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Distinct roles of the steroid receptor coactivator 1 and of MED1 in retinoid-induced transcription and cellular differentiation.

Abstract : Retinoic acid receptors (RARs) are the molecular relays of retinoid action on transcription, cellular differentiation and apoptosis. Transcriptional activation of retinoid-regulated promoters requires the dismissal of corepressors and the recruitment of coactivators to promoter-bound RAR. RARs recruit in vitro a plethora of coactivators whose actual contribution to retinoid-induced transcription is poorly characterized in vivo. Embryonal carcinoma P19 cells, which are highly sensitive to retinoids, were depleted from archetypical coactivators by RNAi. SRC1-deficient P19 cells showed severely compromised retinoid-induced responses, in agreement with the supposed role of SRC1 as a RAR coactivator. Unexpectedly, Med1/TRAP220/DRIP205-depleted cells exhibited an exacerbated response to retinoids, both in terms transcriptional responses and of cellular differentiation. Med1 depletion affected TFIIH and cdk9 detection at the prototypical retinoid-regulated RARbeta2 promoter, and favored a higher RNA polymerase II detection in transcribed regions of the RARbeta2 gene. Furthermore, the nature of the ligand impacted strongly on the ability of RARs to interact with a given coactivator and to activate transcription in intact cells. Thus RAR accomplishes transcriptional activation as a function of the ligand structure, by recruiting regulatory complexes which control distinct molecular events at retinoid-regulated promoters.
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Contributor : Philippe Lefebvre <>
Submitted on : Monday, June 12, 2006 - 11:32:59 AM
Last modification on : Monday, January 13, 2020 - 5:08:04 PM

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Sébastien Flajollet, Bruno Lefebvre, Christophe Rachez, Philippe Lefebvre. Distinct roles of the steroid receptor coactivator 1 and of MED1 in retinoid-induced transcription and cellular differentiation.. Journal of Biological Chemistry, American Society for Biochemistry and Molecular Biology, 2006, 281, pp.20338-48. ⟨10.1074/jbc.M603023200⟩. ⟨inserm-00079314⟩



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