Interaction of thyroid hormone and retinoic acid receptors on the regulation of the rat growth hormone gene promoter.

Retinoic acid transcriptionally regulate growth hormone (GH) gene expression through sequences located in the 5'-flanking region of the gene. A partial induction by retinoic acid was obtained with the -181 bp of the rat GH promoter, and sequences up to -209 were required for a full response. These sequences contain the previously identified thyroid hormone responsive element. The retinoid X receptor RXR increased transactivation by T3 and RA. The retinoid was relatively more effective in stimulating the native GH promoter than an heterologous promoter which contains the response element, thus showing the importance of the promoter context on transactivation by the nuclear receptors.