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Jefferson WN, Couse JF, Padilla-Banks E, Korach KS, Newbold RR. Neonatal exposure to genistein induces estrogen receptor (ER)alpha expression and multioocyte follicles in the maturing mouse ovary: evidence for ERbeta-mediated and nonestrogenic actions. Biol Reprod 2003; 67:1285-96. [PMID: 12297547 DOI: 10.1095/biolreprod67.4.1285] [Citation(s) in RCA: 175] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Outbred CD-1 mice were treated neonatally on Days 1-5 with the phytoestrogen, genistein (1, 10, or 100 micro g per pup per day), and ovaries were collected on Days 5, 12, and 19. Ribonuclease protection assay analysis of ovarian mRNA showed that estrogen receptor beta (ERbeta) predominated over ERalpha in controls and increased with age. Genistein treatment did not alter ERbeta expression, however, ERalpha expression was higher on Days 5 and 12. ERbeta was immunolocalized in granulosa cells, whereas ERalpha was immunolocalized in interstitial and thecal cells. Genistein treatment caused a dramatic increase in ERalpha in granulosa cells. Genistein-treated ERbeta knockout mice showed a similar induction of ERalpha, which is seen in CD-1 mice, suggesting that ERbeta does not mediate this effect. Similar ERalpha induction in granulosa cells was seen in CD-1 mice treated with lavendustin A, a tyrosine kinase inhibitor that has no known estrogenic actions, which suggests that this property of genistein may be responsible. As a functional analysis, genistein-treated mice were superovulated and the number of oocytes was counted. A statistically significant increase in the number of ovulated oocytes was observed with the lowest dose, whereas a decrease was observed with the two higher doses. This increase in ovulatory capacity with the low dose coincided with higher ERalpha expression. Histological evaluations on Day 19 revealed a dose-related increase in multioocyte follicles (MOFs) in genistein-treated mice. Tyrosine kinase inhibition was apparently not responsible for MOFs because they were not present in mice that had been treated with lavendustin; however, ERbeta must play a role, because mice lacking ERbeta showed no MOFs. These data taken together demonstrate alterations in the ovary following neonatal exposure to genistein. Given that human infants are exposed to high levels of genistein in soy-based foods, this study indicates that the effects of such exposure on the developing reproductive tract warrant further investigation.
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Affiliation(s)
- Wendy N Jefferson
- Developmental Endocrinology Section, Laboratory of Molecular Toxicology, Environmental Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, USA
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Zhao H, Hart LL, Keller U, Holth LT, Davie JR. Characterization of stably transfected fusion protein GFP-estrogen receptor-alpha in MCF-7 human breast cancer cells. J Cell Biochem 2002; 86:365-75. [PMID: 12112006 DOI: 10.1002/jcb.10215] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Tagging hormone receptors with the green fluorescent protein (GFP) has increased our knowledge of ligand dependent sub-cellular trafficking of hormone receptors. However, the effect of the tagged hormone receptor expression on the corresponding wild type hormone receptor and endogenous gene expression has not been investigated. In this study, we constructed a MCF-7 cell line stably expressing GFP-tagged human estrogen receptor-alpha (ER) under control of the tetracycline-on system to determine the effect of GFP-ER expression on cell proliferation and expression of endogenous ER and hormone-responsive genes. Further, the inducible system was applied to determine the ligand dependent turnover rates of GFP-ER protein and mRNA. Our results demonstrate that GFP-ER expression did not affect cell cycling. Independent of ligand, GFP-ER markedly reduced the level of endogenous ER mRNA and protein, suggesting that ER negatively autoregulates its expression. Cisplatin cross-linking studies showed that GFP-ER is associated with nuclear DNA in situ, suggesting that GFP-ER is partially replacing ER at estrogen response elements. Furthermore, GFP-ER expression did not affect the estradiol induced temporal expression of hormone responsive genes c-myc and pS2.
