the inner and outer plaques of the yeast microtubule organizing center, the spindle pole body (SPB). These SPB substructures are involved in the attachment of the nuclear and cytoplasmic microtubules, respectively (Byers, B., and L. Goetsch. 1975. J. Bacteriol. 124:511-523). Study of a temperature sensitive tub4-1 allele revealed that TUB4 has essential functions in microtubule organization. Remarkably, SPB duplication and separation are not impaired in tub4-1 cells incubated at the nonpermissive temperature. However, SPBs from such cells contain less or misdirected nuclear microtubules. Further analysis revealed that tub4-1 cells are able to assemble a short bipolar spindle, suggesting that the defect in microtubule organization occurs after spindle formation. A role of Tub4p in microtubule organization is further suggested by an increase in chromosome loss in tub4-1 cells. In addition, cell cycle arrest and survival of tub4-1 cells is dependent on the mitotic checkpoint control gene BUB2 (Hoyt, M.A., L. Totis, B.T. Roberts. 1991. Cell. 66:507-517), one of the cell's monitors of spindle integrity.
Spang
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A
Max-Planck-Institut für Biochemie, Genzentrum, Martinsried, Germany.
Geissler
S
S
Grein
K
K
Schiebel
E
E
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002453:Cell Cycle / Q000235:genetics; D018797:Cell Cycle Proteins; D015825:Chromosomes, Fungal; D004271:DNA, Fungal; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D005816:Genetic Complementation Test; D008870:Microtubules / Q000378:metabolism*; D008969:Molecular Sequence Data; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D015398:Signal Transduction; D008941:Spindle Apparatus / Q000378:metabolism*; D014404:Tubulin / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis
C070351:BUB2 protein, S cerevisiae; D018797:Cell Cycle Proteins; D004271:DNA, Fungal; D005656:Fungal Proteins; D029701:Saccharomyces cerevisiae Proteins; C100764:TUB4 protein, S cerevisiae; D014404:Tubulin