Mechanism of the Estrogen Receptor Interaction with 4-Hydroxytamoxifen

Sasson, Shlomo; Notides, Angelο C.

doi:10.1210/mend-2-4-307

Cited by 35 publications

(17 citation statements)

References 16 publications

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“…Analytical gel filtration analysis showed that the predominant molecular form of this hER preparation, in the presence or absence of estrogen, at protein concentrations ranging from 40 to 300 nM is a homodimer. Monomeric hER and complexes with greater than 2 orders of oligomerization were also identified, and this result is in agreement with previous studies (38,43,44). In the presence of specific labeled oligonucleotide, derived from the vitellogenin A 2 gene of X. laevis response promoter, homodimer-(hER) 2 ERE complex was detected.…”

Section: Discussionsupporting

confidence: 92%

Estrogen Receptor Ligands Modulate Its Interaction with DNA

Cheskis¹,

Karathanasis²,

Lyttle³

1997

Journal of Biological Chemistry

119

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The estrogen receptor (ER) belongs to a superfamily of ligand-inducible transcription factors. Functions of these proteins (dimerization, DNA binding, and interaction with other transcription factors) are modulated by binding of their corresponding ligands. It is, however, controversial whether various ER ligands affect the receptor's ability to bind its specific DNA element (ERE).By using real time interaction analysis we have investigated the kinetics of human (h)ER binding to DNA in the absence and presence of 17␤-estradiol, 17␣-ethynyl estradiol, analogs of tamoxifen, raloxifene, and ICI-182,780. We show that ligand binding dramatically influences the kinetics of hER interaction with specific DNA. We have found that binding of estradiol induces the rapid formation of a relatively unstable ER⅐ERE complex, and binding of ICI-182,780 leads to slow formation (k a is approximately 10 times lower) of a stable receptor-DNA complex (k d is almost 2 orders of magnitude lower). Therefore, binding of estradiol accelerates the frequency of receptor-DNA complex formation more than 50-fold, compared with unliganded ER, and more than 1000-fold compared with ER liganded with ICI-182,780. We hypothesize that a correlation exists between the rate of gene transcription and the frequency of receptor-DNA complex formation. We further show that a good correlation exists between the kinetics of hER-ERE interaction induced by a ligand and its biological effect.Steroid hormones are widely distributed small, lipophilic molecules that participate in intracellular communication and control a wide spectrum of developmental and physiological processes. Their effects are mediated by specific intracellular receptors, a family of proteins that are characterized by a high affinity for the corresponding hormones and an ability to discriminate between structurally closely related ligands. These ligand-inducible receptors can modulate transcription of target genes by virtue of their binding to a specific sequence on DNA in target promoters known as hormone response elements. Although distinct proteins, these receptors are members of a large superfamily of steroid hormone receptors and share many common structural and functional features (1-4).Binding of 17␤-estradiol (E 2 ) 1 to estrogen receptor (ER) is followed by a conformational change, leading to dissociation of the receptor from the complex with the heat shock proteins hsp90 and p59 (5, 6), dimerization (7,8), and activation of DNA binding. After DNA binding the activated receptor can interact with basal transcription factors (9). These interactions are thought to stabilize the preinitiation complex at the promoter, allowing RNA polymerase to initiate transcription (10). Recently a number of transcriptional intermediary factors have been identified that can modify estrogen responsiveness, and several of these proteins interact with the ligand binding domain of the ER in a ligand-dependent manner (11-13). It is obvious that the ligand plays a key role in initiating this cascade of events. ...

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Section: Discussionsupporting

confidence: 92%

Estrogen Receptor Ligands Modulate Its Interaction with DNA

Cheskis¹,

Karathanasis²,

Lyttle³

1997

Journal of Biological Chemistry

119

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“…3), our data suggest that such synergism might occur at the level of ligand binding. The suggested positive cooperativity by 4-OHT is in contrast to the interpretation of non-parallel competition curves reported for [ 3 H]estradiol displacement by 4-OHT (Brandt and Vickery, 1997;Sasson and Notides, 1988). However, these studies were performed on purified proteins in vitro and thus may not properly reflect the in vivo situation.…”

