Reports

Ras-independent growth factor signaling by transcription factor tyrosine phosphorylation

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Science  24 Sep 1993:
Vol. 261, Issue 5129, pp. 1736-1739
DOI: 10.1126/science.8378775

Abstract

Interferons induce transcriptional activation through tyrosine phosphorylation of the latent, cytoplasmic transcription factor interferon-stimulated gene factor-3 (ISGF-3). Growth factors and cytokines were found to use a similar pathway: The 91-kilodalton subunit of ISGF-3 was activated and tyrosine phosphorylated in response to epidermal growth factor (EGF), platelet-derived growth factor, and colony stimulating factor-1. The tyrosine phosphorylated factor acquired DNA binding activity and accumulated in nuclei. Activation required the major sites for autophosphorylation on the EGF receptor that bind Src homology region 2 domain-containing proteins implicated in Ras activation. However, activation of this factor was independent of the normal functioning of Ras.