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1
Song, Sukgil, et Kyung S. Lee. « A Novel Function of Saccharomyces cerevisiae CDC5 in Cytokinesis ». Journal of Cell Biology 152, no 3 (5 février 2001) : 451–70. http://dx.doi.org/10.1083/jcb.152.3.451.
Texte intégralRésumé :
Coordination of mitotic exit with timely initiation of cytokinesis is critical to ensure completion of mitotic events before cell division. The Saccharomyces cerevisiae polo kinase Cdc5 functions in a pathway leading to the degradation of mitotic cyclin Clb2, thereby permitting mitotic exit. Here we provide evidence that Cdc5 also plays a role in regulating cytokinesis and that an intact polo-box, a conserved motif in the noncatalytic COOH-terminal domain of Cdc5, is required for this event. Depletion of Cdc5 function leads to an arrest in cytokinesis. Overexpression of the COOH-terminal domain of Cdc5 (cdc5ΔN), but not the corresponding polo-box mutant, resulted in connected cells. These cells shared cytoplasms with incomplete septa, and possessed aberrant septin ring structures. Provision of additional copies of endogenous CDC5 remedied this phenotype, suggesting a dominant-negative inhibition of cytokinesis. The polo-box–dependent interactions between Cdc5 and septins (Cdc11 and Cdc12) and genetic interactions between the dominant-negative cdc5ΔN and Cyk2/Hof1 or Myo1 suggest that direct interactions between cdc5ΔN and septins resulted in inhibition of Cyk2/Hof1- and Myo1-mediated cytokinetic pathways. Thus, we propose that Cdc5 may coordinate mitotic exit with cytokinesis by participating in both anaphase promoting complex activation and a polo-box–dependent cytokinetic pathway.
2
Luca, Francis C., Manali Mody, Cornelia Kurischko, David M. Roof, Thomas H. Giddings et Mark Winey. « Saccharomyces cerevisiae Mob1p Is Required for Cytokinesis and Mitotic Exit ». Molecular and Cellular Biology 21, no 20 (15 octobre 2001) : 6972–83. http://dx.doi.org/10.1128/mcb.21.20.6972-6983.2001.
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ABSTRACT The Saccharomyces cerevisiae mitotic exit network (MEN) is a conserved set of genes that mediate the transition from mitosis to G1 by regulating mitotic cyclin degradation and the inactivation of cyclin-dependent kinase (CDK). Here, we demonstrate that, in addition to mitotic exit, S. cerevisiae MEN gene MOB1 is required for cytokinesis and cell separation. The cytokinesis defect was evident in mob1mutants under conditions in which there was no mitotic-exit defect. Observation of live cells showed that yeast myosin II, Myo1p, was present in the contractile ring at the bud neck but that the ring failed to contract and disassemble. The cytokinesis defect persisted for several mitotic cycles, resulting in chains of cells with correctly segregated nuclei but with uncontracted actomyosin rings. The cytokinesis proteins Cdc3p (a septin), actin, and Iqg1p/ Cyk1p (an IQGAP-like protein) appeared to correctly localize inmob1 mutants, suggesting that MOB1functions subsequent to actomyosin ring assembly. We also examined the subcellular distribution of Mob1p during the cell cycle and found that Mob1p first localized to the spindle pole bodies during mid-anaphase and then localized to a ring at the bud neck just before and during cytokinesis. Localization of Mob1p to the bud neck requiredCDC3, MEN genes CDC5,CDC14, CDC15, and DBF2, and spindle pole body gene NUD1 but was independent ofMYO1. The localization of Mob1p to both spindle poles was abolished in cdc15 and nud1 mutants and was perturbed in cdc5 and cdc14mutants. These results suggest that the MEN functions during the mitosis-to-G1 transition to control cyclin-CDK inactivation and cytokinesis.
3
Bi, Erfei, Paul Maddox, Daniel J. Lew, E. D. Salmon, John N. McMillan, Elaine Yeh et John R. Pringle. « Involvement of an Actomyosin Contractile Ring in Saccharomyces cerevisiae Cytokinesis ». Journal of Cell Biology 142, no 5 (7 septembre 1998) : 1301–12. http://dx.doi.org/10.1083/jcb.142.5.1301.
Texte intégralRésumé :
In Saccharomyces cerevisiae, the mother cell and bud are connected by a narrow neck. The mechanism by which this neck is closed during cytokinesis has been unclear. Here we report on the role of a contractile actomyosin ring in this process. Myo1p (the only type II myosin in S. cerevisiae) forms a ring at the presumptive bud site shortly before bud emergence. Myo1p ring formation depends on the septins but not on F-actin, and preexisting Myo1p rings are stable when F-actin is depolymerized. The Myo1p ring remains in the mother–bud neck until the end of anaphase, when a ring of F-actin forms in association with it. The actomyosin ring then contracts to a point and disappears. In the absence of F-actin, the Myo1p ring does not contract. After ring contraction, cortical actin patches congregate at the mother–bud neck, and septum formation and cell separation rapidly ensue. Strains deleted for MYO1 are viable; they fail to form the actin ring but show apparently normal congregation of actin patches at the neck. Some myo1Δ strains divide nearly as efficiently as wild type; other myo1Δ strains divide less efficiently, but it is unclear whether the primary defect is in cytokinesis, septum formation, or cell separation. Even cells lacking F-actin can divide, although in this case division is considerably delayed. Thus, the contractile actomyosin ring is not essential for cytokinesis in S. cerevisiae. In its absence, cytokinesis can still be completed by a process (possibly localized cell–wall synthesis leading to septum formation) that appears to require septin function and to be facilitated by F-actin.
4
Bouquin, N., Y. Barral, R. Courbeyrette, M. Blondel, M. Snyder et C. Mann. « Regulation of cytokinesis by the Elm1 protein kinase in Saccharomyces cerevisiae ». Journal of Cell Science 113, no 8 (15 avril 2000) : 1435–45. http://dx.doi.org/10.1242/jcs.113.8.1435.
Texte intégralRésumé :
A Saccharomyces cerevisiae mutant unable to grow in a cdc28-1N background was isolated and shown to be affected in the ELM1 gene. Elm1 is a protein kinase, thought to be a negative regulator of pseudo-hyphal growth. We show that Cdc11, one of the septins, is delocalised in the mutant, indicating that septin localisation is partly controlled by Elm1. Moreover, we show that cytokinesis is delayed in an elm1delta mutant. Elm1 levels peak at the end of the cell cycle and Elm1 is localised at the bud neck in a septin-dependent fashion from bud emergence until the completion of anaphase, at about the time of cell division. Genetic and biochemical evidence suggest that Elm1 and the three other septin-localised protein kinases, Hsl1, Gin4 and Kcc4, work in parallel pathways to regulate septin behaviour and cytokinesis. In addition, the elm1delta;) morphological defects can be suppressed by deletion of the SWE1 gene, but not the cytokinesis defect nor the septin mislocalisation. Our results indicate that cytokinesis in budding yeast is regulated by Elm1.
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Jiménez, Javier, Víctor J. Cid, Rosa Cenamor, María Yuste, Gloria Molero, César Nombela et Miguel Sánchez. « Morphogenesis beyond Cytokinetic Arrest in Saccharomyces cerevisiae ». Journal of Cell Biology 143, no 6 (14 décembre 1998) : 1617–34. http://dx.doi.org/10.1083/jcb.143.6.1617.
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The budding yeast lyt1 mutation causes cell lysis. We report here that lyt1 is an allele of cdc15, a gene which encodes a protein kinase that functions late in the cell cycle. Neither cdc15-1 nor cdc15-lyt1 strains are able to septate at 37°C, even though they may manage to rebud. Cells lyse after a shmoo-like projection appears at the distal pole of the daughter cell. Actin polarizes towards the distal pole but the septins remain at the mother–daughter neck. This morphogenetic response reflects entry into a new round of the cell cycle: the preference for polarization from the distal pole was lost in bud1 cdc15 double mutants; double cdc15-lyt1 cdc28-4 mutants, defective for START, did not develop apical projections and apical polarization was accompanied by DNA replication. The same phenomena were caused by mutations in the genes CDC14, DBF2, and TEM1, which are functionally related to CDC15. Apical polarization was delayed in cdc15 mutants as compared with budding in control cells and this delay was abolished in a septin mutant. Our results suggest that the delayed M/G1 transition in cdc15 mutants is due to a septin-dependent checkpoint that couples initiation of the cell cycle to the completion of cytokinesis.
6
Lee, Philip R., Sukgil Song, Hyeon-Su Ro, Chong J. Park, John Lippincott, Rong Li, John R. Pringle, Claudio De Virgilio, Mark S. Longtine et Kyung S. Lee. « Bni5p, a Septin-Interacting Protein, Is Required for Normal Septin Function and Cytokinesis in Saccharomyces cerevisiae ». Molecular and Cellular Biology 22, no 19 (1 octobre 2002) : 6906–20. http://dx.doi.org/10.1128/mcb.22.19.6906-6920.2002.
