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Stimulation of RAR alpha activation function AF-1 through binding to the general transcription factor TFIIH and

C Rochette-Egly1, S Adam, M Rossignol

  • 1Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, Université Louis Pasteur, Collège de France, Illkirch, Strasbourg.

Cell
|July 11, 1997
PubMed

Insights

Retinoid acid receptor alpha (RAR alpha) activity depends on Ser-77 phosphorylation. Cyclin-dependent kinase 7 (CDK7) and transcription factor TFIIH bind and phosphorylate RAR alpha, enhancing its transactivation function.

Area of Science:

  • Molecular Biology
  • Gene Regulation
  • Protein Phosphorylation

Background:

  • The N-terminal activation function AF-1 of Retinoic Acid Receptor alpha (RAR alpha) is crucial for its activity.
  • Phosphorylation of specific residues, like Ser-77, can modulate RAR alpha's function.

Purpose of the Study:

  • To investigate the role of Ser-77 phosphorylation in RAR alpha transactivation.
  • To identify the kinases responsible for Ser-77 phosphorylation in vivo and in vitro.
  • To explore the interaction between RAR alpha and general transcription factors.

Main Methods:

  • Site-directed mutagenesis to create a S77A RAR mutant.
  • In vitro phosphorylation assays using recombinant RAR alpha and various kinases.
  • In vivo co-expression studies to assess the effect of cdk7 on Ser-77 phosphorylation and transactivation.
  • Co-immunoprecipitation to detect RAR alpha binding to CAK and TFIIH.

Main Results:

  • Mutation of Ser-77 abrogated RAR alpha AF-1 activity.
  • CDK7 co-expression enhanced Ser-77 phosphorylation and RAR alpha transactivation in vivo.
  • Both free CDK-Activating Kinase (CAK) and TFIIH phosphorylated Ser-77 in vitro.
  • RAR alpha directly binds to CAK and TFIIH.

Conclusions:

  • Ser-77 phosphorylation by CDK7 is essential for RAR alpha transactivation.
  • RAR alpha interacts with the general transcription factor TFIIH.
  • This study demonstrates, for the first time, transactivator activation via binding and phosphorylation by a general transcription factor.

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