Regulation of the Fibroblast Growth Factor Receptor 3 Promoter and Intron I Enhancer by Sp1 Family Transcription Factors*
- From the Department of Molecular Biology and Pharmacology, Washington University Medical School, St. Louis, Missouri 63110
Abstract
Fibroblast growth factor receptor 3 (FGFR3) has a complex spatial and temporal pattern of expression and is essential for the normal development of a diverse set of tissues. Recently, mutations have been identified in FGFR3 that result in constitutive tyrosine kinase activity and cause a number of different human skeletal disorders. To examine the regulatory mechanisms governing FGFR3 expression, the promoter for the FGFR3 gene was identified and characterized. It resides in a CpG island, which encompasses the 5′ end of the FGFR3 gene and lacks classical cis-regulatory motifs. As little as 100 base pairs of sequence 5′ to the initiation site can confer a 20–40-fold increase in transcriptional activity upon a promoter-less vector. The transcriptional activity of thesecis-regulatory sequences is further stimulated by elements found within the first intron. Mapping of the enhancer activity found within intron I identified two purine-rich sequence motifs between +340 and +395. Electrophoretic mobility shift assays demonstrated that sequences within this region bind members of the Sp1 family of transcription factors. In a background lacking Sp1-like activity, we demonstrate that Sp1 can enhance transcription of the minimal promoter (which contains five classical Sp1 sites), whereas both Sp1 and Sp3 can enhance transcription through the elements found in intron I. Although these transcription factors are ubiquitously expressed, we demonstrate that the sequences between −220 and +609 of the FGFR3 gene are sufficient to promote the tissue-specific expression of a reporter gene in transgenic mice.
Footnotes
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↵* This work was supported by National Institutes of Health Grant CA60673 and a grant from Monsanto/Searle, Inc.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. E-mail:dornitz{at}pharmdec.wustl.edu.
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↵1 The abbreviations used are: FGF, fibroblast growth factor; FGFR, fibroblast growth factor receptor; HSPG, heparan sulfate proteoglycan; luc, luciferase; i, intron; UTR, untranslated region; RSV, Rous sarcoma virus; EGFR, epidermal growth factor; bp, base pair(s); nt, nucleotide(s); β-gal, β-galactosidase; EMSA, electrophoretic mobility shift assay; InR, initiator region.
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↵2 D. G. McEwen, M. Naski, D. Towler, and D. M. Ornitz, manuscript in preparation.
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↵3 D. G. McEwen and D. M. Ornitz, unpublished observations.
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- Received September 23, 1997.
- Revision received November 13, 1997.
- The American Society for Biochemistry and Molecular Biology, Inc.
