The c-fos proto-oncogene promotor is not regulated by serum, epidermal growth factor, and phorbol ester in embryonal fibroblasts transformed by E1Aad5+cHa-ras-oncogenes]

Regulation of c-fos protooncogene activity in rat embryonal fibroblasts (REF), E1Aad5-immortalized REF cells, and E1Aad5 + cHa-ras transformed REF cells has been investigated. The analysis of regulation of fos-promoter activity was done by means of transient and stable transfection of fos-CAT plasmid into immortalized and transformed cells. In parallel, the regulation of cellular c-fos as well as c-jun and c-myc genes expression has been studied. It has been found that in E1Aad5 + cHa-ras-transformed cells the expression of c-fos promoter has a constitutive, non-inducible character while in REF cells and cells immortalized by E1Aad5 the fos-promoter can be regulated by serum growth factors, EGF, and TPA.