scholarly journals Getting to S: CDK functions and targets on the path to cell-cycle commitment

F1000Research ◽  
2016 ◽  
Vol 5 ◽  
pp. 2374 ◽  
Author(s):  
Robert P. Fisher
Keyword(s):  
Cell Cycle ◽  
Mammalian Cells ◽  
Molecular Mechanisms ◽  
Growth Conditions ◽  
Control Mechanisms ◽  
Cell Fates ◽  
Cycle Arrest ◽  
Distinct Cell ◽  
Cast Doubt ◽  
Multicellular Organisms

How and when eukaryotic cells make the irrevocable commitment to divide remain central questions in the cell-cycle field. Parallel studies in yeast and mammalian cells seemed to suggest analogous control mechanisms operating during the G1 phase—at Start or the restriction (R) point, respectively—to integrate nutritional and developmental signals and decide between distinct cell fates: cell-cycle arrest or exit versus irreversible commitment to a round of division. Recent work has revealed molecular mechanisms underlying this decision-making process in both yeast and mammalian cells but also cast doubt on the nature and timing of cell-cycle commitment in multicellular organisms. These studies suggest an expanded temporal window of mitogen sensing under certain growth conditions, illuminate unexpected obstacles and exit ramps on the path to full cell-cycle commitment, and raise new questions regarding the functions of cyclin-dependent kinases (CDKs) that drive G1 progression and S-phase entry.

Pisosterol Induces G2/M Cell Cycle Arrest and Apoptosis via the ATM/ATR Signaling Pathway in Human Glioma Cells

2020 ◽  
Vol 20 (6) ◽  
pp. 734-750
Author(s):  
Wallax A.S. Ferreira ◽  
Rommel R. Burbano ◽  
Claudia do Ó. Pessoa ◽  
Maria L. Harada ◽  
Bárbara do Nascimento Borges ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Arrest ◽  
Signaling Pathway ◽  
Glioma Cell ◽  
Molecular Mechanisms ◽  
Glioma Cells ◽  
Dependent Manner ◽  
M Cell ◽  
Trypan Blue Exclusion ◽  
Cycle Arrest

Background: Pisosterol, a triterpene derived from Pisolithus tinctorius, exhibits potential antitumor activity in various malignancies. However, the molecular mechanisms that mediate the pisosterol-specific effects on glioma cells remain unknown. Objective: This study aimed to evaluate the antitumoral effects of pisosterol on glioma cell lines. Methods: The 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) and trypan blue exclusion assays were used to evaluate the effect of pisosterol on cell proliferation and viability in glioma cells. The effect of pisosterol on the distribution of the cells in the cell cycle was performed by flow cytometry. The expression and methylation pattern of the promoter region of MYC, ATM, BCL2, BMI1, CASP3, CDK1, CDKN1A, CDKN2A, CDKN2B, CHEK1, MDM2, p14ARF and TP53 was analyzed by RT-qPCR, western blotting and bisulfite sequencing PCR (BSP-PCR). Results: Here, it has been reported that pisosterol markedly induced G2/M arrest and apoptosis and decreased the cell viability and proliferation potential of glioma cells in a dose-dependent manner by increasing the expression of ATM, CASP3, CDK1, CDKN1A, CDKN2A, CDKN2B, CHEK1, p14ARF and TP53 and decreasing the expression of MYC, BCL2, BMI1 and MDM2. Pisosterol also triggered both caspase-independent and caspase-dependent apoptotic pathways by regulating the expression of Bcl-2 and activating caspase-3 and p53. Conclusions: It has been, for the first time, confirmed that the ATM/ATR signaling pathway is a critical mechanism for G2/M arrest in pisosterol-induced glioma cell cycle arrest and suggests that this compound might be a promising anticancer candidate for further investigation.

scholarly journals Cell growth dilutes the cell cycle inhibitor Rb to trigger cell division

2018 ◽  
Author(s):  
Evgeny Zatulovskiy ◽  
Daniel F. Berenson ◽  
Benjamin R. Topacio ◽  
Jan M. Skotheim
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Cell Growth ◽  
Cell Size ◽  
Mammalian Cells ◽  
Molecular Mechanisms ◽  
Inverse Correlation ◽  
Cell Types ◽  
Similar Amount ◽  
Cell Cycle Inhibitor

