51
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Hulf T, Bellosta P, Furrer M, Steiger D, Svensson D, Barbour A, Gallant P. Whole-genome analysis reveals a strong positional bias of conserved dMyc-dependent E-boxes. Mol Cell Biol 2005; 25:3401-10. [PMID: 15831447 PMCID: PMC1084277 DOI: 10.1128/mcb.25.9.3401-3410.2005] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Myc is a transcription factor with diverse biological effects ranging from the control of cellular proliferation and growth to the induction of apoptosis. Here we present a comprehensive analysis of the transcriptional targets of the sole Myc ortholog in Drosophila melanogaster, dMyc. We show that the genes that are down-regulated in response to dmyc inhibition are largely identical to those that are up-regulated after dMyc overexpression and that many of them play a role in growth control. The promoter regions of these targets are characterized by the presence of the E-box sequence CACGTG, a known dMyc binding site. Surprisingly, a large subgroup of (functionally related) dMyc targets contains a single E-box located within the first 100 nucleotides after the transcription start site. The relevance of this E-box and its position was confirmed by a mutational analysis of a selected dMyc target and by the observation of its evolutionary conservation in a different Drosophila species, Drosophila pseudoobscura. These observations raise the possibility that a subset of Myc targets share a distinct regulatory mechanism.
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Affiliation(s)
- Toby Hulf
- Universität Zürich, Zoologisches Institut, Winterthurerstrasse 190, Zürich 8057, Switzerland
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52
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Barrett JF, Lee LA, Dang CV. Stimulation of Myc transactivation by the TATA binding protein in promoter-reporter assays. BMC BIOCHEMISTRY 2005; 6:7. [PMID: 15876353 PMCID: PMC1145180 DOI: 10.1186/1471-2091-6-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/08/2005] [Accepted: 05/05/2005] [Indexed: 12/21/2022]
Abstract
Background The c-Myc oncogenic transcription factor heterodimerizes with Max, binds specific DNA sites and regulates transcription. The role of Myc in transcriptional activation involves its binding to TRRAP and histone acetylases; however, Myc's ability to activate transcription in transient transfection assays is remarkably weak (2 to 5 fold) when compared to other transcription factors. Since a deletion Myc mutant D106-143 and a substitution mutant W135E that weakly binds TRRAP are still fully active in transient transfection reporter assays and the TATA binding protein (TBP) has been reported to directly bind Myc, we sought to determine the effect of TBP on Myc transactivation. Results We report here a potent stimulation of Myc transactivation by TBP, allowing up to 35-fold transactivation of reporter constructs. Although promoters with an initiator (InR) element briskly responded to Myc transactivation, the presence of an InR significantly diminished the response to increasing amounts of TBP. We surmise from these findings that promoters containing both TATA and InR elements may control Myc responsive genes that require brisk increased expression within a narrow window of Myc levels, independent of TBP. In contrast, promoters driven by the TATA element only, may also respond to modulation of TBP activity or levels. Conclusion Our observations not only demonstrate that TBP is limiting for Myc transactivation in transient transfection experiments, but they also suggest that the inclusion of TBP in Myc transactivation assays may further improve the characterization of c-Myc target genes.
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Affiliation(s)
- John F Barrett
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
| | - Linda A Lee
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
| | - Chi V Dang
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
- The Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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53
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Brenner C, Deplus R, Didelot C, Loriot A, Viré E, De Smet C, Gutierrez A, Danovi D, Bernard D, Boon T, Giuseppe Pelicci P, Amati B, Kouzarides T, de Launoit Y, Di Croce L, Fuks F. Myc represses transcription through recruitment of DNA methyltransferase corepressor. EMBO J 2005; 24:336-46. [PMID: 15616584 PMCID: PMC545804 DOI: 10.1038/sj.emboj.7600509] [Citation(s) in RCA: 305] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2004] [Accepted: 11/12/2004] [Indexed: 12/19/2022] Open
Abstract
The Myc transcription factor is an essential mediator of cell growth and proliferation through its ability to both positively and negatively regulate transcription. The mechanisms by which Myc silences gene expression are not well understood. The current model is that Myc represses transcription through functional interference with transcriptional activators. Here we show that Myc binds the corepressor Dnmt3a and associates with DNA methyltransferase activity in vivo. In cells with reduced Dnmt3a levels, we observe specific reactivation of the Myc-repressed p21Cip1 gene, whereas the expression of Myc-activated E-boxes genes is unchanged. In addition, we find that Myc can target Dnmt3a selectively to the promoter of p21Cip1. Myc is known to be recruited to the p21Cip1 promoter by the DNA-binding factor Miz-1. Consistent with this, we observe that Myc and Dnmt3a form a ternary complex with Miz-1 and that this complex can corepress the p21Cip1 promoter. Finally, we show that DNA methylation is required for Myc-mediated repression of p21Cip1. Our data identify a new mechanism by which Myc can silence gene expression not only by passive functional interference but also by active recruitment of corepressor proteins. Furthermore, these findings suggest that targeting of DNA methyltransferases by transcription factors is a wide and general mechanism for the generation of specific DNA methylation patterns within a cell.
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Affiliation(s)
- Carmen Brenner
- Free University of Brussels, Faculty of Medicine, Laboratory of Molecular Virology, Brussels, Belgium
| | - Rachel Deplus
- Free University of Brussels, Faculty of Medicine, Laboratory of Molecular Virology, Brussels, Belgium
| | - Céline Didelot
- Free University of Brussels, Faculty of Medicine, Laboratory of Molecular Virology, Brussels, Belgium
| | - Axelle Loriot
- Ludwig Institute For Cancer Research, UCL, Brussels, Belgium
| | - Emmanuelle Viré
- Free University of Brussels, Faculty of Medicine, Laboratory of Molecular Virology, Brussels, Belgium
| | - Charles De Smet
- Ludwig Institute For Cancer Research, UCL, Brussels, Belgium
| | | | - Davide Danovi
- Department of Experimental Oncology, European Institute of Oncology, Milan, Italy
| | - David Bernard
- Free University of Brussels, Faculty of Medicine, Laboratory of Molecular Virology, Brussels, Belgium
| | - Thierry Boon
- Ludwig Institute For Cancer Research, UCL, Brussels, Belgium
| | | | - Bruno Amati
- Department of Experimental Oncology, European Institute of Oncology, Milan, Italy
| | - Tony Kouzarides
- Wellcome/Cancer Research UK Institute and Department of Pathology, University of Cambridge, Cambridge, UK
| | - Yvan de Launoit
- Free University of Brussels, Faculty of Medicine, Laboratory of Molecular Virology, Brussels, Belgium
- UMR 8117, CNRS Institut Pasteur de Lille, Université de Lille 1, Institut de Biologie de Lille, Lille, Cedex, France
| | - Luciano Di Croce
- ICREA and Center for Genomic Regulation, Barcelona, Spain
- Department of Experimental Oncology, European Institute of Oncology, Milan, Italy
| | - François Fuks
- Free University of Brussels, Faculty of Medicine, Laboratory of Molecular Virology, Brussels, Belgium
- Wellcome/Cancer Research UK Institute and Department of Pathology, University of Cambridge, Cambridge, UK
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54
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Farina A, Faiola F, Martinez E. Reconstitution of an E box-binding Myc:Max complex with recombinant full-length proteins expressed in Escherichia coli. Protein Expr Purif 2004; 34:215-22. [PMID: 15003254 PMCID: PMC4004042 DOI: 10.1016/j.pep.2003.11.021] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2003] [Revised: 11/12/2003] [Indexed: 11/26/2022]
Abstract
The c-Myc oncoprotein (Myc) is a DNA sequence-specific transcription factor that regulates transcription of a wide variety of genes involved in the control of cell growth, proliferation, differentiation, and apoptosis and its deregulated expression is implicated in many types of human cancer. Myc has an N-terminal transcription activation domain (TAD) that interacts with various coactivators and a C-terminal basic-helix-loop-helix-leucine zipper (bHLHZip) domain required for E box-specific DNA-binding and heterodimerization with its obligatory bHLHZip protein partner Max. The analysis of the mechanisms by which the Myc:Max complex regulates transcription at the molecular level in vitro has been hampered by the difficulty in obtaining highly pure recombinant Myc:Max heterodimers that contain full-length Myc with its complete TAD domain and that have sequence-specific DNA-binding activity. Here, we describe a simple method to reconstitute recombinant Myc:Max complexes from highly purified full-length proteins expressed in Escherichia coli that are soluble and highly active in E box-specific DNA-binding in vitro. The reconstituted Myc:Max complexes are stable and lack Max:Max homodimers. This procedure should facilitate the characterization of the DNA-binding and transcription activation functions of full-length Myc:Max complexes in vitro and in particular the role of Myc TAD-interacting cofactors and Myc:Max post-translational modifications.
