scholarly journals Regulation of Cell Size by Glucose Is Exerted via Repression of the CLN1 Promoter

1998 ◽  
Vol 18 (5) ◽  
pp. 2492-2501 ◽  
Author(s):  
Karin Flick ◽  
Daphne Chapman-Shimshoni ◽  
David Stuart ◽  
Marisela Guaderrama ◽  
Curt Wittenberg
Keyword(s):  
Cell Cycle ◽  
Cell Size ◽  
Transcriptional Repression ◽  
Yeast Cells ◽  
Glucose Addition ◽  
Cell Cycle Delay ◽  
Core Elements ◽  
Dependent Cell ◽  
A Cell

ABSTRACT Yeast cells are keenly sensitive to the availability and quality of nutrients. Addition of glucose to cells growing on a poorer carbon source elicits a cell cycle delay during G1 phase and a concomitant increase in the cell size. The signal is transduced through the RAS-cyclic AMP pathway. Using synchronized populations of G1 cells, we show that the increase in cell size required for budding depends upon CLN1 but not other G1 cyclins. This delay in cell cycle initiation is associated specifically with transcriptional repression of CLN1. CLN2 is not repressed. Repression of CLN1 is not limited to the first cycle following glucose addition but occurs in each cell cycle during growth on glucose. A 106-bp fragment of theCLN1 promoter containing the three MluI cell cycle box (MCB) core elements responsible for the majority ofCLN1-associated upstream activation sequence activity is sufficient to confer glucose-induced repression on a heterologous reporter. A mutant CLN2 promoter that is rendered dependent upon its three MCB core elements due to inactivation of its Swi4-dependent cell cycle box (SCB) elements is also repressed by glucose. The response to glucose is partially suppressed by inactivation of SWI4, but not MBP1, which is consistent with the dependence of MCB core elements upon the SCB-binding transcription factor (SBF). We suggest that differential regulation of CLN1 and CLN2 by glucose results from differences in the capacity of SBF to activate transcription driven by SCB and MCB core elements. Finally, we show that transcriptional repression is sufficient to explain the cell cycle delay that occurs in response to glucose.

scholarly journals Telomere Cap Components Influence the Rate of Senescence in Telomerase-Deficient Yeast Cells

2004 ◽  
Vol 24 (2) ◽  
pp. 837-845 ◽  
Author(s):  
Shinichiro Enomoto ◽  
Lynn Glowczewski ◽  
Jodi Lew-Smith ◽  
Judith G. Berman
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Cycle ◽  
Cell Division ◽  
Yeast Cells ◽  
Progressive Reduction ◽  
Delayed Senescence ◽  
Cell Cycle Delay ◽  
Nonsense Mediated Mrna Decay ◽  
A Cell ◽  
Population Doublings

ABSTRACT Cells lacking telomerase undergo senescence, a progressive reduction in cell division that involves a cell cycle delay and culminates in “crisis,” a period when most cells become inviable. In telomerase-deficient Saccharomyces cerevisiae cells lacking components of the nonsense-mediated mRNA decay (NMD) pathway (Upf1,Upf2, or Upf3 proteins), senescence is delayed, with crisis occurring ∼10 to 25 population doublings later than in Upf+ cells. Delayed senescence is seen in upfΔ cells lacking the telomerase holoenzyme components Est2p and TLC1 RNA, as well as in cells lacking the telomerase regulators Est1p and Est3p. The delay of senescence in upfΔ cells is not due to an increased rate of survivor formation. Rather, it is caused by alterations in the telomere cap, composed of Cdc13p, Stn1p, and Ten1p. In upfΔ mutants, STN1 and TEN1 levels are increased. Increasing the levels of Stn1p and Ten1p in Upf+ cells is sufficient to delay senescence. In addition, cdc13-2 mutants exhibit delayed senescence rates similar to those of upfΔ cells. Thus, changes in the telomere cap structure are sufficient to affect the rate of senescence in the absence of telomerase. Furthermore, the NMD pathway affects the rate of senescence in telomerase-deficient cells by altering the stoichiometry of telomere cap components.

scholarly journals The puc1 Cyclin Regulates the G1 Phase of the Fission Yeast Cell Cycle in Response to Cell Size

2000 ◽  
Vol 11 (2) ◽  
pp. 543-554 ◽  
Author(s):  
Cristina Martı́n-Castellanos ◽  
Miguel A. Blanco ◽  
José M. de Prada ◽  
Sergio Moreno
Keyword(s):  
Cell Cycle ◽  
Fission Yeast ◽  
Cell Size ◽  
Yeast Cells ◽  
G1 Phase ◽  
Close Relative ◽  
Cell Cycle Distribution ◽  
Cdk Inhibitor ◽  
Wild Type ◽  
A Cell

