Ž . Molecular Brain Research 55 1998 321–330 Research report Identification of a thyroid hormone response element in the promoter ž / region of the rat lipocalin-type prostaglandin D synthase b-trace gene Luis F. Garcıa-Fernandez a , Yoshihiro Urade b , Osamu Hayaishi b , Juan Bernal a , ´ ´ Alberto Munoz a, ) ˜ a Instituto de InÕestigaciones Biomedicas, Consejo Superior de InÕestigaciones Cientıficas, Arturo Duperier 4, 28029 Madrid, Spain ´ ´ b Osaka Bioscience Institute, 6-2-4 Furuedai, Suita, Osaka 565, Japan Accepted 6 January 1998 Abstract Ž . Ž . We have previously reported that mRNA levels for the rat lipocalin-type prostaglandin PG D synthaserb-trace PGDS gene, the enzyme responsible for the production of PGD2 in the central nervous system, are regulated by thyroid hormone in vivo. In this study, we Ž . Ž . X describe the identification of a thyroid hormone T3 response element T3RE in the 5 -flanking region of the rat PGDS gene. By Ž . radioimmunoprecipitation of genomic fragments using thyroid hormone receptor TR protein and specific anti-TR antibodies, gel-shift, Ž . foot-printing, mutational analysis, and transactivation assays we have identified a spaced four imperfect direct repeat DR4 element, Ž . GGTTCACTTCAGGGTA positions y586ry571 , which functions as a T3RE when fused to a heterologous promoter. Our results suggest that thyroid hormone regulates the expression of the rat lipocalin-type PGDS gene through this element. Remarkably, the element identified also confers regulation by retinoic acid. Giving the important roles proposed for the PGDS enzyme and its product, PGD2, the major PG in the mammalian brain, the altered expression of the PGDS gene may contribute to the deleterious effects of hypothyroidism in the central nervous system. q 1998 Elsevier Science B.V. Keywords: Prostaglandin D2 synthaserb-trace; Thyroid hormone; Promoter; Gene regulation 1. Introduction The glutathione-independent, lipocalin-type prosta- Ž .Ž . glandin D synthase PGDS EC 5.3.99.2 is responsible for the production of PGD2 from its precursor PGH2 in w x the central nervous system, retina, and cochlea 42,21,39,4 . PGD2 is the major PG in the brain of mammals and has been described to play critical roles in several important functions such as the control of the sleep–wake cycle, the regulation of body temperature, neurotransmitter release, w x sensitivity to pain, and others 23,24,27 . In addition, its sequence homology with the lipocalin family of small secretory lipid transporters suggests additional roles of the PGDS in the brain, perhaps as a carrier of its own product and other small lipidic molecules such as retinoids w x 35,25,40 . In addition, the PGDS has been identified as b-trace, one of the most abundant proteins in the cere- ) Corresponding author. Fax: q34-1-5854587; E-mail: amunoz@biomed.iib.uam.es w x brospinal fluid 47 . Interestingly also, PGD2 and its derivative PGJ2 have been found to be activators of the Ž . peroxisome proliferator-activated receptor PPAR -g w x 13,30 . Previously, we identified a cDNA clone down-regulated by hypothyroidism in the neonatal rat brain as the w x lipocalin-type PGDS gene 34,14 . More recent data have Ž . shown that thyroid hormone triiodothyronine, T3 -de- privation indeed alters the expression of this gene and the localization of immunoreactive PGDS protein in specific w x areas of the central nervous system in the rat 15 . T3 is a major regulator in higher organisms acting as a modulator of gene expression in different cell types and organs Ž . through the activation of specific nuclear receptors TRs , the products of the c-erbA proto-oncogenes a and b ww x x 31,49 , reviews . TRs belong to a superfamily of nuclear receptors which include those for steroid hormones, retinoic Ž . Ž . acid RA , vitamin D VitD , and many others with un- known ligands known as orphans receptors. They function as transcriptional modulators with ligand-dependent and -independent activities by binding to regulatory sequences 0169-328Xr98r$19.00 q 1998 Elsevier Science B.V. All rights reserved.