A GATA binding site is involved in the regulation of 15-lipoxygenase-1 expression in human colorectal carcinoma cell line, Caco-2

The data presented implicate a GATA binding site in the transcriptional reg ulation of 15-lipoxygenase-1 (15-LO-1) gene expression in human colorectal carcinoma Caco-2 cells. High expression of GATA-6 mRNA and protein was obse rved, while GATA-4 mRNA was expressed at a very low level in Caco-2 cells, The expression of GATA-6 was down-regulated, while 15-LO-1 expression was d ramatically up-regulated after treatment with sodium butyrate (NaBT), A stu dy using an electrophoretic mobility shift assay indicated that a GATA bind ing site of the 15-LO-1 promoter region binds to GATA proteins present in b oth undifferentiated and, to a lesser extent, NaBT-treated (differentiated) Caco-2 cells. Moreover, that DNA binding shift band was disrupted after th e addition of GATA-6 antibody in a supershift assay in the absence of NaBT, suggesting that GATA-6 is bound to the GATA binding site of the 15-LO-1 pr omoter in undifferentiated cells, In contrast, the addition of GATA-6 antib ody did not affect the DNA binding ability in NaBT-induced differentiated c ells. On the other hand, mutation of the GATA site of the 15-LO-1 promoter decreased the transactivation of the 15-LO-1 promoter as measured by lucife rase activity in both FBS and NaBT cultured cells, indicating an unknown GA TA binding protein to up-regulate 15-LO-1 expression. These implicate the G ATA site at -240 of the proximal region of the 15-LO-1 promoter in the basi c transcription of 15-LO-1 gene expression in Caco-2 cells, with GAT4-6 act ing to repress 15-LO-1 expression, (C) 2000 Federation of European Biochemi cal Societies.