Project description:Retinoic Acid Receptors (RARs) as a functional heterodimer with Retinoid X Receptors (RXRs), bind a diverse series of RA-response elements (RAREs) in regulated genes. Among them, the non-canonical DR0 elements are bound by RXR-RAR with comparable affinities to DR5 elements but DR0 elements do not act transcriptionally as independent RAREs. In this work, we present structural insight for the recognition of DR5 and DR0 elements by RXR-RAR heterodimer using x-ray crystallography, small angle x-ray scattering, and hydrogen/deuterium exchange coupled to mass spectrometry. We solved the crystal structure of RXR-RAR DNA-binding domain in complex with the Rarb2 DR5 and RXR DNA-binding domain in complex with Hoxb13 DR0. While cooperative binding was observed on DR5, on DR0 the two molecules bound non-cooperatively on opposite sides of the DNA. In addition, our data unveil the structural organization and dynamics of the multi-domain RXR-RAR DNA complexes providing evidence for DNA-dependent allosteric communication between domains. Differential binding mode between DR0 and DR5 were observed leading to differences in the conformation and structural dynamics of the multi-domain RXR-RAR DNA complex. These results reveal that the topological organization of the RAR binding element confer regulatory information by modulating the overall topology and structural dynamics of the RXR-RAR heterodimers.
Project description:In mouse embryonic cells, a retinoic acid (RA) stimulation triggers a massive change of gene expression leading the pluripotent, proliferating cells to a lineage-specific differentiation process. The retinoic acid receptor (RAR) plays a key role in this response by inhibiting pluripotency-maintaining genes and simultaneously activating some major actors of cell differentiation. To investigate the mechanism underlying this dual regulation, we performed joint RAR/RXR ChIP-seq and mRNA-seq time series during the first 48 hours of the RA-induced Primitive Endoderm differentiation process in F9 embryonic carcinoma cells. We detected significantly more RAR/RXR binding regions than previous studies and identified among them a handful of typical binding intensity patterns during differentiation. We demonstrate that these patterns are correlated with the coincidental binding of essential transcription factors (TFs) for pluripotency maintenance or PrE differentiation of embryonic stem (ES) cells, as well as the presence of variants of RAR binding motifs. Most importantly, early-bound regions coincide with pluripotency-associated transcription factor binding in ES (like Pou5f1, Sox2, Esrrb and Nr5a2) and display an increased frequency of the DR0 type RAR binding motifs; late-bound sites are associated to the PrE marker Sox17 and are enriched in the canonical DR5 binding motif. Our data offer an unprecedently detailed view on the action of RA in triggering pluripotent cell differentiation. Altogether, this work sheds light on the relocation of RAR/RXR binding sites throughout differentiation, and shows how RAR/RXR progressively shift from DR0 enriched regions, which were specifically identified in undifferentiated models, to canonical RAR binding sites containing loci.
Project description:In mouse embryonic cells, a retinoic acid (RA) stimulation triggers a massive change of gene expression leading the pluripotent, proliferating cells to a lineage-specific differentiation process. The retinoic acid receptor (RAR) plays a key role in this response by inhibiting pluripotency-maintaining genes and simultaneously activating some major actors of cell differentiation. To investigate the mechanism underlying this dual regulation, we performed joint RAR/RXR ChIP-seq and mRNA-seq time series during the first 48 hours of the RA-induced Primitive Endoderm differentiation process in F9 embryonic carcinoma cells. We detected significantly more RAR/RXR binding regions than previous studies and identified among them a handful of typical binding intensity patterns during differentiation. We demonstrate that these patterns are correlated with the coincidental binding of essential transcription factors (TFs) for pluripotency maintenance or PrE differentiation of embryonic stem (ES) cells, as well as the presence of variants of RAR binding motifs. Most importantly, early-bound regions coincide with pluripotency-associated transcription factor binding in ES (like Pou5f1, Sox2, Esrrb and Nr5a2) and display an increased frequency of the DR0 type RAR binding motifs; late-bound sites are associated to the PrE marker Sox17 and are enriched in the canonical DR5 binding motif. Our data offer an unprecedently detailed view on the action of RA in triggering pluripotent cell differentiation. Altogether, this work sheds light on the relocation of RAR/RXR binding sites throughout differentiation, and shows how RAR/RXR progressively shift from DR0 enriched regions, which were specifically identified in undifferentiated models, to canonical RAR binding sites containing loci. Time course (0, 2, 6, 12, 24, 48h) after stimulation of F9 cultured cells by retinoic acid: PanRAR and PanRXR ChIP-seq at 0, 2, 24 and 48h (no replicate); WCE-seq at 0h (no replicate); mRNA-seq at 0, 6, 12, 24, 48h (2 replicates except for time 0h, 4 replicates). Additionally, a control time course (culture in DMSO) sampled at 24 and 48h (no replicates).