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55
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Liu L, Li L, Rao JN, Zou T, Zhang HM, Boneva D, Bernard MS, Wang JY. Polyamine-modulated expression of c-myc plays a critical role in stimulation of normal intestinal epithelial cell proliferation. Am J Physiol Cell Physiol 2004; 288:C89-99. [PMID: 15355849 DOI: 10.1152/ajpcell.00326.2004] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The nuclear protein c-Myc is a transcription factor involved in the control of cell cycle. Our previous studies indicated that cellular polyamines are absolutely required for cell proliferation in crypts of small intestinal mucosa and that polyamines have the ability to stimulate expression of the c-myc gene. The current study went further to determine whether induced nuclear c-Myc plays a role in stimulation of cell proliferation by polyamines in intestinal crypt cells (IEC-6 line). Exposure of normal quiescent cells after 24-h serum deprivation to 5% dialyzed fetal bovine serum (dFBS) increased both cellular polyamines and expression of the c-myc gene. Increased c-Myc protein formed heterodimers with its binding partner, Max, and specifically bound to the Myc/Max binding site, which was associated with an increase in DNA synthesis. Depletion of cellular polyamines by pretreatment with alpha-difluoromethylornithine (DFMO) prevented increases in c-myc expression and DNA synthesis induced by 5% dFBS. c-Myc gene transcription and cell proliferation decreased in polyamine-deficient cells, whereas the natural polyamine spermidine given together with DFMO maintained c-myc gene expression and cell growth at normal levels. Disruption of c-myc expression using specific c-myc antisense oligomers not only inhibited normal cell growth (without DFMO) but also prevented the restoration of cell proliferation by spermidine in polyamine-deficient cells. Ectopic expression of wild-type c-myc by recombinant adenoviral vector containing c-myc cDNA increased cell growth. These results indicate that polyamine-induced nuclear c-Myc interacts with Max, binds to the specific DNA sequence, and plays an important role in stimulation of normal intestinal epithelial cell proliferation.
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Affiliation(s)
- Lan Liu
- Department of Surgery, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA
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56
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Thomas-Tikhonenko A, Viard-Leveugle I, Dews M, Wehrli P, Sevignani C, Yu D, Ricci S, el-Deiry W, Aronow B, Kaya G, Saurat JH, French LE. Myc-transformed epithelial cells down-regulate clusterin, which inhibits their growth in vitro and carcinogenesis in vivo. Cancer Res 2004; 64:3126-36. [PMID: 15126350 DOI: 10.1158/0008-5472.can-03-1953] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Effective treatment of malignant carcinomas requires identification of proteins regulating epithelial cell proliferation. To this end, we compared gene expression profiles in murine colonocytes and their c-Myc-transformed counterparts, which possess enhanced proliferative potential. A surprisingly short list of deregulated genes included the cDNA for clusterin, an extracellular glycoprotein without a firmly established function. We had previously demonstrated that in organs such as skin, clusterin expression is restricted to differentiating but not proliferating cell layers, suggesting a possible negative role in cell division. Indeed, its transient overexpression in Myc-transduced colonocytes decreased cell accumulation. Furthermore, clusterin was down-regulated in rapidly dividing human keratinocytes infected with a Myc-encoding adenovirus. Its knockdown via antisense RNA in neoplastic epidermoid cells enhanced proliferation. Finally, recombinant human clusterin suppressed, in a dose-dependent manner, DNA replication in keratinocytes and other cells of epithelial origin. Thus, clusterin appears to be an inhibitor of epithelial cell proliferation in vitro. To determine whether it also affects neoplastic growth in vivo, we compared wild-type and clusterin-null mice with respect to their sensitivity to 7, 12-dimethylbenz(a)anthracene /12-Otetradecanoylphorbol-13-acetate (DMBA/TPA)-induced skin carcinogenesis. We observed that the mean number of papillomas/mouse was higher in clusterin-null animals. Moreover, these papillomas did not regress as readily as in wild-type mice and persisted beyond week 35. The rate of progression toward squamous cell carcinoma was not altered, although those developing in clusterin-null mice were on average better differentiated. These data suggest that clusterin not only suppresses epithelial cell proliferation in vitro but also interferes with the promotion stage of skin carcinogenesis.
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Affiliation(s)
- Andrei Thomas-Tikhonenko
- Department of Pathobiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6051, USA
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57
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Affiliation(s)
- Bruno Amati
- Department of Experimental Oncology, European Institute of Oncology, Via Ripamonti 435, 20141 Milan, Italy.
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58
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Abstract
Translation initiation is important for the regulation of both cell growth and cell division. It is uniquely poised to coordinate overall cell proliferation by its effects on both growth and division. A number of translation initiation factors are transcriptional targets of c-myc in a variety of assays. In particular, the mRNA cap-binding protein eIF4E has a myc-binding sequence in its promoter that is myc responsive in reporter assays and contains a high-affinity myc-binding site in chromosome immunoprecipitation experiments. Several differential expression screens have demonstrated altered levels of eIF4E, along with several other translation initiation factors, in response to alterations of c-myc levels. The potential for eIF4E and other translational control elements to mediate myc's transforming functions is particularly important because eIF4E is itself a known oncogenic factor. The ability of translation initiation factors to affect both cell division control and cell growth control coincides with myc's remarkable effects on both cell growth and cell division.
