ESTROGEN-RECEPTOR - DNA INTERACTION - DIFFERENCE BETWEEN ACTIVATION BY ESTROGEN AND ANTI-ESTROGEN

  • 1 January 1982
    • journal article
    • research article
    • Vol. 128  (1) , 185-191
Abstract
The interaction of the [rat] cytosol estrogen receptor with calf thymus DNA after its binding to [3H]estradiol or 4-hydroxy[3H]tamoxifen, a high-affinity antiestrogen, was compared in an atempt to find a difference in the nature of these 2 complexes. The activation of the receptor and its binding to DNA were simultaneously obtained during an 18 h incubation at 0.degree. C. The binding of a constnant concentration of estrogen receptor to increasing concentrations of adsorbed DNA was examined. Scatchard representation of the data showed that the antiestrogen-receptor complex has a 2-fold lower for DNA than the estradiol-receptor complex, while the proportion of receptor able to bind DNA was the same whether bound to estradiol or antiestrogen. Similar results were obtained by using soluble DNA and separation of the unbound and DNA-bound receptor on surcrose gradients. The estrogen receptor binds in vitro to non-specific double-stranded DNA with a lower affinity when it was activated by an antiestrogen than when activated by estradiol.