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Affiliation(s)
- Helen Zhao
- Manitoba Institute of Cell Biology, University of Manitoba, 675 McDermot Avenue, Winnipeg, Canada R3E 0V9
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53
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Abstract
The exact molecular mechanisms regulating estrogen receptor (ER)alpha expression in breast tumors are unclear, but studies suggest that the regulation is at least partly transcriptional. We therefore undertook a detailed analysis of ERalpha promoter activity in a number of breast cancer cell lines. We find that the majority of ERalpha promoter activity lies within the first 245bp of the 5'-flanking region of the gene. Three elements essential for full ERalpha promoter transcriptional activity were identified within the -245 to -192bp region in transient transactivation assays using linker-scanner mutation analysis. These three elements include two binding sites for the Sp1 family of transcription factors as well as a non-consensus E box. We show that both Sp1 and Sp3 bind to this region using electrophoretic mobility shift assays. Exogenous expression of Sp1 or Sp3 in Sp1/3-negative Drosophila Schneider SL2 cells results in transactivation of the -245 to +212bp fragment of the ERalpha promoter. These data demonstrate that transcription of ERalpha is dependent upon the expression of members of the Sp1 family.
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Affiliation(s)
- Linda A deGraffenried
- Division of Medical Oncology, The University of Texas Health Science Center, San Antonio 78229, USA
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Inoue A, Hayashi SI, Aoyagi K, Nishigaki M, Sasaki H, Kiyama R. A reporter gene assay for evaluation of tissue-specific responses to estrogens based on the differential use of promoters A to F of the human estrogen receptor alpha gene. J Pharmacol Toxicol Methods 2002; 47:129-35. [PMID: 12628303 DOI: 10.1016/s1056-8719(02)00221-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
INTRODUCTION Reporter gene assays are useful means for monitoring cellular responses. We report here a reporter gene assay for evaluating and monitoring estrogen activities by estrogen-like compounds and xenoestrogens, which is based on the promoters from the human estrogen receptor alpha (ERalpha) gene. METHODS The reporter gene constructs contained a proximal promoter region (containing promoters A and B: ProAB) or either of promoters C to F (ProC, ProD, ProE, and ProF) or fused minor promoters (ProCDEF). These constructs were first used to evaluate promoter activity in cell lines derived from breast (MCF-7 and T-47D cells), ovary (SK-OV-3 cells), endometrium (Ishikawa cells), and stomach (MKN-28 cells). RESULTS Besides very high levels of activity by ProAB in all of the cell lines tested, moderate levels were detected for ProD in the breast and endometrium cell lines and for ProF in the ovary and endometrium cell lines. A moderate level of activity by ProE was detected only in the stomach cells. Differences in estrogen-like activity between ProAB and ProD were observed for tamoxifen and bisphenol A (BPA) in MCF-7 cells. DISCUSSION The assay proposed here might provide expression profiles of cancer cells of various origins for evaluating the estrogen responsiveness and for identifying tissue- or cancer cell-specific transcription factors.
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Affiliation(s)
- Akio Inoue
- National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, 305-8566, Japan
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56
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Denger S, Reid G, Brand H, Kos M, Gannon F. Tissue-specific expression of human ERalpha and ERbeta in the male. Mol Cell Endocrinol 2001; 178:155-60. [PMID: 11403905 DOI: 10.1016/s0303-7207(01)00417-8] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The important role of estrogens in women in physiological and pathological processes is well accepted, but recently it has become evident that estrogens are also important in male physiology, in particular, within bone metabolism and reproduction. Consequently, it is necessary to identify and to characterize the molecular mechanisms of estrogen action in order to evaluate how the pleiotropic effects of estrogens are mediated in a variety of tissues. We have recently shown that human estrogen receptor alpha (ERalpha) mRNA is transcribed from at least six different promoters (1A-1F). Transcription of ERalpha in bone is exclusively dependent on the F-promoter. To study the regulation of ER expression in this tissue, we examined 1 kbp of the F-promoter region of human ERalpha, which is located more than 70 kbp upstream of the transcription start site of the ERalpha gene. Transient transfection experiments demonstrated a basal activity from the F-promoter, which was further increased when ERalpha was cotransfected. We have shown recently that the F-promoter can give rise to at least two ERalpha isoforms in bone. On the contrary, ERbeta expression in primary osteoblasts is extremely low, indicating that this ER isoform plays only a minor role in these cells. In contrast to bone, we have demonstrated that both ERalpha and ERbeta transcripts are readily detected in testis. Here, we report that besides ERalpha, ERbeta transcripts can give rise to two protein isoforms and that this complex situation could have important functional consequences for the signalling of estrogens and their analogs.
