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The adenoviral E1A oncoprotein activates the Smad7 promoter: requirement of a functional E-box

Vandana S Dole1, Hans Smola, Steven Dooley

  • 1Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany.

International Journal of Oncology
|November 4, 2009
PubMed

Insights

Adenovirus (AdV) E1A oncoprotein upregulates Smad7, a transforming growth factor-beta (TGF-β) signaling inhibitor. This study reveals a new mechanism where AdV E1A activates the Smad7 promoter via upstream stimulatory factor, impacting TGF-β pathways.

Area of Science:

  • Molecular Biology
  • Virology
  • Cellular Signaling

Background:

  • DNA tumor viruses, including Adenoviruses (AdV) and Human Papillomaviruses (HPV), employ strategies to disrupt antiproliferative Transforming Growth Factor-beta (TGF-β) signaling.
  • Understanding these viral interference mechanisms is crucial for cancer research and therapeutic development.

Purpose of the Study:

  • To investigate the role of Adenovirus E1A oncoprotein in modulating TGF-β signaling pathways.
  • To identify the specific molecular mechanisms by which AdV interferes with TGF-β signaling.

Main Methods:

  • Analysis of Smad7 expression in response to viral oncoproteins.
  • Reporter assays to assess promoter activity of the Smad7 gene.
  • Electrophoretic mobility shift assays (EMSAs) to identify protein-DNA interactions at the Smad7 promoter.

Main Results:

  • Adenovirus E1A oncoprotein was found to be sufficient for inducing Smad7 expression, a known inhibitor of TGF-β signaling.
  • E1A, but not HPV oncoproteins, activated the Smad7 promoter.
  • A critical E-box element near the Smad7 promoter was essential for E1A-mediated transcriptional activation.
  • Upstream Stimulatory Factor (USF) was identified as the protein binding to the E-box, mediating E1A's effect.

Conclusions:

  • Adenovirus E1A oncoprotein utilizes a novel mechanism to induce Smad7, a cellular inhibitor of TGF-β signaling.
  • This E1A-induced upregulation of Smad7 involves the activation of the Smad7 promoter through binding of Upstream Stimulatory Factor to a proximal E-box.

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