Regulation of Estrogen Receptor Transcription in Breast Carcinoma.

Abstract

Abstract : In this study, we performed a functional mapping of the Estrogen Receptor (ER) promoter region and found a region in the 5' untranslated leader sequence that controlled ER transcription in ER-positive breast carcinoma cell lines. This region contained two binding sites for a transcription factor, Estrogen Receptor Factor-1 (ERF-1). ERF-1 was identified by gel shift assay and was present in ER-positive breast and endometrial carcinoma cells, but absent in ER-negative cell lines, thus inferring a role for ERF-1 in the regulation of ER transcription in breast carcinoma. Mutational analysis of the ERF-1 binding site showed that ERF-1 binding was correlated with transcriptional activity. ERF-1 was purified from MCF7 breast carcinoma cells using ion-exchange and DNA affinity chromatography and the cDNA was isolated from a MCF7 expression cDNA library. ERF-1 was identified as AP2gamma, a member of the AP2 transcription factor family. When binding specificity of ERF-1 was compared to AP2alpha using PCR-Assisted Binding Site selection and competitive gel shift assay, it was found that the two proteins recognized the same DNA sequence. Cotransfection of AP2alpha or AP2gamma with an ER promoter reporter construct demonstrated that activation of the ER promoter is dependent upon cell type.