title: The elongation complex components BRD4 and MLLT3/AF9 are transcriptional coactivators of nuclear retinoid receptors.
abstract: Nuclear all-trans retinoic acid receptors (RARs) initiate early transcriptional events which engage pluripotent cells to differentiate into specific lineages. RAR-controlled transactivation depends mostly on agonist-induced structural transitions in RAR C-terminus (AF-2), thus bridging coactivators or corepressors to chromatin, hence controlling preinitiation complex assembly. However, the contribution of other domains of RAR to its overall transcriptional activity remains poorly defined. A proteomic characterization of nuclear proteins interacting with RAR regions distinct from the AF-2 revealed unsuspected functional properties of the RAR N-terminus. Indeed, mass spectrometry fingerprinting identified the Bromodomain-containing protein 4 (BRD4) and ALL1-fused gene from chromosome 9 (AF9/MLLT3), known to associate with and regulates the activity of Positive Transcription Elongation Factor b (P-TEFb), as novel RAR coactivators. In addition to promoter sequences, RAR binds to genomic, transcribed regions of retinoid-regulated genes, in association with RNA polymerase II and as a function of P-TEFb activity. Knockdown of either AF9 or BRD4 expression affected differentially the neural differentiation of stem cell-like P19 cells. Clusters of retinoid-regulated genes were selectively dependent on BRD4 and/or AF9 expression, which correlated with RAR association to transcribed regions. Thus RAR establishes physical and functional links with components of the elongation complex, enabling the rapid retinoid-induced induction of genes required for neuronal differentiation. Our data thereby extends the previously known RAR interactome from classical transcriptional modulators to components of the elongation machinery, and unravel a functional role of RAR in transcriptional elongation.
authors.affiliation: European Genomic Institute for Diabetes-EGID, FR 3508, Lille, France.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Flajollet
authors.forename: Christophe
authors.initials: C
authors.lastname: Rachez
authors.forename: Maheul
authors.initials: M
authors.lastname: Ploton
authors.forename: Céline
authors.initials: C
authors.lastname: Schulz
authors.forename: Rozenn
authors.initials: R
authors.lastname: Gallais
authors.forename: Raphaël
authors.initials: R
authors.lastname: Métivier
authors.forename: Michal
authors.initials: M
authors.lastname: Pawlak
authors.forename: Aymeric
authors.initials: A
authors.lastname: Leray
authors.forename: Al Amine
authors.initials: AA
authors.lastname: Issulahi
authors.forename: Laurent
authors.initials: L
authors.lastname: Héliot
authors.forename: Bart
authors.initials: B
authors.lastname: Staels
authors.forename: Gilles
authors.initials: G
authors.lastname: Salbert
authors.forename: Philippe
authors.initials: P
authors.lastname: Lefebvre
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D015415:Biomarkers / Q000378:metabolism; D015153:Blotting, Western; D018797:Cell Cycle Proteins; D002454:Cell Differentiation; D049109:Cell Proliferation; D047369:Chromatin Immunoprecipitation; D005455:Fluorescent Antibody Technique; D020869:Gene Expression Profiling; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D039904:Pluripotent Stem Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D042925:Positive Transcriptional Elongation Factor B / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D018168:Receptors, Retinoic Acid / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D014212:Tretinoin / Q000494:pharmacology; D000092468:Bromodomain Containing Proteins
chemical_list: D000970:Antineoplastic Agents; D015415:Biomarkers; D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; D042925:Positive Transcriptional Elongation Factor B; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D018168:Receptors, Retinoic Acid; D014157:Transcription Factors; D014212:Tretinoin; C441289:BRD4 protein, human; D000092468:Bromodomain Containing Proteins; C489901:MLLT3 protein, human