IDENTIFICATION OF AN ADDITIONAL P53-RESPONSIVE SITE IN THE HUMAN EPIDERMAL GROWTH-FACTOR RECEPTOR GENE PROMOTOR

Exogenously introduced wild-type and mutant p53 have recently been rep orted to enhance the human epidermal growth factor receptor (EGF-R) ge ne promoter activity in p53-deficient Saos2 osteosarcoma cells. A p53 binding site residing at position -265/-239 in the EGF-R proximal prom oter has also been identified. We investigated the p53 regulation of E GF-R core promoter activity in human cell lines with varying endogenou r p53 status. Wild-type and mutant p53(Ala143) enhanced the EGF-R core promotor activity in cells that were either p53-deficient or containe d 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(Ala143) Or p53(His273). The -167/-105 segment of the EGF-R promotor contains one perfect and several imperfect consensus p53-bin ding half sites; indeed in gel shift experiments the 62 bp -167/-105 s egment as well as the oligonucleotides corresponding to two p53 consen sus half-sites within the 62 bp fragment, exhibited binding to p53-con taining protein complexes. Thus, we have identified an additional wild -type p53 responsive site in the human EGF-R promoter. This site conta ining consensus p53-binding sequences resides at position -167/-105 an d is proximal to recently identified p53 binding element located at po sition -265/-239 in the EGF-R promotor.