DIFFERENTIAL INDUCTION OF PS2 AND CATHEPSIN-D MESSENGER-RNAS BY STRUCTURALLY ALTERED ESTROGENS

The influence of structural, alterations to the estradiol-17beta (E2) molecule on the induction of pS2 and Cathepsin D (Cath D) mRNAs has be en examined by Northern analysis of RNA extracted from MCF-7 cells. Ex posure of cultures to estratriene did not affect the level of expressi on of these estrogen-responsive genes. Addition of one hydroxyl group to estratriene at either of the hydroxylated positions of E2 (3-phenol ic or 17beta) yielded monohydroxyestrogens which stimulated the synthe sis of Cath D and pS2 mRNAs to a level comparable to that induced by 1 0(-10) M E2 and displayed a decrease in activity at the higher concent rations (10(-8)-10(-7)M) similar to that of the parent estrogen. Both of these genes were induced maximally by estrogens with D-ring alterat ions. Movement of the phenolic hydroxyl group of E2 to other positions on the A-ring yielded ligands which were highly discriminatory in the induction of these messages. 1-Hydroxyestratrien-17beta-ol was capabl e of stimulating maximal synthesis of both pS2 and Cath D mRNAs when a dded to cultures of MCF-7 cells at a concentration of 10(-8) M. Placem ent of the phenolic hydroxyl at position 4 greatly diminished the indu ction of these two estrogen-responsive genes. On the other hand, posit ioning the A-ring hydroxyl group on carbon 2 yielded a ligand which br ought about the induction of one gene (pS2) but was marginally effecti ve in the induction of Cath D mRNA synthesis. 5alpha-Androstanediol an d 5-androstenediol with a 17beta-hydroxyl group were capable of induci ng both genes, provided the 3-hydroxyl group was in the beta-configura tion. These results demonstrate that discrete changes in the structure of estradiol generate ligands (2- or 4-hydroxyestratrien-17beta-ol) w ith affinities for the estrogen receptor which are not related to thei r capacity to regulate certain responsive genes (pS2 or Cath D). It is proposed that the observed discrimination between these two responsiv e genes is the result of variations in the receptor-analogue complex w hich are important in interactions with gene regulatory factors (e.g., estrogen response element and/or transactivation function 2). Further more, the spatial placement of the electronegative isopotential surrou nding the aromatic A-ring of these estrogen analogues appears to be in volved in the modulation of gene regulation.