scholarly journals A conserved C-terminal sequence that is deleted in v-ErbA is essential for the biological activities of c-ErbA (the thyroid hormone receptor).

1993 ◽  
Vol 13 (6) ◽  
pp. 3675-3685 ◽  
Author(s):  
F Saatcioglu ◽  
P Bartunek ◽  
T Deng ◽  
M Zenke ◽  
M Karin
Keyword(s):  
Amino Acid ◽  
Thyroid Hormone ◽  
Transcriptional Activation ◽  
Thyroid Hormone Receptor ◽  
Retinoic Acid Receptor ◽  
Biological Activities ◽  
Erythroid Differentiation ◽  
Dependent Manner ◽  
Transcriptional Interference ◽  
Terminal Sequence

The thyroid hormone (T3) receptor type alpha, the c-ErbA alpha proto-oncoprotein, stimulates transcription of T3-dependent promoters, interferes with AP-1 activity, and induces erythroid differentiation in a ligand-dependent manner. The v-ErbA oncoprotein does not bind hormone and has lost all of these activities. Using c-ErbA/v-ErbA chimeras, we found that a deletion of 9 amino acids, conserved among many members of the nuclear receptor superfamily, which are located at the extreme carboxy terminus of c-ErbA alpha is responsible for loss of both transactivation and transcriptional interference activities. Single, double, and triple amino acid substitutions within this region completely abolished T3-dependent transcriptional activation, interference with AP-1 activity, and decreased T3 binding by c-ErbA alpha. However, the lower T3 binding by these mutants does not fully account for the loss of transactivation and transcriptional interference, since a c-ErbA/v-ErbA chimera which was similarly reduced in T3 binding activity has retained both of these functions. Deletion of homologous residues in the retinoic acid receptor alpha (RAR alpha) resulted in a similar loss of transactivation and transcriptional interference activities. The ability of c-ErbA alpha to induce differentiation of transformed erythroblasts is also impaired by all of the mutations introduced into the conserved carboxy-terminal sequence. We conclude that this 9-amino-acid conserved region is essential for normal biological function of c-ErbA alpha and RAR alpha and possibly other T3 and RA receptors.

A conserved C-terminal sequence that is deleted in v-ErbA is essential for the biological activities of c-ErbA (the thyroid hormone receptor)

1993 ◽  
Vol 13 (6) ◽  
pp. 3675-3685
Author(s):  
F Saatcioglu ◽  
P Bartunek ◽  
T Deng ◽  
M Zenke ◽  
M Karin
Keyword(s):  
Amino Acid ◽  
Thyroid Hormone ◽  
Transcriptional Activation ◽  
Thyroid Hormone Receptor ◽  
Retinoic Acid Receptor ◽  
Biological Activities ◽  
Erythroid Differentiation ◽  
Dependent Manner ◽  
Transcriptional Interference ◽  
Terminal Sequence

The thyroid hormone (T3) receptor type alpha, the c-ErbA alpha proto-oncoprotein, stimulates transcription of T3-dependent promoters, interferes with AP-1 activity, and induces erythroid differentiation in a ligand-dependent manner. The v-ErbA oncoprotein does not bind hormone and has lost all of these activities. Using c-ErbA/v-ErbA chimeras, we found that a deletion of 9 amino acids, conserved among many members of the nuclear receptor superfamily, which are located at the extreme carboxy terminus of c-ErbA alpha is responsible for loss of both transactivation and transcriptional interference activities. Single, double, and triple amino acid substitutions within this region completely abolished T3-dependent transcriptional activation, interference with AP-1 activity, and decreased T3 binding by c-ErbA alpha. However, the lower T3 binding by these mutants does not fully account for the loss of transactivation and transcriptional interference, since a c-ErbA/v-ErbA chimera which was similarly reduced in T3 binding activity has retained both of these functions. Deletion of homologous residues in the retinoic acid receptor alpha (RAR alpha) resulted in a similar loss of transactivation and transcriptional interference activities. The ability of c-ErbA alpha to induce differentiation of transformed erythroblasts is also impaired by all of the mutations introduced into the conserved carboxy-terminal sequence. We conclude that this 9-amino-acid conserved region is essential for normal biological function of c-ErbA alpha and RAR alpha and possibly other T3 and RA receptors.

scholarly journals Mutations in the conserved C-terminal sequence in thyroid hormone receptor dissociate hormone-dependent activation from interference with AP-1 activity.

