TRANSCRIPTION FACTOR AP-2 CONTROLS TRANSCRIPTION OF THE HUMAN TRANSFORMING GROWTH-FACTOR-ALPHA GENE

The epidermal growth factor receptor is vital for normal development a nd plays a role in oncogenesis, The level of activation of this recept or by transforming growth factor-alpha (TGF-alpha) is controlled, in p art, by the rate of transcription of the TGF-alpha gene, In the charac terization of the proximal TGF-alpha promoter by DNase I footprinting, a 43-base pair element (-88 to -130 relative to the transcription sta rt site), designated T alpha RE I, was found that was specifically pro tected by nuclear proteins from human mammary carcinoma MDA468 cells, T alpha RE I was essential for the maximal expression of the TGF-alpha gene as indicated by deletion and mutagenesis analyses, T alpha RE I consists of two cis-acting elements, a proximal regulatory element (PR E, -89 to -103) and a distal regulatory element (DRE, -121 to -128), B oth elements were able to form specific complexes with protein from MD A468 cell nuclear extracts and are necessary for the full activity of the entire 1.1-kilobase pair TGF-alpha promoter, Competition and antib ody studies determined that the DRE contains a binding site for the tr anscription factor AP 2, while the protein that binds to the PRE has y et to be identified, When linked upstream to the heterologous herpes s implex thymidine kinase promoter, the T alpha RE I enhanced transcript ion up to 11-fold in MDA468 cells, Cotransfection of an AP-2 expressio n vector was able to activate transcription from the T alpha REI-TK co nstruct in a DRE-dependent manner. These results further our understan ding of how TGF-alpha transcription is regulated.