Overexpression of c-Fos enhances the transcription of human arachidonate 12-lipoxygenase in A431 cells

The effect of transient transfection with expression vector of c-Fos on the expression of 12-lipoxygenase in human epidermoid carcinoma A431 cells was studied. Overexpression of c-Fos increased the expression of 12-lipoxygena se mRNA and enzyme activity, and also activated the promoter activity of 12 -lipoxygenase gene in a dose-dependent manner. Co-transfection with c-Fos a nd c-Jun expression vectors in cells synergistically increased the promoter activity of 12-lipoxygenase. With the aid of additional 5'-deletion and si te-directed mutagenesis, the downstream and middle Spl sites residing at -1 23 to -114 bp and -158 to -150 bp were found to be critical for the c-Fos r esponse of activating the transcription of human 12-lipoxygenase gene. Furt hermore, the specific role of Spl in c-Fos response was confirmed by using the reporter plasmid driven by SV40 early promoter. These results indicate that the requirement of Spl-binding sites in the promoter region of la-lipo xygenase gene for c-Fos response is similar to that previously observed in EGF response, (C) 1999 Academic Press.