scholarly journals Cdc24, the source of active Cdc42, transiently interacts with septins to create a positive feedback between septin assembly and bud site formation in yeast cells

2019 ◽  
Author(s):  
Julian Chollet ◽  
Alexander Dünkler ◽  
Anne Bäuerle ◽  
Laura Vivero-Pol ◽  
Thomas Gronemeyer ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Positive Feedback ◽  
Daughter Cell ◽  
Yeast Cells ◽  
Site Formation ◽  
Critical Events ◽  
High Concentration ◽  
Assembly Pathway ◽  
The Stability ◽  
Bud Site

AbstractYeast cells select at the beginning of each cell cycle the position of their new bud. The recruitment of the septins to this prospective bud site (PBS) is one of the critical events in a complex assembly pathway that culminates in the outgrowth of a new daughter cell. The septin-rods follow hereby the high concentration of Cdc42GTP that is generated by the focused location of its GEF Cdc24. We show that Cdc24 not only activates Cdc42 but temporarily interacts shortly before budding with Cdc11, the subunit that caps septin rods at its both ends. Mutations in Cdc24 that reduce the affinity to Cdc11 impair septin assembly and decrease the stability of the polarity patch. The interaction between septins and Cdc24 thus reinforces bud assembly at sites where septin structures are formed. Once the septins polymerize into the ring, Cdc24 transfers to its center and directs from there the further outgrowth of the membrane.

scholarly journals Interaction between bud-site selection and polarity-establishment machineries in budding yeast

2013 ◽  
Vol 368 (1629) ◽  
pp. 20130006 ◽  
Author(s):  
Chi-Fang Wu ◽  
Natasha S. Savage ◽  
Daniel J. Lew
Keyword(s):  
Cell Cycle ◽  
Site Selection ◽  
Time Lapse ◽  
Yeast Cells ◽  
Bud Emergence ◽  
Ras Family ◽  
Polarity Establishment ◽  
Diploid Cells ◽  
Bud Site ◽  
Time Lapse Imaging

Saccharomyces cerevisiae yeast cells polarize in order to form a single bud in each cell cycle. Distinct patterns of bud-site selection are observed in haploid and diploid cells. Genetic approaches have identified the molecular machinery responsible for positioning the bud site: during bud formation, specific locations are marked with immobile landmark proteins. In the next cell cycle, landmarks act through the Ras-family GTPase Rsr1 to promote local activation of the conserved Rho-family GTPase, Cdc42. Additional Cdc42 accumulates by positive feedback, creating a concentrated patch of GTP-Cdc42, which polarizes the cytoskeleton to promote bud emergence. Using time-lapse imaging and mathematical modelling, we examined the process of bud-site establishment. Imaging reveals unexpected effects of the bud-site-selection system on the dynamics of polarity establishment, raising new questions about how that system may operate. We found that polarity factors sometimes accumulate at more than one site among the landmark-specified locations, and we suggest that competition between clusters of polarity factors determines the final location of the Cdc42 cluster. Modelling indicated that temporally constant landmark-localized Rsr1 would weaken or block competition, yielding more than one polarity site. Instead, we suggest that polarity factors recruit Rsr1, effectively sequestering it from other locations and thereby terminating landmark activity.

scholarly journals Slk19 clusters kinetochores and facilitates chromosome bipolar attachment

2013 ◽  
Vol 24 (5) ◽  
pp. 566-577 ◽  
Author(s):  
Daniel Richmond ◽  
Raed Rizkallah ◽  
Fengshan Liang ◽  
Myra M. Hurt ◽  
Yanchang Wang
Keyword(s):  
Cell Cycle ◽  
Chromosome Segregation ◽  
Biological Significance ◽  
Yeast Cells ◽  
Eukaryotic Cells ◽  
Large Protein ◽  
Large Protein Complex ◽  
The Stability ◽  
Mutant Cells

