Epidermal growth factor enhances transcription of human arachidonate 12-lipoxygenase in A431 cells

Epidermal growth factor (EGF), determined by immunoprecipitation and Western blot analysis, increased both enzyme activity and protein level of 12-lipoxygenase in the solubilized microsomes of human epidermoid carcinoma A431 cells, respectively. The EGF-induced expression of 12-lipoxygenase mRNA was inhibited by transcription inhibitors such as actinomycin D and 5,6-dichlorobenzimidazole riboside. Promoters of different lengths for human 12-lipoxygenase gene were used to prepare the luciferase fusion vectors. These construct plasmids were transiently transfected into A431 cells, and the induction of luciferase expression by EGF was examined. A 4- to 6-fold increase in luciferase reporter activity stimulated by EGF for 18 h treatment was observed in plasmids with the 5'-flanking region length of -951 bp and that of -224 bp upstream from translation starting site. The time-dependent induction of luciferase activity by EGF paralleled the EGF-induced enzyme activity and expression of 12-lipoxygenase protein. Taken together, the results of this study indicate that EGF enhanced the transcription of the human 12-lipoxygenase gene, resulting in an increase in the amount and activity of 12-lipoxygenase.