Thyroid hormone stimulates renin gene expression through the thyroid hormone response element

We previously reported that thyroid hormone stimulates renin synthesis in vivo and in vitro. Here, we analyzed the 5′-flanking sequence of the human renin gene for promoter activity responsive to thyroid hormone using Calu-6 cells, which secrete renin endogenously and express thyroid hormone receptor-β. The luciferase reporter gene was cloned together with 5′-flanking portions of the human renin gene of various lengths into the pGL3-Basic vector. Luciferase activity assays were performed using the Dual Luciferase Reporter Assay System. 3,3′,5-Triiodo-L-thyronine stimulated the promoter activity of pGL3-Basic-1111/+12 and pGL3-Basic-1298/+12 by 2.3±0.1- and 1.7±0.1-fold, respectively. Shorter constructs (pGL3-Basic-144/+12, pGL3-Basic-226/+12, pGL3-Basic-452/+12, and pGL3-Basic-953/+12) were not stimulated by thyroid hormone. These results suggest that there is a possible thyroid hormone response element (5′-AGG TCA GGT CAc aat GTT CCT-3′) between nucleotides -1111 and -953. In 3 constructs with site-directed mutations in this sequence, basal promoter activities were significantly increased, whereas promoter activation by thyroid hormone was abolished. Electrophoretic mobility shift assays showed that the -1111/-953 DNA fragment of the intact human renin gene was bound to nuclear proteins of Calu-6 cells; however, none of the 3 mutant probes were bound to any nuclear proteins. These results suggest that thyroid hormone stimulates the promoter activity of the human renin gene through thyroid hormone response element-dependent mechanisms in Calu-6 cells.