scholarly journals Ras induces anchorage-independent growth by subverting multiple adhesion-regulated cell cycle events.

1996 ◽  
Vol 16 (7) ◽  
pp. 3370-3380 ◽  
Author(s):  
J S Kang ◽  
R S Krauss
Keyword(s):  
Cell Cycle ◽  
Cell Adhesion ◽  
Cell Cycle Progression ◽  
Molecular Mechanisms ◽  
Kinase Activity ◽  
Cyclin E ◽  
Ectopic Expression ◽  
Cyclin A ◽  
Semisolid Medium ◽  
Anchorage Independent Growth

Anchorage-independent growth is a hallmark of transformed cells, but little is known of the molecular mechanisms that underlie this phenomenon. We describe here studies of cell cycle control of anchorage-independent growth induced by the ras oncogene, with the use of a somatic cell mutant fibroblast line (ER-1-2) that is specifically defective in oncogene-mediated, anchorage-independent growth. Control, nontransformed PKC3-F4 cells and ER-1-2 cells cannot proliferate in semisolid medium. Three important cell cycle events are dependent on adhesion of these cells to a substratum: phosphorylation of the retinoblastoma protein, pRB; cyclin E-dependent kinase activity; and cyclin A expression. PKC3-F4 cells that express ras (PKC3-F4/ras cells) proliferate in nonadherent cultures, and each of these three events occurs in the absence of adhesion in PKC3-F4/ras cells. Thus, ras can override the adhesion requirement of cellular functions that are necessary for cell cycle progression. ER-1-2 cells that express ras (ER-1-2/ras cells) possess hyperphosphorylated forms of pRB and cyclin E-dependent kinase activity in the absence of adhesion but remain adhesion dependent for expression of cyclin A. The adhesion dependence of pRB phosphorylation and cyclin E-dependent kinase activity is therefore dissociable from the adhesion dependence of cyclin A expression. Furthermore, ectopic expression of cyclin A is sufficient to rescue anchorage-independent growth of ER-1-2/ras cells but does not induce anchorage-independent growth of PKC3-F4 or ER-1-2 cells. However, like pRB phosphorylation and cyclin E-dependent kinase activity, the kinase activity associated with ectopically expressed cyclin A is dependent on cell adhesion, and this dependence is overcome by ras. Thus, the induction of anchorage-independent growth by ras may involve multiple signals that lead to both expression of cyclin A and activation of G1 cyclin-dependent kinase activities in the absence of cell adhesion.

scholarly journals Ectopic expression of cyclin D1 but not cyclin E induces anchorage-independent cell cycle progression.

1997 ◽  
Vol 17 (9) ◽  
pp. 5640-5647 ◽  
Author(s):  
D Resnitzky
Keyword(s):  
Cell Cycle ◽  
Cyclin D1 ◽  
Cell Cycle Progression ◽  
Kinase Activity ◽  
Cyclin E ◽  
Ectopic Expression ◽  
S Phase ◽  
G1 Arrest ◽  
Independent Manner ◽  
Cycle Progression

Normal fibroblasts are dependent on adhesion to a substrate for cell cycle progression. Adhesion-deprived Rat1 cells arrest in the G1 phase of the cell cycle, with low cyclin E-dependent kinase activity, low levels of cyclin D1 protein, and high levels of the cyclin-dependent kinase inhibitor p27kip1. To understand the signal transduction pathway underlying adhesion-dependent growth, it is important to know whether prevention of any one of these down-regulation events under conditions of adhesion deprivation is sufficient to prevent the G1 arrest. To that end, sublines of Rat1 fibroblasts capable of expressing cyclin E, cyclin D1, or both in an inducible manner were used. Ectopic expression of cyclin D1 was sufficient to allow cells to enter S phase in an adhesion-independent manner. In contrast, cells expressing exogenous cyclin E at a level high enough to overcome the p27kip1-imposed inhibition of cyclin E-dependent kinase activity still arrested in G1 when deprived of adhesion. Moreover, expression of both cyclins D1 and E in the same cells did not confer any additional growth advantage upon adhesion deprivation compared to the expression of cyclin D1 alone. Exogenously expressed cyclin D1 was down-regulated under conditions of adhesion deprivation, despite the fact that it was expressed from a heterologous promoter. The ability of cyclin D1-induced cells to enter S phase in an adhesion-independent manner disappears as soon as cyclin D1 proteins disappear. These results suggest that adhesion-dependent cell cycle progression is mediated through cyclin D1, at least in Rat1 fibroblasts.

