Previous studies demonstrated that the intraperitoneal injection of epidermal growth factor
(EGF) into mice resulted in the appearance, within minutes, of several tyrosine-
phosphorylated proteins in liver nuclei. Two of these proteins have been identified as the
transcription factors p91/p84 (Stat1 alpha/1 beta)(Ruff-Jamison, S., Chen, K., and Cohen,
S.(1993) Science 261, 1733-1736). We have now identified, by Western blotting and
immunoprecipitation, an additional EGF-modulated transcription factor, Stat3. We find that …