Studies on the activation of the oestrogen receptor bound to the anti-oestrogens 4-hydroxytamoxifen and ICI 164,384 by using three monoclonal antibodies.

Three monoclonal antibodies, H222, H226 and D547, which provided evidence of the structural transformation and change in exposure of the functional domains of the oestrogen receptor from fetal guinea-pig uterus upon activation, were used to study the receptor bound to the anti-oestrogens 4-hydroxytamoxifen and ICI 164,384. No differences in the structure of non-activated 4-hydroxytamoxifen- and ICI 164,384-receptor complexes, as compared with the oestradiol-receptor complex, were detected by the three monoclonal antibodies. When heated at 28 degrees C, both anti-oestrogen-receptor complexes became capable of binding the D547 antibody, which reacts selectively with the activated receptor; however, this binding was lower than that of the oestradiol-receptor complex. The interaction with the H226 antibody showed that anti-oestrogens can induce receptor dimerization, but to a lesser extent than oestradiol. In addition, both anti-oestrogen-receptor complexes can bind to DNA-cellulose and are retained in nuclei from intact cells at 28 degrees C, but less efficiently than the oestradiol-receptor complex. On the other hand, the nuclear receptor seems to have a similar dimeric structure when bound to either anti-oestrogens or oestradiol, as detected by the three monoclonal antibodies. The data suggest that 4-hydroxytamoxifen and ICI 164,384 induce and impaired activation of the oestrogen receptor; this difference, although quantitative rather than qualitative, might be related to the partial agonistic action of these anti-oestrogens in the fetal guinea-pig uterus.

The uteroglobin promoter contains a noncanonical estrogen responsive element.

Uteroglobin is expressed in various tissues of the rabbit under complex hormonal control. In the endometrium the uteroglobin gene is transcribed only in epithelial cells after administration of ovarian hormones. In this paper we demonstrate that within the promoter region of the rabbit uteroglobin gene, there is a functional estrogen-responsive element (ERE) located between -265 and -252. Hybrid constructions containing sequences of the uteroglobin promoter up to -299, linked to the chloramphenicol acetyltransferase gene of E. coli respond to estrogens in gene transfer experiments, whereas a deletion that removes half of the ERE does not. A synthetic oligonucleotide corresponding to the putative ERE is able to confer estrogen inducibility to an otherwise unresponsive promoter. Binding experiments with purified estrogen receptor from calf uterus reveal a DNase-I footprint over the ERE. Within this protected region six guanine residues that have been shown to be contacted by the receptor in other EREs are protected against methylation by dimethylsulfate in the presence of the estrogen receptor. We compare this ERE with the vitellogenin A2 ERE from Xenopus and find that the relative affinity of the uteroglobin ERE is slightly lower than that of the vitellogenin ERE. Thus, this uteroglobin ERE could be involved in physiological regulation of uteroglobin expression in the genital tract.

A possible physiological basis for the dud-stud phenomenon.

Intact male rats were tested on two successive weekly tests with females to determine their level of sexual activity. Nuclear estrogen receptor content was measured in specific brain regions of individual sexually responsive and sexually nonresponsive males. Sexually nonresponsive male rats had significantly reduced nuclear estrogen receptor levels in the preoptic area compared to sexually responsive males. Sexually active males did not differ from inactive males in nuclear estrogen receptors in the medialbasal hypothalamus.