Elk-1 and p35-C/EBPβ synergize in transactivation of the SRE. NIH 3T3 cells were transfected with 0.75 μg of SRE.CAT and 0.75 μg pCMV-SRF alone or with 0.75 μg pCMV-LAP or 0.75 μg pCMV-Elk1 in the absence or presence of 0.75 μg pCMV-Ras.V12. Cells were serum deprived for 40 h prior to harvesting. CAT activity was measured as previously described . Data are the average of 4 determinations, and error bars represent standard error.