Cell size is fundamental to function in different cell types across the human body because it sets the scale of organelle structures, biosynthesis, and surface transport1,2. Tiny erythrocytes squeeze through capillaries to transport oxygen, while the million-fold larger oocyte divides without growth to form the ~100 cell pre-implantation embryo. Despite the vast size range across cell types, cells of a given type are typically uniform in size likely because cells are able to accurately couple cell growth to division3–6. While some genes whose disruption in mammalian cells affects cell size have been identified, the molecular mechanisms through which cell growth drives cell division have remained elusive7–12. Here, we show that cell growth acts to dilute the cell cycle inhibitor Rb to drive cell cycle progression from G1 to S phase in human cells. In contrast, other G1/S regulators remained at nearly constant concentration. Rb is a stable protein that is synthesized during S and G2 phases in an amount that is independent of cell size. Equal partitioning to daughter cells of chromatin bound Rb then ensures that all cells at birth inherit a similar amount of Rb protein. RB overexpression increased cell size in tissue culture and a mouse cancer model, while RB deletion decreased cell size and removed the inverse correlation between cell size at birth and the duration of G1 phase. Thus, Rb-dilution by cell growth in G1 provides a long-sought cell autonomous molecular mechanism for cell size homeostasis.

Abstract W P198: Sphingomyelin Synthases Regulate Neuronal Cell Proliferation and Cell Cycle Progression

Stroke ◽  
2014 ◽  
Vol 45 (suppl_1) ◽  
Author(s):  
Umadevi V Wesley ◽  
Daniel Tremmel ◽  
Robert Dempsey
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Regulation ◽  
Cell Cycle Progression ◽  
Molecular Mechanisms ◽  
Neuronal Cell ◽  
Artery Occlusion ◽  
Cycle Progression ◽  
Cycle Arrest ◽  
Cycle Regulation ◽  
Cerebral Artery Occlusion

Introduction: The molecular mechanisms of cerebral ischemia damage and protection are not completely understood, but a number of reports implicate the contribution of lipid metabolism and cell-cycle regulating proteins in stroke out come. We have previously shown that tricyclodecan-9-yl-xanthogenate (D609) resulted in increased ceramide levels after transient middle cerebral artery occlusion (tMCAO) in spontaneously hypertensive rat (SHR). We hypothesized that D609 induced cell cycle arrest probably by inhibiting sphingomyelin synthase (SMS). In this study, we examined the direct effects of SMS on cell cycle progression and proliferation of neuroblast cells. Methods: Ischemia was induced by middle cerebral artery occlusion (MCAO) and reperfusion. Expression levels were measured by western blot analysis, RT-PCR, and Immunofluorescence staining. SMS1 and 2 expressions were silenced by stable transfection with SMS1/2-targeted shRNA. Cell cycle analysis was performed using Flow cytometry. Data were analyzed using MODFIT cell cycle analysis program. Cell proliferation rate was measured by MTT assay. Results: We have identified that the expression of SMS1is significantly up-regulated in the ischemic hemisphere following MCAO. Neuro-2a cells transfected with SMS specific ShRNA acquired more neuronal like phenotype and exhibited decreased proliferation rate. Also, silencing of both SMS1 and 2 induced cell-cycle arrest as shown by significantly increased percentage of cells in G0/G1 and decreased proportion of cells in S-phase as compared to control cells. This was accompanied by up-regulation of cyclin-dependent kinase (Cdk) inhibitors p21 and decreased levels of phophorylated AKT levels. Furthermore, loss of SMS inhibited the migratory potential of Neuro 2a cells. Summary: Up-regulation of SMS under ischemic/reperfusion conditions suggests that this enzyme potentially contributes to cell cycle regulation and may contribute to maintaining neuronal cell population. Further studies may open up a new direction for identifying the molecular mechanisms of cell cycle regulation and protection following ischemic stroke

Abstract 20492: Mlf1 Regulates Myocyte Proliferation in Postnatal Hearts

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Shalini Muralidhar ◽  
Feng Xiao ◽  
Suwannee Thet ◽  
Hesham Sadek
Keyword(s):  
Cell Cycle ◽  
Transcription Factors ◽  
Cell Cycle Arrest ◽  
Molecular Mechanisms ◽  
Gene Array ◽  
Bhlh Transcription Factor ◽  
Cardiomyocyte Proliferation ◽  
Regenerative Capacity ◽  
Cycle Arrest ◽  
Endogenous Expression