Texte intégralRésumé :
ABSTRACT In the budding yeast Saccharomyces cerevisiae, the Cdc3p, Cdc10p, Cdc11p, Cdc12p, and Sep7p/Shs1p septins assemble early in the cell cycle in a ring that marks the future cytokinetic site. The septins appear to be major structural components of a set of filaments at the mother-bud neck and function as a scaffold for recruiting proteins involved in cytokinesis and other processes. We isolated a novel gene, BNI5, as a dosage suppressor of the cdc12-6 growth defect. Overexpression of BNI5 also suppressed the growth defects of cdc10-1, cdc11-6, and sep7Δ strains. Loss of BNI5 resulted in a cytokinesis defect, as evidenced by the formation of connected cells with shared cytoplasms, and deletion of BNI5 in a cdc3-6, cdc10-1, cdc11-6, cdc12-6, or sep7Δ mutant strain resulted in enhanced defects in septin localization and cytokinesis. Bni5p localizes to the mother-bud neck in a septin-dependent manner shortly after bud emergence and disappears from the neck approximately 2 to 3 min before spindle disassembly. Two-hybrid, in vitro binding, and protein-localization studies suggest that Bni5p interacts with the N-terminal domain of Cdc11p, which also appears to be sufficient for the localization of Cdc11p, its interaction with other septins, and other critical aspects of its function. Our data suggest that the Bni5p-septin interaction is important for septin ring stability and function, which is in turn critical for normal cytokinesis.
7
Schmidt, M. « Survival and cytokinesis of Saccharomyces cerevisiae in the absence of chitin ». Microbiology 150, no 10 (1 octobre 2004) : 3253–60. http://dx.doi.org/10.1099/mic.0.27197-0.
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Luo, Jianying, Elizabeth A. Vallen, Christopher Dravis, Serguei E. Tcheperegine, Becky Drees et Erfei Bi. « Identification and functional analysis of the essential and regulatory light chains of the only type II myosin Myo1p in Saccharomyces cerevisiae ». Journal of Cell Biology 165, no 6 (21 juin 2004) : 843–55. http://dx.doi.org/10.1083/jcb.200401040.
Texte intégralRésumé :
Cytokinesis in Saccharomyces cerevisiae involves coordination between actomyosin ring contraction and septum formation and/or targeted membrane deposition. We show that Mlc1p, a light chain for Myo2p (type V myosin) and Iqg1p (IQGAP), is the essential light chain for Myo1p, the only type II myosin in S. cerevisiae. However, disruption or reduction of Mlc1p–Myo1p interaction by deleting the Mlc1p binding site on Myo1p or by a point mutation in MLC1, mlc1-93, did not cause any obvious defect in cytokinesis. In contrast, a different point mutation, mlc1-11, displayed defects in cytokinesis and in interactions with Myo2p and Iqg1p. These data suggest that the major function of the Mlc1p–Myo1p interaction is not to regulate Myo1p activity but that Mlc1p may interact with Myo1p, Iqg1p, and Myo2p to coordinate actin ring formation and targeted membrane deposition during cytokinesis. We also identify Mlc2p as the regulatory light chain for Myo1p and demonstrate its role in Myo1p ring disassembly, a function likely conserved among eukaryotes.
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Park, Chong Jin, Sukgil Song, Philip R. Lee, Wenying Shou, Raymond J. Deshaies et Kyung S. Lee. « Loss of CDC5 Function in Saccharomyces cerevisiae Leads to Defects in Swe1p Regulation and Bfa1p/Bub2p-Independent Cytokinesis ». Genetics 163, no 1 (1 janvier 2003) : 21–33. http://dx.doi.org/10.1093/genetics/163.1.21.
Texte intégralRésumé :
Abstract In many organisms, polo kinases appear to play multiple roles during M-phase progression. To provide new insights into the function of budding yeast polo kinase Cdc5p, we generated novel temperature-sensitive cdc5 mutants by mutagenizing the C-terminal domain. Here we show that, at a semipermissive temperature, the cdc5-3 mutant exhibited a synergistic bud elongation and growth defect with loss of HSL1, a component important for normal G2/M transition. Loss of SWE1, which phosphorylates and inactivates the budding yeast Cdk1 homolog Cdc28p, suppressed the cdc5-3 hsl1Δ defect, suggesting that Cdc5p functions at a point upstream of Swe1p. In addition, the cdc5-4 and cdc5-7 mutants exhibited chained cell morphologies with shared cytoplasms between the connected cell bodies, indicating a cytokinetic defect. Close examination of these mutants revealed delayed septin assembly at the incipient bud site and loosely organized septin rings at the mother-bud neck. Components in the mitotic exit network (MEN) play important roles in normal cytokinesis. However, loss of BFA1 or BUB2, negative regulators of the MEN, failed to remedy the cytokinetic defect of these mutants, indicating that Cdc5p promotes cytokinesis independently of Bfa1p and Bub2p. Thus, Cdc5p contributes to the activation of the Swe1p-dependent Cdc28p/Clb pathway, normal septin function, and cytokinesis.
10
Powell, Chris D., David E. Quain et Katherine A. Smart. « Chitin scar breaks in aged Saccharomyces cerevisiae ». Microbiology 149, no 11 (1 novembre 2003) : 3129–37. http://dx.doi.org/10.1099/mic.0.25940-0.
Texte intégralRésumé :
Ageing in budding yeast is not determined by chronological lifespan, but by the number of times an individual cell is capable of dividing, termed its replicative capacity. As cells age they are subject to characteristic cell surface changes. Saccharomyces cerevisiae reproduces asexually by budding and as a consequence of this process both mother and daughter cell retain chitinous scar tissue at the point of cytokinesis. Daughter cells exhibit a frail structure known as the birth scar, while mother cells display a more persistent bud scar. The number of bud scars present on the cell surface is directly related to the number of times a cell has divided and thus constitutes a biomarker for replicative cell age. It has been proposed that the birth scar may be subject to stretching caused by expansion of the daughter cell; however, no previous analysis of the effect of cell age on birth or bud scar size has been reported. This paper provides evidence that scar tissue expands with the cell during growth. It is postulated that symmetrically arranged breaks in the bud scar allow these rigid chitinous structures to expand without compromising cellular integrity.
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Tolliday, Nicola, Maria Pitcher et Rong Li. « Direct Evidence for a Critical Role of Myosin II in Budding Yeast Cytokinesis and the Evolvability of New Cytokinetic Mechanisms in the Absence of Myosin II ». Molecular Biology of the Cell 14, no 2 (février 2003) : 798–809. http://dx.doi.org/10.1091/mbc.e02-09-0558.
Texte intégralRésumé :
In the budding yeast Saccharomyces cerevisiae, an actomyosin-based contractile ring is present during cytokinesis, as occurs in animal cells. However, the precise requirement for this structure during budding yeast cytokinesis has been controversial. Here we show that deletion of MYO1, the single myosin II gene, is lethal in a commonly used strain background. The terminal phenotype of myo1Δ is interconnected chains of cells, suggestive of a cytokinesis defect. To further investigate the role of Myo1p in cytokinesis, we conditionally disrupted Myo1 function by using either a dominant negative Myo1p construct or a strain where expression of Myo1p can be shut-off. Both ways of disruption of Myo1 function result in a failure in cytokinesis. Additionally, we show that amyo1Δ strain previously reported to grow nearly as well as the wild type contains a single genetic suppressor that alleviates the severe cytokinesis defects of myo1Δ. Using fluorescence time-lapse imaging and electron microscopy techniques, we show that cytokinesis in this strain is achieved through formation of multiple aberrant septa. Taken together, these results strongly suggest that the actomyosin ring is crucial for successful cytokinesis in budding yeast, but new cytokinetic mechanisms can evolve through genetic changes when myosin II function is impaired.
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Rice, Terri S., Min Ding, David S. Pederson et Nicholas H. Heintz. « The Highly Conserved tRNAHis Guanylyltransferase Thg1p Interacts with the Origin Recognition Complex and Is Required for the G2/M Phase Transition in the Yeast Saccharomyces cerevisiae ». Eukaryotic Cell 4, no 4 (avril 2005) : 832–35. http://dx.doi.org/10.1128/ec.4.4.832-835.2005.
Texte intégralRésumé :
ABSTRACT Here we show that the Saccharomyces cerevisiae tRNAHis guanylyltransferase Thg1p interacts with the origin recognition complex in vivo and in vitro and that overexpression of hemagglutinin-Thg1p selectively impedes growth of orc2-1(Ts) cells at the permissive temperature. Studies with conditional mutants indicate that Thg1p couples nuclear division and migration to cell budding and cytokinesis in yeast.
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McCusker, J. H., D. S. Perlin et J. E. Haber. « Pleiotropic plasma membrane ATPase mutations of Saccharomyces cerevisiae ». Molecular and Cellular Biology 7, no 11 (novembre 1987) : 4082–88. http://dx.doi.org/10.1128/mcb.7.11.4082-4088.1987.
Texte intégralRésumé :
We isolated a large number of mutations in the structural gene for the plasma membrane ATPase (PMA1) of Saccharomyces cerevisiae. These mutations were selected by their resistance to the aminoglycoside antibiotic hygromycin B. Biochemical analysis of purified membrane preparations showed that the plasma membrane ATPase activity of the mutants was reduced as much as 75%. Intragenic complementation of pma1 mutants suggested that the yeast plasma membrane ATPase was a multimeric enzyme. The pma1 mutants were apparently defective in maintaining internal pH; more than half of the mutants were unable to grow either at a low pH or in the presence of a weak acid. Most pma1 mutants were also osmotic pressure sensitive. At a very low temperature (5 degrees C) many pma1 mutants were unable to grow and were arrested as unbudded cells. The three most severely affected mutants were also unable to grow in the presence of NH4+. The most extreme mutant exhibited a severe defect in progression through the cell cycle; on synthetic medium, the cells progressively accumulated nucleus-containing small buds that generally failed to complete bud enlargement and cytokinesis. Most of the pleiotropic phenotypes of pma1 mutants could be suppressed by the addition of 50 mM KCl but not NaCl to the medium.
