Activation of the p21ras pathway couples antigen receptor stimulation to induction of the primary response gene egr-1 in B lymphocytes.

The primary response gene egr-1 encodes a sequence-specific transcription factor whose expression is necessary for antigen receptor-stimulated activation of B lymphocytes. The molecular processes involved in linking egr-1 induction to antigen receptor signaling have not been defined. The present study demonstrates that expression of an activated form of p21ras results in egr-1 induction similar to that previously shown after antigen receptor cross-linking. In addition, both antigen receptor cross-linking and p21ras use the same element in the egr-1 promoter to exert their effects. Using dominant-negative mutants of p21ras and raf-1, we demonstrate that induction of egr-1 after antigen receptor cross-linking is mediated by activation of the p21ras/mitogen-activated protein kinase signaling pathway. While regulation of the p21ras pathway during B cell activation has been intensively studied, this report represents the first description of a biologically relevant event associated with its activation.