Ligand-, cell-, and estrogen receptor subtype (alpha/beta)-dependent activation at GC-rich (Sp1) promoter elements.
17beta-Estradiol (E2) induces expression of several genes via estrogen receptor (ER)-Sp1 protein interactions with GC-rich promoter elements in which Sp1 but not ER binds DNA. This study reports the ligand- and cell context-dependent ER(alpha)/Sp1 and ER(beta)/Sp1 action using an E2-responsive construct (pSp1) containing a GC-rich promoter. Both ER(alpha) and ER(beta) proteins physically interact with Sp1 (coimmunoprecipitation) and preferentially bind to the C-terminal region of this protein in pull-down assays. E2- and antiestrogen-dependent transcriptional activation of ER(alpha)/Sp1 was observed in MCF-7, MDA-MB-231, and LnCaP cells, but not in HeLa cells. E2 did not affect or significantly decrease ER(beta)/Sp1 action, and antiestrogens had minimal effects in the same 4 cell lines. Exchange of activation function-1 (AF-1) domains of ER subtypes gave chimeric ER(alpha/beta) (AF-1alpha/AF-2beta) and ER(beta/alpha) (AF-1beta/AF-2alpha) proteins that resembled wild-type ER (alpha or beta) in terms of physical association with Sp1 protein. Transcriptional activation studies with chimeric ER(beta/alpha) and ER(alpha/beta) showed that only ER(alpha/beta) can activate transcription from an Sp1 element, not ER(beta/alpha). This indicates that the AF-1 domain from ER(alpha) is responsible for activation at an Sp1 element, independent of ER subtype context. In order to further characterize this observation, deletion constructs in the AF-1 domain of both ER(alpha) and ER(alpha/beta) were made, and transactivation studies indicated that the region between amino acids 79 and 117 of this domain is important for activation at an Sp1 element.
Saville
B
B
Department of Veterinary Physiology and Pharmacology, Texas A&M University, College Station, Texas 77843-4466, USA.
Wormke
M
M
Wang
F
F
Nguyen
T
T
Enmark
E
E
Kuiper
G
G
Gustafsson
J A
JA
Safe
S
S
D003001:Cloning, Molecular; D004958:Estradiol / Q000031:analogs & derivatives / Q000494:pharmacology; D004965:Estrogen Antagonists / Q000494:pharmacology; D000077267:Fulvestrant; D005982:Glutathione Transferase / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008024:Ligands; D008954:Models, Biological; D016296:Mutagenesis; D010957:Plasmids; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D014176:Protein Biosynthesis; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D011960:Receptors, Estrogen / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D016329:Sp1 Transcription Factor / Q000378:metabolism*; D013629:Tamoxifen / Q000494:pharmacology; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured
D004965:Estrogen Antagonists; D008024:Ligands; D020033:Protein Isoforms; D011960:Receptors, Estrogen; D016329:Sp1 Transcription Factor; D013629:Tamoxifen; D000077267:Fulvestrant; D004958:Estradiol; D005982:Glutathione Transferase