scholarly journals Adenovirus E1A-Regulated Transcription Factor p120E4F Inhibits Cell Growth and Induces the Stabilization of the cdk Inhibitor p21WAF1

1998 ◽  
Vol 18 (1) ◽  
pp. 459-467 ◽  
Author(s):  
Elma R. Fernandes ◽  
Jun Yuan Zhang ◽  
Robert J. Rooney
Keyword(s):  
Transcription Factor ◽  
Cell Growth ◽  
Cell Cycle Progression ◽  
Kinase Activity ◽  
Fibroblast Cell ◽  
Binding Activity ◽  
Cdk Inhibitor ◽  
Cyclin D ◽  
Fourfold Increase ◽  
Adenovirus E1a

ABSTRACT Adenovirus E1A proteins influence cell growth and phenotype through physical interactions with cellular proteins that regulate basic processes such as cell cycle progression, DNA synthesis, and differentiation. p120E4F is a low-abundance cellular transcription factor that represses the adenovirus E4 promoter and is regulated by E1A, through a phosphorylation-induced reduction of its DNA binding activity, to permit activation of the E4 promoter during early infection. To determine the normal biological role of p120E4F, we assessed its ability to influence fibroblast cell growth and transformation. p120E4F suppressed NIH 3T3 fibroblast colony formation but had little effect when coexpressed with E1A and/or activated ras. Cells that overexpressed p120E4F were inhibited in their ability to enter S phase, had elevated levels of the cdk inhibitor p21 WAF1 , and reduced cyclin D-cdk4/6 kinase activity. The increase of p21 WAF1 levels occurred through a p53-independent posttranscriptional mechanism that included a three- to fourfold increase in the half-life of p21 WAF1 protein. Coexpression of activatedras with p120E4F stimulated cyclin D1 expression, elevated cyclin D-cdk4/6 kinase activity, and accelerated cell growth. These data suggest an important role for p120E4F in normal cell division and demonstrate that p21 WAF1 can be regulated by protein turnover.

Over-Expression of the P65 Subunit of NF-kB and Increased DNA Binding Activity of NF-kB Is a Common Event Both in Philadelphia Positive and Negative Chronic Myeloproliferative Disorders.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 4759-4759
Author(s):  
Alessandro Morotti ◽  
Veronica Ullmannova ◽  
Daniela Cilloni ◽  
Francesca Messa ◽  
Manuela Messa ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Transcription Factor ◽  
Cell Growth ◽  
Dna Binding ◽  
Western Blot ◽  
Cell Line ◽  
Myeloproliferative Disorders ◽  
Binding Activity ◽  
K562 Cell Line ◽  
Dna Binding Activity

Abstract The chronic myeloproliferative diseases (CMPD) are clonal disorders characterized by increased proliferation of cells from one or more myeloid lineages. The most common CMPD is Chronic Myeloid Leukemia which is characterized by the Philadelphia t(9;22) chromosomal translocation. The pathogenesis of Philadelphia negative CMPD is poorly understood, although the activation of tyrosine kinases appears to be an essential feature. For example, a constitutively activated PDGF receptor tyrosine kinase (FIP1L1-PDGFRA) is involved in some cases of the hypereosinophilic syndrome (HES), which is a form of CMPD characterized by increased proliferation of eosinophils. Different reports have demonstrated that the transcription factor NF-kB is essential for Bcr-Abl mediated transformation. NF-kB is a transcription factor which is composed of two subunits (generally p65 and p50). NF-kB dimers are retained into the cytoplasm by the inhibitory protein IkB. Different stimuli trigger the Serine phosphorylation of IkB and its proteolitc degradation. Free NF-kB translocates into the nucleus where it mediates the transcription of different genes involved in cellular proliferation, transformation and in apoptosis resistance. The aim of this work is to evaluate whether NF-kB is active both in Ph positive and in Ph negative CMPD. Bone marrow samples of 8 myeloproliferative disorders (3 Philadelphia positive CML, 3 Ph negative CML-like, 1 HES, 1 Idiopathic Myelofibrosis) have been collected at the diagnosis. The t(9;22) positive K562 cell line, derived form a CML blast crysis, has been used as a positive cellular control of the following experiments. Each samples have been lysed to obtain cytosolic and nuclear extracts. Western blot have been performed to evaluate the expression of the p65 subunit of NF-kB, the regulatory protein IkB and the antiapoptotic protein Bcl-2, whose expression may be regulated by NF-kB. Subsequently the DNA binding activity of NF-kB have been measured with an ELISA method. Our data shows that in all samples p65 is over-expressed both in the cytosol and in the nucleus respect to normal peripheral blood and normal bone marrow samples. The antiapoptotic Bcl-2 is also detectable by western blot in all pathological samples. In normal samples IkB is detected only in the cytosol and not in the nucleus while in CMPD samples it is expressed predominately in the nucleus. Basal DNA binding activity of NF-kB is increased in all the nuclear samples but not in normal samples. To assess whether NF-kB is directly involved in the control of cell growth and apoptosis, we have developed a stable K562 cell line expressing the super repressor IkB. The SR-IkB is a mutated for of IkB which can not be degraded causing an cytosolic sequestration of NF-kB. This stable cell line has a marked reduction of cell growth and is more sensible to the apoptotic stimuli. The data described above suggest that NF-kB activation may be a common mechanism of transformation in both Ph positive and negative CMPD and that its inhibition may be a powerful targeted molecular therapy.