In all eukaryotic cells, DNA is packaged into multiple chromosomes that are linked to microtubules through a large protein complex called a kinetochore. Previous data show that the kinetochores are clustered together during most of the cell cycle, but the mechanism and the biological significance of kinetochore clustering are unknown. As a kinetochore protein in budding yeast, the role of Slk19 in the stability of the anaphase spindle has been well studied, but its function in chromosome segregation has remained elusive. Here we show that Slk19 is required for kinetochore clustering when yeast cells are treated with the microtubule-depolymerizing agent nocodazole. We further find that slk19Δ mutant cells exhibit delayed kinetochore capture and chromosome bipolar attachment after the disruption of the kinetochore–microtubule interaction by nocodazole, which is likely attributed to defective kinetochore clustering. In addition, we show that Slk19 interacts with itself, suggesting that the dimerization of Slk19 may mediate the interaction between kinetochores for clustering. Therefore Slk19 likely acts as kinetochore glue that clusters kinetochores to facilitate efficient and faithful chromosome segregation.

scholarly journals Mobility of the gradient tracking machine in mating yeast depends on Bud1 inactivation and actin-independent vesicle delivery

2021 ◽  
Author(s):  
Xin Wang ◽  
David Stone
Keyword(s):  
Cell Cycle ◽  
Mating Type ◽  
Positive Feedback ◽  
Yeast Cells ◽  
Polarized Growth ◽  
Opposite Mating Type ◽  
Gradient Sensing ◽  
Feedback Mechanisms ◽  
Ras Gtpase ◽  
Sensing Model

Abstract The mating of budding yeast depends on chemotropism, a fundamental cellular process. Haploid yeast cells of opposite mating type signal their positions to one another through the secretion of mating pheromones. We have proposed a deterministic gradient sensing model that explains how these cells orient toward their mating partners. Using the cell-cycle determined default polarity site (DS), cells assemble a gradient tracking machine (GTM) composed of signaling, polarity, and trafficking proteins. After assembly, the GTM redistributes up the gradient, aligns with the pheromone source, and triggers polarized growth toward the partner. Because strong positive feedback mechanisms drive polarized growth at the DS, it is unclear how the GTM is released for tracking after its assembly is complete. What prevents the GTM from triggering polarized growth at the DS? Here we describe two mechanisms that enable tracking. First, the Ras GTPase Bud1 must be inactivated to release the GTM. Second, actin-independent – but not actin-dependent – vesicle delivery must be targeted upgradient to effect GTM redistribution.

scholarly journals Degradation of human thymidine kinase is dependent on serine-13 phosphorylation: involvement of the SCF-mediated pathway

2003 ◽  
Vol 370 (1) ◽  
pp. 265-273 ◽  
Author(s):  
Po-Yuan KE ◽  
Che-Chuan YANG ◽  
I-Chun TSAI ◽  
Zee-Fen CHANG
Keyword(s):  
Cell Cycle ◽  
Protein Degradation ◽  
Thymidine Kinase ◽  
Yeast Cells ◽  
Temperature Sensitive ◽  
Dependent Manner ◽  
Proteolytic Pathway ◽  
A Cell ◽  
The Stability ◽  
Cycle Dependent

The expression level of human thymidine kinase (hTK) is regulated in a cell-cycle-dependent manner. One of the mechanisms responsible for the fluctuation of TK expression in the cell cycle can be attributed to protein degradation during mitosis. Given the facts that cell-cycle-dependent proteolysis is highly conserved in all eukaryotes and yeast cells are an excellent model system for protein-degradation study, here we report on the use of Saccharomyces cerevisiae and Schizosaccharomyces pombe to investigate the degradation signal and mechanism required for hTK degradation. We found that the stability of hTK is significantly reduced in mitotic yeasts. Previously, we have observed that Ser-13 is the site of mitotic phosphorylation of hTK in HeLa cells [Chang, Huang and Chi (1998) J. Biol. Chem. 273, 12095—12100]. Here, we further provide evidence that the replacement of Ser-13 by Ala (S13A) renders hTK stable in S. pombe and S. cerevisiae. Most interestingly, we demonstrated that degradation of hTK is impaired in S. cerevisiae carrying a temperature-sensitive mutation in the proteasomal gene pre1-1 or the Skp1-Cullin-1/CDC53-F-box (SCF) complex gene cdc34 or cdc53, suggesting the contribution of the SCF-mediated pathway in hTK degradation. As phosphorylation is a prerequisite signal for SCF recognition, our results implied that phosphorylation of Ser-13 probably contributes to the degradation signal for hTK via the SCF-mediated proteolytic pathway.

