Differential DNA binding by monomeric, homodimeric, and potentially heteromeric forms of the thyroid hormone receptor

Binding of the thyroid hormone receptor (TR) to thyroid hormone-responsive elements (TREs) is crucial for regulation of gene expression by thyroid hormone. The TR binds to each half-site of a palindromic TRE separately, as a monomer, or simultaneously, as a homodimer. In addition, the TR monomer interacts with a 42-kDa protein that may be responsible for an increase in the apparent size and stability of the TR-TRE complex after incubation with liver nuclear extract. The multiple DNA-binding forms of the TR contact the TRE differently but compete for binding in a dynamic equilibrium which is highly dependent on the relative concentrations of TR and nuclear protein. Thus, protein-protein interactions are likely to determine the context in which the TR binds to target genes and regulates the transcriptional response to thyroid hormone.

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The role of thyroid hormone receptor DNA binding in negative thyroid hormone-mediated gene transcription

Journal of Molecular Endocrinology ◽

10.1677/jme-08-0023 ◽

2008 ◽

Vol 41 (1) ◽

pp. 25-34 ◽

Cited By ~ 6

Author(s):

Anne Wulf ◽

Marianne G Wetzel ◽

Maxim Kebenko ◽

Meike Kröger ◽

Angelika Harneit ◽

...

Keyword(s):

Thyroid Hormone ◽

Dna Binding ◽

Gene Transcription ◽

Hormone Receptor ◽

Target Genes ◽

Thyroid Hormone Receptor ◽

Point Mutations ◽

Chimeric Protein ◽

Functional Consequences ◽

Glycerol 3 Phosphate Dehydrogenase

Thyroid hormone 3,3′,5-tri-iodothyronine (T3) regulates gene expression in a positive and negative manner. Here, we analyzed the regulation of a positively (mitochondrial glycerol-3-phosphate dehydrogenase) and negatively T3-regulated target gene (TSHα). Thyroid hormone receptor (TR) activates mGPDH but not TSH promoter fragments in a mammalian one-hybrid assay. Furthermore, we investigated functional consequences of targeting TR to DNA independent of its own DNA-binding domain (DBD). Using a chimeric fusion protein of the DBD of yeast transcription factor Gal4 with TR, we demonstrated a positive regulation of gene transcription in response to T3. T3-mediated activation of this chimeric protein is further increased after an introduction of point mutations within the DBD of TR. Moreover, we investigated the capacity of TR to negatively regulate gene transcription on a DNA-tethered cofactor platform. A direct binding of TR to DNA via its own DBD is dispensable in this assay. We investigated functional consequences of point mutations affecting different domains of TR. Our data indicate that the DBD of TR plays a key role in direct DNA binding on positively but not on negatively T3-regulated target genes. Nevertheless, the DBD is involved in mediating negative gene regulation independent of its capacity to bind DNA.

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The functional relationship between co-repressor N-CoR and SMRT in mediating transcriptional repression by thyroid hormone receptor α

Biochemical Journal ◽

10.1042/bj20071393 ◽

2008 ◽

Vol 411 (1) ◽

pp. 19-26 ◽

Cited By ~ 11

Author(s):

Kyung-Chul Choi ◽

So-Young Oh ◽

Hee-Bum Kang ◽

Yoo-Hyun Lee ◽

Seungjoo Haam ◽

...

