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).
Kim
Sung-Woo
SW
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
Hong
Seong-June
SJ
Kim
Kyung Min
KM
Ho
Sung-Chul
SC
So
Edward C
EC
Harney
John W
JW
Larsen
P Reed
PR
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