scholarly journals Marine Exopolysaccharide Complexed With Scandium Aimed as Theranostic Agents

Molecules ◽  
2021 ◽  
Vol 26 (4) ◽  
pp. 1143 ◽  
Author(s):  
Mattia Mazza ◽  
Cyrille Alliot ◽  
Corinne Sinquin ◽  
Sylvia Colliec-Jouault ◽  
Pascal E. Reiller ◽  
...  
Keyword(s):  
Nuclear Medicine ◽  
Light Scattering ◽  
Molar Mass ◽  
Field Flow Fractionation ◽  
High Concentration ◽  
New Class ◽  
Free Ion ◽  
Theranostic Agents ◽  
The Stability ◽  
Drug Reference

(1) Background: Exopolysaccharide (EPS) derivatives, produced by Alteromonas infernus bacterium, showed anti-metastatic properties. They may represent a new class of ligands to be combined with theranostic radionuclides, such as 47Sc/44Sc. The goal of this work was to investigate the feasibility of such coupling. (2) Methods: EPSs, as well as heparin used as a drug reference, were characterized in terms of molar mass and dispersity using Asymmetrical Flow Field-Flow Fractionation coupled to Multi-Angle Light Scattering (AF4-MALS). The intrinsic viscosity of EPSs at different ionic strengths were measured in order to establish the conformation. To determine the stability constants of Sc with EPS and heparin, a Free-ion selective radiotracer extraction (FISRE) method has been used. (3) Results: AF4-MALS showed that radical depolymerization produces monodisperse EPSs, suitable for therapeutic use. EPS conformation exhibited a lower hydrodynamic volume for the highest ionic strengths. The resulting random-coiled conformation could affect the complexation with metal for high concentration. The LogK of Sc-EPS complexes have been determined and showing that they are comparable to the Sc-Hep. (4) Conclusions: EPSs are very promising to be coupled with the theranostic pair of scandium for Nuclear Medicine.

Film Elasticity and Film Stabilization in Firefighting Foam Stabilized by Solid Particles

2017 ◽  
Vol 744 ◽  
pp. 346-349
Author(s):  
Xiu Juan Li ◽  
Rui Song Guo ◽  
Min Zhao
Keyword(s):  
Life Time ◽  
Liquid Films ◽  
Thin Liquid Films ◽  
Solid Particles ◽  
High Concentration ◽  
Hydration Effect ◽  
Fixed Area ◽  
The Stability ◽  
Hydration Layers ◽  
Hydration Forces

The structure of the thin liquid films determines the stability of foams and emulsions. In this work the bubbles stretched length with different hollow SiO2 particles concentration is measured when the foam has been stilled for different time. The results show that the bubbles stretched length is longer than that of bubbles when the foam is free of hollow SiO2 particles even when the foam has been stilled for 500mins. The bubbles stretched length increases with increasing the concentration of hollow SiO2 particles. A strong hydration effect leaves a large volume of hydration layers on the solid particles surfaces in aqueous solutions. The water in hydration layers can help the film keep a certain thickness. The existence of hydration forces leads that two particles cannot be too close each other. The high concentration surfactant limited in the fixed area helps the film keep good elasticity. Therefore the film has a long life time with compatible thickness and elasticity and the three-phrase foam is upper stable.

scholarly journals Checkpoint Adaptation Precedes Spontaneous and Damage-Induced Genomic Instability in Yeast

2001 ◽  
Vol 21 (5) ◽  
pp. 1710-1718 ◽  
Author(s):  
David J. Galgoczy ◽  
David P. Toczyski
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Genomic Instability ◽  
Cell Cycle Progression ◽  
Repair Process ◽  
Yeast Cells ◽  
Chromosome Loss ◽  
Checkpoint Adaptation ◽  
Block Cell Cycle Progression ◽  
Break Induced Replication