scholarly journals TATA-Binding Protein-Like Protein (TLP/TRF2/TLF) Negatively Regulates Cell Cycle Progression and Is Required for the Stress-Mediated G2 Checkpoint

2003 ◽  
Vol 23 (12) ◽  
pp. 4107-4120 ◽  
Author(s):  
Miho Shimada ◽  
Tomoyoshi Nakadai ◽  
Taka-aki Tamura
Keyword(s):  
Cell Cycle ◽  
Transcription Factor ◽  
Stress Response ◽  
Cell Growth ◽  
Cell Cycle Progression ◽  
Binding Protein ◽  
Tata Binding Protein ◽  
Cycle Progression ◽  
Stress Dependent ◽  
Dt40 Cells

ABSTRACT The TATA-binding protein (TBP) is a universal transcription factor required for all of the eukaryotic RNA polymerases. In addition to TBP, metazoans commonly express a distantly TBP-related protein referred to as TBP-like protein (TLP/TRF2/TLF). Although the function of TLP in transcriptional regulation is not clear, it is known that TLP is required for embryogenesis and spermiogenesis. In the present study, we investigated the cellular functions of TLP by using TLP knockout chicken DT40 cells. TLP was found to be dispensable for cell growth. Unexpectedly, TLP-null cells exhibited a 20% elevated cell cycle progression rate that was attributed to shortening of the G2 phase. This indicates that TLP functions as a negative regulator of cell growth. Moreover, we found that TLP mainly existed in the cytoplasm and was translocated to the nucleus restrictedly at the G2 phase. Ectopic expression of nuclear localization signal-carrying TLP resulted in an increase (1.5-fold) in the proportion of cells remaining in the G2/M phase and apoptotic state. Notably, TLP-null cells showed an insufficient G2 checkpoint when the cells were exposed to stresses such as UV light and methyl methanesulfonate, and the population of apoptotic cells after stresses decreased to 40%. These phenomena in G2 checkpoint regulation are suggested to be p53 independent because p53 does not function in DT40 cells. Moreover, TLP was transiently translocated to the nucleus shortly (15 min) after stress treatment. The expression of several stress response and cell cycle regulatory genes drifted in a both TLP- and stress-dependent manner. Nucleus-translocating TLP is therefore thought to work by checking cell integrity through its transcription regulatory ability. TLP is considered to be a signal-transducing transcription factor in cell cycle regulation and stress response.

scholarly journals p27Kip1 Inhibits Cyclin D-Cyclin-Dependent Kinase 4 by Two Independent Modes

