A systematic analysis of the AF‐2 domain of human retinoic acid receptor α reveals amino acids critical for transcriptional activation and conformational integrity

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.

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Identification of Amino Acids Critical for the DNA Binding and Dimerization Properties of the Human Retinoic Acid Receptor α

Journal of Biological Chemistry ◽

10.1074/jbc.271.30.17996 ◽

1996 ◽

Vol 271 (30) ◽

pp. 17996-18006 ◽

Cited By ~ 14

Author(s):

Christophe Rachez ◽

Pierre Sautière ◽

Pierre Formstecher ◽

Philippe Lefebvre

Keyword(s):

Amino Acids ◽

Retinoic Acid ◽

Dna Binding ◽

Retinoic Acid Receptor ◽

Acid Receptor ◽

Retinoic Acid Receptor Α

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Identification of Transcripts Initiated from an Internal Promoter in the c-erbAα Locus That Encode Inhibitors of Retinoic Acid Receptor-α and Triiodothyronine Receptor Activities

Molecular Endocrinology ◽

10.1210/mend.11.9.9972 ◽

1997 ◽

Vol 11 (9) ◽

pp. 1278-1290 ◽

Cited By ~ 2

Author(s):

Olivier Chassande ◽

Alexandre Fraichard ◽

Karine Gauthier ◽

Frédéric Flamant ◽

Claude Legrand ◽

...

Keyword(s):

Retinoic Acid ◽

Transcriptional Activation ◽

Hormone Receptors ◽

Thyroid Hormone Receptor ◽

Retinoic Acid Receptor ◽

Expression Patterns ◽

Internal Promoter ◽

Acid Receptor ◽

Retinoic Acid Receptor Α

Abstract The thyroid hormone receptor-coding locus, c-erbAα, generates several mRNAs originating from a single primary transcript that undergoes alternative splicing. We have identified for the first time two new transcripts, called TRΔα1 and TRΔα2[ mRNA for isoform α1 and α2 of the T3 receptor (TR), respectively], whose transcription is initiated from an internal promoter located within intron 7 of the c-erbAα gene. These two new transcripts exhibit tissue-specific patterns of expression in the mouse. These two patterns are in sharp contrast with the expression patterns of the full-length transcripts generated from the c-erbAα locus. TRΔα1 and TRΔα2 mRNAs encode N-terminally truncated isoforms of T3Rα1 and T3Rα2, respectively. The protein product of TRΔα1 antagonizes the transcriptional activation elicited by T3 and retinoic acid. This protein inhibits the ligand-induced activating functions of T3Rα1 and 9-cis-retinoic acid receptor-α but does not affect the retinoic acid-dependent activating function of retinoic acid receptor-α. We predict that these truncated proteins may work as down-regulators of transcriptional activity of nuclear hormone receptors in vivo.

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