Estradiol regulation of uterine nucleolar estradiol binding sites.
Rat uterine nuclei contain two types of estrogen binding sites (I and II). Type I is the classical high-affinity, low-capacity binding component, while Type II has lower affinity and higher capacity. Investigation of the presence and number of estrogen-binding proteins in isolated uterine nucleoli, and the possible role of the estrogen-binding protein(s) in the stimulation of nucleolar RNA synthesis was undertaken. Isolated uterine nucleoli contain a large number of lower-affinity binding sites (Type II) but are devoid of a significant number of high-affinity binding protein(s) (Type I). Following in vivo treatment with estradiol the number of detectable Type II estradiol-binding sites in isolated uterine nucleoli increased with time of estrogen treatment, peaking between 16 and 24 h after hormone administration and gradually decreasing to control levels between 48 and 72 h. The estrogen-activated binding activity but not the basal activity is sensitive to dithiothreitol and insensitive to beta-mercaptoethanol during the in vitro assay, suggesting that important disulfide bonds may be involved in the estrogen-induced nucleolar binding sites. The in vivo activation of nucleolar estradiol-binding sites exhibits steroid specificity. Data indicate that a strong correlation exists between activation of uterine nucleolar transcriptional and estradiol-binding activities.
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D000818:Animals; D002466:Cell Nucleolus / Q000378:metabolism*; D004220:Disulfides / Q000502:physiology; D004229:Dithiothreitol / Q000494:pharmacology; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D066298:In Vitro Techniques; D008623:Mercaptoethanol / Q000494:pharmacology; D012313:RNA / Q000096:biosynthesis; D051381:Rats; D011959:Receptors, Estradiol / Q000187:drug effects / Q000378:metabolism*; D011960:Receptors, Estrogen / Q000378:metabolism*; D014158:Transcription, Genetic; D014599:Uterus / Q000378:metabolism*
D004220:Disulfides; D011959:Receptors, Estradiol; D011960:Receptors, Estrogen; D004958:Estradiol; D008623:Mercaptoethanol; D012313:RNA; D004229:Dithiothreitol