title: Effects of estradiol and 4-hydroxytamoxifen on the conformation, thermal stability, and DNA recognition of estrogen receptor beta.
abstract: Estrogen receptors (ERalpha and ERbeta) are ligand-activated transcription factors. We examined the effects of estradiol (E2), 4-hydroxytamoxifen (HT), and the estrogen response element (ERE) on the helical content and thermal unfolding of ERbeta. A circular dichroism (CD) spectrum of ERbeta showed changes at 210 and 222 nm that were due to the presence of E2, which is indicative of partial unfolding. In contrast, HT did not alter the CD spectrum of ERbeta. The addition of E2 + ERE caused an increase in the alpha-helical content and an increase in the temperature midpoint of folding transition (TM) from 39 +/- 0.7 degrees C to 57.2 +/- 1 degrees C. The addition of E2 + mutant ERE, or E2 + control oligonucleotide, increased the TM of ERbeta to 45 +/- 2 degrees C only. In the presence of HT, ERbeta yielded similar TM values (55-58 degrees C) with ERE, mutant ERE, or control oligodeoxynucleotide. The binding affinity of ERbeta for ERE increased 125.7-fold as a result of the presence of E2, but only 4-fold as a result of HT. These results demonstrate coupled effects of E2 and ERE on ERbeta stability and binding affinity. The increased thermal stability of HT-ERbeta-ERE was associated with reduced specificity of ERbeta-ERE recognition, illustrating profound differences in conformational states of ERbeta induced by E2 and HT.
authors.affiliation: Department of Medicine, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, 125 Paterson Street, NB, NJ 08903, USA.
authors.forename: Veena
authors.initials: V
authors.lastname: Vijayanathan
authors.forename: Norma J
authors.initials: NJ
authors.lastname: Greenfield
authors.forename: T J
authors.initials: TJ
authors.lastname: Thomas
authors.forename: Margarita M
authors.initials: MM
authors.lastname: Ivanova
authors.forename: Valentyn V
authors.initials: VV
authors.lastname: Tyulmenkov
authors.forename: Carolyn M
authors.initials: CM
authors.lastname: Klinge
authors.forename: Michael A
authors.initials: MA
authors.lastname: Gallo
authors.forename: Thresia
authors.initials: T
authors.lastname: Thomas
mesh_terms: D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004958:Estradiol / Q000378:metabolism*; D047629:Estrogen Receptor beta / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D009154:Mutation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020218:Response Elements / Q000502:physiology*; D013629:Tamoxifen / Q000031:analogs & derivatives* / Q000378:metabolism; D013696:Temperature
chemical_list: D004268:DNA-Binding Proteins; D047629:Estrogen Receptor beta; D011994:Recombinant Proteins; D013629:Tamoxifen; C016601:afimoxifene; D004958:Estradiol