Tumor necrosis factor-alpha regulation of thyroid transcription factor-1 and Pax-8 in rat thyroid FRTL-5 cells.
Tumor necrosis factor-alpha (TNF-alpha) is known to modulate the expression of thyroid-specific genes, such as thyroglobulin (TG), contributing to the pathogenesis of autoimmune thyroid disease. In the present study, we show that TNF-alpha suppresses DNA-binding activity of thyroid transcription factors, Pax-8 and thyroid transcription factor-1 (TTF-1), which is, in part, involved in TNF-alpha-induced decrease in TG gene expression. Transfected into rat thyroid FRTL-5 cells, the activity of reporter plasmid containing the rat TG promoter ligated to a luciferase gene was significantly suppressed in the presence of TNF-alpha. In gel mobility shift analyses, protein-DNA complexes formed by TTF-1 and Pax-8 were reduced when the nuclear extracts prepared from TNF-alpha-treated FRTL-5 cells were used. The suppressive effect of TNF-alpha on TTF-1-DNA complex formation is, in part, caused by suppression of TTF-1 gene transcription by TNF-alpha. Expressions of TTF-1 messenger RNA and protein, which were assessed by Northern blot and Western blot analyses, respectively, were decreased by TNF-alpha treatment of FRTL-5 cells. In contrast, TNF-alpha did not affect the expression of Pax-8 messenger RNA. Treatment of FRTL-5 cells with TNF-alpha caused a decrease in Pax-8 protein in nuclear extracts and accumulation of the protein in the cytoplasm, as assessed by Western blot analyses. Mutation of the TTF-1/Pax-8-binding site lost the TNF-alpha-induced decrease in TG promoter activity in a transfection experiment. These results indicate that TNF-alpha suppresses the activity of TTF-1 and Pax-8 by different mechanisms, which, in part, seem to be involved in TNF-alpha-induced decrease in TG gene expression.
Ohmori
M
M
Third Department of Internal Medicine, Yamanashi Medical University, Tamaho, Japan.
Harii
N
N
Endo
T
T
Onaya
T
T
D000818:Animals; D001483:Base Sequence / Q000235:genetics; D001665:Binding Sites / Q000502:physiology; D002460:Cell Line; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D002678:Chimera / Q000235:genetics; D003593:Cytoplasm / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D009154:Mutation / Q000502:physiology; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D000072636:PAX8 Transcription Factor; D051761:Paired Box Transcription Factors; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D012333:RNA, Messenger / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D013954:Thyroglobulin / Q000235:genetics; D013961:Thyroid Gland / Q000166:cytology / Q000378:metabolism*; D000074482:Thyroid Nuclear Factor 1; D015534:Trans-Activators / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology / Q000502:physiology*
D004268:DNA-Binding Proteins; C000614416:Nkx2-1 protein, rat; D009687:Nuclear Proteins; D000072636:PAX8 Transcription Factor; D051761:Paired Box Transcription Factors; C499497:Pax8 protein, rat; D012333:RNA, Messenger; D000074482:Thyroid Nuclear Factor 1; D015534:Trans-Activators; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D004247:DNA; D013954:Thyroglobulin