The structure of corepressor Dax-1 bound to its target nuclear receptor LRH-1

Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94143, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 12/2008; 105(47):18390-5. DOI: 10.1073/pnas.0808936105
Source: PubMed


The Dax-1 protein is an enigmatic nuclear receptor that lacks an expected DNA binding domain, yet functions as a potent corepressor of nuclear receptors. Here we report the structure of Dax-1 bound to one of its targets, liver receptor homolog 1 (LRH-1). Unexpectedly, Dax-1 binds to LRH-1 using a new module, a repressor helix built from a family conserved sequence motif, PCFXXLP. Mutations in this repressor helix that are linked with human endocrine disorders dissociate the complex and attenuate Dax-1 function. The structure of the Dax-1:LRH-1 complex provides the molecular mechanism for the function of Dax-1 as a potent transcriptional repressor.

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    • "Several coregulator peptides, including those corresponding to the coactivator NCoA2 (Krylova et al., 2005; Musille et al., 2012) and corepressor SHP (Li et al., 2005a; Ortlund et al., 2005), have been co-crystallized with and imaged bound to the LRH-1 LBD. In addition, two regulatory protein domains corresponding to the armadillo repeats of human β-catenin (Yumoto et al., 2012) and the C-terminal region of mouse Dax-1 (Sablin et al., 2008), were imaged in association with the LRH-1 LBD. However, no LRH-1 structure has been determined with a peptide corresponding to the regulatory Nterminal region of DAX-1 implicated in nuclear translocation of the receptor. "
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    ABSTRACT: The nuclear receptor LRH-1 (Liver Receptor Homolog-1, NR5A2) is a transcription factor that regulates gene expression programs critical for many aspects of metabolism and reproduction. Although LRH-1 is able to bind phospholipids, it is still considered an orphan nuclear receptor (NR) with an unknown regulatory hormone. Our prior cellular and structural studies demonstrated that the signaling phosphatidylinositols PI(4,5)P2 (PIP2) and PI(3,4,5)P3 (PIP3) bind and regulate SF-1 (Steroidogenic Factor-1, NR5A1), a close homolog of LRH-1. Here, we describe the crystal structure of human LRH-1 ligand binding domain (LBD) bound by PIP3 - the first phospholipid with a head group endogenous to mammals. We show that the phospholipid hormone binds LRH-1 with high affinity, stabilizing the receptor LBD. While the hydrophobic PIP3 tails (C16/C16) are buried inside the LRH-1 ligand binding pocket, the negatively charged PIP3 head group is presented on the receptor surface, similar to the phosphatidylinositol binding mode observed in the PIP3-SF-1 structure. Thus, data presented in this work reinforce our earlier findings demonstrating that signaling phosphatidylinositols regulate the NR5A receptors LRH-1 and SF-1.
    Full-text · Article · Sep 2015 · Journal of Structural Biology
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    • "Additionally, DAX1 contains a potent transcriptional repressor domain in its C-terminus [158] [159]. Although there is not yet a protein structure available for human DAX1, the LBD of the mouse homolog has been resolved (PDB ID: 3F5C [160]) and established that the C-terminal domain does not contain a ligand binding site. "
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    ABSTRACT: Nuclear receptors (NRs), a family of 48 transcriptional factors, have been studied intensively for their roles in cancer development and progression. The presence of distinctive ligand binding sites capable of interacting with small molecules has made NRs attractive targets for developing cancer therapeutics. In particular, a number of drugs have been developed over the years to target human androgen- and estrogen receptors for the treatment of prostate cancer and breast cancer. In contrast, orphan nuclear receptors (ONRs), which in many cases lack known biological functions or ligands, are still largely under investigated. This review is a summary on ONRs that have been implicated in prostate and breast cancers, specifically retinoic acid-receptor-related orphan receptors (RORs), liver X receptors (LXRs), chicken ovalbumin upstream promoter transcription factors (COUP-TFs), estrogen related receptors (ERRs), nerve growth factor 1B-like receptors, and "dosage-sensitive sex reversal, adrenal hypoplasia critical region, on chromosome X, gene 1" (DAX1). Discovery and development of small molecules that can bind at various functional sites on these ONRs will help determine their biological functions. In addition, these molecules have the potential to act as prototypes for future drug development. Ultimately, the therapeutic value of targeting the ONRs may go well beyond prostate and breast cancers.
    Full-text · Article · Oct 2014 · Cancer Treatment Reviews
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    • "The primary sequence of TLX LBD comprises amino-acids 187–385. Similar to DAX1 (dosage-sensitive sex reversal, adrenal hypoplasia critical region, on chromosome X, gene 1; NR0B1) [38], SHP (Small Heterodimer partner, NR0B2) [39] and PNR [37], the structural alignment used for designing the TLX LBD model (Fig. 1) revealed that it is shorter than other NR LBDs and lacks the first helices α1 and α2. The alignment also reveals a unique insertion (aa. "
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    ABSTRACT: Nuclear receptors (NRs) are an important group of ligand-dependent transcriptional factors. Presently, no natural or synthetic ligand has been identified for a large group of orphan NRs. Small molecules to target these orphan NRs will provide unique resources for uncovering regulatory systems that impact human health and to modulate these pathways with drugs. The orphan NR tailless (TLX, NR2E1), a transcriptional repressor, is a major player in neurogenesis and Neural Stem Cell (NSC) derived brain tumors. No chemical probes that modulate TLX activity are available, and it is not clear whether TLX is druggable. To assess TLX ligand binding capacity, we created homology models of the TLX ligand binding domain (LBD). Results suggest that TLX belongs to an emerging class of NRs that lack LBD helices α1 and α2 and that it has potential to form a large open ligand binding pocket (LBP). Using a medium throughput screening strategy, we investigated direct binding of 20,000 compounds to purified human TLX protein and verified interactions with a secondary (orthogonal) assay. We then assessed effects of verified binders on TLX activity using luciferase assays. As a result, we report identification of three compounds (ccrp1, ccrp2 and ccrp3) that bind to recombinant TLX protein with affinities in the high nanomolar to low micromolar range and enhance TLX transcriptional repressive activity. We conclude that TLX is druggable and propose that our lead compounds could serve as scaffolds to derive more potent ligands. While our ligands potentiate TLX repressive activity, the question of whether it is possible to develop ligands to de-repress TLX activity remains open.
    Full-text · Article · Jun 2014 · PLoS ONE
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