TFIIH interacts with the retinoic acid receptor gamma and phosphorylates its AF-1-activating domain through cdk7

Retinoic acid receptor gamma (RAR gamma) is phosphorylated in COS-1 cells a t two conserved serine residues located in the N-terminal region (serines 7 7 and 79 in RAR gamma 1 and serines 66 and 68 in RAR gamma 2) that contains the activation function AF-1. These serines are phosphorylated in vitro by cdk7, a cyclin-dependent kinase associated to cyclin H and MAT1 in the CAK complex (cdk7 cyclin H MAT1), that is found either free or as a component of the transcription/DNA repair factor TFIIH, RAR gamma is more efficiently phosphorylated by TFIIH than by CAK. and interacts not only with cdk7 but also with several additional subunits of TFIIH. RAR gamma phosphorylation a nd interaction with TFIIH occur in a ligand-independent manner. Our data de monstrate also that phosphorylation of the AF-1 function modulates RAR gamm a transcriptional activity in a response gene-dependent manner.