scholarly journals GroES/GroEL and DnaK/DnaJ Have Distinct Roles in Stress Responses and during Cell Cycle Progression in Caulobacter crescentus

2006 ◽  
Vol 188 (23) ◽  
pp. 8044-8053 ◽  
Author(s):  
Michelle F. Susin ◽  
Regina L. Baldini ◽  
Frederico Gueiros-Filho ◽  
Suely L. Gomes
Keyword(s):  
Cell Cycle ◽  
Heat Shock ◽  
Stress Responses ◽  
Cell Cycle Progression ◽  
Caulobacter Crescentus ◽  
Normal Growth ◽  
Growth Conditions ◽  
Cycle Progression ◽  
Lower Survival Rate ◽  
Morphological Defects

ABSTRACT Misfolding and aggregation of protein molecules are major threats to all living organisms. Therefore, cells have evolved quality control systems for proteins consisting of molecular chaperones and proteases, which prevent protein aggregation by either refolding or degrading misfolded proteins. DnaK/DnaJ and GroES/GroEL are the best-characterized molecular chaperone systems in bacteria. In Caulobacter crescentus these chaperone machines are the products of essential genes, which are both induced by heat shock and cell cycle regulated. In this work, we characterized the viabilities of conditional dnaKJ and groESL mutants under different types of environmental stress, as well as under normal physiological conditions. We observed that C. crescentus cells with GroES/EL depleted are quite resistant to heat shock, ethanol, and freezing but are sensitive to oxidative, saline, and osmotic stresses. In contrast, cells with DnaK/J depleted are not affected by the presence of high concentrations of hydrogen peroxide, NaCl, and sucrose but have a lower survival rate after heat shock, exposure to ethanol, and freezing and are unable to acquire thermotolerance. Cells lacking these chaperones also have morphological defects under normal growth conditions. The absence of GroE proteins results in long, pinched filamentous cells with several Z-rings, whereas cells lacking DnaK/J are only somewhat more elongated than normal predivisional cells, and most of them do not have Z-rings. These findings indicate that there is cell division arrest, which occurs at different stages depending on the chaperone machine affected. Thus, the two chaperone systems have distinct roles in stress responses and during cell cycle progression in C. crescentus.

scholarly journals Heat shock protein 27 promotes cell cycle progression by down-regulating E2F transcription factor 4 and retinoblastoma family protein p130

2018 ◽  
Vol 293 (41) ◽  
pp. 15815-15826 ◽  
Author(s):  
Ah-Mee Park ◽  
Ikuo Tsunoda ◽  
Osamu Yoshie
Keyword(s):  
Cell Cycle ◽  
Heat Shock ◽  
Heat Shock Protein ◽  
Cellular Senescence ◽  
Cell Cycle Progression ◽  
Heat Shock Protein 27 ◽  
Serum Starvation ◽  
Cell Cycle Gene ◽  
Cycle Progression ◽  
Human Lung Fibroblast

Heat shock protein 27 (HSP27) protects cells under stress. Here, we demonstrate that HSP27 also promotes cell cycle progression of MRC-5 human lung fibroblast cells. Serum starvation for 24 h induced G1 arrest in these cells, and upon serum refeeding, the cells initiated cell cycle progression accompanied by an increase in HSP27 protein levels. HSP27 levels peaked at 12 h, and transcriptional up-regulation of six G2/M-related genes (CCNA2, CCNB1, CCNB2, CDC25C, CDCA3, and CDK1) peaked at 24–48 h. siRNA-mediated HSP27 silencing in proliferating MRC-5 cells induced G2 arrest coinciding with down-regulation of these six genes. Of note, the promoters of all of these genes have the cell cycle–dependent element and/or the cell cycle gene-homology region. These promoter regions are known to be bound by the E2F family proteins (E2F-1 to E2F-8) and retinoblastoma (RB) family proteins (RB1, p107, and p130), among which E2F-4 and p130 were strongly up-regulated in HSP27-knockdown cells. E2F-4 or p130 knockdown concomitant with the HSP27 knockdown rescued MRC-5 cells from G2 arrest and up-regulated the six cell cycle genes. Moreover, we observed cellular senescence in MRC-5 cells on day 3 after the HSP27 knockdown, as evidenced by increased senescence-associated β-gal activity and up-regulated inflammatory cytokines. The cellular senescence was also suppressed by the concomitant knockdown of E2F-4/HSP27 or p130/HSP27. Our findings indicate that HSP27 promotes cell cycle progression of MRC-5 cells by suppressing expression of the transcriptional repressors E2F-4 and p130.