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McCusker, J. H., D. S. Perlin et J. E. Haber. « Pleiotropic plasma membrane ATPase mutations of Saccharomyces cerevisiae. » Molecular and Cellular Biology 7, no 11 (novembre 1987) : 4082–88. http://dx.doi.org/10.1128/mcb.7.11.4082.
Texte intégralRésumé :
We isolated a large number of mutations in the structural gene for the plasma membrane ATPase (PMA1) of Saccharomyces cerevisiae. These mutations were selected by their resistance to the aminoglycoside antibiotic hygromycin B. Biochemical analysis of purified membrane preparations showed that the plasma membrane ATPase activity of the mutants was reduced as much as 75%. Intragenic complementation of pma1 mutants suggested that the yeast plasma membrane ATPase was a multimeric enzyme. The pma1 mutants were apparently defective in maintaining internal pH; more than half of the mutants were unable to grow either at a low pH or in the presence of a weak acid. Most pma1 mutants were also osmotic pressure sensitive. At a very low temperature (5 degrees C) many pma1 mutants were unable to grow and were arrested as unbudded cells. The three most severely affected mutants were also unable to grow in the presence of NH4+. The most extreme mutant exhibited a severe defect in progression through the cell cycle; on synthetic medium, the cells progressively accumulated nucleus-containing small buds that generally failed to complete bud enlargement and cytokinesis. Most of the pleiotropic phenotypes of pma1 mutants could be suppressed by the addition of 50 mM KCl but not NaCl to the medium.
15
Castrillon, D. H., et S. A. Wasserman. « Diaphanous is required for cytokinesis in Drosophila and shares domains of similarity with the products of the limb deformity gene ». Development 120, no 12 (1 décembre 1994) : 3367–77. http://dx.doi.org/10.1242/dev.120.12.3367.
Texte intégralRésumé :
We show that the Drosophila gene diaphanous is required for cytokinesis. Males homozygous for the dia1 mutation are sterile due to a defect in cytokinesis in the germline. Females trans-heterozygous for dia1 and a deficiency are sterile and lay eggs with defective eggshells; failure of cytokinesis is observed in the follicle cell layer. Null alleles are lethal. Death occurs at the onset of pupation due to the absence of imaginal discs. Mitotic figures in larval neuroblasts were found to be polyploid, apparently due to a defect in cytokinesis. The predicted 123 × 10(3) M(r) protein contains two domains shared by the formin proteins, encoded by the limb deformity gene in the mouse. These formin homology domains, which we have termed FH1 and FH2, are also found in Bni1p, the product of a Saccharomyces cerevisiae gene required for normal cytokinesis in diploid yeast cells.
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Fang, Xiaodong, Jianying Luo, Ryuichi Nishihama, Carsten Wloka, Christopher Dravis, Mirko Travaglia, Masayuki Iwase, Elizabeth A. Vallen et Erfei Bi. « Biphasic targeting and cleavage furrow ingression directed by the tail of a myosin II ». Journal of Cell Biology 191, no 7 (20 décembre 2010) : 1333–50. http://dx.doi.org/10.1083/jcb.201005134.
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Cytokinesis in animal and fungal cells utilizes a contractile actomyosin ring (AMR). However, how myosin II is targeted to the division site and promotes AMR assembly, and how the AMR coordinates with membrane trafficking during cytokinesis, remains poorly understood. Here we show that Myo1 is a two-headed myosin II in Saccharomyces cerevisiae, and that Myo1 localizes to the division site via two distinct targeting signals in its tail that act sequentially during the cell cycle. Before cytokinesis, Myo1 localization depends on the septin-binding protein Bni5. During cytokinesis, Myo1 localization depends on the IQGAP Iqg1. We also show that the Myo1 tail is sufficient for promoting the assembly of a “headless” AMR, which guides membrane deposition and extracellular matrix remodeling at the division site. Our study establishes a biphasic targeting mechanism for myosin II and highlights an underappreciated role of the AMR in cytokinesis beyond force generation.
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Burke, D. J., et D. Church. « Protein synthesis requirements for nuclear division, cytokinesis, and cell separation in Saccharomyces cerevisiae ». Molecular and Cellular Biology 11, no 7 (juillet 1991) : 3691–98. http://dx.doi.org/10.1128/mcb.11.7.3691-3698.1991.
Texte intégralRésumé :
Protein synthesis inhibitors have often been used to identify regulatory steps in cell division. We used cell division cycle mutants of the yeast Saccharomyces cerevisiae and two chemical inhibitors of translation to investigate the requirements for protein synthesis for completing landmark events after the G1 phase of the cell cycle. We show, using cdc2, cdc6, cdc7, cdc8, cdc17 (38 degrees C), and cdc21 (also named tmp1) mutants, that cells arrested in S phase complete DNA synthesis but cannot complete nuclear division if protein synthesis is inhibited. In contrast, we show, using cdc16, cdc17 (36 degrees C), cdc20, cdc23, and nocodazole treatment, that cells that arrest in the G2 stage complete nuclear division in the absence of protein synthesis. Protein synthesis is required late in the cell cycle to complete cytokinesis and cell separation. These studies show that there are requirements for protein synthesis in the cell cycle, after G1, that are restricted to two discrete intervals.
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Burke, D. J., et D. Church. « Protein synthesis requirements for nuclear division, cytokinesis, and cell separation in Saccharomyces cerevisiae. » Molecular and Cellular Biology 11, no 7 (juillet 1991) : 3691–98. http://dx.doi.org/10.1128/mcb.11.7.3691.
Texte intégralRésumé :
Protein synthesis inhibitors have often been used to identify regulatory steps in cell division. We used cell division cycle mutants of the yeast Saccharomyces cerevisiae and two chemical inhibitors of translation to investigate the requirements for protein synthesis for completing landmark events after the G1 phase of the cell cycle. We show, using cdc2, cdc6, cdc7, cdc8, cdc17 (38 degrees C), and cdc21 (also named tmp1) mutants, that cells arrested in S phase complete DNA synthesis but cannot complete nuclear division if protein synthesis is inhibited. In contrast, we show, using cdc16, cdc17 (36 degrees C), cdc20, cdc23, and nocodazole treatment, that cells that arrest in the G2 stage complete nuclear division in the absence of protein synthesis. Protein synthesis is required late in the cell cycle to complete cytokinesis and cell separation. These studies show that there are requirements for protein synthesis in the cell cycle, after G1, that are restricted to two discrete intervals.
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Jin, Quan-Wen, Samriddha Ray, Sung Hugh Choi et Dannel McCollum. « The Nucleolar Net1/Cfi1-related Protein Dnt1 Antagonizes the Septation Initiation Network in Fission Yeast ». Molecular Biology of the Cell 18, no 8 (août 2007) : 2924–34. http://dx.doi.org/10.1091/mbc.e06-09-0853.
Texte intégralRésumé :
The septation initiation network (SIN) and mitotic exit network (MEN) signaling pathways regulate cytokinesis and mitotic exit in the yeasts Schizosaccharomyces pombe, and Saccharomyces cerevisiae, respectively. One function of these pathways is to keep the Cdc14-family phosphatase, called Clp1 in S. pombe, from being sequestered and inhibited in the nucleolus. In S. pombe, the SIN and Clp1 act as part of a cytokinesis checkpoint that allows cells to cope with cytokinesis defects. The SIN promotes checkpoint function by 1) keeping Clp1 out of the nucleolus, 2) maintaining the cytokinetic apparatus, and 3) halting the cell cycle until cytokinesis is completed. In a screen for suppressors of the SIN mutant cytokinesis checkpoint defect, we identified a novel nucleolar protein called Dnt1 and other nucleolar proteins, including Rrn5 and Nuc1, which are known to be required for rDNA transcription. Dnt1 shows sequence homology to Net1/Cfi1, which encodes the nucleolar inhibitor of Cdc14 in budding yeast. Like Net1/Cfi1, Dnt1 is required for rDNA silencing and minichromosome maintenance, and both Dnt1 and Net1/Cfi1 negatively regulate the homologous SIN and MEN pathways. Unlike Net1/Cfi1, which regulates the MEN through the Cdc14 phosphatase, Dnt1 can inhibit SIN signaling independently of Clp1, suggesting a novel connection between the nucleolus and the SIN pathway.
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Amatruda, JF, et JA Cooper. « Purification, characterization, and immunofluorescence localization of Saccharomyces cerevisiae capping protein ». Journal of Cell Biology 117, no 5 (1 juin 1992) : 1067–76. http://dx.doi.org/10.1083/jcb.117.5.1067.