Lower vertebrates, such as newt and zebrafish, retain a robust cardiac regenerative capacity following injury. Although adult mammals lack this cardiac regenerative potential, there is ample interest in understanding how heart regeneration occurs, and to reawaken this process in adult humans. Recently, we showed that mice are capable of regenerating their hearts shortly after birth following injury. This regenerative response is associated with robust proliferation of cardiomyocytes without significant hypertrophy or fibrosis. However, this regenerative capacity is lost by 7 days postnatally, coinciding with cell cycle arrest. In an effort to determine the mechanism of cardiomyocytes cell cycle arrest after the first week of life, we performed a gene array after cardiac injury at multiple post-natal time points. This enabled us to identify a number of transcription factors that are differentially expressed during this postnatal window. We recently reported that one of these transcription factors Meis1 regulates postnatal cell cycle arrest of cardiomyocytes. Furthermore, Myeloid leukemia factor 1 (Mlf1), a bhlh transcription factor that has not been previously studied in the heart has similar dysregulated pattern following injury. Our preliminary data with in-vitro knockdown of Mlf1 in cardiomyocyte resulted in 2-fold increase in cardiomyocyte proliferation. Furthermore, immunohistochemistry results indicated that the endogenous expression and nuclear localization of Mlf1 in the post-natal cardiomyocytes coincides with cell cycle arrest. To explore this pattern, we generated a cardiomyocyte-specific Mlf1 knockout mouse, and showed that loss of Mlf1 results in robust cardiomyocyte proliferation in postnatal hearts (P14). Additionally, we confirmed previous reports that Mlf1 regulates p53 and induces cell cycle arrest by induction of CDK inhibitors like p21 and p57 in these Mlf1 KO mice. This suggests a role of Mlf1 in promoting reactivation of injured myocardium through induction of cardiomyocyte proliferation. These findings will further provide evidences of molecular mechanisms involved in the dormant regenerative capacity in adult mammals that can be a potential target of therapeutic approaches.

scholarly journals Molecular mechanisms of LKB1 induced cell cycle arrest

2013 ◽  
Vol 4 (3) ◽  
pp. 229-233 ◽  
Author(s):  
Dian-sheng Zhong ◽  
Lin-lin Sun ◽  
Li-xia Dong
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Arrest ◽  
Molecular Mechanisms ◽  
Cycle Arrest

MicroRNA-1225-5p acts as a tumor-suppressor in laryngeal cancer via targeting CDC14B

2019 ◽  
Vol 400 (2) ◽  
pp. 237-246 ◽  
Author(s):  
Peng Sun ◽  
Dan Zhang ◽  
Haiping Huang ◽  
Yafeng Yu ◽  
Zhendong Yang ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Death ◽  
Cell Division ◽  
Cell Cycle Arrest ◽  
Molecular Mechanisms ◽  
Normal Tissues ◽  
Cycle Arrest ◽  
Enhanced Expression ◽  
Insight Into

Abstract This study aimed to investigate the role of miRNA-1225-5p (miR-1225) in laryngeal carcinoma (LC). We found that the expression of miR-1225 was suppressed in human LC samples, while CDC14B (cell division cycle 14B) expression was reinforced in comparison with surrounding normal tissues. We also demonstrated that enhanced expression of miR-1225 impaired the proliferation and survival of LC cells, and resulted in G1/S cell cycle arrest. In contrast, reduced expression of miR-1225 promoted cell survival. Moreover, miR-1225 resulted in G1/S cell cycle arrest and enhanced cell death. Further, miR-1225 targets CDC14B 3′-UTR and recovery of CDC14B expression counteracted the suppressive influence of miR-1225 on LC cells. Thus, these findings offer insight into the biological and molecular mechanisms behind the development of LC.

