Effects of dominant negative Ras on SRE/AP-1 activity of c-fos promoter induced by hGM-CSF. The c-fos promoter fragment (nt ;ms 323 to ;ms276) fused to TK-CAT plasmid was transfected to BA/FGMR cells with either SR;ga dn Ras or vector control plasmids. After depletion of mIL-3 for 5 hours, cells were stimulated with hGM-CSF for another 5 hours. CAT activity was analyzed by diffusion assay.