Analysis of Pit-1 in regulating mouse TSH β promoter activity in thyrotropes

• Published in: Molecular and cellular endocrinology Vol. 96; no. 1; pp. 75 - 84
• Main Authors: Gordon, David F., Haugen, Bryan R., Sarapura, Virginia D., Nelson, Angela R., Wood, William M., Ridgway, E.Chester
• Format: Journal Article
• Language: English
• Published: Shannon Elsevier Ireland Ltd 01.10.1993; Elsevier
• Subjects: Animals; Base Sequence; Biological and medical sciences; Blotting, Northern; Blotting, Western; DNA; DNA-Binding Proteins - metabolism; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation; Humans; Mice; Molecular and cellular biology; Molecular genetics; Molecular Sequence Data; Pit-1; Pituitary Gland, Anterior - cytology; Pituitary Gland, Anterior - metabolism; Promoter Regions, Genetic; Protein Biosynthesis; RNA, Messenger - genetics; thyrotrope; Thyrotropin - genetics; Thyrotropin - metabolism; Transcription Factor Pit-1; Transcription Factors - metabolism; Transcription. Transcription factor. Splicing. Rna processing; TSHβ promoter; TtT-97 tumor; Tumor Cells, Cultured; αTSH cell; TSHβ promoter; TtT-97 tumor; αTSH cell; Pit-1; thyrotrope; Adenohypophysis; Transcription factor Pit1; Vertebrata; Mammalia; Adenohypophyseal hormone; Mouse; Transcription promoter; Thyreotropic cell; Rodentia; Beta-Peptide chain; TSH; Gene expression
• ISSN: 0303-7207; 1872-8057
• DOI: 10.1016/0303-7207(93)90097-4

TSHβ gene expression is restricted to pituitary thyrotropes. Since Pit-1 is present in these cells, we characterized Pit-1 RNA and protein in thyrotropes, and tested its function in regulating TSHβ promoter activity. We demonstrate that both TtT-97 thyrotropic tumors and pituitaries contain four Pit-1 transcripts of 3.2, 2.6, 2.4, and 1.9 kb, respectively. Only two transcripts of 2.7 and 2.1 kb were detected in αTSH cells, a thyrotrope derived cell that no longer expresses TSHβ. Western analysis revealed Pit-1 protein in TtT-97 cells but not in αTSH cells. DNase I protection assays localized Pit-1 binding to three areas of the mouse TSHβ promoter. However, basal TSHβ promoter activity was minimally stimulated when αTSH cells or TtT-97 thyrotropes were co-transfected with mouse Pit-1 and a mTSHβ luciferase construct. These studies suggest that Pit-1 is not limiting for cell-specific expression of the TSHβ gene in thyrotrope-derived cells and implies that additional thyrotropic factors are likely required.