Interferon-gamma suppresses thyrotropin receptor promoter activity by reducing thyroid transcription factor-1 (TTF-1) binding to its recognition site
Autor: | Ryoichi Takayanagi, Kenji Ohe, Leonard D. Kohn, Hajime Nawata, Shoichiro Ikuyama |
---|---|
Rok vydání: | 1996 |
Předmět: |
Cell Extracts
endocrine system medicine.medical_specialty endocrine system diseases medicine.medical_treatment Thyroid Nuclear Factor 1 Thyroid Transcription Factor 1 Thyroid Gland Binding Competitive Iodide Peroxidase Thyroglobulin Thyrotropin receptor Chloramphenicol acetyltransferase Interferon-gamma Endocrinology Thyroid peroxidase Internal medicine medicine Animals Humans Interferon gamma RNA Messenger Promoter Regions Genetic Receptor Molecular Biology Cells Cultured Dose-Response Relationship Drug biology Thyroid Nuclear Proteins Receptors Thyrotropin General Medicine Molecular biology Rats DNA-Binding Proteins Repressor Proteins medicine.anatomical_structure Trans-Activators biology.protein Transcription Factors medicine.drug |
Zdroj: | Molecular Endocrinology. 10:826-836 |
ISSN: | 1944-9917 0888-8809 |
Popis: | Interferon-gamma (IFN gamma) is known to suppress the expression of thyroid-specific genes, such as thyroglobulin, thyroid peroxidase, and the TSH receptor (TSHR). In the present study, we show that this reflects, in part, a transcriptional action mediated by thyroid transcription factor-1 (TTF-1). Thus, transfected into rat FRTL-5 cells, the activity of reporter plasmids, containing rat TSHR promoter ligated to a chloramphenicol acetyltransferase gene, was significantly suppressed in the presence of rat IFN gamma. A -199-bp promoter construct showed the greatest suppression by IFN gamma whereas a -177-bp construct, in which the TTF-1 binding site was deleted, showed less suppressibility. The suppressive effect was rat IFN gamma-specific, since human IFN alpha, -beta, and -gamma exhibited no significant effects. The effect was concentration-dependent from 3-50 U/ml. In FRT rat thyroid cells that do not express TTF-1, IFN gamma-induced suppression on the promoter activity was not observed. In addition, when the TTF-1 binding site was mutated so that TTF-1 can not bind, IFN gamma-induced suppression was significantly reduced. In gel mobility shift analyses, a protein-DNA complex formed by TTF-1 was reduced when the nuclear extract prepared from IFN gamma-treated FRTL-5 cells was used; however, expression of TTF-1 mRNA and TTF-1 protein, which were assessed by Northern blot analysis and Western blot analysis, respectively, were not affected by IFN gamma treatment of FRTL-5 cells. Instead, reduction of DNA-binding affinity of TTF-1 was evident when competition analysis was performed in gel mobility shift analysis. From these results, we conclude that IFN gamma suppresses TSHR promoter activity, in part, by reducing TTF-1 binding to its recognition site. We also raise the possibility that the suppressive effect of IFN gamma on promoter activity is mediated by additional element(s) and factor(s) downstream of the TTF-1 site. |
Databáze: | OpenAIRE |
Externí odkaz: |