Keyword(s):

Thyroid Hormone ◽

Hormone Receptor ◽

Transcriptional Repression ◽

Fatty Acid Synthase ◽

Hormone Receptors ◽

Target Genes ◽

Functional Relationship ◽

Thyroid Hormone Receptor ◽

B Cell Lymphoma ◽

Hormone Response Elements

A central issue in mediating repression by nuclear hormone receptors is the distinct or redundant function between co-repressors N-CoR (nuclear receptor co-repressor) and SMRT (silencing mediator of retinoid and thyroid hormone receptor). To address the functional relationship between SMRT and N-CoR in TR (thyroid hormone receptor)-mediated repression, we have identified multiple TR target genes, including BCL3 (B-cell lymphoma 3-encoded protein), Spot14 (thyroid hormone-inducible hepatic protein), FAS (fatty acid synthase), and ADRB2 (β-adrenergic receptor 2). We demonstrated that siRNA (small interfering RNA) treatment against either N-CoR or SMRT is sufficient for the de-repression of multiple TR target genes. By the combination of sequence mining and physical association as determined by ChIP (chromatin immunoprecipitation) assays, we mapped the putative TREs (thyroid hormone response elements) in BCL3, Spot14, FAS and ADRB2 genes. Our data clearly show that SMRT and N-CoR are independently recruited to various TR target genes. We also present evidence that overexpression of N-CoR can restore repression of endogenous genes after knocking down SMRT. Finally, unliganded, co-repressor-free TR is defective in repression and interacts with a co-activator, p300. Collectively, these results suggest that both SMRT and N-CoR are limited in cells and that knocking down either of them results in co-repressor-free TR and consequently de-repression of TR target genes.

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To bind or not to bind – how to down-regulate target genes by liganded thyroid hormone receptor?

Thyroid Research ◽

10.1186/1756-6614-1-4 ◽

2008 ◽

Vol 1 (1) ◽

pp. 4 ◽

Cited By ~ 14

Author(s):

Joachim M Weitzel

Keyword(s):

Thyroid Hormone ◽

Hormone Receptor ◽

Target Genes ◽

Thyroid Hormone Receptor

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In Vivo Activity of the Thyroid Hormone Receptor β- and α-Selective Agonists GC-24 and CO23 on Rat Liver, Heart, and Brain

Endocrinology ◽

10.1210/en.2010-0813 ◽

2011 ◽

Vol 152 (3) ◽

pp. 1136-1142 ◽

Cited By ~ 25

Author(s):

Carmen Grijota-Martínez ◽

Eric Samarut ◽

Thomas S. Scanlan ◽

Beatriz Morte ◽

Juan Bernal

Keyword(s):

Thyroid Hormone ◽

Hormone Receptor ◽

Target Genes ◽

Thyroid Hormone Receptor ◽

Receptor Subtype ◽

Receptor Subtypes ◽

Genetic Modifications ◽

Hormone Analogs ◽

Thyroid Hormone Receptor Β

Thyroid hormone analogs with selective actions through specific thyroid hormone receptor (TR) subtypes are of great interest. They might offer the possibility of mimicking physiological actions of thyroid hormone with receptor subtype or tissue specificity with therapeutic aims. They are also pharmacological tools to dissect biochemical pathways mediated by specific receptor subtypes, in a complementary way to mouse genetic modifications. In this work, we studied the in vivo activity in developing rats of two thyroid hormone agonists, the TRβ-selective GC-24 and the TRα-selective CO23. Our principal goal was to check whether these compounds were active in the rat brain. Analog activity was assessed by measuring the expression of thyroid hormone target genes in liver, heart, and brain, after administration to hypothyroid rats. GC-24 was very selective for TRβ and lacked activity on the brain. On the other hand, CO23 was active in liver, heart, and brain on genes regulated by either TRα or TRβ. This compound, previously shown to be TRα-selective in tadpoles, displayed no selectivity in the rat in vivo.

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A novel orphan receptor specific for a subset of thyroid hormone-responsive elements and its interaction with the retinoid/thyroid hormone receptor subfamily.

Molecular and Cellular Biology ◽

10.1128/mcb.14.10.7025 ◽

1994 ◽

Vol 14 (10) ◽

pp. 7025-7035 ◽

Cited By ~ 242

Author(s):

R Apfel ◽

D Benbrook ◽

E Lernhardt ◽

M A Ortiz ◽

G Salbert ◽

...