1997 ◽  
Vol 17 (8) ◽  
pp. 4687-4695 ◽  
Author(s):  
F Saatcioglu ◽  
G Lopez ◽  
B L West ◽  
E Zandi ◽  
W Feng ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Thyroid Hormone ◽  
Transcriptional Activation ◽  
Hormone Receptor ◽  
Thyroid Hormone Receptor ◽  
Mutational Analysis ◽  
Binding Domain ◽  
Yeast Cells ◽  
Terminal Sequence

A short C-terminal sequence that is deleted in the v-ErbA oncoprotein and conserved in members of the nuclear receptor superfamily is required for normal biological function of its normal cellular counterpart, the thyroid hormone receptor alpha (T3R alpha). We carried out an extensive mutational analysis of this region based on the crystal structure of the hormone-bound ligand binding domain of T3R alpha. Mutagenesis of Leu398 or Glu401, which are surface exposed according to the crystal structure, completely blocks or significantly impairs T3-dependent transcriptional activation but does not affect or only partially diminishes interference with AP-1 activity. These are the first mutations that clearly dissociate these activities for T3R alpha. Substitution of Leu400, which is also surface exposed, does not affect interference with AP-1 activity and only partially diminishes T3-dependent transactivation. None of the mutations affect ligand-independent transactivation, consistent with previous findings that this activity is mediated by the N-terminal domain of T3R alpha. The loss of ligand-dependent transactivation for some mutants can largely be reversed in the presence of GRIP1, which acts as a strong ligand-dependent coactivator for wild-type T3R alpha. There is excellent correlation between T3-dependent in vitro association of GRIP1 with T3R alpha mutants and their ability to support T3-dependent transcriptional activation. Therefore, GRIP1, previously found to interact with the glucocorticoid, estrogen, and androgen receptors, may also have a role in T3R alpha-mediated ligand-dependent transcriptional activation. When fused to a heterologous DNA binding domain, that of the yeast transactivator GAL4, the conserved C terminus of T3R alpha functions as a strong ligand-independent activator in both mammalian and yeast cells. However, point mutations within this region have drastically different effects on these activities compared to their effect on the full-length T3R alpha. We conclude that the C-terminal conserved region contains a recognition surface for GRIP1 or a similar coactivator that facilitates its interaction with the basal transcriptional apparatus. While important for ligand-dependent transactivation, this interaction surface is not directly involved in transrepression of AP-1 activity.

scholarly journals Inhibition of Estrogen Receptor Action by the Orphan Receptor SHP (Short Heterodimer Partner)

1998 ◽  
Vol 12 (10) ◽  
pp. 1551-1557 ◽  
Author(s):  
Wongi Seol ◽  
Bettina Hanstein ◽  
Myles Brown ◽  
David D. Moore
Keyword(s):  
Estrogen Receptor ◽  
Thyroid Hormone ◽  
Transcriptional Activation ◽  
Hormone Receptors ◽  
Thyroid Hormone Receptor ◽  
Orphan Receptor ◽  
Estrogen Signaling ◽  
Dependent Manner ◽  
Interaction Domain ◽  
Short Heterodimer Partner

Abstract SHP (short heterodimer partner) is an unusual orphan receptor that lacks a conventional DNA-binding domain. Previous results have shown that it interacts with several other nuclear hormone receptors, including the retinoid and thyroid hormone receptors, and inhibits their ligand-dependent transcriptional activation. Here we show that SHP also interacts with estrogen receptors and inhibits their function. In mammalian and yeast two-hybrid systems as well as glutathione-S-transferase pull-down assays, SHP interacts specifically with estrogen receptor-α (ERα) in an agonist-dependent manner. The same assay systems using various deletion mutants of SHP map the interaction domain with ERα to the same SHP sequences required for interaction with the nonsteroid hormone receptors such as retinoid X receptor and thyroid hormone receptor. In transient cotransfection assays, SHP inhibits estradiol -dependent activation by ERα by about 5-fold. In contrast, SHP interacts with ERβ independent of ligand and reduces its ability to activate transcription by only 50%. These data suggest that SHP functions to regulate estrogen signaling through a direct interaction with ERα.

scholarly journals tau4/tau c/AF-2 of the thyroid hormone receptor relieves silencing of the retinoic acid receptor silencer core independent of both tau4 activation function and full dissociation of corepressors.

