v-Src activates gene expression mediated by serum response elements (SREs) and TPA response elements (TREs). v-Src-induced SRE- and TRE-mediated gene expressions are both dependent upon HaRas. Protein phosphatase 2A (PP2A) is a serine/threonine phosphatase that has been implicated in v-Src-initiated signals. We report here that expression of the catalytic subunit of PP2A upregulates v-Src- and v-HaRas-induced TRE-mediated gene expression, whereas PP2A downregulates v-Src- and v-HaRas-induced SRE-mediated gene expression. These data suggest that intracellular signals activated by v-Src and mediated by HaRas are differentially regulated by PP2A.