Eukaryotic cells coordinate cell size with cell division by regulating the length of the G1 and G2 phases of the cell cycle. In fission yeast, the length of the G1 phase depends on a precise balance between levels of positive (cig1, cig2, puc1, and cdc13 cyclins) and negative (rum1 and ste9-APC) regulators of cdc2. Early in G1, cyclin proteolysis and rum1 inhibition keep the cdc2/cyclin complexes inactive. At the end of G1, the balance is reversed and cdc2/cyclin activity down-regulates both rum1 and the cyclin-degrading activity of the APC. Here we present data showing that the puc1 cyclin, a close relative of the Cln cyclins in budding yeast, plays an important role in regulating the length of G1. Fission yeast cells lacking cig1 and cig2 have a cell cycle distribution similar to that of wild-type cells, with a short G1 and a long G2. However, when thepuc1 + gene is deleted in this genetic background, the length of G1 is extended and these cells undergo S phase with a greater cell size than wild-type cells. This G1 delay is completely abolished in cells lacking rum1. Cdc2/puc1 function may be important to down-regulate the rum1 Cdk inhibitor at the end of G1.

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.

Three proteins required for early steps in the protein secretory pathway also affect nuclear envelope structure and cell cycle progression in fission yeast

2002 ◽  
Vol 115 (2) ◽  
pp. 421-431
Author(s):  
Anna Matynia ◽  
Sandra S. Salus ◽  
Shelley Sazer
Keyword(s):  
Cell Cycle ◽  
Nuclear Envelope ◽  
Fission Yeast ◽  
Cell Cycle Progression ◽  
Secretory Pathway ◽  
Yeast Cells ◽  
Ran Gtpase ◽  
A Cell ◽  
Cell Cycle Block ◽  
Er Membrane

The Ran GTPase is an essential protein that has multiple functions in eukaryotic cells. Fission yeast cells in which Ran is misregulated arrest after mitosis with condensed, unreplicated chromosomes and abnormal nuclear envelopes. The fission yeast sns mutants arrest with a similar cell cycle block and interact genetically with the Ran system. sns-A10, sns-B2 and sns-B9 have mutations in the fission yeast homologues of S. cerevisiae Sar1p, Sec31p and Sec53p, respectively, which are required for the early steps of the protein secretory pathway. The three sns mutants accumulate a normally secreted protein in the endoplasmic reticulum (ER), have an increased amount of ER membrane, and the ER/nuclear envelope lumen is dilated. Neither a post-ER block in the secretory pathway, nor ER proliferation caused by overexpression of an integral ER membrane protein, results in a cell cycle-specific defect. Therefore, the arrest seen in sns-A10, sns-B2 and sns-B9 is most likely due to nuclear envelope defects that render the cells unable to re-establish the interphase organization of the nucleus after mitosis. As a consequence, these mutants are unable to decondense their chromosomes or to initiate of the next round of DNA replication.

scholarly journals Regulation of Cell Cycle Progression by Swe1p and Hog1p Following Hypertonic Stress

2001 ◽  
Vol 12 (1) ◽  
pp. 53-62 ◽  
Author(s):  
Matthew R. Alexander ◽  
Mike Tyers ◽  
Mireille Perret ◽  
B. Maureen Craig ◽  
Karen S. Fang ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Kinase Activity ◽  
Phosphorylation Site ◽  
S Phase ◽  
Mitogen Activated Protein Kinase ◽  
Yeast Cells ◽  
Hypertonic Stress ◽  
Cell Cycle Delay ◽  
G2 Phase ◽  
Morphogenesis Checkpoint

Exposure of yeast cells to an increase in external osmolarity induces a temporary growth arrest. Recovery from this stress is mediated by the accumulation of intracellular glycerol and the transcription of several stress response genes. Increased external osmolarity causes a transient accumulation of 1N and 2N cells and a concomitant depletion of S phase cells. Hypertonic stress triggers a cell cycle delay in G2 phase cells that appears distinct from the morphogenesis checkpoint, which operates in early S phase cells. Hypertonic stress causes a decrease in CLB2 mRNA, phosphorylation of Cdc28p, and inhibition of Clb2p-Cdc28p kinase activity, whereas Clb2 protein levels are unaffected. Like the morphogenesis checkpoint, the osmotic stress-induced G2 delay is dependent upon the kinase Swe1p, but is not tightly correlated with inhibition of Clb2p-Cdc28p kinase activity. Thus, deletion ofSWE1 does not prevent the hypertonic stress-induced inhibition of Clb2p-Cdc28p kinase activity. Mutation of the Swe1p phosphorylation site on Cdc28p (Y19) does not fully eliminate the Swe1p-dependent cell cycle delay, suggesting that Swe1p may have functions independent of Cdc28p phosphorylation. Conversely, deletion of the mitogen-activated protein kinase HOG1 does prevent Clb2p-Cdc28p inhibition by hypertonic stress, but does not block Cdc28p phosphorylation or alleviate the cell cycle delay. However, Hog1p does contribute to proper nuclear segregation after hypertonic stress in cells that lack Swe1p. These results suggest a hypertonic stress-induced cell cycle delay in G2 phase that is mediated in a novel way by Swe1p in cooperation with Hog1p.

scholarly journals TPR proteins required for anaphase progression mediate ubiquitination of mitotic B-type cyclins in yeast.