Section: Co-stimulation With E 2 and 4-ohtmentioning

confidence: 63%

A genetic, non-transcriptional assay for nuclear receptor ligand binding in yeast

Köhler

Zimmermann

Hager

et al. 2004

Gene

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“…The trans-4-hydroxytamoxifen had a slightly lower affinity and a steeper slope on the semi-log plot than that of estradiol, similar to observations previously reported by Sasson and Notides (23) for the full-length calf uterine estrogen receptor. The non-parallel competition curve for 4-hydroxytamoxifen was interpreted by Sasson and Notides (23) to indicate that estradiol and 4-hydroxytamoxifen bind the receptor differently, and that 4-hydroxytamoxifen binding to one site in the dimer induced the dissociation of estradiol from the other site. Our observation of the non-parallel competition of estradiol by 4-hydroxytamoxifen suggests that the structural features required for this differential binding of the two ligands are retained by the isolated HBD.…”

Section: Expression and Isolation Of The Hbd Peptide-mentioning

confidence: 99%

Cooperativity and Dimerization of Recombinant Human Estrogen Receptor Hormone-binding Domain

Brandt

Vickery

1997

Journal of Biological Chemistry

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The estrogen receptor dimerizes and exhibits cooperative ligand binding as part of its normal functioning. Interaction of the estrogen receptor with its ligands is mediated by a C-terminal hormone-binding domain (HBD), and residues within the HBD are thought to contribute to dimerization. To examine dimer interactions in the isolated HBD, a human estrogen receptor HBD fragment was expressed in high yield as a cleavable fusion protein in Escherichia coli. The isolated HBD peptide exhibited affinity for estradiol, ligand discrimination, and cooperative estradiol binding (Hill coefficient ϳ1.6) similar to the full-length protein. Circular dichroism spectroscopy suggests that the HBD contains significant amounts of ␣-helix (ϳ60%) and some ␤-strand (ϳ7%) and that ligand binding induces little change in secondary structure. HBD dimer dissociation, measured using size exclusion chromatography, exhibited a halflife of ϳ1.2 h, which ligand binding increased ϳ3-fold (estradiol) to ϳ4-fold (4-hydroxytamoxifen). These results suggest that the isolated estrogen receptor HBD dimerizes and undergoes conformational changes associated with cooperative ligand binding in a manner comparable to the full-length protein, and that one effect of ligand binding is to alter the receptor dimer dissociation kinetics.The estrogen receptor is a member of a superfamily of nuclear proteins that includes the receptors for the steroid hormones, for vitamins A and D, and for thyroid hormone (1, 2). The binding of ligands to these receptors is the initial step in a complex series of events culminating in an interaction of the ligand-bound receptor with the transcription machinery and modulation of gene expression. These receptor proteins exhibit four distinct properties required to exert their actions: hormone binding, multimeric complex formation, sequence specific DNA binding, and transcriptional modulation. The currently proposed schematic structure of these receptor proteins (shown in Fig. 1 for the estrogen receptor), based on sequence similarities and deletion analyses (summarized in Ref.2), suggests that these proteins fold into at least three separate structural and functional domains: (i) an N-terminal domain having a highly variable length and amino acid sequence and believed to mediate much of the transcriptional enhancement activity of the protein, (ii) a highly conserved central domain of ϳ80 amino acids involved in DNA binding, and (iii) a less well conserved C-terminal domain of ϳ250 amino acids that is involved in ligand binding.The C-terminal hormone-binding domain (HBD) 1 of the receptor is of particular interest because, in addition to its ligand binding activity, it appears to contain many of the regulatory functions of the protein. Chimeric constructs containing fusions of fragments of the estrogen receptor with unrelated proteins such as the myc oncogene product, for example, display hormonal regulation of the activity of the fused gene products (3). This suggests that, even when removed from its normal environment, the HBD i...

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Mechanism of the Estrogen Receptor Interaction with 4-Hydroxytamoxifen

Cited by 35 publications

References 16 publications

Estrogen Receptor Ligands Modulate Its Interaction with DNA

Estrogen Receptor Ligands Modulate Its Interaction with DNA

A genetic, non-transcriptional assay for nuclear receptor ligand binding in yeast

Cooperativity and Dimerization of Recombinant Human Estrogen Receptor Hormone-binding Domain

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