Identification of an additional p53-responsive site in the human epidermal growth factor receptor gene promotor

Abstract

Exogenously introduced wild-type and mutant p53 have recently been reported to enhance the human epidermal growth factor receptor (EGF-R) gene promoter activity in p53-deficient Saos2 osteosarcoma cells. A p53 binding site residing at position −265/−239 in the EGF-R proximal promoter has also been identified. We investigated the p53 regulation of EGF-R core promoter activity in human cell lines with varying endogenour p53 status. Wild-type and mutant p53^A1a143 enhanced the EGF-R core promotor activity in cells that were either p53-deficient or contained wild-type or mutant endogenous p53. Upon further characterization of the various deletion fragments of the EGF-R promoter, we identified a wild-type p53 responsive 62 bp region residing at position −167/−105. The −167/−105 segment was responsive only to wild-type p53 but not to mutant p53^A1a143 or p53^His273. The −167/−105 segment of the EGF-R promotor contains one perfect and several imperfect consensus p53-binding half sites; indeed in gel shift experiments the 62 bp −167/−105 segment as well as the oligonucleotides corresponding to two p53 consensus half-sites within the 62 bp fragment, exhibited binding to p53-containing protein complexes. Thus, we have identified an additional wild-type p53 responsive site in the human EGF-R promoter. This site containing consensus p53-binding sequences resides at position −167/−105 and is proximal to recently identified p53 binding element located at position −265/−239 in the EGF-R promotor.