Identification of a new isoform of the human estrogen receptor-alpha (hER-alpha) that is encoded by distinct transcripts and that is able to repress hER-alpha activation function 1.
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Flouriot G, Brand H, Denger S, Metivier R, Kos M, Reid G, Sonntag-Buck V, Gannon F
Identification of a new isoform of the human estrogen receptor-alpha (hER-alpha) that is encoded by distinct transcripts and that is able to repress hER-alpha activation function 1.
EMBO J. 2000 Sep 1;19(17):4688-700.
- PubMed ID
- 10970861 [ View in PubMed]
- Abstract
A new isoform of the human estrogen receptor-alpha (hER-alpha) has been identified and characterized. This 46 kDa isoform (hERalpha46) lacks the N-terminal 173 amino acids present in the previously characterized 66 kDa isoform (hERalpha66). hERalpha46 is encoded by a new class of hER-alpha transcript that lacks the first coding exon (exon 1A) of the ER-alpha gene. We demonstrated that these Delta1A hER-alpha transcripts originate from the E and F hER-alpha promoters and are produced by the splicing of exon 1E directly to exon 2. Functional analysis of hERalpha46 showed that, in a cell context sensitive to the transactivation function AF-2, this receptor is an effective ligand-inducible transcription factor. In contrast, hERalpha46 is a powerful inhibitor of hERalpha66 in a cell context where the transactivating function of AF-1 predominates over AF-2. The mechanisms by which the AF-1 dominant-negative action is exerted may involve heterodimeri zation of the two receptor isoforms and/or direct competition for the ER-alpha DNA-binding site. hERalpha66/hERalpha46 ratios change with the cell growth status of the breast carcinoma cell line MCF7, suggesting a role of hERalpha46 in cellular proliferation.