1997 ◽  
Vol 17 (8) ◽  
pp. 4259-4271 ◽  
Author(s):  
A Baniahmad ◽  
D Thormeyer ◽  
R Renkawitz
Keyword(s):  
Amino Acids ◽  
Retinoic Acid ◽  
Thyroid Hormone ◽  
Transcriptional Activation ◽  
Hormone Receptors ◽  
Thyroid Hormone Receptor ◽  
Retinoic Acid Receptor ◽  
Activation Function ◽  
Acid Receptor ◽  
C Terminus

Members of the thyroid hormone (TR)-retinoic acid receptor (RAR) subfamily of nuclear hormone receptors silence gene expression in the absence of hormone. Addition of cognate ligands leads to dissociation of corepressors, association of coactivators, and transcriptional activation. Here, we used the hRAR alpha silencer core, which encompasses the ligand binding domain, including receptor regions D and E of RAR alpha without the activation function called tau4/tau c/AF-2 and without the F region, to analyze the mechanisms by which transcriptional silencing is relieved. Although the RAR silencer core is able to bind ligand, it acts as a constitutive transcriptional silencer. We have fused various small activation domains to the C terminus of the silencer core and analyzed hormone-dependent changes in receptor function. We show that nine amino acids derived from the hTRbeta are sufficient to transform the RAR silencer core into a hormone-dependent activator. Lengthening the linker between the silencer core and these nine amino acids is not critical for mediating ligand-induced relief of silencing and activation. In addition, we show that a transactivation function at the C terminus is not required for relief of silencing by the hormone, but it is required for transcriptional activation. Furthermore, we created functional silencer fusions which lose their repressive function upon addition of hormone, although the corepressors SMRT and N-CoR remain attached to the receptor.

scholarly journals A 10-amino-acid sequence in the N-terminal A/B domain of thyroid hormone receptor alpha is essential for transcriptional activation and interaction with the general transcription factor TFIIB.

1995 ◽  
Vol 15 (8) ◽  
pp. 4507-4517 ◽  
Author(s):  
E Hadzic ◽  
V Desai-Yajnik ◽  
E Helmer ◽  
S Guo ◽  
S Wu ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Thyroid Hormone ◽  
Dna Binding ◽  
Transcriptional Activation ◽  
Thyroid Hormone Receptor ◽  
Alpha Helix ◽  
Binding Domain ◽  
Terminal Region ◽  
Binding Studies

The effects of the thyroid hormone (3,5,3'-triiodo-L-thyronine [T3]) on gene transcription are mediated by nuclear T3 receptors (T3Rs). alpha- and beta-isoform T3Rs (T3R alpha and -beta) are expressed from different genes and are members of a superfamily of ligand-dependent transcription factors that also includes the receptors for steroid hormones, vitamin D, and retinoids. Although T3 activates transcription by mediating a conformational change in the C-terminal approximately 220-amino-acid ligand-binding domain (LBD), the fundamental mechanisms of T3R-mediated transcriptional activation remain to be determined. We found that deletion of the 50-amino-acid N-terminal A/B domain of chicken T3R alpha (cT3R alpha) decreases T3-dependent stimulation of genes regulated by native thyroid hormone response elements about 10- to 20-fold. The requirement of the A/B region for transcriptional activation was mapped to amino acids 21 to 30, which contain a cluster of five basic amino acids. The A/B region of cT3R alpha is not required for T3 binding or for DNA binding of the receptor as a heterodimer with retinoid X receptor. In vitro binding studies indicate that the N-terminal region of cT3R alpha interacts efficiently with TFIIB and that this interaction requires amino acids 21 to 30 of the A/B region. In contrast, the LBD interacts poorly with TFIIB. The region of TFIIB primarily involved in the binding of cT3R alpha includes an amphipathic alpha helix contained within residues 178 to 201. Analysis using a fusion protein containing the DNA-binding domain of GAL4 and the entire A/B region of cT3R alpha suggests that this region does not contain an intrinsic activation domain. These and other studies indicate that cT3R alpha mediates at least some of its effects through TFIIB in vivo and that the N-terminal region of DNA-bound cT3R alpha acts to recruit and/or stabilize the binding of TFIIB to the transcription complex. T3 stimulation could then result from ligand-mediated changes in the LBD which may lead to the interaction of other factors with cT3R alpha, TFIIB, and/or other components involved in the initiation of transcription.

