THYROID TRANSCRIPTION FACTOR-1 ACTIVATES THE PROMOTER OF THE THYROTROPIN RECEPTOR GENE

The TSH receptor (TSHr) is one of the most important thyroid different iation markers. The binding of the TSH hormone to its receptor is an e ssential step in the modulation of thyroid function and differentiatio n. Here we report that the thyroid transcription factor 1 (TTF1), a tr anscription factor essential for thyroid-specific gene expression, bin ds to the TSHr minimal promoter. The promoter, when mutated at this bi nding site, shows a decreased activity in thyroid cells. In cotransfec tion experiments in nonthyroid cells, TTF1 is able to trans-activate t he TSHr minimal promoter. This finding strengthens the importance of T TF1 in the maintenance of thyroid differentiation. The promoters of th e main thyroid differentiation markers thyroglobulin, thyroperoxidase, and now TSHr, are regulated by TTF1.