Discrete positive and negative thyroid hormone-responsive transcription regulatory elements of the rat growth hormone gene.

We have recently shown that a thyroid hormone-responsive transcription stimulatory element exists in the 5'-flanking DNA near the rat growth hormone (rGH) gene (Crew, M. D., and Spindler, S. R. (1986) J. Biol. Chem. 261, 5018-5022). Progressive deletion-transfection analysis of the 5' end of the gene has led to the identification of two genetic elements responsive to thyroid hormone. The first of these is a thyroid hormone-responsive transcription stimulatory element, or TSE. The TSE induced a thyroid hormone-dependent induction-attenuation transcription cycle similar to that of the natural rGH gene. Deletion of sequences between positions -254 and -241 in the rGH 5'-flanking DNA eliminated TSE activity. The second regulatory element is a thyroid hormone-responsive transcription inhibitory element (TIE). When this element was active, thyroid hormone strongly but transiently inhibited rGH promoter utilization. Deletion of sequences between nucleotides -46 and -21 abolished the effects of the TIE. To determine whether the TSE and TIE are enhancer-like, we ligated various regions of rat growth hormone 5'-flanking DNA containing these elements to a chimeric test gene containing the Herpes simplex virus thymidine kinase promoter. Thyroid hormone activated heterologous promoter utilization when a rat growth hormone 5'-flanking DNA fragment containing the TSE (-520 to -115) was linked in cis, regardless of the distance or orientation of the TSE with respect to the promoter. These data suggest that the TSE is a thyroid hormone-dependent enhancer. In contrast, when the TIE was placed immediately 5' to the thymidine kinase promoter, transcription was not effected by 3,5,3'-L-triiodothyronine, suggesting that the TIE is not enhancer-like.