Moxifloxacin Enhances the Antiproliferative and Apoptotic Effects of VP-16 but Inhibits Its Proinflammatory Effects in THP-1 and Jurkat Cells.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 4290-4290
Author(s):  
Ina Fabian ◽  
Debby Haite ◽  
Avital Levitov ◽  
Drora Halperin ◽  
Itamar Shalit
Keyword(s):  
Cell Cycle ◽  
Cell Proliferation ◽  
Cell Cycle Arrest ◽  
Mammalian Cells ◽  
Caspase 3 ◽  
S Phase ◽  
Jurkat Cells ◽  
Cycle Arrest ◽  
Topo Ii ◽  
Number Of Cells

Abstract We previously reported that the fluoroquinolone moxifloxacin (MXF) inhibits NF-kB, mitogen-activated protein kinase activation and the synthesis of proinflammatory cytokines in activated human monocytic cells (AAC48:1974,2004). Since MXF acts on topoisomerase II (Topo II) in mammalian cells, we investigated its effect in combination with another Topo II inhibitor, VP-16, on cell proliferation (by the MTT method), cell cycle, caspase-3 activity and proinflammatory cytokine release in THP-1 and Jurkat cells. THP-1 cells were incubated for 24 h with 0.5–3 μg/ml VP-16 in the presence or absence of 5–20 μg/ml MXF. VP-16 induced a dose dependent decrease in cell proliferation. An additional 2.5-and 1.6-fold decrease in cell proliferation was observed upon incubation of the cells with 0.5 or 1 μg/ml VP-16 and 20 μg/ml MXF, respectively (up to 69% inhibition). To further elucidate the mechanism of the antiproliferative activity of MXF, its effect on cell cycle progression was investigated. In control cultures 1%, 45%,18% and 36% of cells were in G0, G1, S and G2/M phases at 24 h, respectively. In contrast, in cultures treated with 1 μg/ml VP-16 and VP-16+ 20 μg/ml MXF, the number of cells in G1 decreased to 5.4 and 6.5%, respectively, while the number of cells in S phase increased to 25.5 and 42%, respectively and the number of cells in G2/M cells increased to 60 and 44%, respectively. These data provide evidence for S-G2/M cell cycle arrest induced by VP-16 and that addition of MXF shifted the S-G2/M arrest more towards the S phase. Since the antiproliferative effects of MXF could also be attributed to apoptotic cell death in addition to cell cycle arrest, we investigated the effect of the drugs on apoptosis. Using the fluorogenic assay for caspse-3 activity, we show that incubation of THP-1 cells for 6 h with 1.5 μg/ml VP-16 resulted in 630±120 unit/50μg protein of caspase-3 activity while the combination of 1.5 μg/ml VP-16 and 20 μg/ml MXF enhanced caspase-3 activity up to 1700±340 units/50μg protein (vs.233±107 in control cells), indicating that MXF synergises with VP-16 in activation of caspase-3. In Jurkat cells, the addition of 0.5 or 1 μg/ml VP-16, did not affect cell proliferation while in the presence of 20 μg/ml MXF and 1 μg/ml VP-16 there was a 62% decrease in cell proliferation (p<0.05). Exposure of Jurkat cells to 3 μg/ml VP-16 alone resulted in 504±114 units/50μg protein of caspase-3 activity and the addition of 20μg/ml MXF enhanced caspase-3 activity up to 1676± 259 units/50μg protein (vs 226±113 units/50μg protein in control cells). We further examined pro-inflammatory cytokine secretion upon stimulation of THP-1 cells with VP-16, MXF or their combination. VP-16 alone at 3 μg/ml increased IL-8 and TNF-α secretion from THP-1 cells by 2.5 and 1.8-fold respectively. Addition of MXF (5–20 μg/ml) inhibited the two cytokines secretion by 72–77% and 58–72%, respectively. The above combined data indicate that MXF, at clinically attainable concentrations, demonstrates pronounced synergistic effect with VP-16 as an anti-proliferative agent mainly by enhancing caspase-3 activity and apoptosis. At the same time MXF inhibits the pro-inflammatory effects conferred by VP-16 in the tumor cells studied. The clinical significance of the above anti-proliferative and anti-inflammatory effects of MXF in combination with VP-16 should be further investigated in animal models.

