Elk-1 and p35-C/EBPβ synergize in SRF dependent transactivation of a GAL4 reporter construct. NIH 3T3 cells were transfected with 1 μg of pG5CAT alone, with 0.5 μg of pGAL4-SRF, or with 0.5 μg of pGAL4-SRF and 0.5 μg of pCMV-LAP (encoding p35-C/EBPβ) and/or 0.5 μg of pCMV-Elk-1 as indicated, in the absence and presence of 1 μg pCMV-Ras.V12. Total DNA in each transfection was adjusted to 3.5 μg with pUC19. Cells were serum deprived for 40 h prior to harvesting. CAT activity was measured as previously described . Data are the average of 14 determinations, and error bars represent standard error.