Cyclin H binding to the RARalpha activation function (AF)-2 domain directs phosphorylation of the AF-1 domain by cyclin-dependent kinase 7.

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Bour, Gaétan | Gaillard, Emilie | Bruck, Nathalie | Lalevée, Sébastien | Plassat, Jean-Luc | Busso, Didier | Samama, Jean-Pierre | Rochette-Egly, Cécile

Edité par CCSD ; National Academy of Sciences -

International audience. The transcriptional activity of nuclear retinoic acid receptors (RARs), which act as RAR/retinoid X receptor (RXR) heterodimers, depends on two activation functions, AF-1 and AF-2, which are targets for phosphorylations and synergize for the activation of retinoic acid target genes. The N-terminal AF-1 domain of RARalpha is phosphorylated at S77 by the cyclin-dependent kinase (cdk)-activating kinase (CAK) subcomplex (cdk7/cyclin H/MAT1) of the general transcription factor TFIIH. Here, we show that phosphorylation of S77 governing the transcriptional activity of RARalpha depends on cyclin H binding at a RARalpha region that encompasses loop 8-9 and the N-terminal tip of helix 9 of the AF-2 domain. We propose a model in which the structural constraints of this region control the architecture of the RAR/RXR/TFIIH complex and therefore the efficiency of RARalpha phosphorylation by cdk7. To our knowledge, this study provides the first example of a cooperation between the AF-2 and AF-1 domains of RARs through a kinase complex.

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