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Affiliation(s)
- Emmett V Schmidt
- Cancer Research Center at Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA.
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59
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Woo CW, Lucarelli E, Thiele CJ. NGF activation of TrkA decreases N-myc expression via MAPK path leading to a decrease in neuroblastoma cell number. Oncogene 2004; 23:1522-30. [PMID: 14691455 DOI: 10.1038/sj.onc.1207267] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In neuroblastoma (NB), expression of the TrkA receptor is correlated with good prognosis while N-myc amplification is correlated with poor prognosis. Decreased N-myc levels are key to controlling growth and inducing differentiation in NB cells. In this report, we detail mechanisms by which nerve growth factor (NGF) decreases N-myc levels in TrkA-transfected NB cells and its effect on NB cell proliferation. NGF induced a decrease in N-myc mRNA within 1 h of treatment that occurred in the presence of cycloheximide. The stability of N-myc mRNA was not affected by NGF, indicating a transcriptional control of N-myc mRNA by NGF. NGF but not brain-derived neurotrophic factor (BDNF) decreased N-myc levels demonstrating that p75 alone was not involved. The NGF-induced decrease in N-myc expression was blocked by the Trk tyrosine kinase (TK) antagonist K252a indicating that signals transduced by Trk TK downstream targets were involved. Pharmacologic inhibitors implicated the mitogen-activated protein kinase (MAPK) path. This was supported by the finding that expression of a constitutively activated component of the MAPK path, MAPK kinase (MEK), decreased N-myc levels. Alterations in the level of N-myc are known to alter NB cell cycle progression by affecting the levels of E2Fs and p27(kip1). Consistent with these findings, NGF decreased NB cell number and decreased cyclin E-dependent kinase activity via an increase in p27(kip1). Thus, our results indicate that the MAP kinase is selectively involved in the NGF-induced N-myc downregulation through a transcriptional mechanism. Furthermore, NGF affects the time required for 15N TrkA cells to complete a replication cycle by decreasing N-myc, E2Fs, cyclin E kinase activity and increasing p27(kip1) binding to cyclin E kinase.
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Affiliation(s)
- Chan-Wook Woo
- Cell & Molecular Biology Section, Pediatric Oncology Branch, NCI, NIH, Bethesda, MD 20892, USA
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60
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Maines JZ, Stevens LM, Tong X, Stein D. Drosophila dMyc is required for ovary cell growth and endoreplication. Development 2004; 131:775-86. [PMID: 14724122 DOI: 10.1242/dev.00932] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Although the Myc oncogene has long been known to play a role in many human cancers, the mechanisms that mediate its effects in both normal cells and cancer cells are not fully understood. We have initiated a genetic analysis of the Drosophila homolog of the Myc oncoprotein (dMyc),which is encoded by the dm locus. We carried out mosaic analysis to elucidate the functions of dMyc in the germline and somatic cells of the ovary during oogenesis, a process that involves cell proliferation, differentiation and growth. Germline and somatic follicle cells mutant for dm exhibit a profound decrease in their ability to grow and to carry out endoreplication,a modified cell cycle in which DNA replication occurs in the absence of cell division. In contrast to its dramatic effects on growth and endoreplication,dMyc is dispensable for the mitotic division cycles of both germline and somatic components of the ovary. Surprisingly, despite their impaired ability to endoreplicate, dm mutant follicle cells appeared to carry out chorion gene amplification normally. Furthermore, in germline cysts in which the dm mutant cells comprised only a subset of the 16-cell cluster,we observed strictly cell-autonomous growth defects. However, in cases in which the entire germline cyst or the whole follicular epithelium was mutant for dm, the growth of the entire follicle, including the wild-type cells, was delayed. This observation indicates the existence of a signaling mechanism that acts to coordinate the growth rates of the germline and somatic components of the follicle. In summary, dMyc plays an essential role in promoting the rapid growth that must occur in both the germline and the surrounding follicle cells for oogenesis to proceed.
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Affiliation(s)
- Jean Z Maines
- Institute for Cellular and Molecular Biology, The University of Texas at Austin, 1 University Station C-0930, Austin, TX 78712-0253, USA
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61
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Nakahara T, Hashimoto K, Hirano M, Koll M, Martin CR, Preedy VR. Acute and chronic effects of alcohol exposure on skeletal muscle c-myc, p53, and Bcl-2 mRNA expression. Am J Physiol Endocrinol Metab 2003; 285:E1273-81. [PMID: 12876071 DOI: 10.1152/ajpendo.00019.2003] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Skeletal muscle atrophy is a common feature in alcoholism that affects up to two-thirds of alcohol misusers, and women appear to be particularly susceptible. There is also some evidence to suggest that malnutrition exacerbates the effects of alcohol on muscle. However, the mechanisms responsible for the myopathy remain elusive, and some studies suggest that acetaldehyde, rather than alcohol, is the principal pathogenic perturbant. Previous reports on rats dosed acutely with ethanol (<24 h) have suggested that increased proto-oncogene expression (i.e., c-myc) may be a causative process, possibly via activating preapoptotic or transcriptional pathways. We hypothesized that 1) increases in c-myc mRNA levels also occur in muscle exposed chronically to alcohol, 2) muscle of female rats is more sensitive than that from male rats, 3) raising acetaldehyde will also increase c-myc, 4) prior starvation will cause further increases in c-myc mRNA expression in response to ethanol, and 5) other genes involved in apoptosis (i.e., p53 and Bcl-2) would also be affected by alcohol. To test this, we measured c-myc mRNA levels in skeletal muscle of rats dosed either chronically (6-7 wk; ethanol as 35% of total dietary energy) or acutely (2.5 h; ethanol as 75 mmol/kg body wt ip) with ethanol. All experiments were carried out in male Wistar rats (approximately 0.1-0.15 kg body wt) except the study that examined gender susceptibility in male and female rats. At the end of the studies, rats were killed, and c-myc, p53, and Bcl-2 mRNA was analyzed in skeletal muscle by RT-PCR with an endogenous internal standard, GAPDH. The results showed that 1) in male rats fed ethanol chronically, there were no increases in c-myc mRNA; 2) increases, however, occurred in c-myc mRNA in muscle from female rats fed ethanol chronically; 3) raising endogenous acetaldehyde with cyanamide increased c-myc mRNA in acute studies; 4) starvation per se increased c-myc mRNA levels and at 1 day potentiated the acute effects of ethanol, indicative of a sensitization response; 5) the only effect seen with p53 mRNA levels was a decrease in muscle of rats starved for 1 day compared with fed rats, and there was no statistically significant effect on Bcl-2 mRNA in any of the experimental conditions. The increases in c-myc may well represent a preapoptotic effect, or even a nonspecific cellular stress response to alcohol and/or acetaldehyde. These data are important in our understanding of a common muscle pathology induced by alcohol.
