Regulation of retinoic acid receptor []1 gene expression by 17 []-estradiol and 2,3,7,8-tetrachlorodibenzo-P-dioxin (TCDD) in human breast cancer cells /
Retinoic acid receptor α1 (RARα1) gene expression is induced by 17β-estradiol (E2) in estrogen receptor α (ERα)-positive breast cancer cells and the -100 to -49 region of the RARα1 gene promoter was previously identified as E2-responsive. Promoter deletion and mutation analysis showed that GC-rich m...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
2000.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=731981381&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Retinoic acid receptor α1 (RARα1) gene expression is induced by 17β-estradiol (E2) in estrogen receptor α (ERα)-positive breast cancer cells and the -100 to -49 region of the RARα1 gene promoter was previously identified as E2-responsive. Promoter deletion and mutation analysis showed that GC-rich motifs within this region were sufficient for E2 induction. In gel mobility shift assays, Sp1 but not ER bound to this region and ER enhanced Sp1 binding to GC-rich motifs. In ER-negative MDA-MB-231 cells transiently transferred with pRAR2 containing the -79 to -49 region of RARα1 gene promoter, E2-responsiveness was observed only in cells cotransfected with wild-type ER or 11C-ER containing a deletion of the DNA-binding domain. These results demonstrate that interaction of a transcriptionally-active ER/Sp1 complex with GC-rich motifs are required for hormone-inducibility of the downstream GC-rich region of the RARα1 gene promoter. E2 induced RARα1 mRNA levels and chloramphenical acetyltransferase (CAT) reporter gene activity in MCF-7 cells transferred with pRARA12 (containing the -509 to +105 region of the promoter) and both of these responses were inhibited by the indirect antiestrogen 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and the pure antiestrogen ICI 182, 780 but not by the partial antiestrogen tamoxifen. Inhibition of RARα1 gene expression by TCDD is dependent on a functional aryl hydrocarbon receptor (AhR) but is independent of a core inhibitory dioxin responsive element (iDRE) at -110 to -106. Overexpression of coactivators SRC-1 and p300 can not overcome the inhibitory effects of TCDD, suggesting that the antiestrogenic action of TCDD is not due to competition for limiting cellular levels of SRC-1 or p300. Western blot analysis of Sp1 and Sp3 protein levels did not change significantly in cells treated with E2, TCDD or E2 plus TCDD, indicating that inhibitor AhA-ERα crosstalk in MCF-7 cells is not associated with the modulation of Sp1 and Sp3 protein levels. In vitro footprinting of the RARα1 gene promoter indicated that AhR complex may interfere with interactions of the Sp1 protein with the E2 responsive GC-rich motifs in the proximal region of the promoter. |
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| Item Description: | Vita. "Major Subject: Toxicology". In title, symbols used. |
| Physical Description: | xii, 174 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 137-173). |