A major thyroid hormone response element in the third intron of the rat growth hormone gene

The rat growth hormone (RGH) gene constitutes a welldocumented model system for the direct regulation of transcription by thyroid hormones. In order to analyse its interaction with sequences in the RGH gene, we have overproduced the thyroid hormone receptor-α (c-erbA) protein using a vaccinia virus expression system. The expressed protein bound T₃ and DNA-cellulose with expected affinities, and the major binding site for the receptor protein was found to be located in the third intron of the RGH gene. This site displayed significantly higher affinity for the receptor protein than a previously described thyroid hormone response element (TRE) in the promoter of this gene, and also conferred stronger hormone responsiveness in vivo to a heterologous promoter. The data suggest that this novel TRE plays a major role in the regulation of rat growth hormone gene expression by thyroid hormones.