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Capping protein binds the barbed ends of actin filaments and nucleates actin filament assembly in vitro. We purified capping protein from Saccharomyces cervisiae. One of the two subunits is the product of the CAP2 gene, which we previously identified as the gene encoding the beta subunit of capping protein based on its sequence similarity to capping protein beta subunits in chicken and Dictyostelium (Amatruda, J. F., J. F. Cannon, K. Tatchell, C. Hug, and J. A. Cooper. 1990. Nature (Lond.) 344:352-354). Yeast capping protein has activity in critical concentration and low-shear viscometry assays consistent with barbed-end capping activity. Like chicken capping protein, yeast capping protein is inhibited by PIP2. By immunofluorescence microscopy yeast capping protein colocalizes with cortical actin spots at the site of bud emergence and at the tips of growing buds and shmoos. In contrast, capping protein does not colocalize with actin cables or with actin rings at the site of cytokinesis.
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Hiller, Ekkehard, Sonja Heine, Herwig Brunner et Steffen Rupp. « Candida albicans Sun41p, a Putative Glycosidase, Is Involved in Morphogenesis, Cell Wall Biogenesis, and Biofilm Formation ». Eukaryotic Cell 6, no 11 (28 septembre 2007) : 2056–65. http://dx.doi.org/10.1128/ec.00285-07.
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ABSTRACT The SUN gene family has been defined in Saccharomyces cerevisiae and comprises a fungus-specific family of proteins which show high similarity in their C-terminal domains. Genes of this family are involved in different cellular processes, like DNA replication, aging, mitochondrial biogenesis, and cytokinesis. In Candida albicans the SUN family comprises two genes, SUN41 and SIM1. We demonstrate that C. albicans mutants lacking SUN41 show similar defects as found for S. cerevisiae, including defects in cytokinesis. In addition, the SUN41 mutant showed a higher sensitivity towards the cell wall-disturbing agent Congo red, whereas no difference was observed in the presence of calcofluor white. Compared to the wild type, SUN41 deletion strains exhibited a defect in biofilm formation, a reduced adherence on a Caco-2 cell monolayer, and were unable to form hyphae on solid medium under the conditions tested. Interestingly, Sun41p was found to be secreted in the medium of cells growing as blastospores as well as those forming hyphae. Our results support a function of SUN41p as a glycosidase involved in cytokinesis, cell wall biogenesis, adhesion to host tissue, and biofilm formation, indicating an important role in the host-pathogen interaction.
22
Balasubramanian, M. K., D. McCollum et U. Surana. « Tying the knot : linking cytokinesis to the nuclear cycle ». Journal of Cell Science 113, no 9 (1 mai 2000) : 1503–13. http://dx.doi.org/10.1242/jcs.113.9.1503.
Texte intégralRésumé :
For the survival of both the parent and the progeny, it is imperative that the process of their physical division (cytokinesis) be precisely coordinated with progression through the mitotic cell cycle. Recent studies in the budding yeast Saccharomyces cerevisiae and the fission yeast Schizosaccharomyces pombe are beginning to unravel the nature of the links between cytokinesis and the nuclear division cycle. The cyclin-dependent kinases and a novel surveillance mechanism that monitors cytokinesis and/or morphogenesis appear to play important regulatory roles in forging these links. It is becoming increasingly clear that the inactivation of the mitosis-promoting cyclin-dependent kinase, which marks the completion of the nuclear division cycle, is essential for actomyosin ring constriction and division septum assembly in both yeasts. Additionally, the spindle pole bodies are emerging as important transient locale for proteins that might play a key role in coupling the completion of mitosis to the onset of cytokinesis.
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Benton, B. K., A. Tinkelenberg, I. Gonzalez et F. R. Cross. « Cla4p, a Saccharomyces cerevisiae Cdc42p-activated kinase involved in cytokinesis, is activated at mitosis. » Molecular and Cellular Biology 17, no 9 (septembre 1997) : 5067–76. http://dx.doi.org/10.1128/mcb.17.9.5067.
Texte intégralRésumé :
Yeasts have three functionally redundant G1 cyclins required for cell cycle progression through G1. Mutations in GIN4 and CLA4 were isolated in a screen for mutants that are inviable with deletions in the G1 cyclins CLN1 and CLN2. cln1 cln2 cla4 and cln1 cln2 gin4 cells arrest with a cytokinesis defect; this defect was efficiently rescued by CLN1 or CLN2 expression. GIN4 encodes a protein with strong homology to the Snflp serine/threonine kinase. Cla4p is homologous to mammalian p21-activated kinases (PAKs) (kinases activated by the rho-class GTPase Rac or Cdc42). We developed a kinase assay for Cla4p. Cla4p kinase was activated in vivo by the GTP-bound form of Cdc42p. The specific activity of Cla4p was cell cycle regulated, peaking near mitosis. Deletion of the Cla4p pleckstrin domain diminished kinase activity nearly threefold and eliminated in vivo activity. Deletion of the Cla4p Cdc42-binding domain increased kinase activity nearly threefold, but the mutant only weakly rescued cla4 function in vivo. This suggests that kinase activity alone is not sufficient for full function in vivo. Deletion of the Cdc42-binding domain also altered the cell cycle regulation of kinase activity. Instead of peaking at mitosis, the mutant kinase activity exhibited reduced cell cycle regulation and peaked at the G1/S border. Cla4p kinase activity was not reduced by mutational inactivation of gin4, suggesting that Gin4p may be downstream or parallel to Cla4p in the regulation of cytokinesis.
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Paulissen, Scott M., Cindy A. Hunt, Brian C. Seitz, Christian J. Slubowski, Yao Yu, Xheni Mucelli, Dang Truong et al. « A Noncanonical Hippo Pathway Regulates Spindle Disassembly and Cytokinesis During Meiosis in Saccharomyces cerevisiae ». Genetics 216, no 2 (11 août 2020) : 447–62. http://dx.doi.org/10.1534/genetics.120.303584.
Texte intégralRésumé :
Meiosis in the budding yeast Saccharomyces cerevisiae is used to create haploid yeast spores from a diploid mother cell. During meiosis II, cytokinesis occurs by closure of the prospore membrane, a membrane that initiates at the spindle pole body and grows to surround each of the haploid meiotic products. Timely prospore membrane closure requires SPS1, which encodes an STE20 family GCKIII kinase. To identify genes that may activate SPS1, we utilized a histone phosphorylation defect of sps1 mutants to screen for genes with a similar phenotype and found that cdc15 shared this phenotype. CDC15 encodes a Hippo-like kinase that is part of the mitotic exit network. We find that Sps1 complexes with Cdc15, that Sps1 phosphorylation requires Cdc15, and that CDC15 is also required for timely prospore membrane closure. We also find that SPS1, like CDC15, is required for meiosis II spindle disassembly and sustained anaphase II release of Cdc14 in meiosis. However, the NDR-kinase complex encoded by DBF2/DBF20MOB1 which functions downstream of CDC15 in mitotic cells, does not appear to play a role in spindle disassembly, timely prospore membrane closure, or sustained anaphase II Cdc14 release. Taken together, our results suggest that the mitotic exit network is rewired for exit from meiosis II, such that SPS1 replaces the NDR-kinase complex downstream of CDC15.
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Moore, Carol W., Judith McKoy, Robert Del Valle, Donald Armstrong, Edward M. Bernard, Norman Katz et Ronald E. Gordon. « Fungal Cell Wall Septation and Cytokinesis Are Inhibited by Bleomycins ». Antimicrobial Agents and Chemotherapy 47, no 10 (octobre 2003) : 3281–89. http://dx.doi.org/10.1128/aac.47.10.3281-3289.2003.
Texte intégralRésumé :
ABSTRACT When the essential and distinctive cell walls of either pathogenic or nonpathogenic fungi break, cytoplasmic membranes rupture and fungi die. This fungicidal activity was discovered previously on nonproliferating Saccharomyces cerevisiae cells treated briefly with the oxidative tool and anticancer drug family of bleomycins. The present studies investigated effects of bleomycin on growing fungal organisms. These included the medically important Aspergillus fumigatus and Cryptococcus neoformans, as well as the emerging human pathogen and fungal model, S. cerevisiae. Bleomycin had its highest potency against A. fumigatus. Scanning electron microscopy and thin-section transmission electron microscopy were used to study morphological growth characteristics. Killing and growth inhibition were also measured. Long, thin, and segmented hyphae were observed when A. fumigatus was grown without bleomycin but were never observed when the mold was grown with the drug. Bleomycin arrested conidial germination, hyphal development, and the progression and completion of cell wall septation. Similarly, the drug inhibited the construction of yeast cell wall septa, preventing cytokinesis and progression in the cell division cycle of S. cerevisiae. Even when cytoplasms of mother and daughter cells separated, septation and cell division did not necessarily occur. Bizarre cell configurations, abnormally thickened cell walls at mother-daughter necks, abnormal polarized growth, large undivided cells, fragmented cells, and empty cell ghosts were also produced. This is the first report of a fungicidal agent that arrests fungal growth and development, septum formation, and cytokinesis and that also preferentially localizes to cell walls and alters isolated cell walls as well as intact cell walls on nongrowing cells.
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Chen, Hsin, Audrey S. Howell, Alex Robeson et Daniel J. Lew. « Dynamics of septin ring and collar formation in Saccharomyces cerevisiae ». Biological Chemistry 392, no 8-9 (1 août 2011) : 689–97. http://dx.doi.org/10.1515/bc.2011.075.
