Transcription Factor AP-2 Controls Transcription of the Human Transforming Growth Factor-α Gene*
- From the Departments of Medicine and Cell Biology, Division of Endocrinology and Metabolism, The University of Alabama at Birmingham, Birmingham, Alabama 35294
Abstract
The epidermal growth factor receptor is vital for normal development and plays a role in oncogenesis. The level of activation of this receptor by transforming growth factor-α (TGF-α) is controlled, in part, by the rate of transcription of the TGF-α gene. In the characterization of the proximal TGF-α promoter by DNase I footprinting, a 43-base pair element (−88 to −130 relative to the transcription start site), designated TαRE I, was found that was specifically protected by nuclear proteins from human mammary carcinoma MDA468 cells. TαRE I was essential for the maximal expression of the TGF-α gene as indicated by deletion and mutagenesis analyses. TαRE I consists of two cis-acting elements, a proximal regulatory element (PRE, −89 to −103) and a distal regulatory element (DRE, −121 to −128). Both elements were able to form specific complexes with protein from MDA468 cell nuclear extracts and are necessary for the full activity of the entire 1.1-kilobase pair TGF-α promoter. Competition and antibody studies determined that the DRE contains a binding site for the transcription factor AP-2, while the protein that binds to the PRE has yet to be identified. When linked upstream to the heterologous herpes simplex thymidine kinase promoter, the TαRE I enhanced transcription up to 11-fold in MDA468 cells. Cotransfection of an AP-2 expression vector was able to activate transcription from the TαREI-TK construct in a DRE-dependent manner. These results further our understanding of how TGF-α transcription is regulated.
Footnotes
-
↵* This work was supported by a grant from the National Institutes of Health, DK43652.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.
-
↵‡ To whom correspondence should be addressed. Tel.: 205-934-4116; Fax: 205-934-4389; E-mail: Kudlow{at}endo.dreb.uab.edu.
-
↵1 The abbreviations used are: TGF-α, transforming growth factor-α; bp, base pair(s); kb, kilobase pair; CMV, cytomegalovirus; EGF, epidermal growth factor; PRE, proximal regulatory element; DRE, distal regulatory element; TK, thymidine kinase.
-
- Received May 13, 1996.
- Revision received February 18, 1997.
