THYROID-HORMONE RECEPTOR MONOMER, HOMODIMER, AND HETERODIMER (WITH RETINOID-X RECEPTOR) CONTACT DIFFERENT NUCLEOTIDE-SEQUENCES IN THYROID-HORMONE RESPONSE ELEMENTS

被引:43
|
作者
IKEDA, M
RHEE, M
CHIN, WW
机构
[1] HOWARD HUGHES MED INST, BOSTON, MA 02115 USA
[2] HARVARD UNIV, SCH MED, BOSTON, MA 02115 USA
关键词
D O I
10.1210/en.135.4.1628
中图分类号
R5 [内科学];
学科分类号
1002 ; 100201 ;
摘要
Thyroid hormone receptors (TRs) bind as monomers, homodimers, and heterodimers with nuclear proteins such as retinoid-X receptors (RXRs) to thyroid hormone response elements (TREs). However, it is not known which nucleotides each TR complex contacts in a particular TRE. To identify the precise contact sites on a synthetic DR4 (TRE half-sites arranged as a direct repeat with a four-nucleotide spacer) and a chick lysoenzyme TRE, F2 (half-sites arranged as an inverted palindrome with a six-nucleotide spacer), for various TR complexes, mobility shift assays, and dimethylsulfate and KMnO4 DNA modification interference assays were employed. First, TR alpha monomer bound to the down-stream half-site of these TREs, whereas TR alpha homodimer bound to both half-sites. TR alpha/RXR alpha heterodimer also bound to both half-sites, but ''preferred'' to contact the down-stream half-site. Second, the specific flanking and spacing sequences of DR4 influenced the contact sites and the binding of TR alpha monomer and homodimer, but not TR alpha/RXR alpha heterodimer. Finally, cotransfection studies, using reporter plasmids containing DR4 or F2 in both orientations with respect to the basal promoter, provide evidence that preferential contact with the down-stream half-site by TR/RXR heterodimer may be important for maximal transcriptional activation.
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页码:1628 / 1638
页数:11
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