Ligand-, cell-, and estrogen receptor subtype (α/β)-dependent activation at GC-rich (Sp1) promoter elements

Brad Saville, Mark Wormke, Fan Wang, Thu Nguyen, Eva Enmark, George Kuiper, Jan Åke Gustafsson, Stephen Safe

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352 Scopus citations


17β-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(α)/Sp1 and ER(β)/Sp1 action using an E2-responsive construct (pSp1) containing a GC-rich promoter. Both ER(α) and ER(β) 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(α)/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(β)/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(α/β) (AF1α/AF-2β) and ERβ/α (AF-1β/AF-2α) proteins that resembled wild-type ER (α or β) in terms of physical association with Sp1 protein. Transcriptional activation studies with chimeric ER(β/α) and ER(α/β) showed that only ER(α/β), can activate transcription from an Sp1 element, not ER(β/α). This indicates that the AF-1 domain from ER(α) 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(α) and ER(α/β) 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.

Original languageEnglish (US)
Pages (from-to)5379-5387
Number of pages9
JournalJournal of Biological Chemistry
Issue number8
StatePublished - Feb 25 2000

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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