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Fundamentally distinct roles of thyroid hormone receptor isoforms in a thyrotroph cell line are due to differential DNA binding.
- Source :
-
Molecular endocrinology (Baltimore, Md.) [Mol Endocrinol] 2012 Jun; Vol. 26 (6), pp. 926-39. Date of Electronic Publication: 2012 May 08. - Publication Year :
- 2012
-
Abstract
- Thyroid hormones have a profound influence on human development and disease. The hypothalamic-pituitary-thyroid axis involves finely tuned feedback mechanisms to maintain thyroid hormone (TH) levels. Despite the important role of TH-negative feedback in regulating this axis, the mechanism by which this occurs is not clearly defined. Previous in vivo studies suggest separate roles for the two thyroid hormone receptor isoforms, THRA and THRB, in this axis. We performed studies using a unique pituitary thyrotroph cell line (TαT1.1) to determine the relative roles of THRA and THRB in the regulation of Tshb. Using chromatin immunoprecipitation assays, we found that THRB, not THRA, bound to the Tshb promoter. By selectively depleting THRB, THRA, or both THRA and THRB in TαT1.1 cells, we found that simultaneous knockdown of both THRB and THRA abolished T(3)-mediated down-regulation of Tshb at concentrations as high as 100 nm T(3). In contrast, THRA knockdown alone had no effect on T(3)-negative regulation, whereas THRB knockdown alone abolished T(3)-mediated down-regulation of Tshb mRNA levels at 10 nm but not 100 nm T(3) concentrations. Interestingly, chromatin immunoprecipitation assays showed that THRA becomes enriched on the Tshb promoter after knockdown of THRB. Thus, a likely mechanism for the differential effects of THR isoforms on Tshb may be based on their differential DNA-binding affinity to the promoter.
- Subjects :
- Animals
Cell Line
Gene Expression Regulation
Gene Knockdown Techniques
Glycoprotein Hormones, alpha Subunit genetics
Glycoprotein Hormones, alpha Subunit metabolism
Mice
Promoter Regions, Genetic
Protein Binding
Protein Isoforms metabolism
Protein Isoforms physiology
RNA Interference
RNA, Messenger genetics
RNA, Messenger metabolism
Receptors, Thyroid Hormone metabolism
Thyrotropin, beta Subunit genetics
Thyrotropin, beta Subunit metabolism
Transcription, Genetic
Triiodothyronine physiology
DNA metabolism
Receptors, Thyroid Hormone physiology
Thyrotrophs metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 1944-9917
- Volume :
- 26
- Issue :
- 6
- Database :
- MEDLINE
- Journal :
- Molecular endocrinology (Baltimore, Md.)
- Publication Type :
- Academic Journal
- Accession number :
- 22570333
- Full Text :
- https://doi.org/10.1210/me.2011-1290