Hepatocyte nuclear factor 3beta participates in the transcriptional regulation of the thyroperoxidase promoter.

The promoters of the thyroglobulin (Tg) and thyroperoxidase (TPO) genes both contain sequences that match the consensus recognized by the fork-head family of transcription factors. The fork-head recognition element in the TPO promoter is recognized by two proteins, one of which is the transcription factor HNF-3beta, a member of the hepatocyte nuclear factor 3 (HNF-3) family, and the other is a thyroid-specific binding activity previously described as thyroid transcription factor 2 (TTF-2). Differently, only TTF-2 is capable of recognizing the fork-head recognition element in the thyroglobulin promoter, HNF-3beta protein is present in cultured thyroid cells and in the adult thyroid gland, suggesting that it does indeed have a role in modulating thyroid-specific gene expression. The transcriptional activities of TPO promoter mutants impaired in either TTF-2 or HNF-3beta binding suggest that both factors participate in regulating transcription from the TPO promoter.