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Evangelou K, Havaki S, Kotsinas A. E2F transcription factors and digestive system malignancies: How much do we know? World J Gastroenterol 2014; 20:10212-10216. [PMID: 25110451 PMCID: PMC4123353 DOI: 10.3748/wjg.v20.i29.10212] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2013] [Revised: 02/22/2014] [Accepted: 04/16/2014] [Indexed: 02/06/2023] Open
Abstract
The E2F proteins comprise a family of 8 members that function as transcription factors. They are key targets of the retinoblastoma protein (RB) and were initially divided into groups of activators and repressors. Accumulating data suggest that there is no specific role for each individual E2F member. Instead, each E2F can exert a variety of cellular effects, some of which represent opposing ones. For instance, specific E2Fs can activate transcription and repression, promote or hamper cell proliferation, augment or inhibit apoptosis, all being dependent on the cellular context. This complexity reflects the importance that these transcription factors have on a cell’s fate. Thus, delineating the specific role for each E2F member in specific malignancies, although not easy, is a challenging and continuously pursued task, especially in view of potential E2F targeted therapies. Therefore, several reviews are continuously trying to evaluate available data on E2F status in various malignancies. Such reviews have attempted to reach a consensus, often in the simplistic form of oncogenes or tumor suppressor genes for the E2Fs. However they frequently miss spatial and temporal alterations of these factors during tumor development, which should also be considered in conjunction with the status of the regulatory networks that these factors participate in. In the current ‘‘Letter to the Editor’’, we comment on the flaws, misinterpretations and omissions in one such review article published recently in the World Journal of Gastroenterology regarding the role of E2Fs in digestive system malignancies.
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Selective roles of E2Fs for ErbB2- and Myc-mediated mammary tumorigenesis. Oncogene 2013; 34:119-28. [PMID: 24276244 PMCID: PMC4032808 DOI: 10.1038/onc.2013.511] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2013] [Revised: 10/23/2013] [Accepted: 10/25/2013] [Indexed: 11/08/2022]
Abstract
Previous studies have demonstrated that cyclin D1, an upstream regulator of the Rb/E2F pathway, is an essential component of the ErbB2/Ras (but not the Wnt/Myc) oncogenic pathway in the mammary epithelium. However, the role of specific E2fs for ErbB2/Ras-mediated mammary tumorigenesis remains unknown. Here, we show that in the majority of mouse and human primary mammary carcinomas with ErbB2/HER2 overexpression, E2f3a is up-regulated, raising the possibility that E2F3a is a critical effector of the ErbB2 oncogenic signaling pathway in the mammary gland. We examined the consequence of ablating individual E2fs in mice on ErbB2-triggered mammary tumorigenesis in comparison to a comparable Myc-driven mammary tumor model. We found that loss of E2f1 or E2f3 led to a significant delay in tumor onset in both oncogenic models, whereas loss of E2f2 accelerated mammary tumorigenesis driven by Myc-overexpression. Furthermore, southern blot analysis of final tumors derived from conditionally deleted E2f3(-/loxP) mammary glands revealed that there is a selection against E2f3(-/-) cells from developing mammary carcinomas, and that such selection pressure is higher in the presence of ErbB2 activation than in the presence of Myc activation. Taken together, our data suggest oncogenic activities of E2F1 and E2F3 in ErbB2- or Myc-triggered mammary tumorigenesis, and a tumor suppressor role of E2F2 in Myc-mediated mammary tumorigenesis.
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A comprehensive modular map of molecular interactions in RB/E2F pathway. Mol Syst Biol 2008; 4:173. [PMID: 18319725 PMCID: PMC2290939 DOI: 10.1038/msb.2008.7] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2007] [Accepted: 01/23/2008] [Indexed: 12/16/2022] Open
Abstract
We present, here, a detailed and curated map of molecular interactions taking place in the regulation of the cell cycle by the retinoblastoma protein (RB/RB1). Deregulations and/or mutations in this pathway are observed in most human cancers. The map was created using Systems Biology Graphical Notation language with the help of CellDesigner 3.5 software and converted into BioPAX 2.0 pathway description format. In the current state the map contains 78 proteins, 176 genes, 99 protein complexes, 208 distinct chemical species and 165 chemical reactions. Overall, the map recapitulates biological facts from approximately 350 publications annotated in the diagram. The network contains more details about RB/E2F interaction network than existing large-scale pathway databases. Structural analysis of the interaction network revealed a modular organization of the network, which was used to elaborate a more summarized, higher-level representation of RB/E2F network. The simplification of complex networks opens the road for creating realistic computational models of this regulatory pathway.
