scholarly journals The Kinesin-related Proteins, Kip2p and Kip3p, Function Differently in Nuclear Migration in Yeast

1998 ◽  
Vol 9 (8) ◽  
pp. 2051-2068 ◽  
Author(s):  
Rita K. Miller ◽  
Kim K. Heller ◽  
Lotti Frisèn ◽  
Denise L. Wallack ◽  
Diego Loayza ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Genetic Analysis ◽  
Indirect Immunofluorescence ◽  
Nuclear Migration ◽  
Wild Type ◽  
Cytoplasmic Microtubules ◽  
Synthetically Lethal ◽  
Related Proteins ◽  
Microtubule Function ◽  
Do So

The roles of two kinesin-related proteins, Kip2p and Kip3p, in microtubule function and nuclear migration were investigated. Deletion of either gene resulted in nuclear migration defects similar to those described for dynein and kar9 mutants. By indirect immunofluorescence, the cytoplasmic microtubules inkip2Δwere consistently short or absent throughout the cell cycle. In contrast, in kip3Δ strains, the cytoplasmic microtubules were significantly longer than wild type at telophase. Furthermore, in the kip3Δ cells with nuclear positioning defects, the cytoplasmic microtubules were misoriented and failed to extend into the bud. Localization studies found Kip2p exclusively on cytoplasmic microtubules throughout the cell cycle, whereas GFP-Kip3p localized to both spindle and cytoplasmic microtubules. Genetic analysis demonstrated that thekip2Δ kar9Δ double mutants were synthetically lethal, whereas kip3Δkar9Δ double mutants were viable. Conversely,kip3Δ dhc1Δ double mutants were synthetically lethal, whereas kip2Δdhc1Δ double mutants were viable. We suggest that the kinesin-related proteins, Kip2p and Kip3p, function in nuclear migration and that they do so by different mechanisms. We propose that Kip2p stabilizes microtubules and is required as part of the dynein-mediated pathway in nuclear migration. Furthermore, we propose that Kip3p functions, in part, by depolymerizing microtubules and is required for the Kar9p-dependent orientation of the cytoplasmic microtubules.

The SAC3 gene encodes a nuclear protein required for normal progression of mitosis

1996 ◽  
Vol 109 (6) ◽  
pp. 1575-1583
Author(s):  
A. Bauer ◽  
R. Kolling
Keyword(s):  
Cell Cycle ◽  
Actin Cytoskeleton ◽  
Nuclear Protein ◽  
Temperature Sensitive ◽  
Wild Type ◽  
Cell Cycle Delay ◽  
A Cell ◽  
Single Nucleus ◽  
Microtubule Function ◽  
Mitotic Defect

The SAC3 gene of Saccharomyces serevisiae has been implicated in actin function by genetic experiments showing that a temperature sensitive mutation in the essential actin gene (actl-1) can be suppressed by mutations in SAC3. An involvement of SAC3 in actin function is further suggested by the observation that the actin cytoskeleton is altered in SAC3 mutants. Our fractionation experiments, however, point to a nuclear localization of Sac3p. On sucrose density gradients Sac3p co-fractionated with the nuclear organelle markers examined. Furthermore, Sac3p was enriched 10-fold in a nuclei preparation along with the nuclear protein Nop1p. In this report we further show that SAC3 function is required for normal progression of mitosis. SAC3 mutants showed a higher fraction of large-budded cells in culture, indicative of a cell cycle delay. The predominant population among the large-budded sac3 cells were cells with a single nucleus at the bud-neck and a short intranuclear spindle. This suggests that a cell cycle delay occurs in mitosis prior to anaphase. The observation that SAC3 mutants lose chromosomes with higher frequency than wild-type is another indication for a mitotic defect in SAC3 mutants. We further noticed that SAC3 mutants are more resistant against the microtubule destabilizing drug benomyl. This finding suggests that SAC3 is involved, directly or indirectly, in microtubule function. In summary, our data indicate that SAC3 is involved in a process which affects both the actin cytoskeleton and mitosis.

scholarly journals 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.

