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 Inhibition of the Dihydrotestosterone-Activated Androgen Receptor by Nuclear Receptor Corepressor

2002 ◽  
Vol 16 (7) ◽  
pp. 1492-1501 ◽  
Author(s):  
Shinta Cheng ◽  
Sabrina Brzostek ◽  
Suzanne R. Lee ◽  
Anthony N. Hollenberg ◽  
Steven P. Balk
Keyword(s):  
Androgen Receptor ◽  
Ligand Binding ◽  
Nuclear Receptor ◽  
Transcriptional Activity ◽  
Thyroid Hormone Receptor ◽  
Binding Domain ◽  
Ligand Binding Domain ◽  
Steroid Hormone Receptors ◽  
Binding Studies ◽  
Nuclear Receptor Corepressor

Abstract Nuclear receptor corepressor (NCoR) mediates transcriptional repression by unliganded nuclear receptors and certain steroid hormone receptors (SHRs) bound to nonphysiological antagonists, but has not been found to regulate SHRs bound to their natural ligands. This report demonstrates that NCoR interacts directly with the androgen receptor (AR) and represses dihydrotestosterone-stimulated AR transcriptional activity. The NCoR C terminus, containing the receptor interacting domains, was necessary for repression, which was ablated by mutations in the corepressor nuclear receptor (CoRNR) boxes. In contrast, the NCoR N terminus, containing domains that can recruit histone deacetylases, was not necessary for repression. Binding studies in vitro with a series of glutathione-S-transferase-NCoR and -AR fusion proteins demonstrated a direct interaction that was similarly dependent upon the NCoR corepressor nuclear receptor boxes and AR ligand binding domain and was independent of ligand and helix 12 in the AR ligand binding domain. This NCoR-AR interaction was further demonstrated in mammalian two-hybrid assays and by coimmunoprecipitation of the endogenous proteins from a prostate cancer cell line. Finally, AR transcriptional activity could be enhanced in vivo by sequestration of endogenous NCoR with unliganded thyroid hormone receptor. These results demonstrate that AR, in contrast to other SHRs, is regulated by NCoR and suggest the possibility of developing selective AR modulators that enhance this interaction.

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.

scholarly journals The Interaction of TRβ1-N Terminus with Steroid Receptor Coactivator-1 (SRC-1) Serves a Full Transcriptional Activation Function of SRC-1

Endocrinology ◽  
2006 ◽  
Vol 147 (3) ◽  
pp. 1452-1457 ◽  
Author(s):  
Toshiharu Iwasaki ◽  
Akira Takeshita ◽  
Wataru Miyazaki ◽  
William W. Chin ◽  
Noriyuki Koibuchi
Keyword(s):  
Thyroid Hormone ◽  
Nuclear Receptor ◽  
Thyroid Hormone Receptor ◽  
Steroid Receptor ◽  
Activation Function ◽  
Binding Domain ◽  
Expression Vectors ◽  
Response Element ◽  
Steroid Receptor Coactivator ◽  
N Terminus

Steroid receptor coactivator-1 (SRC-1) plays a crucial role in nuclear receptor-mediated transcription including thyroid hormone receptor (TR)-dependent gene expression. Interaction of the TR-ligand binding domain and SRC-1 through LXXLL motifs is required for this action. However, potential interactions between the TRβ1-N terminus (N) and SRC-1 have not been explored and thus are examined in this manuscript. Far-Western studies showed that protein construct containing TRβ1-N + DNA binding domain (DBD) bound to nuclear receptor binding domain (NBD)-1 (amino acid residue, aa 595–780) of SRC-1 without ligand. Mammalian two-hybrid studies showed that NBD-1, as well as SRC-1 (aa 595-1440), bound to TRβ1-N+DBD in the absence of ligand in CV-1 cells. However, NBD-2 (aa 1237–1440) did not bind to this protein. Glutathione-S-transferase pull-down studies showed that TRβ1-N (aa 1–105) bound to the broad region of SRC-1-C terminus. Expression vectors encoding a series of truncations and/or point mutations of TRβ1 were used in transient transfection-based reporter assays in CV-1 cells. N-terminal truncated TRβ1 (ΔN-TRβ1) showed lower activity than that of wild-type in both artificial F2-thyroid hormone response element and native malic enzyme response element. These results suggest that there is the interaction between N terminus of TRβ1 and SRC-1, which may serve a full activation of SRC-1, together with activation function-2 on TRβ1-mediated transcription.

scholarly journals Definition of the Surface in the Thyroid Hormone Receptor Ligand Binding Domain for Association as Homodimers and Heterodimers with Retinoid X Receptor

2001 ◽  
Vol 276 (18) ◽  
pp. 14987-14995 ◽  
Author(s):  
Ralff C. J. Ribeiro ◽  
Weijun Feng ◽  
Richard L. Wagner ◽  
Cláudia H. R. M. Costa ◽  
Alexandre C. Pereira ◽  
...  
Keyword(s):  
Thyroid Hormone ◽  
Ligand Binding ◽  
Hormone Receptor ◽  
Thyroid Hormone Receptor ◽  
Binding Domain ◽  
Ligand Binding Domain ◽  
Retinoid X Receptor ◽  
Receptor Ligand ◽  
Definition Of
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