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Giannakakis A, Sandaltzopoulos R, Greshock J, Liang S, Huang J, Hasegawa K, Li C, O'Brien-Jenkins A, Katsaros D, Weber BL, Simon C, Coukos G, Zhang L. miR-210 links hypoxia with cell cycle regulation and is deleted in human epithelial ovarian cancer. Cancer Biol Ther 2007; 7:255-64. [PMID: 18059191 PMCID: PMC3233968 DOI: 10.4161/cbt.7.2.5297] [Citation(s) in RCA: 275] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Tumor growth results in hypoxia. Understanding the mechanisms of gene expression reprogramming under hypoxia may provide important clues to cancer pathogenesis. We studied miRNA genes that are regulated by hypoxia in ovarian cancer cell lines by TaqMan miRNA assay containing 157 mature miRNAs. MiR-210 was the most prominent miRNA consistently stimulated under hypoxic conditions. We provide evidence for the involvement of the HIF signaling pathway in miR-210 regulation. Biocomputational analysis and in vitro assays demonstrated that e2f transcription factor 3 (e2f3), a key protein in cell cycle, is regulated by miR-210. E2F3 was further confirmed to be downregulated at the protein level upon induction of miR-210. Importantly, we found remarkably high frequency of miR-210 gene copy deletions in ovarian cancer patients (64%, n = 114) and that gene copy number correlates with miR-210 expression levels. Taken together, our results indicate that miR-210 plays a crucial role in tumor onset as a key regulator of the hypoxia response and provide evidence for a link between hypoxia and the regulation of cell cycle.
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Affiliation(s)
- Antonis Giannakakis
- Center for Research on Early Detection and Cure of Ovarian Cancer, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA
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Chen D, Opavsky R, Pacal M, Tanimoto N, Wenzel P, Seeliger MW, Leone G, Bremner R. Rb-mediated neuronal differentiation through cell-cycle-independent regulation of E2f3a. PLoS Biol 2007; 5:e179. [PMID: 17608565 PMCID: PMC1914394 DOI: 10.1371/journal.pbio.0050179] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2007] [Accepted: 05/08/2007] [Indexed: 01/19/2023] Open
Abstract
It has long been known that loss of the retinoblastoma protein (Rb) perturbs neural differentiation, but the underlying mechanism has never been solved. Rb absence impairs cell cycle exit and triggers death of some neurons, so differentiation defects may well be indirect. Indeed, we show that abnormalities in both differentiation and light-evoked electrophysiological responses in Rb-deficient retinal cells are rescued when ectopic division and apoptosis are blocked specifically by deleting E2f transcription factor (E2f) 1. However, comprehensive cell-type analysis of the rescued double-null retina exposed cell-cycle–independent differentiation defects specifically in starburst amacrine cells (SACs), cholinergic interneurons critical in direction selectivity and developmentally important rhythmic bursts. Typically, Rb is thought to block division by repressing E2fs, but to promote differentiation by potentiating tissue-specific factors. Remarkably, however, Rb promotes SAC differentiation by inhibiting E2f3 activity. Two E2f3 isoforms exist, and we find both in the developing retina, although intriguingly they show distinct subcellular distribution. E2f3b is thought to mediate Rb function in quiescent cells. However, in what is to our knowledge the first work to dissect E2f isoform function in vivo we show that Rb promotes SAC differentiation through E2f3a. These data reveal a mechanism through which Rb regulates neural differentiation directly, and, unexpectedly, it involves inhibition of E2f3a, not potentiation of tissue-specific factors. The retinoblastoma protein (Rb), an important tumor suppressor, blocks division and death by inhibiting the E2f transcription factor family. In contrast, Rb is thought to promote differentiation by potentiating tissue-specific transcription factors, although differentiation defects in Rb null cells could be an indirect consequence of E2f-driven division and death. Here, we resolve different mechanisms by which Rb controls division, death, and differentiation in the retina. Removing E2f1 rescues aberrant division of differentiating Rb-deficient retinal neurons, as well as death in cells prone to apoptosis, and restores both normal differentiation and function of major cell types, such as photoreceptors. However, Rb-deficient starburst amacrine neurons differentiate abnormally even when E2f1 is removed, providing an unequivocal example of a direct role for Rb in neuronal differentiation. Rather than potentiating a cell-specific factor, Rb promotes starburst cell differentiation by inhibiting another E2f, E2f3a. This cell-cycle–independent activity broadens the importance of the Rb–E2f pathway, and suggests we should reassess its role in the differentiation of other cell types. The retinoblastoma protein (Rb), a tumor suppressor, promotes the differentiation of starburst amacrine cells in the retina by inhibiting the transcription factor E2f3a, whereas it suppresses retinal cell division and death by inhibiting E2f1.