Project description:Retinoic Acid Receptors (RARs) bind RA-response elements in regulatory regions of their target genes. While canonical RAREs comprise direct repeats of the consensus 5’-RGKTCA-3’ sequence separated by 1, 2 or 5 nucleotides (DR1, DR2, DR5), we show that shortly after RA treatement of mouse embryoid bodies or F9 cells, RARs occupy a large repertoire of DR0, DR2, DR5, DR8 and IR0 elements. In vitro, RAR-RXR bind these non-canonical spacings with comparable affinities to DR2 and DR5. Most DR8 elements comprise three half sites with DR2 and DR0 spacings. This specific half site organisation constitutes a previously unrecognised, but frequent signature of RAR binding elements and acts as an RARE. At later stages of embryoid body differentiation, RARs relocalise to a restricted repertoire of sites comprising predominantly DR5 elements. Differentiation thus involves genomic relocalisation of RARs, and a switch from DR0 and DR8 at early times to DR5 at later stages. Examination of genomic localisation of RAR in differentiating embryoid bodies.
Project description:Many different molecular mechanisms have been suggested to be associated with PML-RAR dependent transformation of haematopoietic progenitors. Here, we investigated the role of PML-RAR and RXR in the organization of epigenetic structures at a genome-wide level. We identified 2722 high confidence PML-RAR binding sites in the leukemic model cell line NB4 and found PML-RAR colocalization with RXR to the vast majority of these binding regions. Importantly, these results could be corroborated and extended in primary blast cells of two APL patients. Through genome-wide epigenetic studies we show that treatment with pharmacological doses of all-trans retinoic acid ATRA induces global alterations in active H3 acetylation and repressive H3K27me3, H3K9me3 and DNA methylation chromatin modifications. However at the PML-RAR/RXR binding sites, ATRA only induces changes in H3 acetylation. These H3 acetylation alterations triggered by the loss of PML-RAR/RXR binding affect H3 acetylation and RNA polymerase II occupancy at nearby genes. Our results suggest that PML-RAR/RXR functions as a local chromatin modulator and that specific recruitment of histone deacetylase activities to genes important for haematopoietic differentiation, RAR signaling and epigenetic control is crucial to the transforming potential of PML-RAR/RXR. Examination of PML, RARa and RXR binding sites in leukemic cells before and after ATRA treatment, association with transcription via RNAPII occupancy and with chromatin modifications.
Project description:Many different molecular mechanisms have been suggested to be associated with PML-RAR dependent transformation of haematopoietic progenitors. Here, we investigated the role of PML-RAR and RXR in the organization of epigenetic structures at a genome-wide level. We identified 2722 high confidence PML-RAR binding sites in the leukemic model cell line NB4 and found PML-RAR colocalization with RXR to the vast majority of these binding regions. Importantly, these results could be corroborated and extended in primary blast cells of two APL patients. Through genome-wide epigenetic studies we show that treatment with pharmacological doses of all-trans retinoic acid ATRA induces global alterations in active H3 acetylation and repressive H3K27me3, H3K9me3 and DNA methylation chromatin modifications. However at the PML-RAR/RXR binding sites, ATRA only induces changes in H3 acetylation. These H3 acetylation alterations triggered by the loss of PML-RAR/RXR binding affect H3 acetylation and RNA polymerase II occupancy at nearby genes. Our results suggest that PML-RAR/RXR functions as a local chromatin modulator and that specific recruitment of histone deacetylase activities to genes important for haematopoietic differentiation, RAR signaling and epigenetic control is crucial to the transforming potential of PML-RAR/RXR.