scholarly journals Effects of iron-depletion on cell cycle progression in normal human T lymphocytes: selective inhibition of the appearance of the cyclin A- associated component of the p33cdk2 kinase

Blood ◽  
1995 ◽  
Vol 86 (6) ◽  
pp. 2268-2280 ◽  
Author(s):  
JJ Lucas ◽  
A Szepesi ◽  
J Domenico ◽  
K Takase ◽  
A Tordai ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Kinase Activity ◽  
Cyclin E ◽  
Chelating Agent ◽  
Cyclin A ◽  
Selective Inhibition ◽  
Major Effect ◽  
G1 Phase ◽  
Cycle Progression

Iron removal by the chelating-agent deferoxamine (DFO) arrests cell cycle progression of activated human T cells in late G1 phase, before the G1/S border. The effects of the drug on molecules that regulate progression through the cell cycle were defined. DFO (10 mumol/L) inhibited induction of transcription of the cdc2 gene, but had no effect on accumulation of cdk2, cdk4, or interleukin (IL)-2- transcripts. No detectable p34cdc2 protein accumulated, but synthesis of the p33cdk2 protein was begun. It accumulated to normal levels during the first 20 to 30 hours of incubation in the presence of DFO. Furthermore, p33cdk2 was activated as an H1 histone kinase. As active p33cdk2 primarily represents complexes of the p33 protein with cyclin E or cyclin A, the effects of DFO on these cyclins were examined. Although the induction of synthesis and early accumulation of cyclin E and cyclin E-associated kinase activity appeared normal, the appearance of cyclin A and cyclin A-associated kinase activity were inhibited by DFO. However, the production of cyclin A mRNA appeared to be normal in the presence of DFO. A major effect of DFO in blocking cell cycle progression may be mediated through inhibition of the appearance of cyclin A protein and, therefore, a major component of p33cdk2 activity. The results also indicate that the p33cdk2/cyclin E activity produced in the presence of DFO was not sufficient for completion of the G1 phase of the cell cycle.

CD4+CD25+ Regulatory T Cells from Cord Blood Have Functional and Molecular Properties of T Cell Anergy.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 316-316
Author(s):  
Lequn Li ◽  
Wayne R. Godfrey ◽  
Stephen B. Porter ◽  
Ying Ge ◽  
Carle H. June ◽  
...  
Keyword(s):  
Cell Cycle ◽  
T Cells ◽  
Regulatory T Cells ◽  
Cord Blood ◽  
Cell Lines ◽  
Cell Cycle Progression ◽  
Map Kinases ◽  
Cyclin E ◽  
Cyclin A ◽  
Cycle Progression