1986 ◽  
Vol 102 (5) ◽  
pp. 1688-1698 ◽  
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.

scholarly journals Kar9p Is a Novel Cortical Protein Required for Cytoplasmic Microtubule Orientation in Yeast

1998 ◽  
Vol 140 (2) ◽  
pp. 377-390 ◽  
Author(s):  
Rita K. Miller ◽  
Mark D. Rose
Keyword(s):  
Nuclear Migration ◽  
Chain Gene ◽  
Cytoplasmic Microtubule ◽  
Microtubule Orientation ◽  
Cell Cycle Dependence ◽  
Cortical Localization ◽  
Cytoplasmic Microtubules ◽  
General Defect ◽  
Synthetically Lethal ◽  
Cycle Dependence

kar9 was originally identified as a bilateral karyogamy mutant, in which the two zygotic nuclei remained widely separated and the cytoplasmic microtubules were misoriented (Kurihara, L.J., C.T. Beh, M. Latterich, R. Schekman, and M.D. Rose. 1994. J. Cell Biol. 126:911–923.). We now report a general defect in nuclear migration and microtubule orientation in kar9 mutants. KAR9 encodes a novel 74-kD protein that is not essential for life. The kar9 mitotic defect was similar to mutations in dhc1/dyn1 (dynein heavy chain gene), jnm1, and act5. kar9Δ dhc1Δ, kar9Δ jnm1Δ, and kar9Δ act5Δ double mutants were synthetically lethal, suggesting that these genes function in partially redundant pathways to carry out nuclear migration. A functional GFP-Kar9p fusion protein localized to a single dot at the tip of the shmoo projection. In mitotic cells, GFP-Kar9p localized to a cortical dot with both mother–daughter asymmetry and cell cycle dependence. In small-budded cells through anaphase, GFP-Kar9p was found at the tip of the growing bud. In telophase and G1 unbudded cells, no localization was observed. By indirect immunofluorescence, cytoplasmic microtubules intersected the GFP-Kar9p dot. Nocodazole experiments demonstrated that Kar9p's cortical localization was microtubule independent. We propose that Kar9p is a component of a cortical adaptor complex that orients cytoplasmic microtubules.

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

1988 ◽  
Vol 106 (6) ◽  
pp. 1997-2010 ◽  
Author(s):  
T C Huffaker ◽  
J H Thomas ◽  
D Botstein
Keyword(s):  
Cell Cycle ◽  
Nuclear Migration ◽  
Mitotic Cell ◽  
Restrictive Temperature ◽  
In Vitro Mutagenesis ◽  
Mitotic Cell Cycle ◽  
Beta Tubulin ◽  
Yeast Saccharomyces Cerevisiae ◽  
Cytoplasmic Microtubule ◽  
Cytoplasmic Microtubules

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.

scholarly journals Negative regulation of G1 and G2 by S-phase cyclins of Saccharomyces cerevisiae.

1995 ◽  
Vol 15 (9) ◽  
pp. 5030-5042 ◽  
Author(s):  
R D Basco ◽  
M D Segal ◽  
S I Reed
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Cycle ◽  
Dna Replication ◽  
Protein Kinase ◽  
Genetic Analysis ◽  
S Phase ◽  
Negative Regulation ◽  
Cycle Phase ◽  
Wild Type ◽  
Mitotic Cyclin

Cell cycle progression in the budding yeast Saccharomyces cerevisiae is controlled by the Cdc28 protein kinase, which is sequentially activated by different sets of cyclins. Previous genetic analysis has revealed that two B-type cyclins, Clb5 and Clb6, have a positive role in DNA replication. In the present study, we show, in addition, that these cyclins negatively regulate G1- and G2-specific functions. The consequences of this negative regulation were most apparent in clb6 mutants, which had a shorter pre-Start G1 phase as well as a shorter G2 phase than congenic wild-type cells. As a consequence, clb6 mutants grew and proliferated more rapidly than wild-type cells. It was more difficult to assess the role of Clb5 in G1 and G2 by genetic analysis because of the extreme prolongation of S phase in clb5 mutants. Nevertheless, both Clb5 and Clb6 were shown to be responsible for down-regulation of the protein kinase activities associated with Cln2, a G1 cyclin, and Clb2, a mitotic cyclin, in vivo. These observations are consistent with the observed cell cycle phase accelerations associated with the clb6 mutant and are suggestive of similar functions for Clb5. Genetic evidence suggested that the inhibition of mitotic cyclin-dependent kinase activities was dependent on and possibly mediated through the CDC6 gene product. Thus, Clb5 and Clb6 may stabilize S phase by promoting DNA replication while inhibiting other cell cycle activities.