scholarly journals Polar Remodeling and Histidine Kinase Activation, Which Is Essential for Caulobacter Cell Cycle Progression, Are Dependent on DNA Replication Initiation

2010 ◽  
Vol 192 (15) ◽  
pp. 3893-3902 ◽  
Author(s):  
Antonio A. Iniesta ◽  
Nathan J. Hillson ◽  
Lucy Shapiro
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Histidine Kinase ◽  
Cell Cycle Progression ◽  
Caulobacter Crescentus ◽  
Replication Initiation ◽  
Cycle Progression ◽  
Dna Replication Initiation ◽  
Flagellar Biosynthesis ◽  
Initiation Of Dna Replication

ABSTRACT Caulobacter crescentus initiates a single round of DNA replication during each cell cycle. Following the initiation of DNA replication, the essential CckA histidine kinase is activated by phosphorylation, which (via the ChpT phosphotransferase) enables the phosphorylation and activation of the CtrA global regulator. CtrA∼P then blocks the reinitiation of replication while regulating the transcription of a large number of cell cycle-controlled genes. It has been shown that DNA replication serves as a checkpoint for flagellar biosynthesis and cell division and that this checkpoint is mediated by the availability of active CtrA. Because CckA∼P promotes the activation of CtrA, we addressed the question of what controls the temporal activation of CckA. We found that the initiation of DNA replication is a prerequisite for remodeling the new cell pole, which includes the localization of the DivL protein kinase to that pole and, consequently, the localization, autophosphorylation, and activation of CckA at that pole. Thus, CckA activation is dependent on polar remodeling and a DNA replication initiation checkpoint that is tightly integrated with the polar phospho-signaling cascade governing cell cycle progression.

scholarly journals Cell Cycle Arrest and Reversion of Ras-Induced Transformation by a Conditionally Activated Form of Mitogen-Activated Protein Kinase Kinase Kinase 3

1999 ◽  
Vol 19 (5) ◽  
pp. 3857-3868 ◽  
Author(s):  
Heidrun Ellinger-Ziegelbauer ◽  
Kathleen Kelly ◽  
Ulrich Siebenlist
Keyword(s):  
Cell Cycle ◽  
Protein Kinase ◽  
Cyclin D1 ◽  
Stress Responses ◽  
Cell Cycle Progression ◽  
Cellular Transformation ◽  
Mitogen Activated Protein Kinase ◽  
Cycle Progression ◽  
Mapk Kinase ◽  
Mitogen Activated Protein

ABSTRACT Signal-induced proliferation, differentiation, or stress responses of cells depend on mitogen-activated protein kinase (MAPK) cascades, the core modules of which consist of members of three successively acting kinase families (MAPK kinase kinase [MAP3K], MAPK kinase, and MAPK). It is demonstrated here that the MEKK3 kinase inhibits cell proliferation, a biologic response not commonly associated with members of the MAP3K family of kinases. A conditionally activated form of MEKK3 stably expressed in fibroblasts arrests these cells in early G1. MEKK3 critically blocks mitogen-driven expression of cyclin D1, a cyclin which is essential for progression of fibroblasts through G1. The MEKK3-induced block of cyclin D1 expression and of cell cycle progression may be mediated via p38 MAPK, a downstream effector of MEKK3. The MEKK3-mediated block of proliferation also reverses Ras-induced cellular transformation, suggesting possible tumor-suppressing functions for this kinase. Together, these results suggest an involvement of the MEKK3 kinase in negative regulation of cell cycle progression, and they provide the first insights into biologic activities of this kinase.

scholarly journals Surface Sensing Stimulates Cellular Differentiation in Caulobacter crescentus

2019 ◽  
Author(s):  
Rhett A. Snyder ◽  
Courtney K. Ellison ◽  
Geoffrey B. Severin ◽  
Christopher M. Waters ◽  
Yves V. Brun
Keyword(s):  
Cell Cycle ◽  
Cell Differentiation ◽  
Cellular Differentiation ◽  
Cell Cycle Progression ◽  
Caulobacter Crescentus ◽  
Chromosome Replication ◽  
Fundamental Aspect ◽  
Cycle Progression ◽  
Surface Sensing ◽  
Surface Contact