2008 ◽  
Vol 29 (4) ◽  
pp. 986-999 ◽  
Author(s):  
Arpita Ray ◽  
Melissa K. James ◽  
Stéphane Larochelle ◽  
Robert P. Fisher ◽  
Stacy W. Blain
Keyword(s):  
Cell Cycle ◽  
Active Site ◽  
Cell Cycle Progression ◽  
Kinase Activity ◽  
Growth Conditions ◽  
Cyclin D ◽  
Cyclin Dependent Kinase ◽  
Proliferating Cells ◽  
Cell Cycle Reentry

ABSTRACT Cell cycle progression is regulated by cyclin-dependent kinases (cdk's), which in turn are regulated by their interactions with stoichiometric inhibitors, such as p27Kip1. Although p27 associates with cyclin D-cyclin-dependent kinase 4 (cdk4) constitutively, whether or not it inhibits this complex is dependent on the absence or presence of a specific tyrosine phosphorylation that converts p27 from a bound inhibitor to a bound noninhibitor under different growth conditions. This phosphorylation occurs within the 3-10 helix of p27 and may dislodge the helix from cdk4's active site to allow ATP binding. Here we show that the interaction of nonphosphorylated p27 with cdk4 also prevents the activating phosphorylation of the T-loop by cyclin H-cdk7, the cdk-activating kinase (CAK). Even though the cyclin H-cdk7 complex is present and active in contact-arrested cells, p27's association with cyclin D-cdk4 prevents T-loop phosphorylation. When p27 is tyrosine phosphorylated in proliferating cells or in vitro with the tyrosine Y kinase Abl, phosphorylation of cdk4 by cyclin H-cdk7 is permitted, even without dissociation of p27. This suggests that upon release from the contact-arrested state, a temporal order for the reactivation of inactive p27-cyclin D-cdk4 complexes must exist: p27 must be Y phosphorylated first, directly permitting cyclin H-cdk7 phosphorylation of residue T172 and the consequent restoration of kinase activity. The non-Y-phosphorylated p27-cyclin D-cdk4 complex could be phosphorylated by purified Csk1, a single-subunit CAK from fission yeast, but was still inactive due to p27's occlusion of the active site. Thus, the two modes by which p27 inhibits cyclin D-cdk4 are independent and may reinforce one another to inhibit kinase activity in contact-arrested cells, while maintaining a reservoir of preformed complex that can be activated rapidly upon cell cycle reentry.

scholarly journals Down-Regulation of CK2α Leads toUp-Regulation of the Cyclin-Dependent Kinase Inhibitor p27KIP1 in Conditions Unfavorable for the Growth of Myoblast Cells

2020 ◽  
Vol 54 (6) ◽  
pp. 1177-1198
Keyword(s):  
Cell Cycle ◽  
Transcription Factor ◽  
Cell Growth ◽  
Knockout Mouse ◽  
Cell Cycle Progression ◽  
Molecular Mechanisms ◽  
Kinase Inhibitor ◽  
Cyclin Dependent Kinase ◽  
Cycle Progression ◽  
Cyclin Dependent Kinase Inhibitor

BACKGROUND/AIMS: Compelling evidence indicates that CK2α, which is one of the two catalytic isoforms of protein kinase CK2, is required for cell viability and plays an important role in cell proliferation and differentiation. While much is known on CK2 in the context of disease states, particularly cancer, its critical role in non-cancerous cell growth has not been extensively investigated. METHODS: In the present study, we have employed a cell line derived from rat heart with inducible down-regulation of CK2α and CK2α-knockout mouse tissue to identify CK2-mediated molecular mechanisms regulating cell growth. For this, we have performed Incucyte® live-cell analysis and applied flow cytometry, western blot, immunoprecipitation, immunohistochemistry, RT-qPCR and luciferase-based methods. RESULTS: Here, we show that lack of CK2α results in significantly delayed cell cycle progression through G1, inhibition of cyclin E-CDK2 complex, decreased phosphorylation of Rb protein at S795, and inactivation of E2F transcription factor. These events are accompanied by nuclear accumulation and up-regulation of the cyclin-dependent kinase inhibitor p27KIP1 in cells and CK2α-knockout mouse tissues. We found that increased levels of p27KIP1 are mainly attributable to post-translational modifications, namely phosphorylation at S10 and T197 amino acid residues catalyzed by Dyrk1B and AMPK, respectively, as silencing of FoxO3A transcription factor, which activates CDKN1B the gene coding for p27KIP1, does not result in markedly decreased expression levels of the corresponding protein. Interestingly, simultaneous silencing of CK2α and p27KIP1 significantly impairs cell cycle progression without increasing cell death. CONCLUSION: Taken together, our study sheds light on the molecular mechanisms controlling cell cycle progression through G1 phase when myoblasts proliferation potential is impaired by CK2α depletion. Our results suggest that elevated levels of p27KIP1,which follows CK2α depletion, contribute to delay the G1-to-S phase transition. Effects seen when p27KIP1 is down-regulated are independent of CK2α and reflect the protective role exerted by p27KIP1 under unfavorable cell growth conditions.