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Affiliation(s)
- S Denger
- European Molecular Biology Laboratory, EMBL, Meyerhofstr. 1, 69117, Heidelberg, Germany.
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Schuur ER, McPherson LA, Yang GP, Weigel RJ. Genomic structure of the promoters of the human estrogen receptor-alpha gene demonstrate changes in chromatin structure induced by AP2gamma. J Biol Chem 2001; 276:15519-26. [PMID: 11278455 DOI: 10.1074/jbc.m009001200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Expression of human estrogen receptor-alpha (ERalpha) involves the activity from several promoters that give rise to alternate untranslated 5' exons. However, the genomic locations of the alternate 5' exons have not been reported previously. We have developed a contig map of the human ERalpha gene that includes all of the known alternate 5' exons. By using S1 nuclease and 5'- rapid amplification of cDNA ends, the cap sites for the alternate ERalpha transcripts E and H were identified. DNase I-hypersensitive sites specific to ERalpha-positive cells were associated with each of the cap sites. A DNase I-hypersensitive site, HS1, was localized to binding sites for AP2 in the untranslated region of exon 1 and was invariably present in the chromatin structure of ERalpha-positive cells. Overexpression of AP2gamma in human mammary epithelial cells generated the HS1-hypersensitive site. The ERalpha promoter was induced by AP2gamma in mammary epithelial cells, and trans-activation was dependent upon the region of the promoter containing the HS1 site. These results demonstrate that AP2gamma trans-activates the ERalpha gene in hormone-responsive tumors by inducing changes in the chromatin structure of the ERalpha promoter. These data are further evidence for a critical role for AP2 in the oncogenesis of hormone-responsive breast cancers.
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Affiliation(s)
- E R Schuur
- Department of Surgery, Stanford University School of Medicine, Stanford, California 94305-3229, USA
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Oesterreich S, Zhang Q, Hopp T, Fuqua SA, Michaelis M, Zhao HH, Davie JR, Osborne CK, Lee AV. Tamoxifen-bound estrogen receptor (ER) strongly interacts with the nuclear matrix protein HET/SAF-B, a novel inhibitor of ER-mediated transactivation. Mol Endocrinol 2000; 14:369-81. [PMID: 10707955 DOI: 10.1210/mend.14.3.0432] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The estrogen receptor (ER) is a ligand-dependent transcription factor that acts in a cell- and promoter-specific manner. Evidence suggests that the activity of the ER can be regulated by a number of other stimuli (e.g. growth factors) and that the effects of the ER are modulated by nuclear factors termed coregulators. While the interplay among these factors may in part explain the pleiotropic effects elicited by the ER, there are several other less well described mechanisms of control, such as interactions with the nuclear matrix. Here we report that the nuclear matrix protein/scaffold attachment factor HET/SAF-B is an ER-interacting protein. ER and HET/SAF-B interact in in vitro binding assays, with HET binding to both the ER DNA-binding domain and the hinge region. Coimmunoprecipitation experiments reveal that HET/SAF-B and ER associate in cell lines in the presence or absence of estradiol, but binding is increased by the antiestrogen tamoxifen. HET/SAF-B enhances tamoxifen antagonism of estrogen-induced ER-mediated transactivation, but at high concentrations can inhibit both estrogen and tamoxifen-induced ER activity. HET/SAF-B-mediated repression of ER activity is dependent upon interaction with the ER-DBD. While the existence of high-affinity binding sites for the ER in the nuclear matrix has been known for some time, we now provide evidence of a specific nuclear matrix protein binding to the ER. Furthermore, our data showing that HET/SAF-B binds to ER particularly strongly in the presence of tamoxifen suggests that it may be important for the antagonist effect of tamoxifen.
