MODULATION OF ESTROGEN-RECEPTOR GENE-EXPRESSION IN HUMAN BREAST-CANCER CELLS - A DECOY STRATEGY WITH SPECIFIC PCR-GENERATED DNA FRAGMENTS

Transcriptional activity of human estrogen receptor (hER) gene was mod ulated by competition with double-stranded PCR-generated DNA fragments (decoys) that contain 5' upstream sequences of the hER gene. Two DNA fragments belonging to the PI canonical promoter and the P3 distal pro moter, 120 and 102 bp in size respectively, were produced by PCR and d irectly transfected in MCF7 breast cancer cells. After 24 hours transf ection, RT-PCR analysis revealed that the 120 bp decoy significantly r educed the expression of the ER gene and estrogen responsive genes (PR and c-myc), whereas the 102 bp decoy increased the ER mRNA level. An ER unrelated PCR product, used as control, had no activity. The biolog ical activity of these ds DNAs was related to their high stability, bi nding affinities, and lack of cytotoxicity. These findings suggest tha t such PCR product decoys may be a non-antisense tool to analyze putat ive regulatory sequences and to study the function of DNA-binding tran scription factors.