1996 ◽  
Vol 7 (5) ◽  
pp. 791-801 ◽  
Author(s):  
W Zachariae ◽  
K Nasmyth
Keyword(s):  
Cell Cycle ◽  
Cyclin B ◽  
Yeast Cells ◽  
Tetratricopeptide Repeat ◽  
Gene Products ◽  
Ubiquitin Pathway ◽  
Ubiquitin Protein Ligase ◽  
A Cell ◽  
Synthesis And Degradation

The abundance of B-type cyclin-CDK complexes is determined by regulated synthesis and degradation of cyclin subunits. Cyclin proteolysis is required for the final exit from mitosis and for the initiation of a new cell cycle. In extracts from frog or clam eggs, degradation is accompanied by ubiquitination of cyclin. Three genes, CDC16, CDC23, and CSE1 have recently been shown to be required specifically for cyclin B proteolysis in yeast. To test whether these genes are required for cyclin ubiquitination, we prepared extracts from G1-arrested yeast cells capable of conjugating ubiquitin to the B-type cyclin Clb2. The ubiquitination activity was cell cycle regulated, required Clb2's destruction box, and was low if not absent in cdc16, cdc23, cdc27, and cse1 mutants. Furthermore all these mutants were also defective in ubiquitination of another mitotic B-type cyclin, Clb3. The Cdc16, Cdc23, and Cdc27 proteins all contain several copies of the tetratricopeptide repeat and are subunits of a complex that is required for the onset of anaphase. The finding that gene products that are required for ubiquitination of Clb2 and Clb3 are also required for cyclin proteolysis in vivo provides the best evidence so far that cyclin B is degraded via the ubiquitin pathway in living cells. Xenopus homologues of Cdc16 and Cdc27 have meanwhile been shown to be associated with a 20S particle that appears to function as a cell cycle-regulated ubiquitin-protein ligase.

scholarly journals Fission Yeast Cells Grow Approximately Exponentially

2018 ◽  
Author(s):  
Mary Pickering ◽  
Lauren Nicole Hollis ◽  
Edridge D’Souza ◽  
Nicholas Rhind
Keyword(s):  
Cell Cycle ◽  
Cell Growth ◽  
Fission Yeast ◽  
Cell Size ◽  
Exponential Growth ◽  
Cell Biology ◽  
Growth Models ◽  
Growth Period ◽  
Yeast Cells ◽  
Yeast Growth

ABSTRACTHow the rate of cell growth is influenced by cell size is a fundamental question of cell biology. The simple model that cell growth is proportional to cell size, based on the proposition that larger cells have proportionally greater synthetic capacity than smaller cells, leads to the predication that the rate of cell growth increases exponentially with cell size. However, other modes of cell growth, including bilinear growth, have been reported. The distinction between exponential and bilinear growth has been explored in particular detail in the fission yeast Schizosaccharomyces pombe. We have revisited the mode of fission yeast cell growth using high-resolution time-lapse microscopy and find, as previously reported, that these two growth models are difficult to distinguish both because of the similarity in shapes between exponential and bilinear curves over the two-fold change in length of a normal cell cycle and because of the substantial biological and experimental noise inherent to these experiments. Therefore, we contrived to have cells grow more than two fold, by holding them in G2 for up to eight hours. Over this extended growth period, in which cells grow up to 5.5-fold, the two growth models diverge to the point that we can confidently exclude bilinear growth as a general model for fission yeast growth. Although the growth we observe is clearly more complicated than predicted by simple exponential growth, we find that exponential growth is a robust approximation of fission yeast growth, both during an unperturbed cell cycle and during extended periods of growth.

scholarly journals Characterizing non-exponential growth and bimodal cell size distributions in Schizosaccharomyces pombe: an analytical approach

2021 ◽  
Author(s):  
Chen Jia ◽  
Abhyudai Singh ◽  
Ramon Grima
Keyword(s):  
Cell Cycle ◽  
Fission Yeast ◽  
Cell Size ◽  
Control Strategy ◽  
Size Control ◽  
Birth Size ◽  
Size Distributions ◽  
Cell Size Distribution ◽  
A Cell ◽  
Cell Size Control

