Transcriptional repression of the eukaryotic initiation factor 4E gene by wild type p53

The eukaryotic initiation factor 4E (eIF4E) plays important roles in transformation and cancer progression. It is frequently overexpressed in malignant cells, one mechanism of which is through transcriptional activation by c-myc. Here, we report that high level of eIF4E expression and its tumorigenicity could be alternatively associated with defects of p53, since we found that induction of wt-p53 repressed eIF4E expression. Gene transfection of p53 inhibited eIF4E promoter activity, while inactivation of p53 either by mutation or by over-expression of MDM2 resulted in stimulation of eIF4E promoter activity. We demonstrated that p53-repression of eIF4E was regulated by c-myc. The wt-p53 can physically bind to c-myc, which inhibited binding of c-myc to eIF4E promoter and c-myc-stimulated promoter activity. These results suggest that the expression of eIF4E is reciprocally regulated by p53 and c-myc, and loss of p53-mediated control over c-myc-dependent transactivation of eIF4E may represent a novel mechanism for eIF4E-mediated neoplastic transformation and cancer progression.