A novel cell type-specific mechanism for thyroid hormone-dependent negative regulation of the human type 1 deiodinase gene.
We have identified a cell type-specific, negative thyroid hormone-responsive element in the human type 1 iodothyronine deiodinase (hdio1) gene. This fragment, termed a JEG response element, bound tightly to a JEG-cell nuclear protein [JEG cell-specific transcription factor (JTF)] also present in placenta but not in COS-7, HeLa, or human embryonic kidney-293 cells. In JEG-3 cells, three copies of the JEG response element conferred a more than 40-fold transcriptional stimulation to the heterologous rat GH promoter which was further increased 2-fold by apo-thyroid hormone receptor (TR) and reduced 3-fold by T(3). Dimethyl sulfide footprinting showed overlapping contact sites for the high-affinity interaction of JTF and low-affinity binding of TR-retinoid X receptor. Expression of the same construct was unaffected by TR or T(3) in COS cells, indicating JTF was required for negative regulation by T(3)-TR. Mutations of the critical thyroid hormone responsive element binding P box amino acids EG to GS in TRalpha1 or TRbeta2 eliminated the apo-TR and T(3)-TR effects. These studies identify a novel mechanism for cell type-specific, promoter-independent negative regulation by T(3).
Division of Endocrinology, Diabetes and Hypertension, Department of Medicine, Brigham and Women's Hospital, Harvard Institute of Medicine, 77 Avenue Louis Pasteur, Boston, Massachusetts 02115, USA. swkim@rics.bwh.harvard.edu
Sung-Woo
SW
Kim
Seong-June
SJ
Hong
Kyung Min
KM
Kim
Sung-Chul
SC
Ho
Edward C
EC
So
John W
JW
Harney
P Reed
PR
Larsen
D000818:Animals; D002460:Cell Line; D018983:DNA Footprinting; D015536:Down-Regulation; D024202:Electrophoretic Mobility Shift Assay; D006801:Humans; D007453:Iodide Peroxidase / Q000235:genetics*; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D011988:Receptors, Thyroid Hormone / Q000502:physiology; D020218:Response Elements / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014284:Triiodothyronine / Q000494:pharmacology / Q000502:physiology*
D009687:Nuclear Proteins; D011988:Receptors, Thyroid Hormone; D014157:Transcription Factors; D014284:Triiodothyronine; C109812:iodothyronine deiodinase type I; D007453:Iodide Peroxidase