A composite hormone response element mediates the transactivation of the rat oxytocin gene by different classes of nuclear hormone receptors.
Transcription factors of the steroid/thyroid hormone receptor superfamily are mediators of development and regulation of the brain. Previous studies have shown that the hypothalamic oxytocin (OT) gene is a potential target of these receptors, since its promoter is stimulated by estrogens and thyroid hormone. Here it is shown that the rat OT promoter is stimulated (at least 20-fold) by retinoic acid through two distinct regions in the 5'-flanking region. The major retinoic acid response element was located between nucleotides -172 and -148 and a minor one between nucleotides -112 and -77, as concluded from the transactivation of 5'-deletion mutants and binding to promoter elements by the retinoic acid receptor. Since the -172/-148 element also conferred estrogen and thyroid hormone responsiveness, it can be considered a composite hormone response element. This element contains a natural variant of the direct repeat of the half-site AGGTCA with spacing zero (DR-0) as well as a palindrome. Analysis of the core sequences of this element by site-directed mutagenesis showed that each of the three TGACC motifs integral to this element contributes to the multihormone sensitivity, but the contribution of each motif is different for the individual receptors. In neonatal rats, vitamin A deficiency and retinoic acid supplementation did not cause changes in hypothalamic OT mRNA levels and OT peptide levels in the pituitary gland and plasma. Gel-retarded protein-DNA complexes were formed between the composite hormone response element and extracts of the hypothalamic supraoptic and paraventricular nuclei. The composite hormone response element has a unique configuration and integrates responses of multiple members of the steroid/thyroid hormone receptor superfamily.
Rudolf Magnus Institute, Department of Pharmacology, University of Utrecht, Medical Faculty, The Netherlands.
R A
RA
Adan
J J
JJ
Cox
T V
TV
Beischlag
J P
JP
Burbach
D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics / Q000502:physiology; D005786:Gene Expression Regulation; D007031:Hypothalamus / Q000378:metabolism*; D008297:Male; D008969:Molecular Sequence Data; D005810:Multigene Family; D016297:Mutagenesis, Site-Directed; D010121:Oxytocin / Q000096:biosynthesis / Q000235:genetics*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017208:Rats, Wistar; D011956:Receptors, Cell Surface / Q000235:genetics / Q000502:physiology*; D011960:Receptors, Estrogen / Q000235:genetics / Q000502:physiology; D018168:Receptors, Retinoic Acid; D011988:Receptors, Thyroid Hormone / Q000235:genetics / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid; D017384:Sequence Deletion; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D015533:Transcriptional Activation; D014212:Tretinoin / Q000494:pharmacology
D002352:Carrier Proteins; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D011960:Receptors, Estrogen; D018168:Receptors, Retinoic Acid; D011988:Receptors, Thyroid Hormone; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D010121:Oxytocin; D014212:Tretinoin