Steroidogenic Factor-1 and Early Growth Response Protein 1 Act through Two Composite DNA Binding Sites to Regulate Luteinizing Hormone β-Subunit Gene Expression*
- From the ‡Division of Genetics, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts 02115, the §Department of Obstetrics and Gynecology, Tufts University School of Medicine, Boston, Massachusetts 02111, and the ‖Division of Endocrinology, Metabolism, and Molecular Medicine, Northwestern University Medical School, Chicago, Illinois 60611
Abstract
Recent in vivo and in vitro studies have implicated the orphan nuclear receptor, steroidogenic factor-1 (SF-1), and the early growth response protein 1 (Egr-1) in the transcriptional regulation of the luteinizing hormone β-subunit (LHβ) gene. We have previously demonstrated the ability of SF-1 to bind to and transactivate the rat LHβ gene promoter acting at a consensus gonadotrope-specific element (GSE) located at position −127. We have now identified a second functional GSE site at position −59. In addition, based on electrophoretic mobility shift assay,in vitro translated Egr-1 is shown to bind to two putative Egr-1 binding sites (positions −112 and −50), which appear to be paired with the identified GSE sites. By transient transfection assay in pituitary-derived GH3 cells, it was seen that Egr-1 increases promoter activity of region −207/+5 of the rat LHβ gene promoter through action at both Egr-1 sites. Furthermore, LHβ gene promoter activity is markedly augmented in the presence of both factors together relative to activity in the presence of SF-1 or Egr-1 alone (150-fold versus 14-fold and 12-fold, respectively). These data define two composite SF-1-Egr-1 response-elements in the proximal LHβ gene promoter and suggest that SF-1 and Egr-1 act synergistically to increase expression of the LHβ gene in the gonadotrope.
Footnotes
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↵* This work was supported in part by National Institutes of Health Grants R03-HD34692 (to L. M. H.), R01-HD19938 (to W. W. C.), and U54-HD29164 (to M. I. and J. L. J.) and by an American Society for Reproductive Medicine-Ortho Pharmaceutical Research Grant in Reproduction (to L. M. H.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵¶ To whom correspondence should be addressed: G. W. Thorn Research Bldg., Rm. 1013, Brigham and Women’s Hospital, 20 Shattuck St., Boston, MA 02115. Tel.: 617-732-5856; Fax: 617-732-5123; E-mail: Halvorson{at}rascal.med.harvard.edu.
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↵1 The abbreviations used are: LHβ, luteinizing hormone β-subunit; FSHβ, follicle-stimulating hormone β-subunit; SF-1, steroidogenic factor-1; Egr-1, early growth response protein 1; EMSA, electrophoretic mobility shift assay; RXR, 9-cis-retinoic acid receptor; DAX-1, dosage-sensitive sex reversal-adrenal hypoplasia congenita critical region on the X chromosome, gene 1; NTA, nitrilotriacetic acid; GSE, gonadotrope-specific element.
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- Received November 5, 1997.
- Revision received February 13, 1998.
- The American Society for Biochemistry and Molecular Biology, Inc.
