Functional divergence of the MAP kinase pathway ERK1 and ERK2 activate specific transcription factors

Abstract

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.