CHARACTERIZATION OF THE PROXIMAL ESTROGEN-RESPONSIVE ELEMENT OF HUMANCATHEPSIN-D GENE

Cathepsin D, a lysosomal proteinase, is induced by estrogens in mammar y cancer cells where its concentration is correlated with a higher ris k of metastasis. Its gene expression is stimulated by estrogens in MCF 7 cells, and we have shown that a short proximal promoter fragment fro m -365 to -122 is required for this induction. We now characterize, at -261, a nonconsensus estrogen-responsive element (ERE) (E2) with two differences in the distal half of its palindrome, which confers estrad iol responsiveness to the heterologous Herpes simplex virus thymidine kinase promoter in transient transfection experiments. This ERE is loc ated in a 21-base pair sequence : 5'GGGCCGGGCTGACCCCGC GGG3', containi ng a GC-rich region in its 3'-part, which is almost perfectly repeated at -362 (the El: site). The E2 site was necessary but not sufficient to mediate an estrogen response and required cooperation with the homo logous E1 element and/or with general transcription sites located down stream. in vitro, the E2 site but not the E1 site was protected by est rogen receptor (ER) against DNAse I digestion, and gel shift experimen ts suggested an interaction with the ER as a dimer. Moreover, we showe d in vivo that ER DNA binding domain was required to mediate estrogen induction from the cathepsin D ERE. We conclude that estradiol inducti on of cathepsin D is mediated by interaction of the ER with a nonconse nsus ERE that requires synergy with other elements located upstream an d/or downstream of this central ERE.