scholarly journals Cyclin-Dependent Kinase 8 Positively Cooperates with Mediator To Promote Thyroid Hormone Receptor-Dependent Transcriptional Activation

2010 ◽  
Vol 30 (10) ◽  
pp. 2437-2448 ◽  
Author(s):  
Madesh Belakavadi ◽  
Joseph D. Fondell
Keyword(s):  
Thyroid Hormone ◽  
Transcriptional Activation ◽  
Target Gene ◽  
Thyroid Hormone Receptor ◽  
Type I ◽  
Dependent Manner ◽  
Gene Promoters ◽  
Cyclin Dependent Kinase ◽  
Pol Ii

ABSTRACT Mediator is a multisubunit assemblage of proteins originally identified in humans as a coactivator bound to thyroid hormone receptors (TRs) and essential for thyroid hormone (T3)-dependent transcription. Cyclin-dependent kinase 8 (CDK8), cyclin C, MED12, and MED13 form a variably associated Mediator subcomplex (termed the CDK8 module) whose functional role in TR-dependent transcription remains unclear. Using in vitro and cellular approaches, we show here that Mediator complexes containing the CDK8 module are specifically recruited into preinitiation complexes at the TR target gene type I deiodinase (DioI) together with RNA polymerase II (Pol II) in a TR- and T3-dependent manner. We found that CDK8 is essential for robust T3-dependent Dio1 transcription and that CDK8 knockdown via RNA interference decreased Pol II occupancy, and also the recruitment of the Pol II kinase CDK9, at the DioI promoter. Chromatin immunoprecipitation revealed CDK8 occupancy at the DioI promoter concurrent with active transcription, thus suggesting CDK8 involvement in transcriptional reinitiation. Mutagenesis assays showed that CDK8 kinase activity is necessary for full T3-dependent DioI activation, whereas in vitro kinase studies indicated that CDK8 may contribute to Pol II phosphorylation. Collectively, our data suggest CDK8 plays an important coactivator role in TR-dependent transcription by promoting Pol II recruitment and activation at TR target gene promoters.

scholarly journals Myb-Ets fusion oncoprotein inhibits thyroid hormone receptor/c-ErbA and retinoic acid receptor functions: a novel mechanism of action for leukemogenic transformation by E26 avian retrovirus.

1996 ◽  
Vol 16 (11) ◽  
pp. 6338-6351 ◽  
Author(s):  
A Rascle ◽  
N Ferrand ◽  
O Gandrillon ◽  
J Samarut
Keyword(s):  
Retinoic Acid ◽  
Thyroid Hormone ◽  
Hormone Receptor ◽  
Thyroid Hormone Receptor ◽  
Retinoic Acid Receptor ◽  
Biological Response ◽  
Erythroid Differentiation ◽  
Acid Receptor ◽  
Hormone Response Elements ◽  
Differentiation Stage

The E26 and avian erythroblastosis virus (AEV) avian retroviruses induce acute leukemia in chickens. E26 can block both erythroid and myeloid differentiation at an early multipotent stage. Moreover, E26 can block erythroid differentiation at the erythroid burst-forming unit/erythroid CFU (BFU-E/CFU-E) stage, which also corresponds to the differentiation stage blocked by AEV. AEV carries two oncogenes, v-erbA and v-erbB, whereas E26 encodes a single 135-kDa Gag-Myb-Ets fusion oncoprotein. v-ErbA is responsible for the erythroid differentiation arrest through negative interferences with both the retinoic acid receptor (RAR) and the thyroid hormone receptor (T3R/c-ErbA). We investigated whether Myb-Ets could block erythroid differentiation in a manner similar to v-ErbA. We show here that Myb-Ets inhibits both RAR and c-ErbA activities on specific hormone response elements in transient-expression assays. Moreover, Myb-Ets abrogates the inactivation of transcription factor AP-1 by RAR and T3R, another feature shared with v-ErbA. Myb-Ets also antagonizes the biological response of erythrocytic progenitor cells to retinoic acid and T3. Analysis of a series of mutants of Myb-Ets reveals that the domains of the oncoprotein involved in these inhibitory activities are the same as those involved in oncogenic transformation of hematopoietic cells. These data demonstrate that the Myb-Ets oncoprotein shares properties with the v-ErbA oncoprotein and that inhibition of ligand-dependent RAR and c-ErbA functions by Myb-Ets is responsible for blocking the differentiation of hematopoietic progenitors.

