DNA binding and interaction with the nuclear receptor corepressor of thyroid hormone receptor are required for ligand-independent stimulation of the mouse preprothyrotropin-releasing hormone gene
被引:25
作者:
Satoh, T
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机构:Gunma Univ, Sch Med, Dept Internal Med 1, Maebashi, Gumma 3718511, Japan
Satoh, T
Monden, T
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机构:Gunma Univ, Sch Med, Dept Internal Med 1, Maebashi, Gumma 3718511, Japan
Monden, T
Ishizuka, T
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机构:Gunma Univ, Sch Med, Dept Internal Med 1, Maebashi, Gumma 3718511, Japan
Ishizuka, T
Mitsuhashi, T
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机构:Gunma Univ, Sch Med, Dept Internal Med 1, Maebashi, Gumma 3718511, Japan
Mitsuhashi, T
Yamada, M
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机构:Gunma Univ, Sch Med, Dept Internal Med 1, Maebashi, Gumma 3718511, Japan
Yamada, M
Mori, M
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机构:Gunma Univ, Sch Med, Dept Internal Med 1, Maebashi, Gumma 3718511, Japan
Mori, M
机构:
[1] Gunma Univ, Sch Med, Dept Internal Med 1, Maebashi, Gumma 3718511, Japan
[2] Univ Tokyo, Fac Med, Dept Internal Med 3, Tokyo 113, Japan
corepressor;
mouse TRH gene;
negative regulation;
thyroid hormone receptor;
D O I:
10.1016/S0303-7207(99)00032-5
中图分类号:
Q2 [细胞生物学];
学科分类号:
071009 ;
090102 ;
摘要:
A negative thyroid hormone response element (TRE) in the mouse preprothyrotropin-releasing hormone (TRH) gene was previously mapped within the proximal promoter element between - 83 and + 53 that contained a TRE half-site motif at - 57 ((-57)TGACCT(-52)). In transfection experiments, the promoter activity is stimulated by unliganded thyroid hormone receptor (TR) and T-3 reverses the basal promoter stimulation. In this study, we determined whether the direct binding of TR to the TRE half-site in the mouse TRH gene is required for the ligand-independent stimulation using a transient transfection assay into CV-1 cells and electrophoretic mobility shift assays (EMSA). In addition, the role of a corepressor protein for the ligand-independent stimulation was examined using a putative splicing variant of the nuclear receptor corepressor (N-CoRI). Point mutations introduced into the TRE half-site at - 57 eliminated the binding of TR and the stimulatory effect of unliganded TR. Two mutant TRs lacking DNA-binding activity and two CoR box mutant TRs showed no stimulation in the wild-type TRH promoter. The cotransfected N-CoRI potentiated the ligand-independent stimulation by the wild-type TR, but did not compensate for the impaired function of the CoR box mutant TR. In EMSA, TR strongly bound as homodimers and weakly as heterodimers with retinoid X receptor (RXR) to the element containing the TRE half-site at - 57. Binding of TR to the TRE half-site was essential to form homo- and heterodimers, and the RXR binding site appeared to be located downstream of the TRE half-site. In vitro translated N-CoRI preferentially bound TR homodimers over TR/RXR heterodimers. These results collectively suggest that the DNA-bound TR/corepressor complex might be directly involved in the ligand-independent stimulation of the mouse TRH gene promoter. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.