Abstract CD4+CD25+ regulatory T cells (Tr) are negative regulators of immune responses. Studies of human Tr are restricted by their small numbers in peripheral blood and their hypoproliferative state. A recently established method achieved in vitro expansion and generation of Tr cell lines (Godfrey et al; Blood 2004,104:453-61). This approach facilitates the evaluation of cultured Tr cells as a novel form of immunosuppressive therapy and provides a system for molecular analysis of Tr. Activation of Ras and MAP kinases is mandatory for IL-2 production, viability and cell cycle progression of T cells. In anergic T cells activation of these signaling events is impaired, whereas activation of Rap1 is retained. Subsequently, anergic cells have defective IL-2 production, impaired cell cycle progression, and increased susceptibility to apoptosis. In the current study, we sought to determine the signaling and biochemical properties of Tr. Human CD4+CD25+ (Tr) and control CD4+CD25− (Tc) cell lines were generated from human cord blood cells. We examined activation of Ras, Rap1 and MAP kinases as well as cell cycle progression and cell viability, in response to TCR/CD3-plus-CD28 mediated stimulation. Stimulation was done for 15 min, 2 and 16 hrs for assessment of signaling events or for 24, 48 and 72 hrs for assessment of cell cycle progression and viability. Although activation of Rap1 was not affected, activation of Ras was reduced in Tr as compared to Tc. Activation of JNK and Erk1/2 MAP kinases was also significantly impaired. Both Tr and Tc entered the cell cycle and expressed cyclin E and cyclin A at 24 and 48 hrs of culture. However, p27 was downregulated only in Tc and not in Tr and hyperphosphorylation of Rb, which is the hallmark of cell cycle progression, was detected only in the Tc and not in the Tr population. At 72 hrs of culture, expression of cyclin E and cyclin A was dramatically diminished in Tr whereas it remained unchanged in Tc. More strikingly, expression of p27 in Tr was increased to levels higher than background. Since Tr do not produce IL-2, we examined whether addition of exogenous IL-2 would downregulate p27 and rescue Tr from defective cell cycle progression, similarly to its effect on anergic cells. Addition of exogenous IL-2 resulted in decrease of p27, sustained increase of cyclin E and cyclin A and cell cycle progression. Besides inhibiting cell cycle progression, p27 also promotes apoptosis. Therefore, we examined whether Tr had a higher susceptibility to apoptosis. As determined by Annexin V staining, Tr had a high degree of apoptosis only at 72 hrs of culture, when p27 expression was highly upregulated. Exogenous IL-2 reversed both p27 upregulation and apoptosis. Addition of IL-2 to Tr, also resulted in sustained IL-2-receptor-mediated activation of Erk1/2 at levels equivalent to those of Tc. Thus Tr cells share many biochemical and molecular characteristics of anergy, including defective TCR/CD3-plus-CD28-mediated activation of Ras and MAP kinases, increased expression of p27, defective cell cycle progression and high susceptibility to apoptosis. Moreover, these results suggest that TCR/CD3-mediated and IL-2 receptor-mediated signals converge at the level of MAP kinases to determine the fate of Tr cells towards expansion or cell cycle arrest and subsequent apoptosis.

scholarly journals BRCA1 Is Phosphorylated at Serine 1497 In Vivo at a Cyclin-Dependent Kinase 2 Phosphorylation Site

1999 ◽  
Vol 19 (7) ◽  
pp. 4843-4854 ◽  
Author(s):  
Heinz Ruffner ◽  
Wei Jiang ◽  
A. Grey Craig ◽  
Tony Hunter ◽  
Inder M. Verma
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Kinase Activity ◽  
Phosphorylation Site ◽  
Cyclin A ◽  
Dominant Negative ◽  
Protein Kinase Activity ◽  
Cyclin Dependent Kinase

ABSTRACT BRCA1 is a cell cycle-regulated nuclear protein that is phosphorylated mainly on serine and to a lesser extent on threonine residues. Changes in phosphorylation occur in response to cell cycle progression and DNA damage. Specifically, BRCA1 undergoes hyperphosphorylation during late G1 and S phases of the cell cycle. Here we report that BRCA1 is phosphorylated in vivo at serine 1497 (S1497), which is part of a cyclin-dependent kinase (CDK) consensus site. S1497 can be phosphorylated in vitro by CDK2-cyclin A or E. BRCA1 coimmunoprecipitates with an endogenous serine-threonine protein kinase activity that phosphorylates S1497 in vitro. This cellular kinase activity is sensitive to transfection of a dominant negative form of CDK2 as well as the application of the CDK inhibitors p21 and butyrolactone I but not p16. Furthermore, BRCA1 coimmunoprecipitates with CDK2 and cyclin A. These results suggest that the endogenous kinase activity is composed of CDK2-cyclin complexes, at least in part, concordant with the G1/S-specific increase in BRCA1 phosphorylation.