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Affiliation(s)
- Danian Chen
- Genetics and Development Division, Toronto Western Research Institute, University Health Network, University of Toronto, Ontario, Canada
- Department of Ophthalmology and Visual Science, University of Toronto, Ontario, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Ontario, Canada
| | - Rene Opavsky
- Human Cancer Genetics Program, Department of Molecular Virology, Immunology and Medical Genetics, Ohio State University, Columbus, Ohio, United States of America
- Department of Molecular Genetics, Ohio State University, Columbus, Ohio, United States of America
- Comprehensive Cancer Center, Ohio State University, Columbus, Ohio, United States of America
| | - Marek Pacal
- Genetics and Development Division, Toronto Western Research Institute, University Health Network, University of Toronto, Ontario, Canada
- Department of Ophthalmology and Visual Science, University of Toronto, Ontario, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Ontario, Canada
| | - Naoyuki Tanimoto
- Ocular Neurodegeneration Research Group, Centre for Ophthalmology, Institute for Ophthalmic Research, University of Tuebingen, Germany
| | - Pamela Wenzel
- Human Cancer Genetics Program, Department of Molecular Virology, Immunology and Medical Genetics, Ohio State University, Columbus, Ohio, United States of America
- Department of Molecular Genetics, Ohio State University, Columbus, Ohio, United States of America
- Comprehensive Cancer Center, Ohio State University, Columbus, Ohio, United States of America
| | - Mathias W Seeliger
- Ocular Neurodegeneration Research Group, Centre for Ophthalmology, Institute for Ophthalmic Research, University of Tuebingen, Germany
| | - Gustavo Leone
- Human Cancer Genetics Program, Department of Molecular Virology, Immunology and Medical Genetics, Ohio State University, Columbus, Ohio, United States of America
- Department of Molecular Genetics, Ohio State University, Columbus, Ohio, United States of America
- Comprehensive Cancer Center, Ohio State University, Columbus, Ohio, United States of America
| | - Rod Bremner
- Genetics and Development Division, Toronto Western Research Institute, University Health Network, University of Toronto, Ontario, Canada
- Department of Ophthalmology and Visual Science, University of Toronto, Ontario, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Ontario, Canada
- * To whom correspondence should be addressed. E-mail:
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Ma Y, Cress WD. Transcriptional upregulation of p57 (Kip2) by the cyclin-dependent kinase inhibitor BMS-387032 is E2F dependent and serves as a negative feedback loop limiting cytotoxicity. Oncogene 2006; 26:3532-40. [PMID: 17173074 PMCID: PMC2128050 DOI: 10.1038/sj.onc.1210143] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In spite of the fact that cyclin-dependent kinase (cdk) inhibiting drugs are potent transcriptional repressors, we discover that p57 (Kip2, CDKN1C) transcription is significantly upregulated by three small molecule cdk inhibitors, including BMS-387032. Treatment of MDA-MB-231 breast cancer cells with BMS-387032 led to a stabilization of the E2F1 protein that was accompanied by significant increases in the p57 mRNA and protein. This increase did not occur in an E2F1-deficient cell line. An E2F1-estrogen receptor fusion protein activated the endogenous p57 promoter in response to hydroxytamoxifen treatment in the presence of cycloheximide. Luciferase constructs driven by the p57 promoter verified that upregulation of p57 mRNA by BMS-387032 is transcriptional and dependent on E2F-binding sites in the promoter. Expression of exogenous p57 significantly decreased the fraction of cells in S phase. Furthermore, p57-deficient MDA-MB-231 cell lines were significantly more sensitive to BMS-387032-induced apoptosis than controls. The results presented in this manuscript demonstrate that small molecule cdk inhibitors transcriptionally activate p57 dependent upon E2F1 and that this activation in turn serves to limit E2F1's death-inducing activity.
