The human, but not rat, dio2 gene is stimulated by thyroid transcription factor-1 (TTF-1).
Types 1 and 2 iodothyronine deiodinases (D1 and D2) catalyze the production of T(3) from T(4). D2 mRNA is abundant in the human thyroid but very low in adult rat thyroid, whereas D1 activity is high in both. To understand the molecular regulation of these genes in thyroid cells, the effect of thyroid transcription factor 1 (TTF-1) and the paired domain-containing protein 8 (Pax-8) on the transcriptional activity of the deiodinase promoters were studied. Both the approximately 6.5-kb hdio2 sequence and its most 3' 633 bp were activated 10-fold by transiently expressed TTF-1 in COS-7 cells, but the hdio1 was unaffected. Surprisingly, the response of the rdio2 gene to TTF-1 was only 3-fold despite the 73% identity with the proximal 633-bp region of hdio2 including complete conservation of a functional cAMP response element at -90. Neither human nor rat dio2 nor human dio1 was induced by Pax-8. The binding affinity of four putative TTF-1 binding sites in hdio2 were compared by a semiquantitative gel retardation assay using in vitro expressed TTF-1 homeodomain protein. Only two sites, D and C1 (both of which are absent in rdio2), had significant affinity. Functional analyses showed that both sites are required for the full response to TTF-1. These results can explain the differential expression of dio2 in thyroid and potentially other tissues in humans and rats.
Gereben
B
B
Thyroid Division, Department of Medicine Brigham and Women's Hospital, Harvard Medical School Boston, Massachusetts 02115, USA.
Salvatore
D
D
Harney
J W
JW
Tu
H M
HM
Larsen
P R
PR
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D017868:Cyclic AMP-Dependent Protein Kinases / Q000494:pharmacology; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects*; D015723:Gene Library; D006801:Humans; D007453:Iodide Peroxidase / Q000235:genetics* / Q000378:metabolism; D007457:Iodine Radioisotopes; D007700:Kinetics; D008297:Male; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism / Q000494:pharmacology*; D000072636:PAX8 Transcription Factor; D051761:Paired Box Transcription Factors; D011401:Promoter Regions, Genetic; D011441:Propylthiouracil / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D017385:Sequence Homology; D013045:Species Specificity; D013961:Thyroid Gland / Q000201:enzymology*; D000074482:Thyroid Nuclear Factor 1; D013974:Thyroxine / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism / Q000494:pharmacology; D014157:Transcription Factors / Q000378:metabolism / Q000494:pharmacology*; D014158:Transcription, Genetic / Q000187:drug effects
D004268:DNA-Binding Proteins; D007457:Iodine Radioisotopes; C000614412:NKX2-1 protein, human; C000614416:Nkx2-1 protein, rat; D009687:Nuclear Proteins; D000072636:PAX8 Transcription Factor; C083325:PAX8 protein, human; D051761:Paired Box Transcription Factors; C499497:Pax8 protein, rat; D012333:RNA, Messenger; D000074482:Thyroid Nuclear Factor 1; D015534:Trans-Activators; D014157:Transcription Factors; D011441:Propylthiouracil; D004247:DNA; D007453:Iodide Peroxidase; D017868:Cyclic AMP-Dependent Protein Kinases; D013974:Thyroxine