scholarly journals Multiple Functions of Fubp1 in Cell Cycle Progression and Cell Survival

Cells ◽  
2020 ◽  
Vol 9 (6) ◽  
pp. 1347 ◽  
Author(s):  
Mingyu Kang ◽  
Hyeon Ji Kim ◽  
Tae-Jun Kim ◽  
Jin-Seok Byun ◽  
Jae-Ho Lee ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Molecular Mechanisms ◽  
Expression Patterns ◽  
Metabolic Stress ◽  
Cyclin A ◽  
S Phase ◽  
Cycle Progression ◽  
Genes Encoding ◽  
Double Agent

The discovery of novel and critical genes implicated in malignant development is a topic of high interest in cancer research. Intriguingly, a group of genes named “double-agent” genes were reported to have both oncogenic and tumor-suppressive functions. To date, less than 100 “double-agent” genes have been documented. Fubp1 is a master transcriptional regulator of a subset of genes by interacting with a far upstream element (FUSE). Mounting evidence has collectively demonstrated both the oncogenic and tumor suppressive roles of Fubp1 and the debate regarding its roles in tumorigenesis has been around for several years. Therefore, the detailed molecular mechanisms of Fubp1 need to be determined in each context. In the present study, we showed that the Fubp1 protein level was enriched in the S phase and we identified that Fubp1 deficiency altered cell cycle progression, especially in the S phase, by downregulating the mRNA expression levels of Ccna genes encoding cyclin A. Although this Fubp1-cyclin A axis appears to exist in several types of tumors, Fubp1 showed heterogeneous expression patterns among various cancer tissues, suggesting it exhibits multiple and complicated functions in cancer development. In addition, we showed that Fubp1 deficiency confers survival advantages to cells against metabolic stress and anti-cancer drugs, suggesting that Fubp1 may play both positive and negative roles in malignant development.

scholarly journals Requirement for p27KIP1 in Retinoblastoma Protein-Mediated Senescence

2001 ◽  
Vol 21 (11) ◽  
pp. 3616-3631 ◽  
Author(s):  
Kamilah Alexander ◽  
Philip W. Hinds
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Arrest ◽  
Kinase Activity ◽  
Kinase Inhibitor ◽  
Cyclin E ◽  
Ectopic Expression ◽  
Retinoblastoma Protein ◽  
Morphological Transformation ◽  
Cycle Arrest

ABSTRACT In vivo and in vitro evidence indicate that cells do not divide indefinitely but instead stop growing and undergo a process termed cellular proliferative senescence. Very little is known about how senescence occurs, but there are several indications that the retinoblastoma protein (pRb) is involved, the most striking being that reintroduction of RB into RB −/−tumor cell lines induces senescence. In investigating the mechanism by which pRb induces senescence, we have found that pRb causes a posttranscriptional accumulation of the cyclin-dependent kinase inhibitor p27KIP1 that is accompanied by an increase in p27KIP1 specifically bound to cyclin E and a concomitant decrease in cyclin E-associated kinase activity. In contrast, pRb-related proteins p107 and p130, which also decrease cyclin E-kinase activity, do not cause an accumulation of p27KIP1 and induce senescence poorly. In addition, the use of pRb proteins mutated in the pocket domain demonstrates that pRb upregulation of p27KIP1 and senescence induction do not require the interaction of pRb with E2F. Furthermore, ectopic expression of p21CIP1 or p27KIP1 induces senescence but not the morphology change associated with pRb-mediated senescence, uncoupling senescence from the morphological transformation. Finally, the ability of pRb to maintain cell cycle arrest and induce senescence is reversibly abrogated by ablation of p27KIP1 expression. These findings suggest that prolonged cell cycle arrest through the persistent and specific inhibition of cdk2 activity by p27KIP1 is critical for pRb-induced senescence.