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Affiliation(s)
- Y Ma
- Molecular Oncology Program, H Lee Moffitt Cancer Center and Research Institute, University of South Florida, College of Medicine, Tampa, FL 33612-9497, USA
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Rodriguez JM, Glozak MA, Ma Y, Cress WD. Bok, Bcl-2-related Ovarian Killer, Is Cell Cycle-regulated and Sensitizes to Stress-induced Apoptosis. J Biol Chem 2006; 281:22729-35. [PMID: 16772296 PMCID: PMC2134790 DOI: 10.1074/jbc.m604705200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Bok/Mtd (Bcl-2-related ovarian killer/Matador) is considered a pro-apoptotic member of the Bcl-2 family. Although identified in 1997, little is known about its biological role. We have previously demonstrated that Bok mRNA is up-regulated following E2F1 overexpression. In the current work, we demonstrate that Bok RNA is low in quiescent cells and rises upon serum stimulation. To determine the mechanism underlying this regulation, we cloned and characterized the mouse Bok promoter. We find that the mouse promoter contains a conserved E2F binding site (-43 to -49) and that a Bok promoter-driven luciferase reporter is activated by serum stimulation dependent on this site. Chromatin immunoprecipitation assays demonstrate that endogenous E2F1 and E2F3 associate with the Bok promoter in vivo. Surprisingly, we find that H1299 cells can stably express high levels of exogenous Bok protein. However, these cells are highly sensitive to chemotherapeutic drug treatment. Taken together these results demonstrate that Bok represents a cell cycle-regulated pro-apoptotic member of the Bcl-2 family, which may predispose growing cells to chemotherapeutic treatment.
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Affiliation(s)
- Jose M Rodriguez
- Molecular Oncology Program, H. Lee Moffitt Cancer Center and Research Institute, Department of Interdisciplinary Oncology, Cancer Biology Ph.D. Program, University of South Florida, Tampa, Florida 33612
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He W, Staples D, Smith C, Fisher C. Direct activation of cyclin-dependent kinase 2 by human papillomavirus E7. J Virol 2003; 77:10566-74. [PMID: 12970441 PMCID: PMC228519 DOI: 10.1128/jvi.77.19.10566-10574.2003] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2003] [Accepted: 07/10/2003] [Indexed: 12/16/2022] Open
Abstract
Addition of human papillomavirus (HPV) E7 CDK2/cyclin A or CDK2/cyclin E, purified from either insect cells or bacteria, dramatically upregulates histone H1 kinase activity. Activation is substrate specific, with a smaller effect noted for retinoblastoma protein (Rb). The CDK2 stimulatory activity is equivalent in high-risk (HPV type 16 [HPV16] and HPV31) and low-risk (HPV6b) E7. Mutational analyses of HPV16 E7 indicate that the major activity resides in amino acids 9 to 38, spanning CR1 and CR2, and does not require casein kinase II or Rb-binding domain functions. Synthetic peptides spanning HPV16 amino acid residues 9 to 38 also activate CDK2. Peptides containing this sequence that carry biotin on the carboxy terminus, as well as a photoactivated cross-linking group (benzophenone), also activate the complex and covalently associate with the CDK2/cyclin A complex in a specific manner requiring UV. Cross-linking studies that use protein monomers detect association of the E7 peptides with cyclin A but not CDK2. Together, our results indicate a novel mechanism whereby E7 promotes HPV replication by directly altering CDK2 activity and substrate specificity.
