Diverse effects of beta-tubulin mutations on microtubule formation and function.

We have used in vitro mutagenesis and gene replacement to construct five new cold-sensitive mutations in TUB2, the sole gene encoding beta-tubulin in the yeast Saccharomyces cerevisiae. These and one previously isolated tub2 mutant display diverse phenotypes that have allowed us to define the functions of yeast microtubules in vivo. At the restrictive temperature, all of the tub2 mutations inhibit chromosome segregation and block the mitotic cell cycle. However, different microtubule arrays are present in these arrested cells depending on the tub2 allele. One mutant (tub2-401) contains no detectable microtubules, two (tub2-403 and tub2-405) contain greatly diminished levels of both nuclear and cytoplasmic microtubules, one (tub2-104) contains predominantly nuclear microtubules, one (tub2-402) contains predominantly cytoplasmic microtubules, and one (tub2-404) contains prominent nuclear and cytoplasmic microtubule arrays. Using these mutants we demonstrate here that cytoplasmic microtubules are necessary for nuclear migration during the mitotic cell cycle and for nuclear migration and fusion during conjugation; only those mutants that possess cytoplasmic microtubules are able to perform these functions. We also show that microtubules are not required for secretory vesicle transport in yeast; bud growth and invertase secretion occur in cells which contain no microtubules.

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Induction of yeast histone genes by stimulation of stationary-phase cells

Molecular and Cellular Biology ◽

10.1128/mcb.10.12.6356-6361.1990 ◽

1990 ◽

Vol 10 (12) ◽

pp. 6356-6361

Author(s):

M A Drebot ◽

L M Veinot-Drebot ◽

R A Singer ◽

G C Johnston

Keyword(s):

Gene Expression ◽

Cell Cycle ◽

Stationary Phase ◽

Mitotic Cell ◽

Specific Gene ◽

Mitotic Cell Cycle ◽

Histone Genes ◽

Yeast Saccharomyces Cerevisiae ◽

Alpha Factor ◽

Stimulation Of

In the cell cycle of the budding yeast Saccharomyces cerevisiae, expression of the histone genes H2A and H2B of the TRT1 and TRT2 loci is regulated by the performance of "start," the step that also regulates the cell cycle. Here we show that histone production is also subject to an additional form of regulation that is unrelated to the mitotic cell cycle. Expression of histone genes, as assessed by Northern (RNA) analysis, was shown to increase promptly after the stimulation, brought about by fresh medium, that activates stationary-phase cells to reenter the mitotic cell cycle. The use of a yeast mutant that is conditionally blocked in the resumption of proliferation at a step that is not part of the mitotic cell cycle (M.A. Drebot, G.C. Johnston, and R.A. Singer, Proc. Natl. Acad. Sci. 84:7948, 1987) showed that this increased gene expression that occurs upon stimulation of stationary-phase cells took place in the absence of DNA synthesis and without the performance of start. This stimulation-specific gene expression was blocked by the mating pheromone alpha-factor, indicating that alpha-factor directly inhibits expression of these histone genes, independently of start.

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The distribution of cytoplasmic microtubules throughout the cell cycle of the centric diatom Stephanopyxis turris: their role in nuclear migration and positioning the mitotic spindle during cytokinesis.

The Journal of Cell Biology ◽

10.1083/jcb.102.5.1688 ◽

1986 ◽

Vol 102 (5) ◽

pp. 1688-1698 ◽

Cited By ~ 26

Author(s):

L Wordeman ◽

K L McDonald ◽

W Z Cande

Keyword(s):