Texte intégralRésumé :
Abstract Although the septin ring and collar in budding yeast were described over 20 years ago, there is still controversy regarding the organization of septin filaments within these structures and about the way in which the ring first forms and about how it converts into a collar at the mother-bud neck. Here we present quantitative analyses of the recruitment of fluorescently-tagged septins to the ring and collar through the cell cycle. Septin ring assembly began several minutes after polarity establishment and this interval was longer in daughter than in mother cells, suggesting asymmetric inheritance of septin regulators. Septins formed an initial faint and irregular ring, which became more regular as septins were recruited at a constant rate. This steady rate of septin recruitment continued for several minutes after the ring converted to a collar at bud emergence. We did not detect a stepwise change in septin fluorescence during the ring-to-collar transition. After collar formation, septins continued to accumulate at the bud neck, though at a reduced rate, until the onset of cytokinesis when the amount of neck-localized septins rapidly decreased. Implications for the mechanism of septin ring assembly are discussed.
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McGrew, J. T., L. Goetsch, B. Byers et P. Baum. « Requirement for ESP1 in the nuclear division of Saccharomyces cerevisiae. » Molecular Biology of the Cell 3, no 12 (décembre 1992) : 1443–54. http://dx.doi.org/10.1091/mbc.3.12.1443.
Texte intégralRésumé :
Mutations in the ESP1 gene of Saccharomyces cerevisiae disrupt normal cell-cycle control and cause many cells in a mutant population to accumulate extra spindle pole bodies. To determine the stage at which the esp1 gene product becomes essential for normal cell-cycle progression, synchronous cultures of ESP1 mutant cells were exposed to the nonpermissive temperature for various periods of time. The mutant cells retained viability until the onset of mitosis, when their viability dropped markedly. Examination of these cells by fluorescence and electron microscopy showed the first detectable defect to be a structural failure in the spindle. Additionally, flow cytometric analysis of DNA content demonstrated that massive chromosome missegregation accompanied this failure of spindle function. Cytokinesis occurred despite the aberrant nuclear division, which often resulted in segregation of both spindle poles to the same cell. At later times, the missegregated spindle pole bodies entered a new cycle of duplication, thereby leading to the accumulation of extra spindle pole bodies within a single nucleus. The DNA sequence predicts a protein product similar to those of two other genes that are also required for nuclear division: the cut1 gene of Schizosaccharomyces pombe and the bimB gene of Aspergillus nidulans.
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Brockerhoff, S. E., et T. N. Davis. « Calmodulin concentrates at regions of cell growth in Saccharomyces cerevisiae. » Journal of Cell Biology 118, no 3 (1 août 1992) : 619–29. http://dx.doi.org/10.1083/jcb.118.3.619.
Texte intégralRésumé :
Calmodulin was localized in Saccharomyces cerevisiae by indirect immunofluorescence using affinity-purified polyclonal antibodies. Calmodulin displays an asymmetric distribution that changes during the cell cycle. In unbudded cells, calmodulin concentrates at the presumptive site of bud formation approximately 10 min before bud emergence. In small budded cells, calmodulin accumulates throughout the bud. As the bud grows, calmodulin concentrates at the tip, then disperses, and finally concentrates in the neck region before cytokinesis. An identical staining pattern is observed when wild-type calmodulin is replaced with mutant forms of calmodulin impaired in binding Ca2+. Thus, the localization of calmodulin does not depend on its ability to bind Ca2+ with a high affinity. Double labeling of yeast cells with affinity-purified anti-calmodulin antibody and rhodamine-conjugated phalloidin indicates that calmodulin and actin concentrate in overlapping regions during the cell cycle. Furthermore, disrupting calmodulin function using a temperature-sensitive calmodulin mutant delocalizes actin, and act1-4 mutants contain a random calmodulin distribution. Thus, calmodulin and actin distributions are interdependent. Finally, calmodulin localizes to the shmoo tip in cells treated with alpha-factor. This distribution, at sites of cell growth, implicates calmodulin in polarized cell growth in yeast.
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Vallen, Elizabeth A., Juliane Caviston et Erfei Bi. « Roles of Hof1p, Bni1p, Bnr1p, and Myo1p in Cytokinesis inSaccharomyces cerevisiae ». Molecular Biology of the Cell 11, no 2 (février 2000) : 593–611. http://dx.doi.org/10.1091/mbc.11.2.593.
Texte intégralRésumé :
Cytokinesis in Saccharomyces cerevisiae occurs by the concerted action of the actomyosin system and septum formation. Here we report on the roles of HOF1,BNI1, and BNR1 in cytokinesis, focusing on Hof1p. Deletion of HOF1 causes a temperature-sensitive defect in septum formation. A Hof1p ring forms on the mother side of the bud neck in G2/M, followed by the formation of a daughter-side ring. Around telophase, Hof1p is phosphorylated and the double rings merge into a single ring that contracts slightly and may colocalize with the actomyosin structure. Upon septum formation, Hof1p splits into two rings, disappearing upon cell separation. Hof1p localization is dependent on septins but not Myo1p. Synthetic lethality suggests that Bni1p and Myo1p belong to one functional pathway, whereas Hof1p and Bnr1p belong to another. These results suggest that Hof1p may function as an adapter linking the primary septum synthesis machinery to the actomyosin system. The formation of the actomyosin ring is not affected by bni1Δ, hof1Δ, orbnr1Δ. However, Myo1p contraction is affected bybni1Δ but not by hof1Δ orbnr1Δ. In bni1Δ cells that lack the actomyosin contraction, septum formation is often slow and asymmetric, suggesting that actomyosin contraction may provide directionality for efficient septum formation.
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Finger, Fern P., et Peter Novick. « Synthetic Interactions of the Post-Golgi sec Mutations of Saccharomyces cerevisiae ». Genetics 156, no 3 (1 novembre 2000) : 943–51. http://dx.doi.org/10.1093/genetics/156.3.943.
Texte intégralRésumé :
Abstract In the budding yeast Saccharomyces cerevisiae, synthetic lethality has been extensively used both to characterize interactions between genes previously identified as likely to be involved in similar processes as well as to uncover new interactions. We have performed a large study of the synthetic lethal interactions of the post-Golgi sec mutations. Included in this study are the interactions of the post-Golgi sec mutations with each other, with mutations affecting earlier stages of the secretory pathway, with selected mutations affecting the actin cytoskeleton, and with selected cell division cycle (cdc) mutations affecting processes thought to be important for or involving secretion, such as polarity establishment and cytokinesis. Synthetic negative interactions of the post-Golgi sec mutations appear (as predicted) to be largely stage specific, although there are some notable exceptions. The significance of these results is discussed in the context of both secretory pathway function and the utility of synthetic lethality studies and their interpretation.
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Feng, Zhonghui, Satoshi Okada, Guoping Cai, Bing Zhou et Erfei Bi. « Myosin‑II heavy chain and formin mediate the targeting of myosin essential light chain to the division site before and during cytokinesis ». Molecular Biology of the Cell 26, no 7 (avril 2015) : 1211–24. http://dx.doi.org/10.1091/mbc.e14-09-1363.
Texte intégralRésumé :
MLC1 is a haploinsufficient gene encoding the essential light chain for Myo1, the sole myosin‑II heavy chain in the budding yeast Saccharomyces cerevisiae. Mlc1 defines an essential hub that coordinates actomyosin ring function, membrane trafficking, and septum formation during cytokinesis by binding to IQGAP, myosin‑II, and myosin‑V. However, the mechanism of how Mlc1 is targeted to the division site during the cell cycle remains unsolved. By constructing a GFP‑tagged MLC1 under its own promoter control and using quantitative live‑cell imaging coupled with yeast mutants, we found that septin ring and actin filaments mediate the targeting of Mlc1 to the division site before and during cytokinesis, respectively. Both mechanisms contribute to and are collectively required for the accumulation of Mlc1 at the division site during cytokinesis. We also found that Myo1 plays a major role in the septin‑dependent Mlc1 localization before cytokinesis, whereas the formin Bni1 plays a major role in the actin filament–dependent Mlc1 localization during cytokinesis. Such a two‑tiered mechanism for Mlc1 localization is presumably required for the ordered assembly and robustness of cytokinesis machinery and is likely conserved across species.
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Jiang, Yu. « Regulation of the Cell Cycle by Protein Phosphatase 2A in Saccharomyces cerevisiae ». Microbiology and Molecular Biology Reviews 70, no 2 (juin 2006) : 440–49. http://dx.doi.org/10.1128/mmbr.00049-05.
Texte intégralRésumé :
SUMMARY Protein phosphatase 2A (PP2A) has long been implicated in cell cycle regulation in many different organisms. In the yeast Saccharomyces cerevisiae, PP2A controls cell cycle progression mainly through modulation of cyclin-dependent kinase (CDK) at the G2/M transition. However, CDK does not appear to be a direct target of PP2A. PP2A affects CDK activity through its roles in checkpoint controls. Inactivation of PP2A downregulates CDK by activating the morphogenesis checkpoint and, consequently, delays mitotic entry. Defects in PP2A also compromise the spindle checkpoint and predispose the cell to an error-prone mitotic exit. In addition, PP2A is involved in controlling the G1/S transition and cytokinesis. These findings suggest that PP2A functions in many stages of the cell cycle and its effect on cell cycle progression is pleiotropic.
