Inhibition of the translocation of estrogen receptor from the cytoplasm into the nucleus by estrogen receptor-binding factors.
The molecular mechanism of the translocation of estrogen receptor (ER) from the cytoplasm into the nucleus was studied in an in vitro system taking into account the specific interactions of the basic constituents of the uterine ER-system which had been reported previously (Murayama, A. et al. (1980) J. Biochem. 88, 1457). It was found that ER is translocated from the cytoplasm into the nucleus in the form of vero-ER . estradiol (basic ER-unit bound with estradiol; sedimentation coefficient, 4.5S; Stokes radius, 44 A; Kd for estradiol, approximately 10(-10) M) dissociated from coexisting estrogen receptor-binding factors (ERBFs). ERBFs inhibited the translocation of vero-ER into nuclei through binding with it. The apparent equilibrium dissociation constants (Kd) of ERBFs for vero-ER were estimated by Scatchard analysis to be 2.6 X 10(-10) M ["5S" ER-forming factor ("5S" ER-FF)], 3.0 X 10(-9) M ("6S" ER-FF), and 2.5 X 10(-9) M ("8S" ER-FF), respectively. The inhibitory effects of ERBFs on the binding of vero-ER to the nucleus paralleled their association constants.
D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism*; D005260:Female; D066298:In Vitro Techniques; D007700:Kinetics; D011960:Receptors, Estrogen / Q000378:metabolism*; D013552:Swine; D014599:Uterus / Q000378:metabolism
D011960:Receptors, Estrogen