Project description:Among its many roles in development, retinoic acid determines the anterior-posterior identity of differentiating motor neurons by activating Retinoic Acid Receptor (RAR)-mediated transcription. RAR is thought to bind the genome constitutively, and only induce transcription in the presence of the retinoid ligand. However, little is known about where RAR binds to the genome or how it selects target sites. We tested the constitutive RAR binding model using the retinoic acid-driven differentiation of mouse embryonic stem cells into differentiated motor neurons. We find that retinoic acid treatment results in widespread changes in RAR genomic binding, including novel binding to genes directly responsible for anterior-posterior specification, as well as the subsequent recruitment of the basal polymerase machinery. Finally, we discovered that the binding of transcription factors at the embryonic stem cell stage can accurately predict where in the genome RAR binds after initial differentiation. We have characterized a ligand-dependent shift in RAR genomic occupancy at the initiation of neurogenesis. Our data also suggests that enhancers active in pluripotent embryonic stem cells may be preselecting regions that will be activated by RAR during neuronal differentiation. The differentiation of ventral motor neurons is induced by treating embryonic stem cell cultures with retinoic acid. Here, ChIP-seq is used to profile the genome-wide occupancy of RAR isofroms both immediately prior to and during exposure of the cells to retinoic acid. ChIP-seq is also used to profile the genomic occupancy of Pol2 with phosphorylated serine 5 (Pol2-S5P) and phosphorylated serine 2 (Pol2-S2P) after exposure to retinoic acid.
Project description:Among its many roles in development, retinoic acid determines the anterior-posterior identity of differentiating motor neurons by activating Retinoic Acid Receptor (RAR)-mediated transcription. RAR is thought to bind the genome constitutively, and only induce transcription in the presence of the retinoid ligand. However, little is known about where RAR binds to the genome or how it selects target sites. We tested the constitutive RAR binding model using the retinoic acid-driven differentiation of mouse embryonic stem cells into differentiated motor neurons. We find that retinoic acid treatment results in widespread changes in RAR genomic binding, including novel binding to genes directly responsible for anterior-posterior specification, as well as the subsequent recruitment of the basal polymerase machinery. Finally, we discovered that the binding of transcription factors at the embryonic stem cell stage can accurately predict where in the genome RAR binds after initial differentiation. We have characterized a ligand-dependent shift in RAR genomic occupancy at the initiation of neurogenesis. Our data also suggests that enhancers active in pluripotent embryonic stem cells may be preselecting regions that will be activated by RAR during neuronal differentiation.
Project description:Nuclear hormone receptors (NRs) are ligand-binding transcription factors that are important therapeutic targets in malignancy. Hormone binding triggers NR activation and their subsequent proteasomal degradation through unknown ligand-dependent ubiquitin ligase machinery. NR degradation is therapeutically relevant: the oncogenic PML-RARA fusion between PML and the retinoic acid receptor (RARA) drives acute promyelocytic leukemia and degradation of PML-RARA induced by all-trans-retinoic acid (ATRA) is required for anti-tumor activity. Our work establishes UBR5-driven NR degradation as an integral regulator of transcriptional signaling by nuclear hormones.
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 (RARα,
β and γ) 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 RARα/γ but is
well-suited to the larger RARβ 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
RARβ, 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 RARα, β and
γ.
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.
Project description:Nuclear hormone receptors (NRs) are ligand-binding transcription factors that are important therapeutic targets in malignancy. Hormone binding triggers NR activation and their subsequent proteasomal degradation through unknown ligand-dependent ubiquitin ligase machinery. NR degradation is therapeutically relevant: the oncogenic PML-RARA fusion between PML and the retinoic acid receptor (RARA) drives acute promyelocytic leukemia and degradation of PML-RARA induced by all-trans-retinoic acid (ATRA) is required for anti-tumor activity. We identify a Leu-X-X-Leu-Leu (LxxLL) binding motif that associates with a conserved degron in RARA. A high-resolution crystal structure of the RARA ligand binding domain in complex with this LxxLL motif shows how UBR5 binding is mutually exclusive with nuclear co-activator engagement. Our work establishes UBR5-driven NR degradation as an integral regulator of transcriptional signaling by nuclear hormones.
Project description:The aim of this study is to profile gene expression dynamics during the in vitro differentiation of embryonic stem cells into ventral motor neurons. Expression levels were profiled using Affymetrix microarrays at six timepoints during in vitro differentiation: ES cells (Day 0), embryoid bodies (Day 2), retinoid induction of neurogenesis (Day 2 +8hours of exposure to retinoic acid), neural precursors (Day 3), progenitor motor neurons (Day 4), postmitotic motor neurons (Day 7). The differentiation of ventral motor neurons is induced by treating embryonic stem cell cultures with retinoic acid and hedgehog agonist. Here, gene expression patterns are profiled at various defined stages during the differentiation process using Affymetrix expression arrays.
