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A Study of Allostery Within Liganded RARα:RXR Heterodimers at the Genome Scale [CUT&Run]

ABSTRACT: We provide evidence of coordination between heterodimeric nuclear hormone receptor ligands at the genome scale to reveal three unique transcriptional outcomes. First, when stimulated in pancreatic acinar cells, distinct doubly-liganded complexes of the retinoic acid receptor-α (RARα) and retinoid-X-receptor (RXR) bind divergent DNA hormone response elements (HRE). Furthermore, the link between ligand pairs and HRE specificity is correlated with RNA transcript formation. Second, RXR ligands can function as either silent partners or as cooperative effectors on distinct HREs, also with correlated transcriptional outcomes. Third, the absence of unique binding sites on DNA by unliganded RARα:RXR suggests that productive HRE recognition and binding is an exclusive feature of the agonist-bound heterodimer. To achieve the above, DNA-bound heterodimers of RARα:RXR were isolated separately with an RARα-specific antibody, RARα-specific and RXR-specific agonists and the pan-ligand, 9-cis retinoic acid, using the CUT&RUN technique. At each liganded state, transcriptional activity was detected by mRNA sequencing.

ORGANISM(S): Mus musculus

PROVIDER: GSE290328 | GEO | 2025/02/24

REPOSITORIES: GEO

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Project description:We defined the RARα interactome in the MDA-MB453 breast cancer cell line genetically engineered to over-express an N-terminally tagged version of the nuclear retinoic acid receptor. Twenty eight nuclear proteins which interact with RARα and whose interaction is stimulated or reduced by the pan-RAR ligand, all-trans retinoic acid (ATRA) were identified. Given the potential significance of the S100A3 calcium-binding protein in the control of tumor progression, we focused our attention on this factor. Using the two models represented by the ATRA-sensitive SKBR3 and MCF7 breast cancer cell lines characterized by constitutive expression of S100A3 and RARα, we demonstrate that the endogenous forms of S100A3 and RARα interact in physiological conditions. The interaction of S100A3 with RARα is cell context independent and it is observed not only in breast cancer but also in acute promyelocytioc leukemia (APL) cells, characterized by expression of the RARα-derived PML-RARα oncogene, which is the product of the t(15:17) chromosomal translocation. S100A3 interacts directly and specifically with RARα and PML-RARα, being unable to bind other members of the RAR/RXR family of retinoid nuclear receptors. The interaction surface maps to the carboxyl-terminal region of the RARα ligand binding domain. Binding of S100A3 to RARα and PML-RARα controls the constitutive and ATRA-dependent degradation of the two receptors. Silencing of the S100A3 gene decreases the amounts of RARα in breast SK-BR-3 and lung A549 cancer cells, rendering them more refractory to the anti-proliferative action of ATRA. In SK-BR-3 cells, this effect is accompanied by a decrease in the lactogenic/differentiating action of ATRA. In APL-derived NB4 cells, S100A3 knock-down reduces the amounts of both RARα and PML-RARα. Contemporaneous down-regulation of the two receptors is associated with an increase in the basal and ATRA-induced expression of many granulocytic differentiation markers. Opposite on RARα and PML-RARα levels as well as ATRA induced differentiation markers are observed upon over-expression of S100A3 in NB4 cells.

Project description:Haffez2017 - RAR interaction with synthetic analogues This model is described in the article: The molecular basis of the interactions between synthetic retinoic acid analogues and the retinoic acid receptors Hesham Haffez, David R. Chisholm, Roy Valentine, Ehmke Pohl, Christopher Redfern and Andrew Whiting MedChemComm Abstract: All-trans-retinoic acid (ATRA) and its synthetic analogues EC23 and EC19 direct cellular differentiation by interacting as ligands for the retinoic acid receptor (RARÎ±, Î² and Î³) family of nuclear receptor proteins. To date, a number of crystal structures of natural and synthetic ligands complexed to their target proteins have been solved, providing molecular level snap-shots of ligand binding. However, a deeper understanding of receptor and ligand flexibility and conformational freedom is required to develop stable and effective ATRA analogues for clinical use. Therefore, we have used molecular modelling techniques to define RAR interactions with ATRA and two synthetic analogues, EC19 and EC23, and compared their predicted biochemical activities to experimental measurements of relative ligand affinity and recruitment of coactivator proteins. A comprehensive molecular docking approach that explored the conformational space of the ligands indicated that ATRA is able to bind the three RAR proteins in a number of conformations with one extended structure being favoured. In contrast the biologically-distinct isomer, 9-cis-retinoic acid (9CRA), showed significantly less conformational flexibility in the RAR binding pockets. These findings were used to inform docking studies of the synthetic retinoids EC23 and EC19, and their respective methyl esters. EC23 was found to be an excellent mimic for ATRA, and occupied similar binding modes to ATRA in all three target RAR proteins. In comparison, EC19 exhibited an alternative binding mode which reduces the strength of key polar interactions in RARÎ±/Î³ but is well-suited to the larger RARÎ² binding pocket. In contrast, docking of the corresponding esters revealed the loss of key polar interactions which may explain the much reduced biological activity. Our computational results were complemented using an in vitro binding assay based on FRET measurements, which showed that EC23 was a strongly binding, pan-agonist of the RARs, while EC19 exhibited specificity for RARÎ², as predicted by the docking studies. These findings can account for the distinct behaviour of EC23 and EC19 in cellular differentiation assays, and additionally, the methods described herein can be further applied to the understanding of the molecular basis for the selectivity of different retinoids to RARÎ±, Î² and Î³. This model is hosted on BioModels Database and identified by: BIOMD0000000629. To cite BioModels Database, please use: BioModels Database: An enhanced, curated and annotated resource for published quantitative kinetic models. To the extent possible under law, all copyright and related or neighbouring rights to this encoded model have been dedicated to the public domain worldwide. Please refer to CC0 Public Domain Dedication for more information.

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A Study of Allostery Within Liganded RARα:RXR Heterodimers at the Genome Scale [CUT&Run]

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