Project description:Retinoic Acid Receptors (RARs) bind RA-response elements in regulatory regions of their target genes. While canonical RAREs comprise direct repeats of the consensus 5’-RGKTCA-3’ sequence separated by 1, 2 or 5 nucleotides (DR1, DR2, DR5), we show that shortly after RA treatement of mouse embryoid bodies or F9 cells, RARs occupy a large repertoire of DR0, DR2, DR5, DR8 and IR0 elements. In vitro, RAR-RXR bind these non-canonical spacings with comparable affinities to DR2 and DR5. Most DR8 elements comprise three half sites with DR2 and DR0 spacings. This specific half site organisation constitutes a previously unrecognised, but frequent signature of RAR binding elements and acts as an RARE. At later stages of embryoid body differentiation, RARs relocalise to a restricted repertoire of sites comprising predominantly DR5 elements. Differentiation thus involves genomic relocalisation of RARs, and a switch from DR0 and DR8 at early times to DR5 at later stages.
Project description:Retinoic acid receptors (RARs) ?, ?, and ? heterodimerize with Retinoid X receptors (RXR) ?, ?, and ? and bind the cis-acting response elements known as RAREs to execute the biological functions of retinoic acid during mammalian development. RAR? mediates the anti-proliferative and apoptotic effects of retinoids in certain tissues and cancer cells, such as melanoma and neuroblastoma cells. Furthermore, ablation of RAR? enhanced the tumor incidence of Ras transformed keratinocytes and was associated with resistance to retinoid mediated growth arrest and apoptosis. We used microarray analysis to identify genes, which upon 8 or 24 hr of treatment with all-trans retinoic acid display differential expression in RAR? knockout (RAR?KO) murine embryonic stem cells relative to CCE WT cells. We demonstrate that following RA treatment the majority of inducible transcripts are present at lower levels in RAR?KO ES cells compared to WT ES cells. Murine embryonic stem cells (WT and RAR?KO) were treated with either all-trans retinoic acid (up to 24 hr) or with vehicle control (EtOH).
Project description:To understand the manner by which RAR and RXR program cell state transitions, we performed ChIP-seq to identify their compendium of target genes in an unbiased manner. We exposed the mesenchymal NAMEC8 and SUM159 cancer cells to retinoid treatment, followed by the genome-wide analyses of target gene binding sites for RXR, RAR, H3K27ac and p300. Exposure to bexarotene, a RXR ligand, led to a subset of genes that became bound by RXR, as well as RAR, since both could form heterodimers. These genes furthermore showed increases in p300 binding, and H3K27ac (histone 3, lysine 27 acetylation) modification, which marks gene enhancers.
Project description:CD14+ human monocytes differentiating into DCs in the presence of IL4 and GM-CSF were treated with agonists for RXR and its partners or vehicle 18 hours after plating (experiment with RXR and permissive partners, donor 1-3) or 14 hours after plating (experiment with nonpermissive partners, donor 4-6). Cells were harvested 12 hours thereafter. Experiments were performed in biological triplicates representing samples from three different donors. In this study all probable RXR-signaling pathways induced by agonists for RXR, LXRs, PPARs, RAR and VDR were identified in differentiating human monocyte-derived dendritic cells. In the experiments, differentiating dendritic cells were treated for 12 hours with one of the following compounds (ligands): vehicle (DMS:EtOH 1:1) LG268 (RXR agonist) 9-cis retinoic acid (9cisRA, agonist of RAR and RXR) GW3965 (LXRalpha/beta panagonist) rosiglitazone (RSG, PPARgamma agonist) GW1516 (PPARdelta agonist) AM580 (RARalpha agonist) 1,25-dihydroxyvitamin D3 (VDR agonist)