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Sci. Signal., 5 May 2009
Vol. 2, Issue 69, p. ra20
[DOI: 10.1126/scisignal.1164302]


Complexity in Transcription Control at the Activation Domain–Mediator Interface

Michael A. Balamotis1, Mario A. Pennella1, Jennitte L. Stevens2, Bohdan Wasylyk3, Andrew S. Belmont4, and Arnold J. Berk1*

1 Department of Microbiology, Immunology and Molecular Genetics, Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA.
2 Protein Sciences Department, Amgen Inc., Thousand Oaks, CA 91320, USA.
3 Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch cedex 67404, France.
4 Department of Cell and Structural Biology, University of Illinois, Urbana-Champaign, Urbana, IL 61801, USA.

Abstract: Transcript elongation by polymerase II paused at the Egr1 promoter is activated by mitogen-activated protein kinase phosphorylation of the ternary complex factor (TCF) ELK1 bound at multiple upstream sites and subsequent phospho-ELK1 interaction with mediator through the MED23 subunit. Consequently, Med23 knockout (KO) nearly eliminates Egr1 (early growth response factor 1) transcription in embryonic stem (ES) cells, leaving a paused polymerase at the promoter. Med23 KO did not, however, eliminate Egr1 transcription in fibroblasts. Chromatin immunoprecipitation analysis and direct visualization of fluorescently labeled TCF derivatives and mediator subunits revealed that three closely related TCFs bound to the same control regions. The relative amounts of these TCFs, which responded differently to the loss of MED23, differed in ES cells and fibroblasts. Transcriptome analysis suggests that most genes expressed in both cell types, such as Egr1, are regulated by alternative transcription factors in the two cell types that respond differently to the same signal transduction pathways.

* To whom correspondence should be addressed. E-mail: berk{at}

Citation: M. A. Balamotis, M. A. Pennella, J. L. Stevens, B. Wasylyk, A. S. Belmont, A. J. Berk, Complexity in Transcription Control at the Activation Domain–Mediator Interface. Sci. Signal. 2, ra20 (2009).

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