The Orphan Nuclear Receptor TR2 Suppresses a DR4 Hormone Response Element of the Mouse CRABP-I Gene Promoter

Abstract

The mouse orphan nuclear receptor TR2-11-f suppressed the expression of reporters fused to a hormone response element of the mouse cellular retinoic acid-binding protein I gene promoter. TR2-11-f was able to bind to a direct repeat with four nucleotides in the spacer (5'TGACCTTTGGGGACCT3') located within this hormone response element as homodimers. The specificity of protein-DNA interactions was demonstrated by competition in gel retardation and antibody-mediated supershift reactions. The residues critical for TR2-11-f binding were mapped to both repeated sequences, whereas the spacer and the flanking sequences were less important. The Kd and Bmax of TR2-11-f homodimer binding to this direct repeat were determined to be 2.6 nM and 0.012 nM, respectively. By using a yeast two-hybrid system, it was demonstrated that dimerization of TR2-11-f was mediated by its ligand-binding domain. The actions of TR2-11-f in regulating cellular retinoic acid-binding protein I gene will likely influence retinoic action and availability within the cells.

Constitutive Activation of Retinoic Acid Receptor β2 Promoter by Orphan Nuclear Receptor TR2

“…Like many other orphan nuclear receptors, the activities of TR2 have been demonstrated to be primarily repressive in many systems without putative ligands (14,15,19). Many genes that are demonstrated to contain a DNA response element for TR2 are involved in RA metabolism, such as cellular retinoic acid-binding protein I and cellular retinol-binding protein II.…”

“…A fragment containing only the DR5 (16) was also prepared by annealing oligonucleotides spanning DR5 site and used as a control for TR2 binding. ␤2 by TR2 Expression-Previously, the biological activity of orphan receptor TR2 was demonstrated to be primarily suppressive on both RA induction of DR5-containing reporters (16,17) and reporters regulated by some hormone response elements such as DR4 (14) and DR1 (15). It was demonstrated that the suppressive activity required the intact LBD and DBD but not the N-terminal A/B domains of the molecule (16).…”

“…Like many other orphan receptors, the biological activity of TR2 was first demonstrated in several reporter systems. For instance, TR2 repressed reporters driven by a direct repeat (DR)-4 hormone response element derived from the mouse cellular retinoic acid-binding protein I gene promoter (14) and a DR1-type RA response element derived from the cellular retinol-binding protein II gene promoter (15). Moreover, TR2 strongly suppressed RA induction of a reporter driven by the DR5 derived from RA receptor ␤2 (RAR ␤2 ) promoter, mediated by competitive binding of TR2 to this DR5 (16 -18).…”

A constitutive nuclear localization signal from the second zinc-finger of orphan nuclear receptor TR2

“…By using a retinoic acid (RA)-responsive reporter that contains a direct repeat (DR)-5 (DR5) type RA response element (RARE) of the retinoic acid receptor (RAR ) gene (Sucov et al 1990), we have demonstrated that TR2, but not TR2-11-t, repressed RA induction of this reporter in a dose-dependent manner (Lee et al 1996a. By using a reporter containing a DR4-type hormone response element of the mouse cellular retinoic acid binding protein I (CRABP-I) gene, we have also shown that TR2, but not TR2-11-t, strongly repressed this reporter (Chinpaisal et al 1997). In other promoter systems such as the Simian virus (SV) 40 promoter (Lee & Chang 1995) and the erythropoietin gene promoter (Lee et al 1996b), TR2 also functions primarily as a transcriptional repressor (Lin et al 1995).…”

Molecular cloning and characterization of chicken orphan nuclear receptor cTR21

“…The mammalian forms of TR2 are expressed at a high level in adult testis and particularly in the postmeiotic germ cells (11)(12)(13)(14). Previous studies have demonstrated that TR2 is a potent repressor of retinoic acid (RA), thyroid hormone (T3) and vitamin D3 mediated transcriptional activity of their cognate receptors via competitive binding to the hormone response elements of DR series (18)(19)(20)(21)(22)(23)(24)(25). However, a recent report also demonstrated a role of TR2 as an activator of RAR2 gene promoter where TR2 in association with CREM activates the gene (26).…”