REDUNDANT DOMAINS CONTRIBUTE TO THE TRANSCRIPTIONAL ACTIVITY OF THE THYROID-TRANSCRIPTION-FACTOR-1

The thyroid transcription factor 1 (TTF-1) is a homeodomain-containing protein implicated in the activation of thyroid-specific gene express ion. Here we report that TTF-1 is capable of activating transcription from thyroglobulin and, to a lesser extent, thyroperoxidase gene promo ters in nonthyroid cells. Full transcriptional activation of the thyro globulin promoter by TTF-1 requires the presence of at least two TTF-1 binding sites. TTF-1 activates transcription via two functionally red undant transcriptional activation domains that as suggested by competi tion experiments, could use a common intermediary factor.