CYTOPLASMIC-NUCLEAR TRAFFICKING OF PROGESTERONE-RECEPTOR - IN-VIVO STUDY OF THE MECHANISM OF ACTION OF ANTIPROGESTINS

The signal responsible for the nuclear localization of the progesteron e receptor has been characterized. The study of the mechanism of this nuclear localization has revealed that the receptor continuously shutt les between the nucleus and the cytoplasm. The receptor diffuses into the cytoplasm and is constantly and actively transported back into the nucleus. Preliminary evidence suggests that the same mechanism exists for estradiol and glucocorticoid receptors. Experiments designed to s tudy the traffic of steroid hormone receptors have been applied to the determination of the molecular mechanism of action of antisteroids. U sing these techniques, we have shown that two major antiprogestins, RU 486 and ZK98299, act at the same point in the cell as the hormone.