AbstractCellular differentiation is a fundamental strategy used by cells to generate specialized functions at specific stages of development. The bacterium C. crescentus employs a specialized dimorphic life cycle consisting of two differentiated cell types. How environmental cues, including mechanical inputs such as contact with a surface, regulate this cell cycle remain unclear. Here, we find that surface sensing by the physical perturbation of retracting extracellular pilus filaments accelerates cell cycle progression and cellular differentiation. We show that physical obstruction of dynamic pilus activity by chemical perturbation or by a mutation in the outer membrane pilus pore protein, CpaC, stimulates early initiation of chromosome replication. In addition, we find that surface contact stimulates cell cycle progression by demonstrating that surface-stimulated cells initiate early chromosome replication to the same extent as planktonic cells with obstructed pilus activity. Finally, we show that obstruction of pilus retraction stimulates the synthesis of the cell cycle regulator, cyclic diguanylate monophosphate (c-di-GMP) through changes in the activity and localization of two key regulatory histidine kinases that control cell fate and differentiation. Together, these results demonstrate that surface contact and mechanosensing by alterations in pilus activity stimulate C. crescentus to bypass its developmentally programmed temporal delay in cell differentiation to more quickly adapt to a surface-associated lifestyle.SignificanceCells from all domains of life sense and respond to mechanical cues [1–3]. In eukaryotes, mechanical signals such as adhesion and surface stiffness are important for regulating fundamental processes including cell differentiation during embryonic development [4]. While mechanobiology is abundantly studied in eukaryotes, the role of mechanical influences on prokaryotic biology remains under-investigated. Here, we demonstrate that mechanosensing mediated through obstruction of the dynamic extension and retraction of tight adherence (tad) pili stimulates cell differentiation and cell cycle progression in the dimorphic α-proteobacterium Caulobacter crescentus. Our results demonstrate an important intersection between mechanical stimuli and the regulation of a fundamental aspect of cell biology.

scholarly journals Regulation of Bacterial Cell Cycle Progression by Redundant Phosphatases

2020 ◽  
Vol 202 (17) ◽  
Author(s):  
Jérôme Coppine ◽  
Andreas Kaczmarczyk ◽  
Kenny Petit ◽  
Thomas Brochier ◽  
Urs Jenal ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Environmental Changes ◽  
Caulobacter Crescentus ◽  
Response Regulator ◽  
Model Organism ◽  
Replication Initiation ◽  
Cycle Progression ◽  
Content Type ◽  
Two Component

ABSTRACT In the model organism Caulobacter crescentus, a network of two-component systems involving the response regulators CtrA, DivK, and PleD coordinates cell cycle progression with differentiation. Active phosphorylated CtrA prevents chromosome replication in G1 cells while simultaneously regulating expression of genes required for morphogenesis and development. At the G1-S transition, phosphorylated DivK (DivK∼P) and PleD (PleD∼P) accumulate to indirectly inactivate CtrA, which triggers DNA replication initiation and concomitant cellular differentiation. The phosphatase PleC plays a pivotal role in this developmental program by keeping DivK and PleD phosphorylation levels low during G1, thereby preventing premature CtrA inactivation. Here, we describe CckN as a second phosphatase akin to PleC that dephosphorylates DivK∼P and PleD∼P in G1 cells. However, in contrast to PleC, no kinase activity was detected with CckN. The effects of CckN inactivation are largely masked by PleC but become evident when PleC and DivJ, the major kinase for DivK and PleD, are absent. Accordingly, mild overexpression of cckN restores most phenotypic defects of a pleC null mutant. We also show that CckN and PleC are proteolytically degraded in a ClpXP-dependent way before the onset of the S phase. Surprisingly, known ClpX adaptors are dispensable for PleC and CckN proteolysis, raising the possibility that as yet unidentified proteolytic adaptors are required for the degradation of both phosphatases. Since cckN expression is induced in stationary phase, depending on the stress alarmone (p)ppGpp, we propose that CckN acts as an auxiliary factor responding to environmental stimuli to modulate CtrA activity under suboptimal conditions. IMPORTANCE Two-component signal transduction systems are widely used by bacteria to adequately respond to environmental changes by adjusting cellular parameters, including the cell cycle. In Caulobacter crescentus, PleC acts as a phosphatase that indirectly protects the response regulator CtrA from premature inactivation during the G1 phase of the cell cycle. Here, we provide genetic and biochemical evidence that PleC is seconded by another phosphatase, CckN. The activity of PleC and CckN phosphatases is restricted to the G1 phase since both proteins are degraded by ClpXP protease before the G1-S transition. Degradation is independent of any known proteolytic adaptors and relies, in the case of CckN, on an unsuspected N-terminal degron. Our work illustrates a typical example of redundant functions between two-component proteins.