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Affiliation(s)
- Tatsuo Nakahara
- Department of Chemistry, Faculty of Science, Kyushu University Ropponmatsu, Fukuoka 810-8560, Japan
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62
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Löhr K, Hartmann O, Schäfer H, Dobbelstein M. Mutual interference of adenovirus infection and myc expression. J Virol 2003; 77:7936-44. [PMID: 12829833 PMCID: PMC161938 DOI: 10.1128/jvi.77.14.7936-7944.2003] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
During infection with adenovirus, massive changes in the transcription of virus genes are observed, suggesting that the expression of cellular genes may also be modulated. To characterize the levels of cellular RNA species in infected cells, cDNA arrays were screened 24 h after infection of HeLa cells with wild-type adenovirus type 5, strain dl309. Despite complete transduction of the cells, fewer than 20 cellular genes (out of 4,600 analyzed and 1,200 found detectable and expressed above background) were altered more than threefold in their corresponding RNA levels compared to mock-infected cells. In particular, the expression of the myc oncogene was reduced at the mRNA level. This reduction was dependent on the replication of virus DNA and partially dependent on the presence of the adenovirus gene products E1B-55 kDa and E4orf6, but not E4orf3. On the other hand, MYC protein had an increased half-life in infected cells, resulting in roughly constant steady-state protein levels. The adenovirus E1A gene product is necessary and sufficient to stabilize MYC. Overexpressed MYC inhibited adenovirus replication and the proper formation of the virus replication centers. We conclude that adenovirus infection leads to the stabilization of MYC, perhaps as a side effect of E1A activities. On the other hand, myc mRNA levels are negatively regulated during adenovirus infection, and this may avoid the detrimental effect of excessive MYC on adenovirus replication.
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Affiliation(s)
- Kristina Löhr
- Institut für Virologie, Philipps-Universität Marburg, Robert Koch Strasse 17, 35037 Marburg, Germany
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63
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Frank SR, Parisi T, Taubert S, Fernandez P, Fuchs M, Chan HM, Livingston DM, Amati B. MYC recruits the TIP60 histone acetyltransferase complex to chromatin. EMBO Rep 2003; 4:575-80. [PMID: 12776177 PMCID: PMC1319201 DOI: 10.1038/sj.embor.embor861] [Citation(s) in RCA: 287] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2002] [Revised: 04/15/2003] [Accepted: 04/16/2003] [Indexed: 02/08/2023] Open
Abstract
The transcription factor MYC binds specific DNA sites in cellular chromatin and induces the acetylation of histones H3 and H4. However, the histone acetyltransferases (HATs) that are responsible for these modifications have not yet been identified. MYC associates with TRRAP, a subunit of distinct macromolecular complexes that contain the HATs GCN5/PCAF or TIP60. Although the association of MYC with GCN5 has been shown, its interaction with TIP60 has never been analysed. Here, we show that MYC associates with TIP60 and recruits it to chromatin in vivo with four other components of the TIP60 complex: TRRAP, p400, TIP48 and TIP49. Overexpression of enzymatically inactive TIP60 delays the MYC-induced acetylation of histone H4, and also reduces the level of MYC binding to chromatin. Thus, the TIP60 HAT complex is recruited to MYC-target genes and, probably with other other HATs, contributes to histone acetylation in response to mitogenic signals.
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Affiliation(s)
- Scott R. Frank
- DNAX Research Institute, 901 California Avenue, Palo Alto, California 94304, USA
| | - Tiziana Parisi
- DNAX Research Institute, 901 California Avenue, Palo Alto, California 94304, USA
| | - Stefan Taubert
- DNAX Research Institute, 901 California Avenue, Palo Alto, California 94304, USA
| | - Paula Fernandez
- DNAX Research Institute, 901 California Avenue, Palo Alto, California 94304, USA
- Present address: University of Bern, Länggassstrasse 122, CH-3001 Bern, Switzerland
| | - Miriam Fuchs
- Dana–Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Ho-Man Chan
- Dana–Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - David M. Livingston
- Dana–Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Bruno Amati
- DNAX Research Institute, 901 California Avenue, Palo Alto, California 94304, USA
- Department of Experimental Oncology, European Institute of Oncology, Via Ripamonti 435, 20141 Milan, Italy
- Tel: +39 02 57 489 824; Fax: +39 02 57 489 851;
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64
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Liu X, Tesfai J, Evrard YA, Dent SYR, Martinez E. c-Myc transformation domain recruits the human STAGA complex and requires TRRAP and GCN5 acetylase activity for transcription activation. J Biol Chem 2003; 278:20405-12. [PMID: 12660246 PMCID: PMC4031917 DOI: 10.1074/jbc.m211795200] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Deregulation of the c-Myc oncoprotein (Myc) is implicated in many types of cancer. Myc is a sequence-specific transcription factor that regulates transcription of genes involved in the control of cell proliferation and apoptosis via mechanisms that are still poorly understood. Cell transformation by Myc involves its association with the transformation-transactivation domain-associated protein (TRRAP) and the human histone acetyltransferase (HAT) GCN5. TRRAP and GCN5 are components of a variety of shared and distinct multiprotein HAT complexes with diverse functions. Myc induces TRRAP recruitment and histone hyperacetylation at specific Myc-activated genes in vivo. However, the identity of the HAT complexes recruited by Myc and the roles of TRRAP and GCN5 in Myc function are still unclear. Here we show that Myc co-recruits TRRAP and GCN5 via direct physical interactions of its N-terminal activation/transformation domain with the human STAGA (SPT3-TAF-GCN5 acetylase) coactivator complex. We demonstrate that GCN5 and TRRAP cooperate to enhance transcription activation by the N-terminal activation domain of Myc in vivo and that this synergy requires both the SPT3/GCN5 interaction domain of TRRAP and the HAT activity of GCN5. Thus, TRRAP might function as an adaptor within the STAGA complex, which helps recruit GCN5 HAT activity to Myc during transcription activation.
