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Molecular and Cellular Biology, December 2000, p. 8731-8739, Vol. 20, No. 23
Graduate School of Biological Sciences, Nara
Institute of Science and Technology, Ikoma, Nara
630-0101,1 and Department of Genetics
and Molecular Biology, Institute for Virus Research, Kyoto
University, Kyoto 606-8507,2 Japan
Received 18 February 2000/Returned for modification 1 May
2000/Accepted 18 September 2000
Malformations in the eye can be caused by either an excess or
deficiency of retinoids. An early target gene of the retinoid metabolite, retinoic acid (RA), is that encoding one of its own receptors, the retinoic acid receptor
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Copyright © 2000, American Society for Microbiology. All rights reserved.
Cell-Type-Specific Regulation of the Retinoic Acid
Receptor Mediated by the Orphan Nuclear Receptor TLX
(RAR
). To better
understand the mechanisms underlying this autologous regulation, we
characterized the chick RAR
2 promoter. The region surrounding the
transcription start site of the avian RAR
2 promoter is over 90%
conserved with the corresponding region in mammals and confers strong
RA-dependent transactivation in primary cultured embryonic retina
cells. This response is selective for RAR but not retinoid X
receptor-specific agonists, demonstrating a principal role for RAR(s)
in retina cells. Retina cells exhibit a far higher sensitivity to RA
than do fibroblasts or osteoblasts, a property we found likely due to
expression of the orphan nuclear receptor TLX. Ectopic expression of
TLX in fibroblasts resulted in increased sensitivity to RA induction,
an effect that is conserved between chick and mammals. We have
identified a cis element, the silencing element relieved by
TLX (SET), within the RAR
2 promoter region which confers TLX- and
RA-dependent transactivation. These results indicate an important role
for TLX in autologous regulation of the RAR
gene in the eye.
*
Corresponding author. Mailing address: Department of
Pharmacology, Joan & Sanford I. Weill Medical College of Cornell
University, 1300 York Ave., Room E-505, New York, NY 10021. Phone:
(212) 746-6453. Fax: (212) 746-6241. E-mail:
mik2007{at}med.cornell.edu.
This paper is dedicated to K. Umesono.
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