Molecular Mechanisms of Spindle Checkpoint-Apoptosis Linkage and Karyotypic Stability in Stem Cells.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 3361-3361
Author(s):  
Charlie Mantel ◽  
Sara Rhorabough ◽  
Ying Guo ◽  
Man-Ryul Lee ◽  
Myung-Kwan Han ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Stem Cells ◽  
Cell Fate ◽  
Mammalian Cells ◽  
Molecular Mechanisms ◽  
Ex Vivo ◽  
Spindle Checkpoint ◽  
Cyclin B1 ◽  
Polyploid Cell ◽  
Mitotic Slippage

Abstract Ex-vivo expansion of human HSC prior to bone marrow transplantation is still an unrealized goal that could greatly extend the usefulness of this mainstay strategy for treating numerous human hematologic diseases. The safety of this process for potential use in humans depends in large part on the maintenance of karyotypic stability of HSC during expansion, a lack of which could contribute to serious, even fatal, complications such as cancer, and could also contribute to engraftment failure. The spindle checkpoint and its linkage to apoptosis initiation is one of the most important cellular processes that helps maintain chromosomal stability in rapidly proliferating cell populations by removing aneuploid and karyotypically abnormal cells via activation of cell death programs. Detailed understanding of the molecular regulation of this vital cell cycle checkpoint is important to maximize safety of in-vitro HSC expansion techniques. It is widely accepted that mammalian cells enter the next G1-phase with 4N DNA after slippage from prolonged drug-induced mitotic block caused by activation of the transient spindle checkpoint that it is from this state that polyploid/aneuploid cells initiate apoptosis. However, definitive biochemical evidence for G1 is scarce or unconvincing; in part because of methods of protein extraction required for immunoblot analysis that cannot take into account the cell cycle heterogeneity of cell cultures. We used single-cell-intracellular-flow-cytometric analysis to define important factors determining cell fate after mitotic slippage. Results from human and mouse embryonic stem cells that reenter polyploid cell cycles are compared to human somatic hematopoietic cells that die after MS. We now report for the first time that phosphorylation status of pRb, p53, CDK1, and cyclin B1 levels are important for cell fate/apoptosis decision in mitotic-slippage cells, which occurs in a unique, intervening, non-G1, tetraploid subphase. Hyperphosphorylated Rb was extremely abundant in mitotic-slippage cells, a cell signaling event usually associated with early G1-S phase transition. P53 was phosphorylated at sites known to be associated with apoptosis regulation. Cyclin A and B1 were undetectable in mitotic slippage cells; yet, CDK1 was phosphorylated at sites typically associated with its activation. Evidence is also presented raising the possibility of cyclin B1-independent CDK1 activity in mitotic-slippage cells. These findings challenge the current models of spindle checkpoint-apoptosis linkages. Our new model could have important implications for methods to maintain karyotypic stability during ex-vivo HSC expansion.

scholarly journals ROS-Mediated Apoptosis and Genotoxicity Induced by Palladium Nanoparticles in Human Skin Malignant Melanoma Cells

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
Saud Alarifi ◽  
Daoud Ali ◽  
Saad Alkahtani ◽  
Rafa S. Almeer
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Malignant Melanoma ◽  
Cell Cycle Arrest ◽  
Human Skin ◽  
Palladium Nanoparticles ◽  
Molecular Mechanisms ◽  
Time Dependent ◽  
Cycle Arrest ◽  
A375 Cells

The present work was designed to investigate the effect of palladium nanoparticles (PdNPs) on human skin malignant melanoma (A375) cells, for example, induction of apoptosis, cytotoxicity, and DNA damage. Diseases resulting from dermal exposure may have a significant impact on human health. There is a little study that has been reported on the toxic potential of PdNPs on A375. Cytotoxic potential of PdNPs (0, 5, 10, 20, and 40 μg/ml) was measured by tetrazolium bromide (MTT assay) and NRU assay in A375 cells. PdNPs elicited concentration and time-dependent cytotoxicity, and longer exposure period induced more cytotoxicity as measured by MTT and NRU assay. The molecular mechanisms of cytotoxicity through cell cycle arrest and apoptosis were investigated by AO (acridine orange)/EtBr (ethidium bromide) stain and flow cytometry. PdNPs not only inhibit proliferation of A375 cells in a dose- and time-dependent model but also induce apoptosis and cell cycle arrest at G2/M phase (before 12 h) and S phase (after 24 h). The induction of oxidative stress in A375 cells treated with above concentration PdNPs for 24 and 48 h increased ROS level; on the other hand, glutathione level was declined. Apoptosis and DNA damage was significantly increased after treatment of PdNPs. Considering all results, PdNPs showed cytotoxicity and genotoxic effect in A375 cells.

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