Rapamycin-induced G1 arrest in cycling B-CLL cells is associated with reduced expression of cyclin D3, cyclin E, cyclin A, and survivin

Blood ◽  
2003 ◽  
Vol 101 (1) ◽  
pp. 278-285 ◽  
Author(s):  
Thomas Decker ◽  
Susanne Hipp ◽  
Ingo Ringshausen ◽  
Christian Bogner ◽  
Madlene Oelsner ◽  
...  
Keyword(s):  
Cell Cycle ◽  
B Cells ◽  
Cell Cycle Regulation ◽  
Cell Cycle Progression ◽  
Cyclin E ◽  
Cyclin A ◽  
Cyclin D3 ◽  
G1 Arrest ◽  
Cycle Progression ◽  
Cycle Regulation

Abstract In B-cell chronic lymphocytic leukemia (B-CLL), malignant cells seem to be arrested in the G0/early G1phase of the cell cycle, and defective apoptosis might be involved in disease progression. However, increasing evidence exists that B-CLL is more than a disease consisting of slowly accumulating resting B cells: a proliferating pool of cells has been described in lymph nodes and bone marrow and might feed the accumulating pool in the blood. Rapamycin has been reported to inhibit cell cycle progression in a variety of cell types, including human B cells, and has shown activity against a broad range of human tumor cell lines. Therefore, we investigated the ability of rapamycin to block cell cycle progression in proliferating B-CLL cells. We have recently demonstrated that stimulation with CpG-oligonucleotides and interleukin-2 provides a valuable model for studying cell cycle regulation in malignant B cells. In our present study, we demonstrated that rapamycin induced cell cycle arrest in proliferating B-CLL cells and inhibited phosphorylation of p70s6 kinase (p70s6k). In contrast to previous reports on nonmalignant B cells, the expression of the cell cycle inhibitor p27 was not changed in rapamycin-treated leukemic cells. Treatment with rapamycin prevented retinoblastoma protein (RB) phosphorylation in B-CLL cells without affecting the expression of cyclin D2, but cyclin D3 was no longer detectable in rapamycin-treated B-CLL cells. In addition, rapamycin treatment inhibited cyclin-dependent kinase 2 activity by preventing up-regulation of cyclin E and cyclin A. Interestingly, survivin, which is expressed in the proliferation centers of B-CLL patients in vivo, is not up-regulated in rapamycin-treated cells. Therefore, rapamycin interferes with the expression of many critical molecules for cell cycle regulation in cycling B-CLL cells. We conclude from our study that rapamycin might be an attractive substance for therapy for B-CLL patients by inducing a G1 arrest in proliferating tumor cells.

scholarly journals SCAPER, a novel cyclin A–interacting protein that regulates cell cycle progression

2007 ◽  
Vol 178 (4) ◽  
pp. 621-633 ◽  
Author(s):  
William Y. Tsang ◽  
Leyu Wang ◽  
Zhihong Chen ◽  
Irma Sánchez ◽  
Brian David Dynlacht
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Regulatory Protein ◽  
Ectopic Expression ◽  
Cyclin A ◽  
Eukaryotic Cell ◽  
S Phase ◽  
Interacting Protein ◽  
M Phase

Cyclin A/Cdk2 plays an important role during S and G2/M phases of the eukaryotic cell cycle, but the mechanisms by which it regulates cell cycle events are not fully understood. We have biochemically purified and identified SCAPER, a novel protein that specifically interacts with cyclin A/Cdk2 in vivo. Its expression is cell cycle independent, and it associates with cyclin A/Cdk2 at multiple phases of the cell cycle. SCAPER localizes primarily to the endoplasmic reticulum. Ectopic expression of SCAPER sequesters cyclin A from the nucleus and results specifically in an accumulation of cells in M phase of the cell cycle. RNAi-mediated depletion of SCAPER decreases the cytoplasmic pool of cyclin A and delays the G1/S phase transition upon cell cycle re-entry from quiescence. We propose that SCAPER represents a novel cyclin A/Cdk2 regulatory protein that transiently maintains this kinase in the cytoplasm. SCAPER could play a role in distinguishing S phase– from M phase–specific functions of cyclin A/Cdk2.