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Sullivan, D. S., et T. C. Huffaker. « Astral microtubules are not required for anaphase B in Saccharomyces cerevisiae. » Journal of Cell Biology 119, no 2 (15 octobre 1992) : 379–88. http://dx.doi.org/10.1083/jcb.119.2.379.
Texte intégralRésumé :
tub2-401 is a cold-sensitive allele of TUB2, the sole gene encoding beta-tubulin in the yeast, Saccharomyces cerevisiae. At 18 degrees C, tub2-401 cells are able to assemble spindle microtubules but lack astral microtubules. Under these conditions, movement of the spindle to the bud neck is blocked. However, spindle elongation and chromosome separation are unimpeded and occur entirely within the mother cell. Subsequent cytokinesis produces one cell with two nuclei and one cell without a nucleus. The anucleate daughter can not bud. The binucleate daughter proceeds through another cell cycle to produce a cell with four nuclei and another anucleate cell. With additional time in the cold, the number of nuclei in the nucleated cells continues to increase and the percentage of anucleate cells in the population rises. The results indicate that astral microtubules are needed to position the spindle in the bud neck but are not required for spindle elongation at anaphase B. In addition, cell cycle progression does not depend on the location or orientation of the spindle.
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Sheu, Yi-Jun, Yves Barral et Michael Snyder. « Polarized Growth Controls Cell Shape and Bipolar Bud Site Selection in Saccharomyces cerevisiae ». Molecular and Cellular Biology 20, no 14 (15 juillet 2000) : 5235–47. http://dx.doi.org/10.1128/mcb.20.14.5235-5247.2000.
Texte intégralRésumé :
ABSTRACT We examined the relationship between polarized growth and division site selection, two fundamental processes important for proper development of eukaryotes. Diploid Saccharomyces cerevisiaecells exhibit an ellipsoidal shape and a specific division pattern (a bipolar budding pattern). We found that the polarity genesSPA2, PEA2, BUD6, andBNI1 participate in a crucial step of bud morphogenesis, apical growth. Deleting these genes results in round cells and diminishes bud elongation in mutants that exhibit pronounced apical growth. Examination of distribution of the polarized secretion marker Sec4 demonstrates that spa2Δ, pea2Δ,bud6Δ, and bni1Δ mutants fail to concentrate Sec4 at the bud tip during apical growth and at the division site during repolarization just prior to cytokinesis. Moreover, cell surface expansion is not confined to the distal tip of the bud in these mutants. In addition, we found that the p21-activated kinase homologue Ste20 is also important for both apical growth and bipolar bud site selection. We further examined how the duration of polarized growth affects bipolar bud site selection by using mutations in cell cycle regulators that control the timing of growth phases. Thegrr1Δ mutation enhances apical growth by stabilizing G1 cyclins and increases the distal-pole budding in diploids. Prolonging polarized growth phases by disrupting the G2/M cyclin gene CLB2 enhances the accuracy of bud site selection in wild-type, spa2Δ, andste20Δ cells, whereas shortening the polarized growth phases by deleting SWE1 decreases the fidelity of bipolar budding. This study reports the identification of components required for apical growth and demonstrates the critical role of polarized growth in bipolar bud site selection. We propose that apical growth and repolarization at the site of cytokinesis are crucial for establishing spatial cues used by diploid yeast cells to position division planes.
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Frenz, L. M., S. E. Lee, D. Fesquet et L. H. Johnston. « The budding yeast Dbf2 protein kinase localises to the centrosome and moves to the bud neck in late mitosis ». Journal of Cell Science 113, no 19 (1 octobre 2000) : 3399–408. http://dx.doi.org/10.1242/jcs.113.19.3399.
Texte intégralRésumé :
Dbf2 is a multifunctional protein kinase in Saccharomyces cerevisiae that functions in transcription, the stress response and as part of a network of genes in exit from mitosis. By analogy with fission yeast it seemed likely that these mitotic exit genes would be involved in cytokinesis. As a preliminary investigation of this we have used Dbf2 tagged with GFP to examine intracellular localisation of the protein in living cells. Dbf2 is found on the centrosomes/spindle pole bodies (SPBs) and also at the bud neck where it forms a double ring. The localisation of Dbf2 is cell cycle regulated. It is on the SPBs for much of the cell cycle and migrates from there to the bud neck in late mitosis, consistent with a role in cytokinesis. Dbf2 partly co-localises with septins at the bud neck. A temperature-sensitive mutant of dbf2 also blocks progression of cytokinesis at 37 degrees C. Following cytokinesis some Dbf2 moves into the nascent bud. Localisation to the bud neck depends upon the septins and also the mitotic exit network proteins Mob1, Cdc5, Cdc14 and Cdc15. The above data are consistent with Dbf2 acting downstream in a pathway controlling cytokinesis.
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Roncero, Cesar, Rubén Celador, Noelia Sánchez, Patricia García et Yolanda Sánchez. « The Role of the Cell Integrity Pathway in Septum Assembly in Yeast ». Journal of Fungi 7, no 9 (6 septembre 2021) : 729. http://dx.doi.org/10.3390/jof7090729.
Texte intégralRésumé :
Cytokinesis divides a mother cell into two daughter cells at the end of each cell cycle and proceeds via the assembly and constriction of a contractile actomyosin ring (CAR). Ring constriction promotes division furrow ingression, after sister chromatids are segregated to opposing sides of the cleavage plane. Cytokinesis contributes to genome integrity because the cells that fail to complete cytokinesis often reduplicate their chromosomes. While in animal cells, the last steps of cytokinesis involve extracellular matrix remodelling and mid-body abscission, in yeast, CAR constriction is coupled to the synthesis of a polysaccharide septum. To preserve cell integrity during cytokinesis, fungal cells remodel their cell wall through signalling pathways that connect receptors to downstream effectors, initiating a cascade of biological signals. One of the best-studied signalling pathways is the cell wall integrity pathway (CWI) of the budding yeast Saccharomyces cerevisiae and its counterpart in the fission yeast Schizosaccharomyces pombe, the cell integrity pathway (CIP). Both are signal transduction pathways relying upon a cascade of MAP kinases. However, despite strong similarities in the assembly of the septa in both yeasts, there are significant mechanistic differences, including the relationship of this process with the cell integrity signalling pathways.
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Holly, Stephen P., et Kendall J. Blumer. « Pak-Family Kinases Regulate Cell and Actin Polarization Throughout the Cell Cycle of Saccharomyces cerevisiae ». Journal of Cell Biology 147, no 4 (15 novembre 1999) : 845–56. http://dx.doi.org/10.1083/jcb.147.4.845.
Texte intégralRésumé :
During the cell cycle of the yeast Saccharomyces cerevisiae, the actin cytoskeleton and cell surface growth are polarized, mediating bud emergence, bud growth, and cytokinesis. We have determined whether p21-activated kinase (PAK)-family kinases regulate cell and actin polarization at one or several points during the yeast cell cycle. Inactivation of the PAK homologues Ste20 and Cla4 at various points in the cell cycle resulted in loss of cell and actin cytoskeletal polarity, but not in depolymerization of F-actin. Loss of PAK function in G1 depolarized the cortical actin cytoskeleton and blocked bud emergence, but allowed isotropic growth and led to defects in septin assembly, indicating that PAKs are effectors of the Rho–guanosine triphosphatase Cdc42. PAK inactivation in S/G2 resulted in depolarized growth of the mother and bud and a loss of actin polarity. Loss of PAK function in mitosis caused a defect in cytokinesis and a failure to polarize the cortical actin cytoskeleton to the mother-bud neck. Cla4–green fluorescent protein localized to sites where the cortical actin cytoskeleton and cell surface growth are polarized, independently of an intact actin cytoskeleton. Thus, PAK family kinases are primary regulators of cell and actin cytoskeletal polarity throughout most or all of the yeast cell cycle. PAK-family kinases in higher organisms may have similar functions.
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Oh, Younghoon, Kuang-Jung Chang, Peter Orlean, Carsten Wloka, Raymond Deshaies et Erfei Bi. « Mitotic exit kinase Dbf2 directly phosphorylates chitin synthase Chs2 to regulate cytokinesis in budding yeast ». Molecular Biology of the Cell 23, no 13 (juillet 2012) : 2445–56. http://dx.doi.org/10.1091/mbc.e12-01-0033.
Texte intégralRésumé :
How cell cycle machinery regulates extracellular matrix (ECM) remodeling during cytokinesis remains poorly understood. In the budding yeast Saccharomyces cerevisiae, the primary septum (PS), a functional equivalent of animal ECM, is synthesized during cytokinesis by the chitin synthase Chs2. Here, we report that Dbf2, a conserved mitotic exit kinase, localizes to the division site after Chs2 and directly phosphorylates Chs2 on several residues, including Ser-217. Both phosphodeficient (chs2‑S217A) and phosphomimic (chs2‑S217D) mutations cause defects in cytokinesis, suggesting that dynamic phosphorylation–dephosphorylation of Ser-217 is critical for Chs2 function. It is striking that Chs2‑S217A constricts asymmetrically with the actomyosin ring (AMR), whereas Chs2-S217D displays little or no constriction and remains highly mobile at the division site. These data suggest that Chs2 phosphorylation by Dbf2 triggers its dissociation from the AMR during the late stage of cytokinesis. Of interest, both chs2‑S217A and chs2‑S217D mutants are robustly suppressed by increased dosage of Cyk3, a cytokinesis protein that displays Dbf2‑dependent localization and also stimulates Chs2‑mediated chitin synthesis. Thus Dbf2 regulates PS formation through at least two independent pathways: direct phosphorylation and Cyk3‑mediated activation of Chs2. Our study establishes a mechanism for direct cell cycle control of ECM remodeling during cytokinesis.
