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.

scholarly journals Growth Suppression by Acute PromyelocyticLeukemia-Associated Protein PLZF Is Mediated by Repression ofc-mycExpression

2003 ◽  
Vol 23 (24) ◽  
pp. 9375-9388 ◽  
Author(s):  
Melanie J. McConnell ◽  
Nathalie Chevallier ◽  
Windy Berkofsky-Fessler ◽  
Jena M. Giltnane ◽  
Rupal B. Malani ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Growth ◽  
Cell Cycle Arrest ◽  
Target Genes ◽  
Ectopic Expression ◽  
Growth Suppression ◽  
Quiescent State ◽  
Cycle Arrest

ABSTRACT The transcriptional repressor PLZF was identified by its translocation with retinoic acid receptor alpha in t(11;17) acute promyelocytic leukemia (APL). Ectopic expression of PLZF leads to cell cycle arrest and growth suppression, while disruption of normal PLZF function is implicated in the development of APL. To clarify the function of PLZF in cell growth and survival, we used an inducible PLZF cell line in a microarray analysis to identify the target genes repressed by PLZF. One prominent gene identified was c-myc. The array analysis demonstrated that repression of c-myc by PLZF led to a reduction in c-myc-activated transcripts and an increase in c-myc-repressed transcripts. Regulation of c-myc by PLZF was shown to be both direct and reversible. An interaction between PLZF and the c-myc promoter could be detected both in vitro and in vivo. PLZF repressed the wild-type c-myc promoter in a reporter assay, dependent on the integrity of the binding site identified in vitro. PLZF binding in vivo was coincident with a decrease in RNA polymerase occupation of the c-myc promoter, indicating that repression occurred via a reduction in the initiation of transcription. Finally, expression of c-myc reversed the cell cycle arrest induced by PLZF. These data suggest that PLZF expression maintains a cell in a quiescent state by repressing c-myc expression and preventing cell cycle progression. Loss of this repression through the translocation that occurs in t(11;17) would have serious consequences for cell growth control.

scholarly journals Cell Cycle Inhibition by FoxO Forkhead Transcription Factors Involves Downregulation of Cyclin D

2002 ◽  
Vol 22 (22) ◽  
pp. 7842-7852 ◽  
Author(s):  
Marc Schmidt ◽  
Sylvia Fernandez de Mattos ◽  
Armando van der Horst ◽  
Rob Klompmaker ◽  
Geert J. P. L Kops ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Transcription Factors ◽  
Protein Expression ◽  
Cell Cycle Arrest ◽  
Cellular Proliferation ◽  
Kinase Inhibitor ◽  
Ectopic Expression ◽  
Forkhead Transcription Factors ◽  
Cycle Arrest ◽  
Cell Cycle Inhibition

ABSTRACT The FoxO forkhead transcription factors FoxO4 (AFX), FoxO3a (FKHR.L1), and FoxO1a (FKHR) represent important physiological targets of phosphatidylinositol-3 kinase (PI3K)/protein kinase B (PKB) signaling. Overexpression or conditional activation of FoxO factors is able to antagonize many responses to constitutive PI3K/PKB activation including its effect on cellular proliferation. It was previously shown that the FoxO-induced cell cycle arrest is partially mediated by enhanced transcription and protein expression of the cyclin-dependent kinase inhibitor p27kip1 (R. H. Medema, G. J. Kops, J. L. Bos, and B. M. Burgering, Nature 404:782-787, 2000). Here we have identified a p27kip1-independent mechanism that plays an important role in the antiproliferative effect of FoxO factors. Forced expression or conditional activation of FoxO factors leads to reduced protein expression of the D-type cyclins D1 and D2 and is associated with an impaired capacity of CDK4 to phosphorylate and inactivate the S-phase repressor pRb. Downregulation of D-type cyclins involves a transcriptional repression mechanism and does not require p27kip1 function. Ectopic expression of cyclin D1 can partially overcome FoxO factor-induced cell cycle arrest, demonstrating that downregulation of D-type cyclins represents a physiologically relevant mechanism of FoxO-induced cell cycle inhibition.

Phosphorylation-deficient Stat1 inhibits retinoic acid–induced differentiation and cell cycle arrest in U-937 monoblasts

Blood ◽  
2000 ◽  
Vol 96 (8) ◽  
pp. 2870-2878
Author(s):  
Anna Dimberg ◽  
Kenneth Nilsson ◽  
Fredrik Öberg
Keyword(s):  
Cell Cycle ◽  
Retinoic Acid ◽  
Cell Cycle Arrest ◽  
Nuclear Translocation ◽  
Ectopic Expression ◽  
Leukemic Cell ◽  
Potent Inducer ◽  
Cycle Arrest

All-trans retinoic acid (ATRA) is a potent inducer of terminal differentiation of immature leukemic cell lines in vitro and of acute promyelocytic leukemia (APL) cells in vivo. Recent reports have shown that ATRA induces the expression of several interferon-regulated genes, including signal transducer and activator of transcription (Stat)1. To investigate the role of Stat1 activation in ATRA signaling, sublines were established for the human monoblastic cell line U-937 constitutively expressing wild-type or phosphorylation-defective Stat1, mutated in the conserved tyrosine 701 required for dimerization and nuclear translocation. Results showed that ATRA induction leads to activation of Stat1 by the phosphorylation of tyrosine 701 and subsequent nuclear translocation. Consistent with a functional importance of this activation, ectopic expression of Stat1Y701F suppressed ATRA-induced morphologic differentiation and expression of the monocytic surface markers CD11c and the granulocyte colony-stimulating factor receptor. Moreover, ATRA-induced growth arrest in the G0/G1phase of the cell cycle was inhibited by phosphorylation-deficient Stat1. Taken together, these results indicate that Stat1 is a key mediator of ATRA-induced cell cycle arrest and differentiation of U-937 cells.

