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Mol. Cell. Biol., 05 1997, 2401-2412, Vol 17, No. 5
SA McCarthy, D Chen, BS Yang, JJ Garcia Ramirez, H Cherwinski, XR Chen, M Klagsbrun, CA Hauser, MC Ostrowski and M McMahon
Heparin-binding epidermal growth factor (HB-EGF) gene transcription is
rapidly activated in NIH 3T3 cells transformed by oncogenic Ras and Raf and
mediates the autocrine activation of the c-Jun N-terminal kinases (JNKs)
observed in these cells. A 1.7-kb fragment of the promoter of the murine
HB-EGF gene linked to a luciferase reporter was strongly induced following
activation of deltaRaf-1:ER, a conditionally active form of oncogenic human
Raf-1. Promoter activation by deltaRaf-1:ER required a composite AP-1/Ets
transcription factor binding site located between bp -974 and -988 upstream
of the translation initiation site. In vivo genomic footprinting indicated
that the basal level of occupancy of this composite AP-1/Ets element
increased following deltaRaf-1:ER activation. Cotransfection of Ets-2 and
p44 mitogen- activated protein (MAP) kinase expression vectors strongly
potentiated HB-EGF promoter activation in response to deltaRaf-1:ER.
Potentiated activation required both p44 MAP kinase catalytic activity and
threonine 72 in the Pointed domain of Ets-2. Biochemical assays
demonstrated the ability of the p42 and p44 MAP kinases to phosphorylate
Ets-2 on threonine 72. Importantly, in intact cells, the kinetics of
phosphorylation of Ets-2 on this residue closely mirror the activation of
the p42 and p44 MAP kinases and the observed onset of HB- EGF gene
transcription following deltaRaf-1:ER activation. These data firmly
establish Ets-2 as a direct target of the Raf-MEK-MAP kinase signaling
pathway and strongly implicate Ets-2 in the regulation of HB- EGF gene
expression.
Copyright © 1997, American Society for Microbiology
Rapid phosphorylation of Ets-2 accompanies mitogen-activated protein kinase activation and the induction of heparin-binding epidermal growth factor gene expression by oncogenic Raf-1
Department of Cell Signaling, DNAX Research Institute, Palo Alto, California 94304, USA.
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