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Activation of ternary complex factor Elk-1 by MAP kinases
R Janknecht1, W H Ernst, V Pingoud
1Institute for Molecular Biology, Hannover Medical School, Germany.
The EMBO Journal
|December 15, 1993
Summary
Mitogen-activated protein kinases (MAPKs) likely control Ternary Complex Factors (TCFs) like Elk-1 activity through direct in vivo phosphorylation. This phosphorylation enhances Elk-1
Area of Science:
- Molecular Biology
- Cell Signaling
- Gene Regulation
Background:
- Ternary complex factors (TCFs), including Elk-1, are involved in mediating c-fos induction.
- TCFs are known to be phosphorylated by mitogen-activated protein kinases (MAPKs) in vitro.
Purpose of the Study:
- To investigate the in vivo phosphorylation of Elk-1 by MAPKs.
- To determine the functional consequences of Elk-1 phosphorylation on its transactivation potential.
- To explore the role of Elk-1 in regulating different sets of genes.
Main Methods:
- Overexpression of MAPKs and constitutively activated Raf-1 kinase in vivo.
- Analysis of Elk-1 hyperphosphorylation and conformational changes.
- Site-directed mutagenesis of potential MAPK phosphorylation sites on Elk-1.
- Transcriptional assays using c-fos serum response element and Ets binding site.
Main Results:
- Recombinant Elk-1 undergoes hyperphosphorylation in vivo when MAPKs and activated Raf-1 are co-overexpressed.
- Phosphorylation induces a conformational change in Elk-1, enhancing its transactivation potential.
- Mutating mapped in vivo phosphorylation sites reduces Elk-1-mediated transcription.
- Elk-1 stimulates transcription from both the c-fos serum response element and Ets binding sites.
Conclusions:
- MAPKs likely control Elk-1 activity through direct in vivo phosphorylation.
- TCFs, specifically Elk-1, may regulate distinct gene sets via interactions with serum response factor and autonomous binding to Ets sites.