Multiple functions of the TR2-11 orphan receptor in modulating activation of two key cis-acting elements involved in the retinoic acid signal transduction system.
The testicular receptor 2 (TR2) orphan receptor binds to hormone response elements (HREs) consisting of two AGGTCA half-site direct repeat consensus sequences (DR) with various spacing in the following order: DR1 > DR2 > DR5 DR4 DR6 > DR3. When binding to natural HREs, TR2 orphan receptor remains flexible with higher binding affinities to (a) cellular retinol-binding protein II promoter region (CRBPIIp) (DR1), SV40 +55 region (DR2), and retinoic acid response element beta (RARE beta) (DR5) than to (b) NGFI-B response element (NBRE) and also to (c) the palindromic thyroid hormone response element (TREpal). This wide spectrum of HRE recognition sequences suggests possible versatility of the TR2 orphan receptor in cross-talking with other signal transduction systems. Chloramphenicol acetyltransferase (CAT) assay demonstrates that the TR2 orphan receptor competes with CRBPIIp- and RARE beta-CAT gene expression activated by retinoid X receptor alpha (RXR alpha) and retinoic acid receptor alpha (RAR alpha)/RXR alpha heterodimers, respectively. In addition, this suppression may not be mediated by the formation of heterodimers between TR2 orphan receptor and either RXR alpha or RAR alpha. Instead, a minimum of 100-fold higher affinity of the TR2 orphan receptor for CRBPIIp than RXR alpha may explain why the TR2 orphan receptor dominates RXR alpha in CRBPIIp-CAT activation. Together, our data suggest that the TR2 orphan receptor may be a master regulator in modulating the activation of two key HREs, RARE beta and CRBPIIp, involved in the retinoic acid signal transduction pathway.
University of Wisconsin Comprehensive Cancer Center, University of Wisconsin, Madison 53792, USA.
T M
TM
Lin
W J
WJ
Young
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C
Chang
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D015500:Chloramphenicol O-Acetyltransferase / Q000096:biosynthesis; D002522:Chlorocebus aethiops; D016384:Consensus Sequence; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005333:Fetus; D015870:Gene Expression; D006801:Humans; D017403:In Situ Hybridization; D007668:Kidney; D007700:Kinetics; D051379:Mice; D008969:Molecular Sequence Data; D057107:Nuclear Receptor Subfamily 2, Group C, Member 1; D009838:Oligodeoxyribonucleotides / Q000737:chemistry / Q000378:metabolism; D016133:Polymerase Chain Reaction; D014176:Protein Biosynthesis; D018168:Receptors, Retinoic Acid / Q000096:biosynthesis / Q000378:metabolism; D011988:Receptors, Thyroid Hormone / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism; D012091:Repetitive Sequences, Nucleic Acid; D000072482:Retinoic Acid Receptor alpha; D047488:Retinoid X Receptors; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D014157:Transcription Factors / Q000096:biosynthesis / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection; D014212:Tretinoin / Q000494:pharmacology*
D017931:DNA Primers; D004268:DNA-Binding Proteins; C539822:NR2C1 protein, human; C539823:Nr2c1 protein, mouse; D057107:Nuclear Receptor Subfamily 2, Group C, Member 1; D009838:Oligodeoxyribonucleotides; C000607071:RARA protein, human; C000607072:Rara protein, mouse; D018168:Receptors, Retinoic Acid; D011988:Receptors, Thyroid Hormone; D011994:Recombinant Proteins; D000072482:Retinoic Acid Receptor alpha; D047488:Retinoid X Receptors; D014157:Transcription Factors; D014212:Tretinoin; D015500:Chloramphenicol O-Acetyltransferase