FUNCTIONAL DIVERGENCE OF THE MAP KINASE PATHWAY - ERK1 AND ERK2 ACTIVATE SPECIFIC TRANSCRIPTION FACTORS

Growth factor-receptor interactions at the cell surface eventually leading to the transcriptional activation of immediate early genes is mediated by the mitogen-activated protein kinase (MAP kinase/MAPK) cascade. Here we show that overexpression of extracellular signal-regulated kinase 1 (ERK1) cDNA, encoding p44(mapk), results in the activation of Elk-1, the serum response factor accessory protein. We also show that overexpression of ERK2, encoding p42(mapk), activates Myc, but not Elk-1. Therefore, the MAP kinase cascade diverges with at least one specific target for each MAP kinase isoform and provides a novel mechanism for differential regulation of this signaling pathway.