scholarly journals Inhibitors of the Transcription Factor STAT3 Decrease Growth and Induce Immune Response Genes in Models of Malignant Pleural Mesothelioma (MPM)

Cancers ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 7
Author(s):  
Moshe Lapidot ◽  
Abigail E. Case ◽  
Dalia Larios ◽  
Helen I. Gandler ◽  
Chengcheng Meng ◽  
...  
Keyword(s):  
Gene Expression ◽  
Immune Response ◽  
Transcription Factor ◽  
Cell Growth ◽  
Malignant Pleural Mesothelioma ◽  
Cell Cycle Progression ◽  
Pleural Mesothelioma ◽  
Loss Of Function ◽  
P53 Response

Malignant pleural mesothelioma (MPM) is an aggressive cancer defined by loss-of-function mutations with few therapeutic options. We examined the contribution of the transcription factor Signal transducer and activator of transcription 3 (STAT3) to cell growth and gene expression in preclinical models of MPM. STAT3 is activated in a variety of tumors and is thought to be required for the maintenance of cancer stem cells. Targeting STAT3 using specific small hairpin RNAs (shRNAs) or with the pharmacologic inhibitors atovaquone or pyrimethamine efficiently reduced cell growth in established cell lines and primary-derived lines while showing minimal effects in nontransformed LP9 mesothelial cells. Moreover, atovaquone significantly reduced viability and tumor growth in microfluidic cultures of primary MPM as well as in an in vivo xenotransplant model. Biological changes were linked to modulation of gene expression associated with STAT3 signaling, including cell cycle progression and altered p53 response. Reflecting the role of STAT3 in inducing localized immune suppression, using both atovaquone and pyrimethamine resulted in the modulation of immunoregulatory genes predicted to enhance an immune response, including upregulation of ICOSLG (Inducible T-Cell Costimulator Ligand or B7H2). Thus, our data strongly support a role for STAT3 inhibitors as anti-MPM therapeutics.

scholarly journals Serum induction of MEF2/RSRF expression in vascular myocytes is mediated at the level of translation.

1995 ◽  
Vol 15 (6) ◽  
pp. 3415-3423 ◽  
Author(s):  
E Suzuki ◽  
K Guo ◽  
M Kolman ◽  
Y T Yu ◽  
K Walsh
Keyword(s):  
Cell Cycle ◽  
Transcription Factor ◽  
Smooth Muscle ◽  
Dna Binding ◽  
Cell Cycle Progression ◽  
Vascular Tissue ◽  
Binding Activity ◽  
Cycle Progression ◽  
Dna Binding Activity ◽  
Vascular Myocytes

Vascular smooth muscle cells (VSMCs) reversibly coordinate the expression of VSMC-specific genes and the genes required for cell cycle progression. Here we demonstrate that isoforms of the MEF2/RSRF transcription factor are expressed in VSMCs and in vascular tissue. The MEF2A DNA-binding activity was upregulated when quiescent VSMCs were stimulated to proliferate with serum mitogens. The serum-induction of MEF2A DNA-binding activity occurred approximately 4 h following serum activation, and this correlated with an increase in the level of MEF2A protein without changes in the level of MEF2A mRNA or protein stability. These results indicate that MEF2A induction by serum is regulated at the level of translation.