Project description:Nuclear hormone receptors (NRs) are ligand-binding transcription factors that are widely targeted therapeutically. Hormone binding triggers NR activation and their subsequent proteasomal degradation through unknown ligand-dependent ubiquitin ligase machinery. NR degradation is therapeutically relevant. Efficacy of all-trans-retinoic acid (ATRA) for the treatment of acute promyelocytic leukemia requires degradation of the oncogenic fusion between the Promyelocytic Leukemia Protein (PML) with the Retinoic Acid Receptor Alpha (RARA). Here we use CRISPR-based screens to identify the HECT E3 ubiquitin ligase UBR5 as a ligase for PML-RARA and RARA and observe an agonist-dependent association between RARA and UBR5, which occurs directly on chromatin to regulate transcription. We present the cryo-EM structure of full-length human UBR5 and identify a Leu-X-X-Leu-Leu (LxxLL) binding motif that associates with a conserved degron in RARA. A high-resolution crystal structure of the RARA ligand binding domain in complex with this LxxLL motif shows how UBR5 binding is mutually exclusive with nuclear co-activator engagement. We demonstrate that UBR5 utilizes this conserved degron to additionally regulate hormone dependent protein stability for the glucocorticoid, progesterone, and vitamin D receptors. Our work establishes UBR5-driven NR degradation as an integral regulator of transcriptional signaling by nuclear hormones.
Project description:Nuclear hormone receptors (NRs) are ligand-binding transcription factors that are widely targeted therapeutically. Hormone binding triggers NR activation and their subsequent proteasomal degradation through unknown ligand-dependent ubiquitin ligase machinery. NR degradation is therapeutically relevant. Efficacy of all-trans-retinoic acid (ATRA) for the treatment of acute promyelocytic leukemia requires degradation of the oncogenic fusion between the Promyelocytic Leukemia Protein (PML) with the Retinoic Acid Receptor Alpha (RARA). Here we use CRISPR-based screens to identify the HECT E3 ubiquitin ligase UBR5 as a ligase for PML-RARA and RARA and observe an agonist-dependent association between RARA and UBR5, which occurs directly on chromatin to regulate transcription. We present the cryo-EM structure of full-length human UBR5 and identify a Leu-X-X-Leu-Leu (LxxLL) binding motif that associates with a conserved degron in RARA. A high-resolution crystal structure of the RARA ligand binding domain in complex with this LxxLL motif shows how UBR5 binding is mutually exclusive with nuclear co-activator engagement. We demonstrate that UBR5 utilizes this conserved degron to additionally regulate hormone dependent protein stability for the glucocorticoid, progesterone, and vitamin D receptors. Our work establishes UBR5-driven NR degradation as an integral regulator of transcriptional signaling by nuclear hormones.
Project description:The retinoic acid receptor-related orphan receptor γ (RORγ) is a ligand-dependent transcription factor that both underpins metabolic and immune functions and provides vantage to manipulate those processes pharmacologically. Despite its importance, our understanding of the ligand-dependent activities of RORγ is far from complete and developing a detailed structural model for RORγ pharmacology could provide a path towards the development of safe and efficacious therapeutics targeting the receptor. Herein, we examine the ligand-dependent assembly of recombinant RORγ:coregulator complexes on cognate DNA response elements using structural proteomics and small angle x-ray scattering. These studies reveal that the RORγ DNA binding domain can bind multiple different sequences of DNA, and that coregulatory proteins may be able to ‘sense’ the ligand- and DNA-bound status of RORγ. Overall, the efforts described herein will illuminate important aspects of RORγ activity and drug development that could lead to more efficacious treatments targeting this important receptor.
Project description:The retinoic acid receptor-related orphan receptor γ (RORγ) is a ligand-dependent transcription factor that both underpins metabolic and immune functions and provides vantage to manipulate those processes pharmacologically. Despite its importance, our understanding of the ligand-dependent activities of RORγ is far from complete and developing a detailed structural model for RORγ pharmacology could provide a path towards the development of safe and efficacious therapeutics targeting the receptor. Herein, we examine the ligand-dependent assembly of recombinant RORγ:coregulator complexes on cognate DNA response elements using structural proteomics and small angle x-ray scattering. These studies reveal that the RORγ DNA binding domain can bind multiple different sequences of DNA, and that coregulatory proteins may be able to ‘sense’ the ligand- and DNA-bound status of RORγ. Overall, the efforts described herein will illuminate important aspects of RORγ activity and drug development that could lead to more efficacious treatments targeting this important receptor.