MUTATED RAS INDUCED PLDI GENE EXPRESSION THROUGH INCREASED Spl TRASCRIPTION FACTOR

摘要

The underlying mechanisms of oncogene-induced phospholipase D (PLD) activation have not been fully elucidated. The effect of the mutated-ras on PLD mRNA was examined using colon cancer cell lines as well as mock- and mutated ras-transfected NIH3T3 cells. Ras-mutation and activation were correlated, and cells with enhanced ras-activation showed increased PLDI mRNA and protein. Analysis of the 5' PLDI promoter using a representative cell line, DLD-1 and also mutated ras-NIH3T3, showed one Spl-site as the important ras-responsible motif. Spl inhibition with mithramycin A and Spl siRNA inhibited PLD1 protein expression and its promoter activity. Spl but not Sp3 protein level and increased Spl-motif binding activity were correlated with ras ativation. Furthermore, overexpression of Spl in drosophila SL2 cells lacking Sp family proteins increased PLD1 promoter activity. EMSA and chromatin immunoprecipitation assay confirmed the importance of Spl protein binding to the Spl-motif in ras-induced PLDI mRNA expression.