Cell Cycle ◽

Mitotic Spindle ◽

Nuclear Migration ◽

Spindle Pole ◽

Centric Diatom ◽

Mitotic Spindles ◽

Animal Cells ◽

Microtubule Organizing Center ◽

Cytoplasmic Microtubule ◽

Cytoplasmic Microtubules

The cell cycle of the marine centric diatom Stephanopyxis turris consists of a series of spatially and temporally well-ordered events. We have used immunofluorescence microscopy to examine the role of cytoplasmic microtubules in these events. At interphase, microtubules radiate out from the microtubule-organizing center, forming a network around the nucleus and extending much of the length and breadth of the cell. As the cell enters mitosis, this network breaks down and a highly ordered mitotic spindle is formed. Peripheral microtubule bundles radiate out from each spindle pole and swing out and away from the central spindle during anaphase. Treatment of synchronized cells with 2.5 X 10(-8) M Nocodazole reversibly inhibited nuclear migration concurrent with the disappearance of the extensive cytoplasmic microtubule arrays associated with migrating nuclei. Microtubule arrays and mitotic spindles that reformed after the drug was washed out appeared normal. In contrast, cells treated with 5.0 X 10(-8) M Nocodazole were not able to complete nuclear migration after the drug was washed out and the mitotic spindles that formed were multipolar. Normal and multipolar spindles that were displaced toward one end of the cell by the drug treatment had no effect on the plane of division during cytokinesis. The cleavage furrow always bisected the cell regardless of the position of the mitotic spindle, resulting in binucleate/anucleate daughter cells. This suggests that in S. turris, unlike animal cells, the location of the plane of division is cortically determined before mitosis.

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Induced recombination in the mitotic cell cycle of the yeastSaccharomyces cerevisiae

Genetics Research ◽

10.1017/s0016672300025659 ◽

1984 ◽

Vol 43 (1) ◽

pp. 1-10 ◽

Cited By ~ 2

Author(s):

Leland H. Johnston ◽

Anthony L. Johnson

Keyword(s):

Cell Cycle ◽

Yeast Cell ◽

Nuclear Division ◽

Mitotic Cell ◽

S Phase ◽

Yeast Cell Cycle ◽

Restrictive Temperature ◽

Mitotic Cell Cycle ◽

Unambiguous Determination

SUMMARYThe occurrence of induced recombination in the mitotic cell cycle in yeast has been analysed using conditional cell-cycle mutants held at the restrictive temperature. The strains used were heteroallelic atgalland assaying for functional galactokinase shortly after irradiation (Johnston, 1982) allowed an unambiguous determination of the cell cycle stages in which recombination could occur. Recombination was observed in most strains, including those with thecdc36mutation, defective in ‘start’; thecdc4, 7anddbf4mutations which arrest cells in G1; thedbf1, 2andcdc6mutations affecting S phase;cdc16andcdc17which block cells in G2 and alsocdc14and15which arrest cells in ‘late nuclear division’. Recombination can therefore occur within each of the major phases of the yeast cell cycle. This analysis has also revealed that thecdc8mutation results in a defect in induced mitotic recombination.

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Induction of yeast histone genes by stimulation of stationary-phase cells.

Molecular and Cellular Biology ◽

10.1128/mcb.10.12.6356 ◽

1990 ◽

Vol 10 (12) ◽

pp. 6356-6361 ◽

Cited By ~ 3

Author(s):

M A Drebot ◽

L M Veinot-Drebot ◽

R A Singer ◽

G C Johnston

Keyword(s):

Gene Expression ◽

Cell Cycle ◽

Stationary Phase ◽

Mitotic Cell ◽

Specific Gene ◽

Mitotic Cell Cycle ◽

Histone Genes ◽

Yeast Saccharomyces Cerevisiae ◽

Alpha Factor ◽

Stimulation Of

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Inducible nucleotide excision repair (NER) of UV-induced cyclobutane pyrimidine dimers in the cell cycle of the budding yeast Saccharomyces cerevisiae : evidence that inducible NER is confined to the G1 phase of the mitotic cell cycle

MGG Molecular & General Genetics ◽

10.1007/s004380050389 ◽

1997 ◽

Vol 254 (1) ◽

pp. 43-53 ◽

Cited By ~ 10

Author(s):