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Affiliation(s)
- Xiaohui Liu
- Department of Biochemistry, University of California, Riverside, California 92521
| | - Jerusalem Tesfai
- Department of Biochemistry, University of California, Riverside, California 92521
| | - Yvonne A. Evrard
- Department of Biochemistry and Molecular Biology, University of Texas, M. D. Anderson Cancer Center, Houston, Texas 77030
| | - Sharon Y. R. Dent
- Department of Biochemistry and Molecular Biology, University of Texas, M. D. Anderson Cancer Center, Houston, Texas 77030
| | - Ernest Martinez
- Department of Biochemistry, University of California, Riverside, California 92521
- To whom correspondence should be addressed: Dept. of Biochemistry, University of California, Riverside, CA 92521. Tel.: 909-787-2031; Fax: 909-787-4434;
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65
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Vervoorts J, Lüscher-Firzlaff JM, Rottmann S, Lilischkis R, Walsemann G, Dohmann K, Austen M, Lüscher B. Stimulation of c-MYC transcriptional activity and acetylation by recruitment of the cofactor CBP. EMBO Rep 2003; 4:484-90. [PMID: 12776737 PMCID: PMC1319176 DOI: 10.1038/sj.embor.embor821] [Citation(s) in RCA: 208] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The c-MYC oncoprotein regulates various aspects of cell behaviour by modulating gene expression. Here, we report the identification of the cAMP-response-element-binding protein (CBP) as a novel c-MYC binding partner. The two proteins interact both in vitro and in cells, and CBP binds to the carboxy-terminal region of c-MYC. Importantly, CBP, as well as p300, is associated with E-box-containing promoter regions of genes that are regulated by c-MYC. Furthermore, c-MYC and CBP/p300 function synergistically in the activation of reporter-gene constructs. Thus, CBP and p300 function as positive cofactors for c-MYC. In addition, c-MYC is acetylated in cells. This modification does not require MYC box II, suggesting that it is independent of TRRAP complexes. Instead, CBP acetylates c-MYC in vitro, and co-expression of CBP with c-MYC stimulates in vivo acetylation. Functionally, this results in a decrease in ubiquitination and stabilization of c-MYC proteins. Thus, CBP and p300 are novel functional binding partners of c-MYC.
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Affiliation(s)
- Jörg Vervoorts
- Institut für Molekularbiologie, Medizinische Hochschule Hannover, Carl-Neubergstrasse 1, 30625 Hannover, Germany
| | - Juliane M. Lüscher-Firzlaff
- Abteilung Biochemie und Molekularbiologie, Institut für Biochemie, Klinikum der RWTH, Pauwelsstrasse 30, 52057 Aachen, Germany
| | - Sabine Rottmann
- Abteilung Biochemie und Molekularbiologie, Institut für Biochemie, Klinikum der RWTH, Pauwelsstrasse 30, 52057 Aachen, Germany
| | - Richard Lilischkis
- Abteilung Biochemie und Molekularbiologie, Institut für Biochemie, Klinikum der RWTH, Pauwelsstrasse 30, 52057 Aachen, Germany
| | - Gesa Walsemann
- Abteilung Biochemie und Molekularbiologie, Institut für Biochemie, Klinikum der RWTH, Pauwelsstrasse 30, 52057 Aachen, Germany
| | - Karen Dohmann
- Institut für Molekularbiologie, Medizinische Hochschule Hannover, Carl-Neubergstrasse 1, 30625 Hannover, Germany
- Present address: Institut für Mikrobiologie und Tierseuche, Tierärztliche Hochschule, Bischofsholer Damm 15, 30173 Hannover, Germany
| | - Matthias Austen
- Institut für Molekularbiologie, Medizinische Hochschule Hannover, Carl-Neubergstrasse 1, 30625 Hannover, Germany
- Present address: Develogen AG, Rudolf-Wissellstrasse 28, 37079 Göttingen, Germany
| | - Bernhard Lüscher
- Abteilung Biochemie und Molekularbiologie, Institut für Biochemie, Klinikum der RWTH, Pauwelsstrasse 30, 52057 Aachen, Germany
- Tel: +49 241 8088850; Fax: +49 241 8082427;
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66
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Orian A, van Steensel B, Delrow J, Bussemaker HJ, Li L, Sawado T, Williams E, Loo LWM, Cowley SM, Yost C, Pierce S, Edgar BA, Parkhurst SM, Eisenman RN. Genomic binding by the Drosophila Myc, Max, Mad/Mnt transcription factor network. Genes Dev 2003; 17:1101-14. [PMID: 12695332 PMCID: PMC196053 DOI: 10.1101/gad.1066903] [Citation(s) in RCA: 317] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The Myc/Max/Mad transcription factor network is critically involved in cell behavior; however, there is relatively little information on its genomic binding sites. We have employed the DamID method to carry out global genomic mapping of the Drosophila Myc, Max, and Mad/Mnt proteins. Each protein was tethered to Escherichia coli DNA adenine-methyltransferase (Dam) permitting methylation proximal to in vivo binding sites in Kc cells. Microarray analyses of methylated DNA fragments reveals binding to multiple loci on all major Drosophila chromosomes. This approach also reveals dynamic interactions among network members as we find that increased levels of dMax influence the extent of dMyc, but not dMnt, binding. Computer analysis using the REDUCE algorithm demonstrates that binding regions correlate with the presence of E-boxes, CG repeats, and other sequence motifs. The surprisingly large number of directly bound loci ( approximately 15% of coding regions) suggests that the network interacts widely with the genome. Furthermore, we employ microarray expression analysis to demonstrate that hundreds of DamID-binding loci correspond to genes whose expression is directly regulated by dMyc in larvae. These results suggest that a fundamental aspect of Max network function involves widespread binding and regulation of gene expression.
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Affiliation(s)
- Amir Orian
- Division of Basic Sciences and Divison of Human Biology, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA
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67
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Schorl C, Sedivy JM. Loss of protooncogene c-Myc function impedes G1 phase progression both before and after the restriction point. Mol Biol Cell 2003; 14:823-35. [PMID: 12631706 PMCID: PMC151562 DOI: 10.1091/mbc.e02-10-0649] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
c-myc is an important protooncogene whose misregulation is believed to causally affect the development of numerous human cancers. c-myc null rat fibroblasts are viable but display a severe (two- to threefold) retardation of proliferation. The rates of RNA and protein synthesis are reduced by approximately the same factor, whereas cell size remains unaffected. We have performed a detailed kinetic cell cycle analysis of c-myc(-/-) cells by using several labeling and synchronization methods. The majority of cells (>90%) in asynchronous, exponential phase c-myc(-/-) cultures cycle continuously with uniformly elongated cell cycles. Cell cycle elongation is due to a major lengthening of G(1) phase (four- to fivefold) and a more limited lengthening of G(2) phase (twofold), whereas S phase duration is largely unaffected. Progression from mitosis to the G1 restriction point and the subsequent progression from the restriction point into S phase are both drastically delayed. These results are best explained by a model in which c-Myc directly affects cell growth (accumulation of mass) and cell proliferation (the cell cycle machinery) by independent pathways.
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Affiliation(s)
- Christoph Schorl
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island 02912, USA
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68
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Wu S, Cetinkaya C, Munoz-Alonso MJ, von der Lehr N, Bahram F, Beuger V, Eilers M, Leon J, Larsson LG. Myc represses differentiation-induced p21CIP1 expression via Miz-1-dependent interaction with the p21 core promoter. Oncogene 2003; 22:351-60. [PMID: 12545156 DOI: 10.1038/sj.onc.1206145] [Citation(s) in RCA: 239] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Inhibition of cellular differentiation is one of the well-known biological activities of c-Myc-family proteins. We show here that Myc represses differentiation-induced expression of the cyclin-dependent kinase (CDK) inhibitor p21CIP1 (CDKN1A, p21), known to play an important role in cell fate decisions during growth and differentiation, in hematopoietic cells. Our results demonstrate that the c-Myc-responsive region is situated in the p21 core promoter. c-Myc binds to this region in vitro and in vivo through interaction with the initiator-binding Zn-finger transcription factor Miz-1, which associates directly with the promoter. Association of Myc with the promoter in vivo correlates inversely with p21 expression. Using mutants of c-Myc with impaired binding to Miz-1, our results further show that repression of p21 promoter/reporters as well as the endogenous p21 gene by Myc depends on interaction with Miz-1. Expression of Miz-1 increases during hematopoietic differentiation and Miz-1 activates the p21 promoter under conditions of low Myc levels, indicating a positive role for free Miz-1 in this process. In conclusion, repression of differentiation-induced p21 expression through Miz-1 may be an important mechanism by which Myc blocks differentiation.