Unlike many single-celled organisms, the growth of fission yeast cells within a cell cycle is not exponential. It is rather characterized by three distinct phases (elongation, septation and fission), each with a different growth rate. Experiments also show that the distribution of cell size in a lineage is often bimodal, unlike the unimodal distributions measured for the bacterium Escherichia coli. Here we construct a detailed stochastic model of cell size dynamics in fission yeast. The theory leads to analytic expressions for the cell size and the birth size distributions, and explains the origin of bimodality seen in experiments. In particular our theory shows that the left peak in the bimodal distribution is associated with cells in the elongation phase while the right peak is due to cells in the septation and fission phases. We show that the size control strategy, the variability in the added size during a cell cycle and the fraction of time spent in each of the three cell growth phases have a strong bearing on the shape of the cell size distribution. Furthermore we infer all the parameters of our model by matching the theoretical cell size and birth size distributions to those from experimental single cell time-course data for seven different growth conditions. Our method provides a much more accurate means of determining the cell size control strategy (timer, adder or sizer) than the standard method based on the slope of the best linear fit between the birth and division sizes. We also show that the variability in added size and the strength of cell size control of fission yeast depend weakly on the temperature but strongly on the culture medium.

scholarly journals Rate of cell cycle initiation of yeast cells when cell size is not a rate-determining factor

1983 ◽  
Vol 59 (1) ◽  
pp. 183-201 ◽  
Author(s):  
P.G. Lord ◽  
A.E. Wheals
Keyword(s):  
Cell Cycle ◽  
Steady State ◽  
Cell Size ◽  
Cycle Time ◽  
Yeast Cells ◽  
Size Difference ◽  
Birth Size ◽  
Daughter Cells ◽  
Alpha Factor ◽  
Determining Factor

The control of cell proliferation under steady-state conditions in the budding yeast, Saccharomyces cerevisiae, is well described by either the tandem or sloppy size control models, both of which suggest that differences in cycle time between individual cells or between parents and daughters is largely due to differences in birth size. These models have been investigated further under conditions in which cell size has not been a rate-determining factor for cell cycle initiation. Two approaches have been used. The first involves the growth of cells in low concentrations of hydroxyurea (HU), which has the effect of prolonging the duration of DNA synthesis. This leads to a lengthening of the budded period, which in turn leads to daughter cells being larger at division than the normal cell cycle initiation size of daughters in steady-state populations. The second approach involves the accumulation of cells at the key control point of the cycle, called start, using the pheromone alpha-factor. Since growth is unaffected, all cells eventually become larger than the volume at which they would normally initiate the cell cycle. The kinetics of proliferation were followed after release from alpha-factor arrest. The results from both approaches were broadly consistent with the predictions of both models. However, abolition of birth-size differences between parents and daughters in the presence of HU did not lead to a complete disappearance of differences in either cycle time or proliferation kinetics. Furthermore, following release from alpha-factor arrest, the rate of cell cycle initiation of parent cells was slower than in steady-state culture and the daughters' cells behaved as if comprising two separate populations. These discrepancies suggest that besides a size difference, there are additional physiological differences between parent and daughter cells.

scholarly journals The oscillation of mitotic kinase governs cell cycle latches

2021 ◽  
Author(s):  
Bela Novak ◽  
John J Tyson
Keyword(s):  
Cell Cycle ◽  
Negative Feedback ◽  
Molecular Switches ◽  
Feedback Loops ◽  
Yeast Cells ◽  
Cyclin Dependent Kinases ◽  
Mitotic Kinase ◽  
Daughter Cells ◽  
Negative Feedback Loops ◽  
A Cell

SummaryIn order to transmit a eukaryotic cell’s genome accurately from mother cell to daughter cells, it is essential that the basic events of the cell division cycle (DNA synthesis and mitosis) occur once and only once per cycle, i.e., that a cell progresses irreversibly from G1 to S to G2 to M and back to G1. Irreversible progression through the cell cycle is assured by a sequence of ‘latching’ molecular switches, based on molecular interactions among cyclin-dependent kinases and their auxiliary partners. Positive feedback loops (++ or −−) create bistable switches with latching properties, and negative feedback loops drive progression from one stage to the next. In budding yeast (Saccharomyces cerevisiae) these events are coordinated by double-negative feedback loops between Clb-dependent kinases (Clb1-6) and their antagonists (APC:Cdh1 and Sic1). If the coordinating signal is compromised, either by deletion of Clb1-5 proteins or expression of non-degradable Clb2, then irreversibility is lost and yeast cells exhibit multiple rounds of DNA replication or mitotic exit events (Cdc14 endocycles). Using mathematical modelling of a stripped-down control network, we show how endocycles arise because the switches fail to latch, and the gates swing back and forth by the action of the negative feedback loops.

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