Influence of AUF1 targeting siRNA on cell cycle-related proteins in thyroid cancer cell lines

2006 ◽  
Vol 114 (S 1) ◽  
Author(s):  
B Trojanowicz ◽  
Z Chen ◽  
J Bialek ◽  
Y Radestock ◽  
S Hombach-Klonisch ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Thyroid Cancer ◽  
Cell Lines ◽  
Cancer Cell ◽  
Cancer Cell Lines ◽  
Thyroid Cancer Cell ◽  
Thyroid Cancer Cell Lines ◽  
Related Proteins

scholarly journals Functional expression of a yeast mitochondrial intron-encoded protein requires RNA processing at a conserved dodecamer sequence at the 3' end of the gene.

1989 ◽  
Vol 9 (4) ◽  
pp. 1507-1512 ◽  
Author(s):  
H Zhu ◽  
H Conrad-Webb ◽  
X S Liao ◽  
P S Perlman ◽  
R A Butow
Keyword(s):  
Genetic Analysis ◽  
Rna Processing ◽  
Fold Increase ◽  
Functional Expression ◽  
Rrna Gene ◽  
Yeast Mitochondria ◽  
Wild Type ◽  
Site Specific ◽  
Var1 Gene ◽  
A Site

All mRNAs of yeast mitochondria are processed at their 3' ends within a conserved dodecamer sequence, 5'-AAUAAUAUUCUU-3'. A dominant nuclear suppressor, SUV3-I, was previously isolated because it suppresses a dodecamer deletion at the 3' end of the var1 gene. We have tested the effects of SUV3-1 on a mutant containing two adjacent transversions within a dodecamer at the 3' end of fit1, a gene located within the 1,143-base-pair intron of the 21S rRNA gene, whose product is a site-specific endonuclease required in crosses for the quantitative transmission of that intron to 21S alleles that lack it. The fit1 dodecamer mutations blocked both intron transmission and dodecamer cleavage, neither of which was suppressed by SUV3-1 when present in heterozygous or homozygous configurations. Unexpectedly, we found that SUV3-1 completely blocked cleavage of the wild-type fit1 dodecamer and, in SUV3-1 homozygous crosses, intron conversion. In addition, SUV3-1 resulted in at least a 40-fold increase in the amount of excised intron accumulated. Genetic analysis showed that these phenotypes resulted from the same mutation. We conclude that cleavage of a wild-type dodecamer sequence at the 3' end of the fit1 gene is essential for fit1 expression.

Deregulation of cell cycle and related microRNA expression induced by vinyl chloride monomer in hepatocytes of rats

2021 ◽  
pp. 074823372110155
Author(s):  
Weizhe Pan ◽  
Shengnan Yu ◽  
Jin Jia ◽  
Junyang Hu ◽  
Liang Jie ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Vinyl Chloride ◽  
Male Rats ◽  
Cell Cycle Distribution ◽  
Vinyl Chloride Monomer ◽  
Dynamic Changes ◽  
Cell Cycle Deregulation ◽  
Change Dynamic ◽  
Related Proteins

Vinyl chloride (VC) is a confirmed human carcinogen associated with hepatocellular carcinoma and angiosarcoma. However, the role of microRNAs (miRNAs) in liver cell cycle changes under VC exposure remains unclear, which prevents research on the mechanism of VC-induced carcinogenesis. In this study, male rats were injected intraperitoneally with VC (0, 5, 25, and 125 mg/kg body weight) for 6, 8, and 12 weeks. Cell cycle analysis of liver cells, miRNA-222, miRNA-199a, miRNA-195, and miRNA-125b expression in the liver and serum, and target protein expression were performed at different time points. The results showed a higher percentage of hepatocytes in the G1/G0 and S phases at the end of 6 and 12 weeks of VC exposure, respectively. MiRNA-222 expression decreased initially and then increased, whereas miRNA-199a, miRNA-195, and miRNA-125b expression increased initially and then decreased, which corresponded with changes in cell cycle distribution and related target proteins expression (p27, cyclinA, cyclinD1, and CDK6). The corresponding expression levels of miRNAs in serum did not change. Dynamic changes in miR-222, miR-199a, miR-195, and miR-125b induced by VC can lead to cell cycle deregulation by affecting cell cycle-related proteins, and these miRNAs can serve as early biomarkers for malignant transformation caused by VC.

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