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Affiliation(s)
- Wanxia He
- Genomics-ID, Kalamazoo, Michigan 49006, USA
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Abstract
We have previously demonstrated that ectopic expression of E2F1 is sufficient to drive quiescent cells into S phase and that E2F1 expression can contribute to oncogenic transformation. Key target genes in this process include master regulators of the cell cycle, such as cyclin E, which regulates G(1) progression, and cyclin A, which is required for the initiation of DNA synthesis. In the present work, we present novel evidence that a second G(1) cyclin, cyclin D3, is also potently activated by E2F1. First, an estrogen receptor-E2F1 fusion protein (ER-E2F1) potently activates the endogenous cyclin D3 mRNA upon treatment with 4-hydroxytamoxifen, which induces nuclear accumulation of the otherwise cytosolic fusion protein. Furthermore, trans-activation of cyclin D3 by ER-E2F1 occurs even in the presence of the protein synthesis inhibitor cycloheximide and thus appears direct. Second, all of the growth-stimulatory members of the E2F family (E2F1, -2, and -3A) potently activate a cyclin D3 promoter reporter, whereas growth-restraining members of the family (E2F4, -5, and -6) have little effect. Third, recombinant E2F1 binds with high affinity to the cyclin D3 promoter in vitro. Fourth, chromatin immunoprecipitation assays demonstrate that endogenous E2F1 is associated with the cyclin D3 promoter in vivo. Finally, mapping experiments localize the essential E2F regulatory element of the cyclin D3 promoter to a noncanonical E2F site in the promoter between nucleotides -143 and -135 relative to the initiating methionine codon. We conclude that in addition to cyclins E and A, E2F family members can also activate one member of the D-type cyclins, further contributing to the ability of the stimulatory E2F family members to drive cellular proliferation.
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Affiliation(s)
- Yihong Ma
- Program in Molecular Oncology, H. Lee Moffitt Comprehensive Cancer Center, Tampa, Florida 33612, USA
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Okazaki K, Li J, Yu H, Fukui N, Sandell LJ. CCAAT/enhancer-binding proteins beta and delta mediate the repression of gene transcription of cartilage-derived retinoic acid-sensitive protein induced by interleukin-1 beta. J Biol Chem 2002; 277:31526-33. [PMID: 12072435 DOI: 10.1074/jbc.m202815200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Cartilage-derived retinoic acid-sensitive protein (CD-RAP) is a secreted protein expressed by chondrocytes; the expression is repressed by interleukin 1 beta (IL-1 beta). To investigate the transcriptional mechanism, by which CD-RAP expression is suppressed by IL-1 beta, deletion constructs of the mouse CD-RAP promoter were transfected into rat chondrocytes treated with or without IL-1 beta. The results revealed an IL-1 beta-responsive element located between -2138 and -2068 bp. As this element contains a CAAT/enhancer-binding protein (C/EBP) motif, the function of C/EBP beta and C/EBP delta was examined. IL-1 beta stimulated the expression of C/EBP beta and -delta, and the direct binding of C/EBP beta to the C/EBP motif was confirmed. The -2251-bp CD-RAP promoter activity was down-regulated by co-transfection with C/EBP expression vectors. Mutation of the C/EBP motif abolished the inhibitory response to IL-1 beta. Additionally, C/EBP expression vectors were found to down-regulate the construct containing the promoter and enhancer of the type II collagen gene. Finally, the enhancer factor, Sox9, was shown to bind adjacent to the C/EBP site competing with C/EBP binding. Taken together, these results suggest that C/EBP beta and -delta may play an important role in the IL-1 beta-induced repression of cartilage-specific proteins and that expression of matrix proteins will be influenced by the availability of positive and negative trans-acting factors.
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Affiliation(s)
- Ken Okazaki
- Department of Orthopaedic Surgery, Washington University School of Medicine at Barnes-Jewish Hospital, St. Louis, Missouri 63110, USA
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