Induction of 12-lipoxygenase expression by transforming growth factor-alpha in human epidermoid carcinoma A431 cells

Transforming growth factor-alpha (TGF-alpha) increased the expression of 12 -lipoxygenase activity in a time-dependent manner in human epidermoid carci noma A431 cells. The increase of 12-lipoxygenase activity was accompanied b y an increase in 12-lipoxygenase mRNA. The effect of TGF-alpha on the promo ter activation of 12-lipoxygenase gene was analyzed by using the luciferase fusion vectors. A dose-dependent effect of TGF-alpha on the reporter activ ity was observed, which paralleled with its effect on enzyme activity. Tran sient transfection with a series of 5'-deleted constructs showed that the 5 '-flanking region spanning from -224 to -100 bp from translation starting s ite played an important role for TGF-alpha response. Site-directed mutagene sis and gel mobility shift assay indicated that two Sp1 binding sequences r esiding at -158 to -150 bp and -123 to -114 bp were responsible for the TGF -alpha in activation of human 12-lipoxygenase gene transcription. Expressio n of Sp1, but not Sp3, stimulated the promoter activity of 12-lipoxygenase in SL2 cells, indicating that the binding of Sp1 with Sp1 binding sequences played a significant role in the regulation of 12-lipoxygenase gene. (C) 1 999 Federation of European Biochemical Societies.