scholarly journals Identification of Cyclin D3 as a Direct Target of E2A Using DamID

2004 ◽  
Vol 24 (19) ◽  
pp. 8790-8802 ◽  
Author(s):  
Siyuan Song ◽  
Jonathan Cooperman ◽  
Danielle L. Letting ◽  
Gerd A. Blobel ◽  
John Kim Choi
Keyword(s):  
Transcription Factor ◽  
Dna Binding ◽  
B Cell ◽  
Cell Cycle Progression ◽  
Gene Promoter ◽  
Cell Types ◽  
Binding Activity ◽  
Cyclin D3 ◽  
Fusion Construct ◽  
E Boxes

ABSTRACT The transcription factor E2A can promote precursor B cell expansion, promote G1 cell cycle progression, and induce the expressions of multiple G1-phase cyclins. To better understand the mechanism by which E2A induces these cyclins, we characterized the relationship between E2A and the cyclin D3 gene promoter. E2A transactivated the 1-kb promoter of cyclin D3, which contains two E boxes. However, deletion of the E boxes did not disrupt the transactivation by E2A, raising the possibility of indirect activation via another transcription factor or binding of E2A to non-E-box DNA elements. To distinguish between these two possibilities, promoter occupancy was examined using the DamID approach. A fusion construct composed of E2A and the Escherichia coli DNA adenosine methyltransferase (E47Dam) was subcloned in lentivirus vectors and used to transduce precursor B-cell and myeloid progenitor cell lines. In both cell types, specific adenosine methylation was identified at the cyclin D3 promoter. Chromatin immunoprecipitation analysis confirmed the DamID findings and localized the binding to within 1 kb of the two E boxes. The methylation by E47Dam was not disrupted by mutations in the E2A portion that block DNA binding. We conclude that E2A can be recruited to the cyclin D3 promoter independently of E boxes or E2A DNA binding activity.

scholarly journals Inhibition of cyclin-dependent kinases by p21.

1995 ◽  
Vol 6 (4) ◽  
pp. 387-400 ◽  
Author(s):  
J W Harper ◽  
S J Elledge ◽  
K Keyomarsi ◽  
B Dynlacht ◽  
L H Tsai ◽  
...  
Keyword(s):  
Cell Cycle Progression ◽  
Kinase Activity ◽  
Cyclin B ◽  
Cdk Inhibitor ◽  
Cyclin Dependent Kinase ◽  
Biochemical Mechanism ◽  
Inhibitory Potency ◽  
Cycle Progression ◽  
Cyclin Dependent Kinases ◽  
Multiple Molecules

p21Cip1 is a cyclin-dependent kinase (Cdk) inhibitor that is transcriptionally activated by p53 in response to DNA damage. We have explored the interaction of p21 with the currently known Cdks. p21 effectively inhibits Cdk2, Cdk3, Cdk4, and Cdk6 kinases (Ki 0.5-15 nM) but is much less effective toward Cdc2/cyclin B (Ki approximately 400 nM) and Cdk5/p35 (Ki > 2 microM), and does not associate with Cdk7/cyclin H. Overexpression of P21 arrests cells in G1. Thus, p21 is not a universal inhibitor of Cdks but displays selectivity for G1/S Cdk/cyclin complexes. Association of p21 with Cdks is greatly enhanced by cyclin binding. This property is shared by the structurally related inhibitor p27, suggesting a common biochemical mechanism for inhibition. With respect to Cdk2 and Cdk4 complexes, p27 shares the inhibitory potency of p21 but has slightly different kinase specificities. In normal diploid fibroblasts, the vast majority of active Cdk2 is associated with p21, but this active kinase can be fully inhibited by addition of exogenous p21. Reconstruction experiments using purified components indicate that multiple molecules of p21 can associate with Cdk/cyclin complexes and inactive complexes contain more than one molecule of p21. Together, these data suggest a model whereby p21 functions as an inhibitory buffer whose levels determine the threshold kinase activity required for cell cycle progression.

Sign in / Sign up

Export Citation Format

Share Document