title: Divergent effects of 9-cis-retinoic acid receptor on positive and negative thyroid hormone receptor-dependent gene expression.
abstract: The thyroid hormone (TH)-inducible expression of some genes has recently been shown to be enhanced by 9-cis-retinoic acid (9-cis-RA) receptor (RXR). This effect appears to be at least partially elicited by the ability of RXR to heterodimerize with TH receptor (THR) and enhance its binding to the cis-acting thyroid hormone responsive elements (TREs) found within those genes. However, whether RXR beta enhances TH/THR-mediated transactivation of all Tre-containing genes, and if RXR has any effect on TH-dependent negative regulation are not known. In the present study, we show that the TH/THR-inducible expression of the myelin basic protein (MBP) gene is not enhanced by RXR beta, despite high affinity binding of the RXR beta.THR alpha heterodimer to the MBP-TRE. We also demonstrate that RXR beta reverses the TH/THR-dependent down-regulation mediated by the negative TRE found within the promoter of the mouse thyroid stimulating hormone gene (TSH). The ligand for RXR beta (9-cis-RA), either alone or in combination with TH, did not enhance the transcription mediated by either the MBP-TRE, TSH-TRE, or the malic enzyme (ME)-TRE. However, the ME-TRE is known to confer RXR beta-dependent enhancement of TH-induced gene expression. Thus, the capacity of RXR beta to modulate TH-dependent transcriptional regulation depends upon the nature of the TRE.
authors.affiliation: Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: P L
authors.initials: PL
authors.lastname: Hallenbeck
authors.forename: M
authors.initials: M
authors.lastname: Phyillaier
authors.forename: V M
authors.initials: VM
authors.lastname: Nikodem
mesh_terms: D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000502:physiology*; D005786:Gene Expression Regulation / Q000502:physiology*; D008291:Malate Dehydrogenase / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D004676:Myelin Basic Protein / Q000235:genetics; D009841:Oligonucleotides; D051381:Rats; D018168:Receptors, Retinoic Acid; D011988:Receptors, Thyroid Hormone / Q000502:physiology*; D013963:Thyroid Hormones / Q000502:physiology*; D013972:Thyrotropin / Q000235:genetics; D014158:Transcription, Genetic
chemical_list: D002352:Carrier Proteins; D004676:Myelin Basic Protein; D009841:Oligonucleotides; D018168:Receptors, Retinoic Acid; D011988:Receptors, Thyroid Hormone; D013963:Thyroid Hormones; D013972:Thyrotropin; D008291:Malate Dehydrogenase