scholarly journals Proper division plane orientation and mitotic progression together allow normal growth of maize

2017 ◽  
Vol 114 (10) ◽  
pp. 2759-2764 ◽  
Author(s):  
Pablo Martinez ◽  
Anding Luo ◽  
Anne Sylvester ◽  
Carolyn G. Rasmussen
Keyword(s):  
Cell Cycle ◽  
Cell Biology ◽  
Cell Cycle Progression ◽  
Normal Growth ◽  
Mitotic Progression ◽  
Wild Type ◽  
Cycle Progression ◽  
Division Plane ◽  
Plane Orientation ◽  
Division Plane Orientation

How growth, microtubule dynamics, and cell-cycle progression are coordinated is one of the unsolved mysteries of cell biology. A maize mutant,tangled1, with known defects in growth and proper division plane orientation, and a recently characterized cell-cycle delay identified by time-lapse imaging, was used to clarify the relationship between growth, cell cycle, and proper division plane orientation. Thetangled1mutant was fully rescued by introduction of cortical division site localized TANGLED1-YFP. A CYCLIN1B destruction box was fused to TANGLED1-YFP to generate a line that mostly rescued the division plane defect but still showed cell-cycle delays when expressed in thetangled1mutant. Although an intermediate growth phenotype between wild-type and thetangled1mutant was expected, these partially rescued plants grew as well as wild-type siblings, indicating that mitotic progression delays alone do not alter overall growth. These data indicate that division plane orientation, together with proper cell-cycle progression, is critical for plant growth.

scholarly journals Increased Expression of Cyclin D2 during Multiple States of Growth Arrest in Primary and Established Cells

1998 ◽  
Vol 18 (6) ◽  
pp. 3163-3172 ◽  
Author(s):  
Muthupalaniappan Meyyappan ◽  
Howard Wong ◽  
Christopher Hull ◽  
Karl T. Riabowol
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Growth Arrest ◽  
Growth Conditions ◽  
Cellular Growth ◽  
Serum Starvation ◽  
Cyclin D2 ◽  
Cycle Progression ◽  
Quiescent Cells ◽  
D2 Protein

ABSTRACT Cyclin D2 is a member of the family of D-type cyclins that is implicated in cell cycle regulation, differentiation, and oncogenic transformation. To better understand the role of this cyclin in the control of cell proliferation, cyclin D2 expression was monitored under various growth conditions in primary human and established murine fibroblasts. In different states of cellular growth arrest initiated by contact inhibition, serum starvation, or cellular senescence, marked increases (5- to 20-fold) were seen in the expression levels of cyclin D2 mRNA and protein. Indirect immunofluorescence studies showed that cyclin D2 protein localized to the nucleus in G0, suggesting a nuclear function for cyclin D2 in quiescent cells. Cyclin D2 was also found to be associated with the cyclin-dependent kinases CDK2 and CDK4 but not CDK6 during growth arrest. Cyclin D2-CDK2 complexes increased in amounts but were inactive as histone H1 kinases in quiescent cells. Transient transfection and needle microinjection of cyclin D2 expression constructs demonstrated that overexpression of cyclin D2 protein efficiently inhibited cell cycle progression and DNA synthesis. These data suggest that in addition to a role in promoting cell cycle progression through phosphorylation of retinoblastoma family proteins in some cell systems, cyclin D2 may contribute to the induction and/or maintenance of a nonproliferative state, possibly through sequestration of the CDK2 catalytic subunit.

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