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Affiliation(s)
- Siqin Wu
- Upsala Genetic Center, Department of Plant Biology, Swedish University of Agricultural Sciences
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69
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A novel signaling pathway of nitric oxide on transcriptional regulation of mouse kappa opioid receptor gene. J Neurosci 2002. [PMID: 12223547 DOI: 10.1523/jneurosci.22-18-07941.2002] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Nitric oxide (NO) suppressed the transcription of the mouse kappa opioid receptor (KOR) gene, mediated by a rapid downregulation of c-myc gene expression. KOR was constitutively expressed in postnatal day 19 (P19) embryonal carcinoma stem cells and is suppressed by NO donors [sodium nitroprusside (SNP), 3-morpholinosydnonimine-1, and S-nitrosoglutathione] in P19 stem cells within 4 hr. The suppression was reversed by 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, an NO scavenger, but could not be blocked by dithiothreitol, ruling out S-nitrosylation as the underlying mechanism. The suppressive effect of NO on KOR occurred at the level of gene transcription, mediated by E boxes located in promoters I and II of this gene. Protein-DNA complexes that formed on these E boxes contained c-myc; c-myc expression was suppressed by NO in P19 stem cells within 2 hr of treatment. Furthermore, chromatin immunoprecipitation demonstrated reduced c-myc binding to the E boxes and hypoacetylation of histone H3 on the chromatin of endogenous KOR promoters in P19 stem cells treated with SNP. It is proposed that NO regulates KOR at the level of gene transcription, mediated by a rapid suppression of c-myc gene expression and its binding to KOR promoters, and followed by chromatin hypoacetylation of and reduced transcription from KOR promoters in P19 stem cells. A novel pathway mediating the potential interplay between NO and opioid systems is discussed.
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70
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Shiio Y, Donohoe S, Yi EC, Goodlett DR, Aebersold R, Eisenman RN. Quantitative proteomic analysis of Myc oncoprotein function. EMBO J 2002; 21:5088-96. [PMID: 12356725 PMCID: PMC129047 DOI: 10.1093/emboj/cdf525] [Citation(s) in RCA: 143] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
This study applies a new quantitative proteomics technology to the analysis of the function of the Myc oncoprotein in mammalian cells. Employing isotope-coded affinity tag (ICAT) reagent labeling and tandem mass spectrometry, the global pattern of protein expression in rat myc-null cells was compared with that of myc-plus cells (myc-null cells in which myc has been introduced) to generate a differential protein expression catalog. Expression differences among many functionally related proteins were identified, including reduction of proteases, induction of protein synthesis pathways and upregulation of anabolic enzymes in myc-plus cells, which are predicted to lead to increased cell mass (cell growth). In addition, reduction in the levels of adhesion molecules, actin network proteins and Rho pathway proteins were observed in myc-plus cells, leading to reduced focal adhesions and actin stress fibers as well as altered morphology. These effects are dependent on the highly conserved Myc Box II region. Our results reveal a novel cytoskeletal function for Myc and indicate the feasibility of quantitative whole-proteome analysis in mammalian cells.
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Affiliation(s)
| | - Sam Donohoe
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North, Seattle, WA 98109-1024 and
Institute for Systems Biology, Seattle, WA 98103, USA Corresponding authors e-mail: or
| | - Eugene C. Yi
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North, Seattle, WA 98109-1024 and
Institute for Systems Biology, Seattle, WA 98103, USA Corresponding authors e-mail: or
| | - David R. Goodlett
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North, Seattle, WA 98109-1024 and
Institute for Systems Biology, Seattle, WA 98103, USA Corresponding authors e-mail: or
| | - Ruedi Aebersold
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North, Seattle, WA 98109-1024 and
Institute for Systems Biology, Seattle, WA 98103, USA Corresponding authors e-mail: or
| | - Robert N. Eisenman
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North, Seattle, WA 98109-1024 and
Institute for Systems Biology, Seattle, WA 98103, USA Corresponding authors e-mail: or
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71
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James L, Eisenman RN. Myc and Mad bHLHZ domains possess identical DNA-binding specificities but only partially overlapping functions in vivo. Proc Natl Acad Sci U S A 2002; 99:10429-34. [PMID: 12149476 PMCID: PMC124931 DOI: 10.1073/pnas.162369299] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The opposing transcriptional activities of the basic-helix-loop-helix-leucine zipper proteins Myc and Mad, taken together with information related to their expression patterns and biological effects, have led to a model of the Myc/Max/Mad network in which Myc and Mad proteins function as antagonists. This antagonism is presumed to operate at the level of genes targeted by these complexes, where Myc:Max activates and Mad:Max represses expression of the same set of genes. However, a detailed analysis of the DNA-binding preferences for Mad proteins has not been performed. Furthermore, the model does not address the findings that Myc:Max indirectly represses transcription of several regulatory genes. To examine these issues relating to DNA-binding specificity and biological responses, we have determined the DNA-binding preferences of Mad1 by using selection and amplification of randomized oligonucleotides and demonstrated that its intrinsic specificity is identical with that of c-Myc. We have also used a chimeric Myc protein, containing a substitution of the entire Mad basic-helix-loop-helix-leucine zipper motif, and shown that it can reproduce the growth-promoting activities of Myc, but not its apoptotic function. Our results suggest that Myc and Mad, although possessing identical in vitro DNA-binding specificities, do not have an identical set of target genes in vivo, and that apoptosis is one biological outcome in which the transcriptional effects of Myc are not directly antagonized by those of Mad.
