Hypoxia Induces c-fos Transcription via a Mitogen-activated Protein Kinase-dependent Pathway*
- From the Institute of Biochemistry and Molecular Biology, Albert-Ludwigs-Universität Freiburg, Hermann-Herder-Strasse 7, D-79104 Freiburg, Germany
Abstract
Hypoxia is a pathophysiological condition that occurs during injury, ischemia, and stroke. It is characterized by a decrease of reactive oxygen intermediates and a change of the intracellular redox level. In tumors hypoxia is regarded as a trigger for enhanced growth and metastasis. Here we report that in HeLa cells, hypoxic conditions induce the transcriptional activation of c-fos transcription via the serum response element. Mutations in the binding site for the ternary complex factor Elk-1 and the serum response factor abolished this induction, indicating that a ternary complex at the serum response element is necessary for the induction of the c-fos gene under hypoxia. The transcription factor Elk-1 was covalently modified by phosphorylation in response to hypoxia. Furthermore this hyperphosphorylation of Elk-1, the activation of mitogen-activated protein kinase (MAPK), and the induction of c-fos transcripts were blocked by PD98059, a specific inhibitor of mitogen-activated protein kinase kinase/extracellular signal-regulated protein kinase kinase 1. Anin vitro kinase assay with Elk-1 as substrate showed that MAPK is activated under hypoxia. The activation of MAPK corresponds temporally with the phosphorylation and activation of Elk-1. Thus, a decrease of the intracellular reactive oxygen intermediate level by hypoxia induces c-fos via the MAPK pathway. These results suggest that the intracellular redox levels may be directly coupled to tumor growth, invasion, and metastasis via Elk-1-dependent induction of c-Fos controlled genes.
Footnotes
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↵* This work was supported by Grant Ru 601/1-1 of the Deutsche Forschungsgemeinschaft (to R. A. R.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵‡ Present address: Inst. for Experimental Cancer Research, Tumor Biology Center, Breisacher Str. 117, D-79106 Freiburg, Germany.
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↵§ Present address: Tularik Inc., Two Corporate Dr., South San Francisco, CA 94080.
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↵¶ To whom correspondence should be addressed. Present address: Dept. of Dermatology, Ludwig-Maximilians-Universität, Frauenlobstr. 9-11, D-80337 München, Germany.
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↵1 The abbreviations used are: SRE, serum response element; AP-1, activator protein 1; EMSA, electrophoretic mobility shift assay; ERK, extracellular signal-regulated protein kinase; MAPK, mitogen-activated protein kinase; MEK, mitogen-activated protein kinase kinase/extracellular signal-regulated protein kinase kinase; PMA, phorbol 12-myristate 13-acetate; ROI, reactive oxygen intermediate; SRF, serum response factor; TCF, ternary complex factor; SAP, stress-activated protein.
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- Received March 4, 1997.
- Revision received June 23, 1997.