A. D. Scott ◽

R. Waters

Keyword(s):

Saccharomyces Cerevisiae ◽

Cell Cycle ◽

Excision Repair ◽

Mitotic Cell ◽

G1 Phase ◽

Mitotic Cell Cycle ◽

Cyclobutane Pyrimidine Dimers ◽

Yeast Saccharomyces Cerevisiae ◽

Pyrimidine Dimers ◽

Nucleotide Excision

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Regulation of proliferation by the budding yeast Saccharomyces cerevisiae

Biochemistry and Cell Biology ◽

10.1139/o90-060 ◽

1990 ◽

Vol 68 (2) ◽

pp. 427-435 ◽

Cited By ~ 3

Author(s):

Gerald C. Johnston ◽

Richard A. Singer

Keyword(s):

Saccharomyces Cerevisiae ◽

Cell Cycle ◽

Stationary Phase ◽

Budding Yeast ◽

Developmental State ◽

Mitotic Cell ◽

Mitotic Cell Cycle ◽

Proliferating Cells ◽

Yeast Saccharomyces Cerevisiae ◽

Regulation Of Proliferation

Mutations in the budding yeast Saccharomyces cerevisiae define regulatory activities both for the mitotic cell cycle and for resumption of proliferation from the quiescent stationary-phase state. In each case, the regulation of proliferation occurs in the prereplicative interval that precedes the initiation of DNA replication. This regulation is particularly responsive to the nutrient environment and the biosynthetic capacity of the cell. Mutations in components of the cAMP-mediated effector pathway and in components of the biosynthetic machinery itself affect regulation of proliferation within the mitotic cell cycle. In the extreme case of nutrient starvation, cells cease proliferation and enter stationary phase. Mutations in newly defined genes prevent stationary-phase cells from reentering the mitotic cell cycle, but have no effect on proliferating cells. Thus stationary phase represents a unique developmental state, with requirements to resume proliferation that differ from those for the maintenance of proliferation in the mitotic cell cycle.Key words: Saccharomyces cerevisiae, cell cycle, growth, cAMP, stationary phase.

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EFFECTS OF THE MITOTIC CELL-CYCLE MUTATION cdc4 ON YEAST MEIOSIS

Genetics ◽

10.1093/genetics/86.1.57 ◽

1977 ◽

Vol 86 (1) ◽

pp. 57-72

Author(s):

G Simchen ◽

J Hirschberg

Keyword(s):

Cell Cycle ◽

Dna Replication ◽

Nuclear Dna ◽

Mitotic Cell ◽

Restrictive Temperature ◽

Mitotic Cell Cycle ◽

Sporulation Medium ◽

Permissive Temperature ◽

Yeast Meiosis ◽

High Degree

ABSTRACT The mitotic cell-cycle mutation cdc4 has been reported to block the initiation of nuclear DNA replication and the separation of spindle plaques after their replication. Meiosis in cdc4/cdc4 diploids is normal at the permissive temperature (25°) and is arrested at the first division (one-nucleus stage) at the restrictive temperature (34° or 36°). Arrested cells at 34° show a high degree of commitment to recombination (at least 50% of the controls) but no haploidization, while cells arrested at 36° are not committed to recombination. Meiotic cells arrested at 34° show a delayed and reduced synthesis of DNA (at most 40% of the control), at least half of which is probably mitochondrial. It is suggested that recombination commitment does not depend on the completion of nuclear premeiotic DNA replication in sporulation medium.—Transfer of cdc4/cdc4 cells to the restrictive temperature at the onset of sporulation produces a uniform phenotype of arrest at a 1-nucleus morphology. On the other hand, shifts of the meiotic cells to the restrictive temperature at later times produce two additional phenotypes of arrest, thus suggesting that the function of cdc4 is required at several points in meiosis (at least at three different times).

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