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Affiliation(s)
- S Oesterreich
- Department of Medicine, University of Texas Health Science Center, San Antonio 78284, USA.
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Tian Y, Ke S, Thomas T, Meeker RJ, Gallo MA. Transcriptional suppression of estrogen receptor gene expression by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). J Steroid Biochem Mol Biol 1998; 67:17-24. [PMID: 9780025 DOI: 10.1016/s0960-0760(98)00067-3] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
TCDD, the most potent congener of the polychlorinated dioxins, has been shown to be an antiestrogen. The mechanisms of TCDD-induced antiestrogenicity are still under investigation. In this study, we investigated the effects of TCDD on the expression of the estrogen receptor (ER) gene. We studied the levels of un-spliced ER transcript (hnRNA) as well as the ER mRNA in ovary, uterus and liver of TCDD-treated mice with different genetic backgrounds. To quantitate the ER hnRNA levels, the intron and exon boundary of ER hnRNA was amplified by competitive RT-PCR. The ER mRNA from these mice was quantitated by competitive RT-PCR amplifying exons separated by an intron. ER hnRNA and ER mRNA levels were quantitated 4 days after a single i.p. dose of TCDD (5 microg/kg) in female C57BL/6J (B6) mice, which carry the responsive allele to TCDD. TCDD treatment significantly (p < 0.05) suppressed the levels of ER hnRNA in the ovary (27.4%) and uterus (21.9%). The decreases in ER hnRNA were coordinated with significant (p < 0.01) decreases in ER mRNA in ovary (57.7%) and uterus (37.6%). There was a significant decrease (20.3%, p < 0.05) in liver ER mRNA, however, the changes of ER hnRNA in liver were not significant. The coordinated decreases in ER hnRNA and mRNA in TCDD-treated mice suggest a suppression of transcription of the ER gene. We performed the same study on DBA/2J (D2) mice, which possess the "non-responsive" allele of the aryl hydrocarbon receptor (AhR). These mice demonstrated no significant decrease in either the ER mRNA or hnRNA after TCDD treatment. Overall, these results suggest that TCDD suppresses the gene expression of the ER receptor by decreasing its transcription, and the AhR plays an important role in mediating this response.
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Affiliation(s)
- Y Tian
- Environmental and Occupational Health Sciences Institute, UMDNJ-Robert Wood Johnson Medical School, Piscataway 08855-1179, USA
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Abstract
Estrogen receptor (ER)3 gene expression in breast epithelium is an intricately regulated event. The human ER gene is transcribed from at least three different promoters which are expressed in a cell- and tissue-specific manner, and result in mRNA isoforms with unique 5'-untranslated exons. The ER is overexpressed in about two thirds of breast tumors, and even in early premalignant breast lesions compared with adjacent normal breast epithelium. Furthermore, normal breast epithelium as well as breast cancer tissue contains alternatively spliced ER mRNA variants where single or multiple exons are skipped. It is still unclear if any or all of the ER mRNA splicing variants are translated in vivo, and if a change in the balance of ER variants could effect tumor development and progression to hormone-independent growth. Although infrequent in primary breast cancer, single amino acid changes within the ER in metastatic disease which might influence cell proliferation may also contribute to neoplastic progression of the mammary epithelium.
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Affiliation(s)
- T A Hopp
- Department of Medicine, The University of Texas, Health Science Center at San Antonio, USA
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