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Affiliation(s)
- Leonard James
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
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72
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La Rocca SA, Vannucchi S, Pompili M, Pinney DF, Emerson CP, Grossi M, Tatò F. Selective repression of myoD transcription by v-Myc prevents terminal differentiation of quail embryo myoblasts transformed by the MC29 strain of avian myelocytomatosis virus. Oncogene 2002; 21:4838-42. [PMID: 12101422 DOI: 10.1038/sj.onc.1205586] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2002] [Revised: 04/04/2002] [Accepted: 04/15/2002] [Indexed: 11/09/2022]
Abstract
We have investigated the mechanism by which expression of the v-myc oncogene interferes with the competence of primary quail myoblasts to undergo terminal differentiation. Previous studies have established that quail myoblasts transformed by myc oncogenes are severely impaired in the accumulation of mRNAs encoding the myogenic transcription factors Myf-5, MyoD and Myogenin. However, the mechanism responsible for such a repression remains largely unknown. Here we present evidence that v-Myc selectively interferes with quail myoD expression at the transcriptional level. Cis-regulatory elements involved in the auto-activation of qmyoD are specifically targeted in this unique example of transrepression by v-Myc, without the apparent participation of Myc-specific E-boxes or InR sequences. Transiently expressed v-Myc efficiently interfered with MyoD-dependent transactivation of the qmyoD regulatory elements, while the myogenin promoter was unaffected. Finally, we show that forced expression of MyoD in v-myc-transformed quail myoblasts restored myogenin expression and promoted extensive terminal differentiation. These data suggest that transcriptional repression of qmyoD is a major and rate-limiting step in the molecular pathway by which v-Myc severely inhibits terminal differentiation in myogenic cells.
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Affiliation(s)
- Severina A La Rocca
- Istituto Pasteur-Fondazione Cenci-Bolognetti, Dipartimento di Biologia Cellulare e dello Sviluppo, Sezione di Scienze Microbiologiche, Universita' di Roma 'La Sapienza', 00185-Roma, Italy
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73
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Wentzensen N, Ridder R, Klaes R, Vinokurova S, Schaefer U, Doeberitz MVK. Characterization of viral-cellular fusion transcripts in a large series of HPV16 and 18 positive anogenital lesions. Oncogene 2002; 21:419-26. [PMID: 11821954 DOI: 10.1038/sj.onc.1205104] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2001] [Revised: 10/09/2001] [Accepted: 10/29/2001] [Indexed: 11/08/2022]
Abstract
Persistent high risk type human papillomavirus (HR-HPVs) infections induce dysplasia or cancer of the anogenital tract, most notably of the uterine cervix. The viral genome usually persists and replicates as an episomal molecule in early dysplasia, whereas in advanced dysplasia or cervical cancer HPV genomes are frequently integrated into the chromosomal DNA of the host cell. Previous studies suggested that modification of critical cellular sequences by integration of HPV genomes might significantly contribute to the neoplastic transformation of anogenital epithelia (insertional mutagenesis). This prompted us to characterize the integration loci of high risk HPV genomes in a large set of genital lesions. We amplified E6/E7 oncogene transcripts derived from integrated HPV16 and HPV18 genomes and characterized in detail the co-transcribed cellular sequences of 64 primary genital lesions and five cervical cancer cell lines. Database analyses of the cellular parts of these fusion transcripts revealed 51 different integration loci, including 26 transcribed genes (14 known genes, 12 EST sequences with unknown gene function). Seventeen sequences showed similarity to repetitive elements, and 26 sequences did not show any database match other than genomic sequence. Chromosomal integration loci were distributed over almost all human chromosomes. Although we found HPV sequences integrated into cancer related genes and close to fragile sites, no preferential site or integration motif could be identified. These data demonstrate that target directed insertional mutagenesis might occur in few HPV-induced anogenital lesions, however, it is rather the exception than the rule.
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Affiliation(s)
- Nicolas Wentzensen
- Division of Molecular Pathology, Department of Pathology, University of Heidelberg, Im Neuenheimer Feld 110, 69120 Heidelberg, Germany
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74
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Cerni C, Skrzypek B, Popov N, Sasgary S, Schmidt G, Larsson LG, Lüscher B, Henriksson M. Repression of in vivo growth of Myc/Ras transformed tumor cells by Mad1. Oncogene 2002; 21:447-59. [PMID: 11821957 DOI: 10.1038/sj.onc.1205107] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2001] [Revised: 10/09/2001] [Accepted: 10/29/2001] [Indexed: 11/09/2022]
Abstract
The Myc/Max/Mad network of transcriptional regulatory proteins plays an essential role in cell proliferation, growth, apoptosis, and differentiation. Whereas Myc proteins affect cell cycle progression positively, Mad proteins are negative regulators of cell proliferation. It has been shown in several in vitro systems that Mad proteins antagonize c-Myc functions. In this report we describe the inhibition of tumor cell outgrowth in vivo by Mad1 expression. Transformed cell lines were generated by co-transfection of c-myc, c-H-ras, and a chimeric mad1ER construct into primary rat embryo cells (MRMad1ER cells). Activation of Mad1 by 4-Hydroxy-Tamoxifen (OHT) resulted in abrogation of telomerase activity, reduced cloning efficiency, and decreased proportion of cells in S phase. Injection of MRMad1ER cells into syngenic rats induced aggressively growing tumors after a short latency period. This tumor growth was inhibited by OHT-treatment of animals, with the extent of inhibition correlating with the amount of OHT injected. No effect of OHT on tumor growth was observed with similarly transformed Myc/Ras cell lines which did not express Mad1ER. These data demonstrate that Mad1 is able to suppress Myc/Ras-mediated transformation under in vivo conditions.
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MESH Headings
- Animals
- Basic Helix-Loop-Helix Leucine Zipper Transcription Factors
- Blotting, Western
- Cell Cycle Proteins/metabolism
- Cell Division/drug effects
- Cell Division/genetics
- Cell Line, Transformed
- Cell Transformation, Neoplastic/genetics
- Cell Transformation, Neoplastic/metabolism
- Cell Transformation, Neoplastic/pathology
- Cells, Cultured
- Flow Cytometry
- Gene Expression Regulation, Neoplastic
- Genes, myc/genetics
- Genes, ras/genetics
- Male
- Nuclear Proteins
- Phosphoproteins/genetics
- Phosphoproteins/metabolism
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Rats
- Rats, Inbred F344
- Repressor Proteins/genetics
- Repressor Proteins/metabolism
- Tamoxifen/analogs & derivatives
- Tamoxifen/pharmacology
- Telomerase/antagonists & inhibitors
- Telomerase/metabolism
- Transgenes/genetics
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Affiliation(s)
- Christa Cerni
- Institute of Cancer Research, University of Vienna, Borschkegasse 8a, A-1090 Wien, Austria.
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75
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Hölzel M, Kohlhuber F, Schlosser I, Hölzel D, Lüscher B, Eick D. Myc/Max/Mad regulate the frequency but not the duration of productive cell cycles. EMBO Rep 2001; 2:1125-32. [PMID: 11743027 PMCID: PMC1084169 DOI: 10.1093/embo-reports/kve251] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Upregulation of the proto-oncoprotein Myc, a basic, helix-loop-helix, leucin zipper domain transcription factor has profound consequences on cell proliferation, cell growth and apoptosis. Cell cultures of somatic c-myc-/- rat fibroblasts show extremely prolonged doubling times of 52 h. Using time-lapse microscopy, we show here that individual c-myc-/- cells proceeded within approximately 24 h through the cell cycle as fast as c-myc+/+ cells. However, c-myc-/- cells were highly sensitive to contact inhibition and readily arrested in the cell cycle already at low density. Activation of conditional MycER overcame cell cycle arrest in c-myc-/- cells and led to continuous proliferation at the expense of increased apoptosis at high cell density. Conditional expression of Mad1, a Myc antagonist, represses proliferation of different cell types including U2OS cells. In analogy to the effect of Myc, this occurs mainly by reducing the probability of cells remaining in the cycle. Our data demonstrate that the Myc/Max/Mad network does not regulate the duration of the cell cycle, but the decision of cells to enter or exit the cell cycle.