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Jiang, Wei, et Richard L. Hallberg. « Isolation and Characterization of par1+ and par2+ : Two Schizosaccharomyces pombe Genes Encoding B′ Subunits of Protein Phosphatase 2A ». Genetics 154, no 3 (1 mars 2000) : 1025–38. http://dx.doi.org/10.1093/genetics/154.3.1025.
Texte intégralRésumé :
Abstract Protein phosphatase 2A (PP2A) is one of the major serine/threonine phosphatases found in eukaryotic cells. We cloned two genes, par1+ and par2+, encoding distinct B′ subunits of PP2A in fission yeast. They share 52% identity at the amino acid sequence level. Neither gene is essential but together they are required for normal septum positioning and cytokinesis, for growth at both high and low temperature, and for growth under a number of stressful conditions. Immunofluorescence microscopy revealed that Par2p has a cell-cycle-related localization pattern, being localized at cell ends during interphase and forming a medial ring in cells that are undergoing septation and cytokinesis. Our analyses also indicate that Par1p is more abundant than Par2p in the cell. Cross-organism studies showed that both par1+ and par2+ could complement the rts1Δ allele in Saccharomyces cerevisiae, albeit to different extents, in spite of the fact that neither contains a serine/threonine-rich N-terminal domain like that found in the S. cerevisiae homolog Rts1p. Thus, while Schizosaccharomyces pombe is more similar to higher eukaryotes with respect to its complement of B′-encoding genes, the function of those proteins is conserved relative to that of Rts1p.
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Snyder, M., S. Gehrung et B. D. Page. « Studies concerning the temporal and genetic control of cell polarity in Saccharomyces cerevisiae. » Journal of Cell Biology 114, no 3 (1 août 1991) : 515–32. http://dx.doi.org/10.1083/jcb.114.3.515.
Texte intégralRésumé :
The establishment of cell polarity was examined in the budding yeast, S. cerevisiae. The distribution of a polarized protein, the SPA2 protein, was followed throughout the yeast cell cycle using synchronized cells and cdc mutants. The SPA2 protein localizes to a patch at the presumptive bud site of G1 cells. Later it concentrates at the bud tip in budded cells. At cytokinesis, the SPA2 protein is at the neck between the mother and daughter cells. Analysis of unbudded haploid cells has suggested a series of events that occurs during G1. The SPA2 patch is established very early in G1, while the spindle pole body residues on the distal side of the nucleus. Later, microtubules emanating from the spindle pole body intersect the SPA2 crescent, and the nucleus probably rotates towards the SPA2 patch. By middle G1, most cells contain the SPB on the side of the nucleus proximal to the SPA2 patch, and a long extranuclear microtubule bundle intersects this patch. We suggest that a microtubule capture site exists in the SPA2 staining region that stabilizes the long microtubule bundle; this capture site may be responsible for rotation of the nucleus. Cells containing a polarized distribution of the SPA2 protein also possess a polarized distribution of actin spots in the same region, although the actin staining is much more diffuse. Moreover, cdc4 mutants, which form multiple buds at the restrictive temperature, exhibit simultaneous staining of the SPA2 protein and actin spots in a subset of the bud tips. spa2 mutants contain a polarized distribution of actin spots, and act1-1 and act1-2 mutants often contain a polarized distribution of the SPA2 protein suggesting that the SPA2 protein is not required for localization of the actin spots and the actin spots are not required for localization of the SPA2 protein. cdc24 mutants, which fail to form buds at the restrictive temperature, fail to exhibit polarized localization of the SPA2 protein and actin spots, indicating that the CDC24 protein is directly or indirectly responsible for controlling the polarity of these proteins. Based on the cell cycle distribution of the SPA2 protein, a "cytokinesis tag" model is proposed to explain the mechanism of the non-random positioning of bud sites in haploid yeast cells.
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Misu, Kenjiro, Konomi Fujimura-Kamada, Takashi Ueda, Akihiko Nakano, Hiroyuki Katoh et Kazuma Tanaka. « Cdc50p, a Conserved Endosomal Membrane Protein, Controls Polarized Growth in Saccharomyces cerevisiae ». Molecular Biology of the Cell 14, no 2 (février 2003) : 730–47. http://dx.doi.org/10.1091/mbc.e02-06-0314.
Texte intégralRésumé :
During the cell cycle of the yeast Saccharomyces cerevisiae, the actin cytoskeleton and the growth of cell surface are polarized, mediating bud emergence, bud growth, and cytokinesis. We identified CDC50 as a multicopy suppressor of the myo3 myo5-360 temperature-sensitive mutant, which is defective in organization of cortical actin patches. The cdc50 null mutant showed cold-sensitive cell cycle arrest with a small bud as reported previously. Cortical actin patches and Myo5p, which are normally localized to polarization sites, were depolarized in the cdc50 mutant. Furthermore, actin cables disappeared, and Bni1p and Gic1p, effectors of the Cdc42p small GTPase, were mislocalized in the cdc50 mutant. As predicted by its amino acid sequence, Cdc50p appears to be a transmembrane protein because it was solubilized from the membranes by detergent treatment. Cdc50p colocalized with Vps21p in endosomal compartments and was also localized to the class E compartment in thevps27 mutant. The cdc50 mutant showed defects in a late stage of endocytosis but not in the internalization step. It showed, however, only modest defects in vacuolar protein sorting. Our results indicate that Cdc50p is a novel endosomal protein that regulates polarized cell growth.
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Lepore, Dante, Olya Spassibojko, Gabrielle Pinto et Ruth N. Collins. « Cell cycle–dependent phosphorylation of Sec4p controls membrane deposition during cytokinesis ». Journal of Cell Biology 214, no 6 (12 septembre 2016) : 691–703. http://dx.doi.org/10.1083/jcb.201602038.
Texte intégralRésumé :
Intracellular trafficking is an essential and conserved eukaryotic process. Rab GTPases are a family of proteins that regulate and provide specificity for discrete membrane trafficking steps by harnessing a nucleotide-bound cycle. Global proteomic screens have revealed many Rab GTPases as phosphoproteins, but the effects of this modification are not well understood. Using the Saccharomyces cerevisiae Rab GTPase Sec4p as a model, we have found that phosphorylation negatively regulates Sec4p function by disrupting the interaction with the exocyst complex via Sec15p. We demonstrate that phosphorylation of Sec4p is a cell cycle–dependent process associated with cytokinesis. Through a genomic kinase screen, we have also identified the polo-like kinase Cdc5p as a positive regulator of Sec4p phosphorylation. Sec4p spatially and temporally localizes with Cdc5p exclusively when Sec4p phosphorylation levels peak during the cell cycle, indicating Sec4p is a direct Cdc5p substrate. Our data suggest the physiological relevance of Sec4p phosphorylation is to facilitate the coordination of membrane-trafficking events during cytokinesis.
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Heasley, Lydia R., et Michael A. McMurray. « Roles of septins in prospore membrane morphogenesis and spore wall assembly inSaccharomyces cerevisiae ». Molecular Biology of the Cell 27, no 3 (février 2016) : 442–50. http://dx.doi.org/10.1091/mbc.e15-10-0721.
Texte intégralRésumé :
The highly conserved family of septin proteins has important functions in cytokinesis in mitotically proliferating cells. A different form of cytokinesis occurs during gametogenesis in Saccharomyces cerevisiae, in which four haploid meiotic products become encased by prospore membrane (PSMs) and specialized, stress-resistant spore walls. Septins are known to localize in a series of structures near the growing PSM, but previous studies noted only mild sporulation defects upon septin mutation. We report that directed PSM extension fails in many septin-mutant cells, and, for those that do succeed, walls are abnormal, leading to increased susceptibility to heating, freezing, and digestion by the Drosophila gut. Septin mutants mislocalize the leading-edge protein (LEP) complex required for normal PSM and wall biogenesis, and ectopic expression of the LEP protein Ssp1 perturbs mitotic septin localization and function, suggesting a functional interaction. Strikingly, extra copies of septin CDC10 rescue sporulation and LEP localization in cells lacking Sma1, a phospholipase D–associated protein dispensable for initiation of PSM assembly and PSM curvature but required for PSM extension. These findings point to key septin functions in directing efficient membrane and cell wall synthesis during budding yeast gametogenesis.
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Nishihama, Ryuichi, Jennifer H. Schreiter, Masayuki Onishi, Elizabeth A. Vallen, Julia Hanna, Katarina Moravcevic, Margaret F. Lippincott et al. « Role of Inn1 and its interactions with Hof1 and Cyk3 in promoting cleavage furrow and septum formation in S. cerevisiae ». Journal of Cell Biology 185, no 6 (15 juin 2009) : 995–1012. http://dx.doi.org/10.1083/jcb.200903125.