ABSTRACT Despite the fact that eukaryotic cells enlist checkpoints to block cell cycle progression when their DNA is damaged, cells still undergo frequent genetic rearrangements, both spontaneously and in response to genotoxic agents. We and others have previously characterized a phenomenon (adaptation) in which yeast cells that are arrested at a DNA damage checkpoint eventually override this arrest and reenter the cell cycle, despite the fact that they have not repaired the DNA damage that elicited the arrest. Here, we use mutants that are defective in checkpoint adaptation to show that adaptation is important for achieving the highest possible viability after exposure to DNA-damaging agents, but it also acts as an entrée into some forms of genomic instability. Specifically, the spontaneous and X-ray-induced frequencies of chromosome loss, translocations, and a repair process called break-induced replication occur at significantly reduced rates in adaptation-defective mutants. This indicates that these events occur after a cell has first arrested at the checkpoint and then adapted to that arrest. Because malignant progression frequently involves loss of genes that function in DNA repair, adaptation may promote tumorigenesis by allowing genomic instability to occur in the absence of repair.

scholarly journals Positive Feedback Between PU.1 and the Cell Cycle Controls Myeloid Differentiation

Science ◽  
2013 ◽  
Vol 341 (6146) ◽  
pp. 670-673 ◽  
Author(s):  
Hao Yuan Kueh ◽  
Ameya Champhekar ◽  
Stephen L. Nutt ◽  
Michael B. Elowitz ◽  
Ellen V. Rothenberg
Keyword(s):  
Cell Cycle ◽  
Cell Fate ◽  
Positive Feedback ◽  
Regulatory Gene ◽  
Control Cell ◽  
Stem Cell Differentiation ◽  
Myeloid Differentiation ◽  
Cycle Duration ◽  
Gene Circuits ◽  
Cell Cycles

Regulatory gene circuits with positive-feedback loops control stem cell differentiation, but several mechanisms can contribute to positive feedback. Here, we dissect feedback mechanisms through which the transcription factor PU.1 controls lymphoid and myeloid differentiation. Quantitative live-cell imaging revealed that developing B cells decrease PU.1 levels by reducing PU.1 transcription, whereas developing macrophages increase PU.1 levels by lengthening their cell cycles, which causes stable PU.1 accumulation. Exogenous PU.1 expression in progenitors increases endogenous PU.1 levels by inducing cell cycle lengthening, implying positive feedback between a regulatory factor and the cell cycle. Mathematical modeling showed that this cell cycle–coupled feedback architecture effectively stabilizes a slow-dividing differentiated state. These results show that cell cycle duration functions as an integral part of a positive autoregulatory circuit to control cell fate.

scholarly journals The Small Subunit Processome Is Required for Cell Cycle Progression at G1

2004 ◽  
Vol 15 (11) ◽  
pp. 5038-5046 ◽  
Author(s):  
Kara A. Bernstein ◽  
Susan J. Baserga
Keyword(s):  
Cell Cycle ◽  
Ribosome Biogenesis ◽  
Cell Cycle Progression ◽  
Small Subunit ◽  
Cellular Growth ◽  
Yeast Cells ◽  
G1 Phase ◽  
Relay Cell ◽  
Ssu Processome ◽  
Nucleolar Rna

Without ribosome biogenesis, translation of mRNA into protein ceases and cellular growth stops. We asked whether ribosome biogenesis is cell cycle regulated in the yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe, and we determined that it is not regulated in the same manner as in metazoan cells. We therefore turned our attention to cellular sensors that relay cell size information via ribosome biogenesis. Our results indicate that the small subunit (SSU) processome, a complex consisting of 40 proteins and the U3 small nucleolar RNA necessary for ribosome biogenesis, is not mitotically regulated. Furthermore, Nan1/Utp17, an SSU processome protein, does not provide a link between ribosome biogenesis and cell growth. However, when individual SSU processome proteins are depleted, cells arrest in the G1 phase of the cell cycle. This arrest was further supported by the lack of staining for proteins expressed in post-G1. Similarly, synchronized cells depleted of SSU processome proteins did not enter G2. This suggests that when ribosomes are no longer made, the cells stall in the G1. Therefore, yeast cells must grow to a critical size, which is dependent upon having a sufficient number of ribosomes during the G1 phase of the cell cycle, before cell division can occur.

Sign in / Sign up

Export Citation Format

Share Document