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Affiliation(s)
- M Hölzel
- Institute for Clinical Molecular Biology and Tumor Genetics, GSF-Research Centre, Marchioninistrasse 25, D-81377 Munich, Germany
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76
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Deleu L, Shellard S, Alevizopoulos K, Amati B, Land H. Recruitment of TRRAP required for oncogenic transformation by E1A. Oncogene 2001; 20:8270-5. [PMID: 11781841 DOI: 10.1038/sj.onc.1205159] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2001] [Accepted: 11/05/2001] [Indexed: 12/17/2022]
Abstract
TRRAP links Myc with histone acetylases and appears to be an important mediator of its oncogenic function. Here we show that interaction with TRRAP is required for cellular transformation not only by Myc, but also by the adenovirus E1A protein. Substitution of the 262 N-terminal residues of Myc with a small domain of E1A (residues 12-54) restores Myc transforming function. E1A(12-54) contains a TRRAP-interaction domain, that recruits TRRAP to either E1A-Myc chimeras, or the native 12S E1A protein. Overexpression of a competing TRRAP fragment in vivo blocks interaction of cellular TRRAP with either E1A-Myc or E1A, and suppresses cellular transformation by both oncoproteins. Moreover, E1A(Delta26-35) that fails to bind TRRAP but is capable of binding the Retinoblastoma (Rb)-family and p300/CBP proteins is defective in cellular immortalization, transformation and cell cycle deregulation. Thus in addition to disrupting Rb and p300/CBP functions, E1A must recruit TRRAP to transform cells.
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Affiliation(s)
- L Deleu
- Department of Biomedical Genetics, University of Rochester Medical Center, 601 Elmwood Avenue, Rochester, NY 14642, USA
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77
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Krippner-Heidenreich A, Talanian RV, Sekul R, Kraft R, Thole H, Ottleben H, Lüscher B. Targeting of the transcription factor Max during apoptosis: phosphorylation-regulated cleavage by caspase-5 at an unusual glutamic acid residue in position P1. Biochem J 2001; 358:705-15. [PMID: 11535131 PMCID: PMC1222104 DOI: 10.1042/0264-6021:3580705] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Max is the central component of the Myc/Max/Mad network of transcription factors that regulate growth, differentiation and apoptosis. Whereas the Myc and Mad genes and proteins are highly regulated, Max expression is constitutive and no post-translational regulation is known. We have found that Max is targeted during Fas-induced apoptosis. Max is first dephosphorylated and subsequently cleaved by caspases. Two specific cleavage sites for caspases in Max were identified, one at IEVE(10) decreasing S and one at SAFD(135) decreasing G near the C-terminus, which are cleaved in vitro by caspase-5 and caspase-7 respectively. Mutational analysis indicates that both sites are also used in vivo. Thus Max represents the first caspase-5 substrate. The unusual cleavage after a glutamic acid residue is observed only with full-length, DNA-binding competent Max protein but not with corresponding peptides, suggesting that structural determinants might be important for this activity. Furthermore, cleavage by caspase-5 is inhibited by the protein kinase CK2-mediated phosphorylation of Max at Ser-11, a previously mapped phosphorylation site in vivo. These findings suggest that Fas-mediated dephosphorylation of Max is required for cleavage by caspase-5. The modifications that occur on Max in response to Fas signalling affect the DNA-binding activity of Max/Max homodimers. Taken together, our findings uncover three distinct processes, namely dephosphorylation and cleavage by caspase-5 and caspase-7, that target Max during Fas-mediated apoptosis, suggesting the regulation of the Myc/Max/Mad network through its central component.
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Affiliation(s)
- A Krippner-Heidenreich
- Institut für Molekularbiologie, Medizinische Hochschule Hannover, Carl-Neuberg Strasse 1, 30623 Hannover, Germany
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78
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Affiliation(s)
- R N Eisenman
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109-1024, USA.
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79
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Bouchard C, Dittrich O, Kiermaier A, Dohmann K, Menkel A, Eilers M, Lüscher B. Regulation of cyclin D2 gene expression by the Myc/Max/Mad network: Myc-dependent TRRAP recruitment and histone acetylation at the cyclin D2 promoter. Genes Dev 2001; 15:2042-7. [PMID: 11511535 PMCID: PMC312761 DOI: 10.1101/gad.907901] [Citation(s) in RCA: 266] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Myc oncoproteins promote cell cycle progression in part through the transcriptional up-regulation of the cyclin D2 gene. We now show that Myc is bound to the cyclin D2 promoter in vivo. Binding of Myc induces cyclin D2 expression and histone acetylation at a single nucleosome in a MycBoxII/TRRAP-dependent manner. Down-regulation of cyclin D2 mRNA expression in differentiating HL60 cells is preceded by a switch of promoter occupancy from Myc/Max to Mad/Max complexes, loss of TRRAP binding, increased HDAC1 binding, and histone deacetylation. Thus, recruitment of TRRAP and regulation of histone acetylation are critical for transcriptional activation by Myc.
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Affiliation(s)
- C Bouchard
- Institute for Molecular Biology and Tumor Research, 35033 Marburg, Germany
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Frank SR, Schroeder M, Fernandez P, Taubert S, Amati B. Binding of c-Myc to chromatin mediates mitogen-induced acetylation of histone H4 and gene activation. Genes Dev 2001; 15:2069-82. [PMID: 11511539 PMCID: PMC312758 DOI: 10.1101/gad.906601] [Citation(s) in RCA: 411] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The Myc protein binds DNA and activates transcription by mechanisms that are still unclear. We used chromatin immunoprecipitation (ChIP) to evaluate Myc-dependent changes in histone acetylation at seven target loci. Upon serum stimulation of Rat1 fibroblasts, Myc associated with chromatin, histone H4 became locally hyperacetylated, and gene expression was induced. These responses were lost or severely impaired in Myc-deficient cells, but were restored by adenoviral delivery of Myc simultaneous with mitogenic stimulation. When targeted to chromatin in the absence of mitogens, Myc directly induced H4 acetylation. In addition, Myc recruited TRRAP to chromatin, consistent with a role for this cofactor in histone acetylation. Finally, unlike serum, Myc alone was very inefficient in inducing expression of most target genes. Myc therefore governs a step, most likely H4 acetylation, that is required but not sufficient for transcriptional activation. We propose that Myc acts as a permissive factor, allowing additional signals to activate target promoters.
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Affiliation(s)
- S R Frank
- Department of Oncology, DNAX Research Institute, Palo Alto, California 94304, USA
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