Tumor necrosis factor-alpha and interferon-gamma suppress both gene expression and deoxyribonucleic acid-binding of TTF-2 in FRTL-5 cells.
Tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) are cytokines that can individually or additively suppress thyroid cell function and the expression of thyroid-specific genes, such as thyroglobulin (TG) and thyroperoxidase (TPO). Thyroid transcription factor-2 (TTF-2) is a DNA-binding protein that modulates the expression of TG and TPO genes. In the present study, we examine the effects of TNF-alpha and IFN-gamma on TTF-2 gene expression, as well as the DNA-binding activity of TTF-2. FRTL-5 cells were maintained in 5H medium containing 0.2% calf serum for 7 days, then incubated with TNF-alpha, IFN-gamma, or TNF-alpha plus IFN-gamma. Total RNA was isolated and Northern blotted. TNF-alpha (50 ng/ml) only slightly suppressed (61+/-2% compared with control), whereas IFN-gamma (100 U/ml) modestly decreased TTF-2 messenger RNA (mRNA) levels (34+/-4%). TNF-alpha and IFN-gamma simultaneously caused a marked decrease in TTF-2 mRNA levels (13+/-2%). The suppressive effects of TNF-alpha and IFN-gamma on TTF-2 mRNA levels were concentration dependent and maximal at 50 ng/ml TNF-alpha with 100 U/ml IFN-gamma. The suppressive effect was also time dependent, reaching a maximum 12 h after exposure. Moreover, the suppressive effects of TNF-alpha and IFN-gamma upon rat TG and TTF-2 mRNA levels were similar. To test whether TNF-alpha and IFN-gamma alter TTF-2-binding to DNA, we performed electrophoretic mobility shift assays using a TTF-2-binding element in the rat TG gene as a probe. Formation of the TTF-2/DNA complex was decreased by TNF-alpha and/or IFN-gamma. Our results demonstrate that TNF-alpha and IFN-gamma additively reduce the gene expression and DNA-binding of TTF-2. These data suggest that TTF-2 is involved in the TNF-alpha and IFN-gamma-induced suppression of thyroid-specific gene expression.
Miyazaki
A
A
Third Department of Internal Medicine, Yamanashi Medical University, Tamaho, Japan.
Shimura
H
H
Endo
T
T
Haraguchi
K
K
Onaya
T
T
D000818:Animals; D002460:Cell Line; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D051858:Forkhead Transcription Factors; D015870:Gene Expression / Q000187:drug effects*; D007371:Interferon-gamma / Q000494:pharmacology*; D012333:RNA, Messenger / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D004268:DNA-Binding Proteins; C106894:FOXE1 protein, human; D051858:Forkhead Transcription Factors; D012333:RNA, Messenger; D012097:Repressor Proteins; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma; D004247:DNA