scholarly journals Activating Signal Cointegrator 2 Belongs to a Novel Steady-State Complex That Contains a Subset of Trithorax Group Proteins

2003 ◽  
Vol 23 (1) ◽  
pp. 140-149 ◽  
Author(s):  
Young-Hwa Goo ◽  
Young Chang Sohn ◽  
Dae-Hwan Kim ◽  
Seung-Whan Kim ◽  
Min-Jung Kang ◽  
...  
Keyword(s):  
Transcription Factors ◽  
Steady State ◽  
Nuclear Receptors ◽  
Transcriptional Activation ◽  
Retinoic Acid Receptor ◽  
Dependent Manner ◽  
Trithorax Group ◽  
Trithorax Group Proteins

ABSTRACT Many transcription coactivators interact with nuclear receptors in a ligand- and C-terminal transactivation function (AF2)-dependent manner. These include activating signal cointegrator 2 (ASC-2), a recently isolated transcriptional coactivator molecule, which is amplified in human cancers and stimulates transactivation by nuclear receptors and numerous other transcription factors. In this report, we show that ASC-2 belongs to a steady-state complex of approximately 2 MDa (ASC-2 complex [ASCOM]) in HeLa nuclei. ASCOM contains retinoblastoma-binding protein RBQ-3, α/β-tubulins, and trithorax group proteins ALR-1, ALR-2, HALR, and ASH2. In particular, ALR-1/2 and HALR contain a highly conserved 130- to 140-amino-acid motif termed the SET domain, which was recently implicated in histone H3 lysine-specific methylation activities. Indeed, recombinant ALR-1, HALR, and immunopurified ASCOM exhibit very weak but specific H3-lysine 4 methylation activities in vitro, and transactivation by retinoic acid receptor appears to involve ligand-dependent recruitment of ASCOM and subsequent transient H3-lysine 4 methylation of the promoter region in vivo. Thus, ASCOM may represent a distinct coactivator complex of nuclear receptors. Further characterization of ASCOM will lead to a better understanding of how nuclear receptors and other transcription factors mediate transcriptional activation.

scholarly journals An Inhibitory Region of the DNA-Binding Domain of Thyroid Hormone Receptor Blocks Hormone-Dependent Transactivation

1998 ◽  
Vol 12 (1) ◽  
pp. 34-44 ◽  
Author(s):  
Ying Liu ◽  
Akira Takeshita ◽  
Takashi Nagaya ◽  
Aria Baniahmad ◽  
William W. Chin ◽  
...  
Keyword(s):  
Thyroid Hormone ◽  
Dna Binding ◽  
Ligand Binding ◽  
Transcriptional Activation ◽  
Thyroid Hormone Receptor ◽  
Binding Domain ◽  
Dna Binding Domain ◽  
Chimeric Receptor ◽  
Receptor System ◽  
Inhibitory Region

Abstract We have employed a chimeric receptor system in which we cotransfected yeast GAL4 DNA-binding domain/retinoid X receptor β ligand-binding domain chimeric receptor (GAL4RXR), thyroid hormone receptor-β (TRβ), and upstream activating sequence-reporter plasmids into CV-1 cells to study repression, derepression, and transcriptional activation. In the absence of T3, unliganded TR repressed transcription to 20% of basal level, and in the presence of T3, liganded TRβ derepressed transcription to basal level. Using this system and a battery of TRβ mutants, we found that TRβ/RXR heterodimer formation is necessary and sufficient for basal repression and derepression in this system. Additionally, an AF-2 domain mutant (E457A) mediated basal repression but not derepression, suggesting that interaction with a putative coactivator at this site may be critical for derepression. Interestingly, a mutant containing only the TRβ ligand binding domain (LBD) not only mediated derepression, but also stimulated transcriptional activation 10-fold higher than basal level. Studies using deletion and domain swap mutants localized an inhibitory region to the TRβ DNA-binding domain. Titration studies further suggested that allosteric changes promoting interaction with coactivators may account for enhanced transcriptional activity by LBD. In summary, our findings suggest that TR heterodimer formation with RXR is important for repression and derepression, and coactivator interaction with the AF-2 domain may be needed for derepression in this chimeric system. Additionally, there may be an inhibitory region in the DNA-binding domain, which reduces TR interaction with coactivators, and prevents full-length wild-type TRβ from achieving transcriptional activation above basal level in this chimeric receptor system.

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