scholarly journals Increased expression of senescence markers in cystic fibrosis airways

2013 ◽  
Vol 304 (6) ◽  
pp. L394-L400 ◽  
Author(s):  
Bernard M. Fischer ◽  
Jessica K. Wong ◽  
Simone Degan ◽  
Apparao B. Kummarapurugu ◽  
Shuo Zheng ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cystic Fibrosis ◽  
Cell Cycle Arrest ◽  
Airway Epithelium ◽  
Kinase Activity ◽  
Kinase Inhibitor ◽  
Airway Epithelial Cells ◽  
Cyclin Dependent Kinase ◽  
Control Subjects ◽  
Cycle Arrest

Cystic Fibrosis (CF) is a chronic lung disease characterized by chronic neutrophilic airway inflammation and increased levels of neutrophil elastase (NE) in the airways. We have previously reported that NE treatment triggers cell cycle arrest. Cell cycle arrest can lead to senescence, a complete loss of replicative capacity. Importantly, senescent cells can be proinflammatory and would perpetuate CF chronic inflammation. By immunohistochemistry, we evaluated whether airway sections from CF and control subjects expressed markers of senescence, including p16INK4a(p16), a cyclin-dependent kinase inhibitor, phospho-Histone H2A.X (γH2A.X), and phospho-checkpoint 2 kinase (phospho-Chk2), which are also DNA damage response markers. Compared with airway epithelium from control subjects, CF airway epithelium had increased levels of expression of all three senescence markers. We hypothesized that the high load of NE in the CF airway triggers epithelial senescence by upregulating expression of p16, which inhibits cyclin-dependent kinase 4 (CDK4). Normal human bronchial epithelial (NHBE) cells, cultured in air-liquid interface were treated with NE (0, 200, and 500 nM) to induce visible injury. Total cell lysates were collected and evaluated by Western analysis for p16 protein expression and CDK4 kinase activity. NE significantly increased p16 expression and decreased CDK4 kinase activity in NHBE cells. These results support the concept that NE triggers expression of senescence markers in CF airway epithelial cells.

Phosphorylation-deficient Stat1 inhibits retinoic acid–induced differentiation and cell cycle arrest in U-937 monoblasts

Blood ◽  
2000 ◽  
Vol 96 (8) ◽  
pp. 2870-2878 ◽  
Author(s):  
Anna Dimberg ◽  
Kenneth Nilsson ◽  
Fredrik Öberg
Keyword(s):  
Cell Cycle ◽  
Retinoic Acid ◽  
Cell Cycle Arrest ◽  
Nuclear Translocation ◽  
Ectopic Expression ◽  
Leukemic Cell ◽  
Potent Inducer ◽  
Cycle Arrest

Abstract All-trans retinoic acid (ATRA) is a potent inducer of terminal differentiation of immature leukemic cell lines in vitro and of acute promyelocytic leukemia (APL) cells in vivo. Recent reports have shown that ATRA induces the expression of several interferon-regulated genes, including signal transducer and activator of transcription (Stat)1. To investigate the role of Stat1 activation in ATRA signaling, sublines were established for the human monoblastic cell line U-937 constitutively expressing wild-type or phosphorylation-defective Stat1, mutated in the conserved tyrosine 701 required for dimerization and nuclear translocation. Results showed that ATRA induction leads to activation of Stat1 by the phosphorylation of tyrosine 701 and subsequent nuclear translocation. Consistent with a functional importance of this activation, ectopic expression of Stat1Y701F suppressed ATRA-induced morphologic differentiation and expression of the monocytic surface markers CD11c and the granulocyte colony-stimulating factor receptor. Moreover, ATRA-induced growth arrest in the G0/G1phase of the cell cycle was inhibited by phosphorylation-deficient Stat1. Taken together, these results indicate that Stat1 is a key mediator of ATRA-induced cell cycle arrest and differentiation of U-937 cells.

scholarly journals miR-34a directly targets tRNAiMet precursors and affects cellular proliferation, cell cycle, and apoptosis

2018 ◽  
Vol 115 (28) ◽  
pp. 7392-7397 ◽  
Author(s):  
Bo Wang ◽  
Dongping Li ◽  
Igor Kovalchuk ◽  
Ingrid J. Apel ◽  
Arul M. Chinnaiyan ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Proliferation ◽  
Cell Cycle Arrest ◽  
Breast Cancer Cells ◽  
Cellular Proliferation ◽  
Ectopic Expression ◽  
Breast Carcinogenesis ◽  
Argonaute 2 ◽  
Cycle Arrest

It remains unknown whether microRNA (miRNA/miR) can target transfer RNA (tRNA) molecules. Here we provide evidence that miR-34a physically interacts with and functionally targets tRNAiMet precursors in both in vitro pulldown and Argonaute 2 (AGO2) cleavage assays. We find that miR-34a suppresses breast carcinogenesis, at least in part by lowering the levels of tRNAiMet through AGO2-mediated repression, consequently inhibiting the proliferation of breast cancer cells and inducing cell cycle arrest and apoptosis. Moreover, miR-34a expression is negatively correlated with tRNAiMet levels in cancer cell lines. Furthermore, we find that tRNAiMet knockdown also reduces cell proliferation while inducing cell cycle arrest and apoptosis. Conversely, ectopic expression of tRNAiMet promotes cell proliferation, inhibits apoptosis, and accelerates the S/G2 transition. Moreover, the enforced expression of modified tRNAiMet completely restores the phenotypic changes induced by miR-34a. Our results demonstrate that miR-34a directly targets tRNAiMet precursors via AGO2-mediated cleavage, and that tRNAiMet functions as an oncogene, potentially representing a target molecule for therapeutic intervention.

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