scholarly journals c-Myc Is Necessary for DNA Damage-Induced Apoptosis in the G2 Phase of the Cell Cycle

2001 ◽  
Vol 21 (15) ◽  
pp. 4929-4937 ◽  
Author(s):  
Susumu Adachi ◽  
Alvaro J. Obaya ◽  
Zhiyong Han ◽  
Noemi Ramos-Desimone ◽  
James H. Wyche ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Cell Cycle Progression ◽  
Cellular Proliferation ◽  
Ectopic Expression ◽  
Cyclin A ◽  
Cycle Progression ◽  
Downstream Effector ◽  
Induced Apoptosis ◽  
Kinetics Of

ABSTRACT The c-myc proto-oncogene encodes a transcription factor that participates in the regulation of cellular proliferation, differentiation, and apoptosis. Ectopic overexpression of c-Myc has been shown to sensitize cells to apoptosis. We report here that cells lacking c-Myc activity due to disruption of the c-myc gene by targeted homologous recombination are defective in DNA damage-initiated apoptosis in the G2 phase of the cell cycle. The downstream effector of c-Myc is cyclin A, whose ectopic expression in c-myc −/− cells rescues the apoptosis defect. The kinetics of the G2 response indicate that the induction of cyclin A and the concomitant activation of Cdk2 represent an early step during commitment to apoptosis. In contrast, expression of cyclins E and D1 does not rescue the apoptosis defect, and apoptotic processes in G1 phase are not affected in c-myc −/− cells. These observations link DNA damage-induced apoptosis with cell cycle progression and implicate c-Myc in the functioning of a subset of these pathways.

Cyclin A transcriptional suppression is the major mechanism mediating homocysteine-induced endothelial cell growth inhibition

Blood ◽  
2002 ◽  
Vol 99 (3) ◽  
pp. 939-945 ◽  
Author(s):  
Hong Wang ◽  
XiaoHua Jiang ◽  
Fan Yang ◽  
Gary B. Chapman ◽  
William Durante ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Endothelial Cells ◽  
Cell Growth ◽  
Growth Inhibition ◽  
Cyclin D1 ◽  
Messenger Rna ◽  
Molecular Mechanisms ◽  
Kinase Activity ◽  
Cyclin A ◽  
Dependent Manner

Abstract Previously, it was reported that homocysteine (Hcy) specifically inhibits the growth of endothelial cells (ECs), suppresses Ras/mitogen-activated protein (MAP) signaling, and arrests cell growth at the G1/S transition of the cell cycle. The present study investigated the molecular mechanisms underlying this cell-cycle effect. Results showed that clinically relevant concentrations (50 μM) of Hcy significantly inhibited the expression of cyclin A messenger RNA (mRNA) in ECs in a dose- and time-dependent manner. G1/S-associated molecules that might account for this block were not changed, because Hcy did not affect mRNA and protein expression of cyclin D1 and cyclin E. Cyclin D1- and E-associated kinase activities were unchanged. In contrast, cyclin A–associated kinase activity and CDK2 kinase activity were markedly suppressed. Nuclear run-on assay demonstrated that Hcy decreased the transcription rate of the cyclin A gene but had no effect on the half-life of cyclin A mRNA. In transient transfection experiments, Hcy significantly inhibited cyclin A promoter activity in endothelial cells, but not in vascular smooth muscle cells. Finally, adenovirus-transduced cyclin A expression restored EC growth inhibition and overcame the S phase block imposed by Hcy. Taken together, these findings indicate that cyclin A is a critical functional target of Hcy-mediated EC growth inhibition.

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