On the Denaturation Mechanisms of the Ligand Binding Domain of Thyroid Hormone Receptors

2010 ◽  
Vol 114 (3) ◽  
pp. 1529-1540 ◽  
Author(s):  
Leandro Martínez ◽  
Paulo C. T. Souza ◽  
Wanius Garcia ◽  
Fernanda A. H. Batista ◽  
Rodrigo V. Portugal ◽  
...  
Keyword(s):  
Thyroid Hormone ◽  
Ligand Binding ◽  
Hormone Receptors ◽  
Binding Domain ◽  
Ligand Binding Domain ◽  
Thyroid Hormone Receptors

scholarly journals Novel Mechanism of Nuclear Receptor Corepressor Interaction Dictated by Activation Function 2 Helix Determinants

2002 ◽  
Vol 22 (19) ◽  
pp. 6831-6841 ◽  
Author(s):  
Anna N. Moraitis ◽  
Vincent Giguère ◽  
Catherine C. Thompson
Keyword(s):  
Retinoic Acid ◽  
Thyroid Hormone ◽  
Ligand Binding ◽  
Nuclear Receptor ◽  
Thyroid Hormone Receptor ◽  
Activation Function ◽  
Binding Domain ◽  
Ligand Binding Domain ◽  
Cerebellar Development ◽  
Nuclear Receptor Corepressor

ABSTRACT Transcriptional regulation by nuclear receptors is controlled by the concerted action of coactivator and corepressor proteins. The product of the thyroid hormone-regulated mammalian gene hairless (Hr) was recently shown to function as a thyroid hormone receptor corepressor. Here we report that Hr acts as a potent repressor of transcriptional activation by RORα, an orphan nuclear receptor essential for cerebellar development. In contrast to other corepressor-nuclear receptor interactions, Hr binding to RORα is mediated by two LXXLL-containing motifs, a mechanism associated with coactivator interaction. Mutagenesis of conserved amino acids in the ligand binding domain indicates that RORα activity is ligand-dependent, suggesting that corepressor activity is maintained in the presence of ligand. Despite similar recognition helices shared with coactivators, Hr does not compete for the same molecular determinants at the surface of the RORα ligand binding domain, indicating that Hr-mediated repression is not simply through displacement of coactivators. Remarkably, the specificity of Hr corepressor action can be transferred to a retinoic acid receptor by exchanging the activation function 2 (AF-2) helix. Repression of the chimeric receptor is observed in the presence of retinoic acid, demonstrating that in this context, Hr is indeed a ligand-oblivious nuclear receptor corepressor. These results suggest a novel molecular mechanism for corepressor action and demonstrate that the AF-2 helix can play a dynamic role in controlling corepressor as well as coactivator interactions. The interaction of Hr with RORα provides direct evidence for the convergence of thyroid hormone and RORα-mediated pathways in cerebellar development.

scholarly journals The tau 4 activation domain of the thyroid hormone receptor is required for release of a putative corepressor(s) necessary for transcriptional silencing.

1995 ◽  
Vol 15 (1) ◽  
pp. 76-86 ◽  
Author(s):  
A Baniahmad ◽  
X Leng ◽  
T P Burris ◽  
S Y Tsai ◽  
M J Tsai ◽  
...  
Keyword(s):  
Amino Acids ◽  
Thyroid Hormone ◽  
Ligand Binding ◽  
Hormone Receptor ◽  
Thyroid Hormone Receptor ◽  
Binding Domain ◽  
Ligand Binding Domain ◽  
Activation Domain ◽  
C Terminus

The C terminus of nuclear hormone receptors is a complex structure that contains multiple functions. We are interested in the mechanism by which thyroid hormone converts its receptor from a transcriptional silencer to an activator of transcription. Both regulatory functions are localized in the ligand binding domain of this receptor superfamily member. In this study, we have identified and characterized several functional domains within the ligand binding domain of the human thyroid hormone receptor (TR beta) conferring transactivation. Interestingly, these domains are localized adjacent to hormone binding sites. One activation domain, designated tau 4, is only 17 amino acids in length and is localized at the extreme C terminus of TR. Deletion of six amino acids of tau 4 resulted in a receptor that could still bind hormone but acted as a constitutive silencer, indicating that tau 4 is required for both transactivation and relief of the silencing functions. In addition, we performed in vivo competition experiments, the results of which suggest that in the absence of tau 4 or hormone, TR is bound by a corepressor protein(s) and that one role of hormone is to release corepressor from the receptor. We propose a general model in which the role of hormone is to induce a conformational change in the receptor that subsequently affects the action of tau 4, leading to both relief of silencing and transcriptional activation.

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