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Cell. 1997 Jul 11;90(1):97-107.

Stimulation of RAR alpha activation function AF-1 through binding to the general transcription factor TFIIH and phosphorylation by CDK7.

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


The activity of the N-terminal activation function AF-1 of RAR alpha1 is abrogated upon mutation of a phosphorylatable serine residue (Ser-77). Recombinant RAR alpha was phosphorylated by a variety of proline-directed protein kinases in vitro. However, only the coexpression of cdk7 stimulated Ser-77 phosphorylation in vivo and enhanced transactivation by RAR alpha, but not by a S77A RAR mutant. Both free CAK (cdk7, cyclin H, MAT1) and the CAK-containing general transcription factor TFIIH phosphorylated Ser-77 in vitro. Furthermore RAR alpha bound free CAK and purified TFIIH in vitro, and RAR alpha-TFIIH complexes could be isolated from HeLa nuclear extracts. These findings represent the first example of activation of a transactivator through binding to and phosphorylation by a general transcription factor.

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