Keyword(s):

Amino Acid ◽

Thyroid Hormone ◽

Dna Binding ◽

Nuclear Receptors ◽

Nuclear Receptor ◽

Dna Sequences ◽

Hormone Receptor ◽

Thyroid Hormone Receptor ◽

Orphan Receptor ◽

Retinoid Receptor

The steroid/hormone nuclear receptor superfamily comprises several subfamilies of receptors that interact with overlapping DNA sequences and/or related ligands. The thyroid/retinoid hormone receptor subfamily has recently attracted much interest because of the complex network of its receptor interactions. The retinoid X receptors (RXRs), for instance, play a very central role in this subfamily, forming heterodimers with several receptors. Here we describe a novel member of this subfamily that interacts with RXR. Using a v-erbA probe, we obtained a cDNA which encodes a novel 445-amino-acid protein, RLD-1, that contains the characteristic domains of nuclear receptors. Northern (RNA) blot analysis showed that in mature rats, the receptor is highly expressed in spleen, pituitary, lung, liver, and fat. In addition, weaker expression is observed in several other tissues. Amino acid sequence alignment and DNA-binding data revealed that the DNA-binding domain of the new receptor is related to that of the thyroid/retinoid subgroup of nuclear receptors. RLD-1 preferentially binds as a heterodimer with RXR to a direct repeat of the half-site sequence 5'-G/AGGTCA-3', separated by four nucleotides (DR-4). Surprisingly, this binding is dependent to a high degree on the nature of the spacing nucleotides. None of the known nuclear receptor ligands activated RLD-1. In contrast, a DR-4-dependent constitutive transcriptional activation of a chloramphenicol acetyltransferase reporter gene by the RLD-1/RXR alpha heterodimer was observed. Our data suggest a highly specific role for this novel receptor within the network of gene regulation by the thyroid/retinoid receptor subfamily.

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Transgenic Analysis Reveals that Thyroid Hormone Receptor Is Sufficient To Mediate the Thyroid Hormone Signal in Frog Metamorphosis

Molecular and Cellular Biology ◽

10.1128/mcb.24.20.9026-9037.2004 ◽

2004 ◽

Vol 24 (20) ◽

pp. 9026-9037 ◽

Cited By ~ 96

Author(s):

Daniel R. Buchholz ◽

Akihiro Tomita ◽

Liezhen Fu ◽

Bindu D. Paul ◽

Yun-Bo Shi

Keyword(s):

Thyroid Hormone ◽

Hormone Receptor ◽

Target Genes ◽

Thyroid Hormone Receptor ◽

Gene Activation ◽

Inducible Promoter ◽

Vertebrate Development ◽

Transcription System

ABSTRACT Thyroid hormone (T3) has long been known to be important for vertebrate development and adult organ function. Whereas thyroid hormone receptor (TR) knockout and transgenic studies of mice have implicated TR involvement in mammalian development, the underlying molecular bases for the resulting phenotypes remain to be determined in vivo, especially considering that T3 is known to have both genomic, i.e., through TRs, and nongenomic effects on cells. Amphibian metamorphosis is an excellent model for studying the role of TR in vertebrate development because of its total dependence on T3. Here we investigated the role of TR in metamorphosis by developing a dominant positive mutant thyroid hormone receptor (dpTR). In the frog oocyte transcription system, dpTR bound a T3-responsive promoter and activated the promoter independently of T3. Transgenic expression of dpTR under the control of a heat shock-inducible promoter in premetamorphic tadpoles led to precocious metamorphic transformations. Molecular analyses showed that dpTR induced metamorphosis by specifically binding to known T3 target genes, leading to increased local histone acetylation and gene activation, similar to T3-bound TR during natural metamorphosis. Our experiments indicated that the metamorphic role of T3 is through genomic action of the hormone, at least on the developmental parameters tested. They further provide the first example where TR is shown to mediate directly and sufficiently these developmental effects of T3 in individual organs by regulating target gene expression in these organs.

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