Texte intégralRésumé :
Cytokinesis requires coordination of actomyosin ring (AMR) contraction with rearrangements of the plasma membrane and extracellular matrix. In Saccharomyces cerevisiae, new membrane, the chitin synthase Chs2 (which forms the primary septum [PS]), and the protein Inn1 are all delivered to the division site upon mitotic exit even when the AMR is absent. Inn1 is essential for PS formation but not for Chs2 localization. The Inn1 C-terminal region is necessary for localization, and distinct PXXP motifs in this region mediate functionally important interactions with SH3 domains in the cytokinesis proteins Hof1 (an F-BAR protein) and Cyk3 (whose overexpression can restore PS formation in inn1Δ cells). The Inn1 N terminus resembles C2 domains but does not appear to bind phospholipids; nonetheless, when overexpressed or fused to Hof1, it can provide Inn1 function even in the absence of the AMR. Thus, Inn1 and Cyk3 appear to cooperate in activating Chs2 for PS formation, which allows coordination of AMR contraction with ingression of the cleavage furrow.
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Zhang, Dan, Yijia Wang et Shiwu Zhang. « Asymmetric Cell Division in Polyploid Giant Cancer Cells and Low Eukaryotic Cells ». BioMed Research International 2014 (2014) : 1–8. http://dx.doi.org/10.1155/2014/432652.
Texte intégralRésumé :
Asymmetric cell division is critical for generating cell diversity in low eukaryotic organisms. We previously have reported that polyploid giant cancer cells (PGCCs) induced by cobalt chloride demonstrate the ability to use an evolutionarily conserved process for renewal and fast reproduction, which is normally confined to simpler organisms. The budding yeast,Saccharomyces cerevisiae, which reproduces by asymmetric cell division, has long been a model for asymmetric cell division studies. PGCCs produce daughter cells asymmetrically in a manner similar to yeast, in that both use budding for cell polarization and cytokinesis. Here, we review the results of recent studies and discuss the similarities in the budding process between yeast and PGCCs.
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Tully, Gregory H., Ryuichi Nishihama, John R. Pringle et David O. Morgan. « The Anaphase-promoting Complex Promotes Actomyosin-Ring Disassembly during Cytokinesis in Yeast ». Molecular Biology of the Cell 20, no 4 (15 février 2009) : 1201–12. http://dx.doi.org/10.1091/mbc.e08-08-0822.
Texte intégralRésumé :
The anaphase-promoting complex (APC) is a ubiquitin ligase that controls progression through mitosis by targeting specific proteins for degradation. It is unclear whether the APC also contributes to the control of cytokinesis, the process that divides the cell after mitosis. We addressed this question in the yeast Saccharomyces cerevisiae by studying the effects of APC mutations on the actomyosin ring, a structure containing actin, myosin, and several other proteins that forms at the division site and is important for cytokinesis. In wild-type cells, actomyosin-ring constituents are removed progressively from the ring during contraction and disassembled completely thereafter. In cells lacking the APC activator Cdh1, the actomyosin ring contracts at a normal rate, but ring constituents are not disassembled normally during or after contraction. After cytokinesis in mutant cells, aggregates of ring proteins remain at the division site and at additional foci in other parts of the cell. A key target of APCCdh1 is the ring component Iqg1, the destruction of which contributes to actomyosin-ring disassembly. Deletion of CDH1 also exacerbates actomyosin-ring disassembly defects in cells with mutations in the myosin light-chain Mlc2, suggesting that Mlc2 and the APC employ independent mechanisms to promote ring disassembly during cytokinesis.
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An, Hanbing, Jennifer L. Morrell, Jennifer L. Jennings, Andrew J. Link et Kathleen L. Gould. « Requirements of Fission Yeast Septins for Complex Formation, Localization, and Function ». Molecular Biology of the Cell 15, no 12 (décembre 2004) : 5551–64. http://dx.doi.org/10.1091/mbc.e04-07-0640.
Texte intégralRésumé :
Septins are GTP binding proteins important for cytokinesis in many eukaryotes. The Schizosaccaromyces pombe genome sequence predicts orthologues of four of five Saccharomyces cerevisiae septins involved in cytokinesis and these are named Spns1-4p. That spns1-4 are not essential genes permitted the application of a combined genetic and proteomics approach to determine their functional relationships. Our findings indicate that Spns1-4p are present throughout interphase as a diffusely localized ∼8.5S complex containing two copies of each septin linked together as a chain in the order Spn3p-Spn4p-Spn1p-Spn2p. Septin recruitment to the medial region of the cell is genetically separable from ring formation, and whereas it is normally restricted to mitosis, it can be promoted without activation of the mitotic cell cycle machinery. Coalescence into ring structures requires Spn1p and Spn4p associate with at least one other septin subunit and the expression of Mid2p that is normally restricted to mitosis. This study establishes the functional requirements for septin complex organization in vivo.
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Berlin, Ana, Anne Paoletti et Fred Chang. « Mid2p stabilizes septin rings during cytokinesis in fission yeast ». Journal of Cell Biology 160, no 7 (24 mars 2003) : 1083–92. http://dx.doi.org/10.1083/jcb.200212016.
Texte intégralRésumé :
Septins are filament-forming proteins with a conserved role in cytokinesis. In the fission yeast Schizosaccharomyces pombe, septin rings appear to be involved primarily in cell–cell separation, a late stage in cytokinesis. Here, we identified a protein Mid2p on the basis of its sequence similarity to S. pombe Mid1p, Saccharomyces cerevisiae Bud4p, and Candida albicans Int1p. Like septin mutants, mid2Δ mutants had delays in cell–cell separation. mid2Δ mutants were defective in septin organization but not contractile ring closure or septum formation. In wild-type cells, septins assembled first during mitosis in a single ring and during septation developed into double rings that did not contract. In mid2Δ cells, septins initially assembled in a single ring but during septation appeared in the cleavage furrow, forming a washer or disc structure. FRAP studies showed that septins are stable in wild-type cells but exchange 30-fold more rapidly in mid2Δ cells. Mid2p colocalized with septins and required septins for its localization. A COOH-terminal pleckstrin homology domain of Mid2p was required for its localization and function. No genetic interactions were found between mid2 and the related gene mid1. Thus, these studies identify a new factor responsible for the proper stability and function of septins during cytokinesis.
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Breeding, Connie S., James Hudson, Mohan K. Balasubramanian, Sean M. Hemmingsen, Paul G. Young et Kathleen L. Gould. « Thecdr2+Gene Encodes a Regulator of G2/M Progression and Cytokinesis inSchizosaccharomyces pombe ». Molecular Biology of the Cell 9, no 12 (décembre 1998) : 3399–415. http://dx.doi.org/10.1091/mbc.9.12.3399.
Texte intégralRésumé :
Schizosaccharomyces pombe cells respond to nutrient deprivation by altering G2/M cell size control. The G2/M transition is controlled by activation of the cyclin-dependent kinase Cdc2p. Cdc2p activation is regulated both positively and negatively. cdr2+was identified in a screen for regulators of mitotic control during nutrient deprivation. We have cloned cdr2+and have found that it encodes a putative serine-threonine protein kinase that is related to Saccharomyces cerevisiae Gin4p and S. pombe Cdr1p/Nim1p.cdr2+is not essential for viability, but cells lacking cdr2+are elongated relative to wild-type cells, spending a longer period of time in G2. Because of this property, upon nitrogen deprivationcdr2+mutants do not arrest in G1, but rather undergo another round of S phase and arrest in G2from which they are able to enter a state of quiescence. Genetic evidence suggests thatcdr2+acts as a mitotic inducer, functioning through wee1+, and is also important for the completion of cytokinesis at 36°C. Defects in cytokinesis are also generated by the overproduction of Cdr2p, but these defects are independent of wee1+, suggesting thatcdr2+encodes a second activity involved in cytokinesis.
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Nanninga, Nanne. « Cytokinesis in Prokaryotes and Eukaryotes : Common Principles and Different Solutions ». Microbiology and Molecular Biology Reviews 65, no 2 (1 juin 2001) : 319–33. http://dx.doi.org/10.1128/mmbr.65.2.319-333.2001.
Texte intégralRésumé :
SUMMARY Cytokinesis requires duplication of cellular structures followed by bipolarization of the predivisional cell. As a common principle, this applies to prokaryotes as well as eukaryotes. With respect to eukaryotes, the discussion has focused mainly on Saccharomyces cerevisiae and on Schizosaccharomyces pombe. Escherichia coli and to a lesser extent Bacillus subtilis have been used as prokaryotic examples. To establish a bipolar cell, duplication of a eukaryotic origin of DNA replication as well as its genome is not sufficient. Duplication of the microtubule-organizing center is required as a prelude to mitosis, and it is here that the dynamic cytoskeleton with all its associated proteins comes to the fore. In prokaryotes, a cytoskeleton that pervades the cytoplasm appears to be absent. DNA replication and the concomitant DNA segregation seem to occur without help from extensive cytosolic supramacromolecular assemblies but with help from the elongating cellular envelope. Prokaryotic cytokinesis proceeds through a contracting ring, which has a roughly 100-fold-smaller circumference than its eukaryotic counterpart. Although the ring contains proteins that can be considered as predecessors of actin, tubulin, and microtubule-associated proteins, its macromolecular composition is essentially different.