Estrogen-induced retinoic acid receptor alpha 1 gene expression: role of estrogen receptor-Sp1 complex.

Abstract

Retinoic acid receptor alpha 1 (RAR alpha 1) gene expression is induced by 17 beta-estradiol (E2) in estrogen receptor (ER)-positive breast cancer cells, and the -100 to -49 region of the RAR alpha 1 gene promoter was previously shown to be required for E2-responsiveness. This region of the RAR alpha 1 promoter was further analyzed using the following oligonucleotides: -100 to -49 (RAR4); -79 to -56 (RAR3); -79 to -49 (RAR2); -100 to -58 (RAR1); and their derived promoter reporter constructs (pRAR4, pRAR3, pRAR2, and pRAR1). In transient transfection studies in MCF-7 human breast cancer cells, pRAR2 and pRAR1 were E2-responsive; both of the RAR alpha 1 gene promoter inserts contained two GC-rich sites and bound Sp1 protein in gel mobility shift assays. Using wild-type [32P]RAR2 and oligonucleotides mutated in one or both GC-rich sites, it was shown that ER enhanced Sp1 binding to both sites, but a ternary ER-Sp1-DNA complex was not observed in gel mobility shift assays. In transient transfection assays, each of the GC-rich motifs were sufficient for E2-induced transactivation. In ER-negative MDA-MB-231 cells transiently transfected with pRAR2, E2 responsiveness was observed only in cells cotransfected with wild-type ER or 11C-ER containing a deletion of the DNA-binding domain but not with ER variants that express activation function-1 (AF-1) or AF-2. Using a similar approach, it was shown that the GC-rich sites in RAR1 were also sufficient for ER activation. These results demonstrate that interaction of a transcriptionally active ER/Sp1 complex with GC-rich motifs is required for hormone inducibility of the downstream region of the RAR alpha 1 gene promoter.

• Authors: G Sun, W Porter, S Safe
• Journal: Molecular endocrinology (Baltimore, Md.) (Mol Endocrinol) Vol. 12 Issue 6 Pg. 882-90 (Jun 1998) ISSN: 0888-8809 [Print] United States
• PMID: 9626663 (Publication Type: Comparative Study, Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Estrogens
• Macromolecular Substances
• Neoplasm Proteins
• RARA protein, human
• Receptors, Estrogen
• Receptors, Retinoic Acid
• Retinoic Acid Receptor alpha
• Sp1 Transcription Factor
• Estradiol

Topics

• Adenocarcinoma (pathology)
• Breast Neoplasms (pathology)
• Estradiol (pharmacology)
• Estrogens
• Female
• Gene Expression Regulation (drug effects)
• Gene Expression Regulation, Neoplastic (drug effects)
• Humans
• Macromolecular Substances
• Neoplasm Proteins (biosynthesis, genetics)
• Neoplasms, Hormone-Dependent (pathology)
• Promoter Regions, Genetic
• Receptors, Estrogen (physiology)
• Receptors, Retinoic Acid (biosynthesis, genetics)
• Retinoic Acid Receptor alpha
• Sequence Deletion
• Sp1 Transcription Factor (physiology)
• Transfection
• Tumor Cells, Cultured