Estrogen receptor inducibility of the human Na⁺/H⁺ exchanger regulatory factor/ezrin-radixin-moesin binding protein 50 (NHE-RF/EBP50) gene involving multiple half-estrogen response elements

The Na⁺/H⁺ exchanger regulatory factor (NHE-RF; also known as ezrin-radixin-moesin binding protein 50) is a primary response gene under estrogen receptor (ER) control that may provide a link between estrogen action and the regulation of cytoskeletal and cell-signaling pathways. These studies were undertaken to define the human NHE-RF genomic regions and regulatory sequences mediating its robust estrogen responsiveness. Screening of a human genomic library yielded NHE-RF clones comprising the full gene, including the 5′-regulatory region and first exon, which were found to contain a large number (13) of consensus half-estrogen response elements (EREs), but to lack palindromic full EREs. Transfection-transactivation assays with wild-type and mutant ERs and reporter gene constructs linked to progressive deletions, or containing mutations, of the 5′-flanking region including a portion of exon I, and electrophoretic mobility and competitive gel shift assays were performed. These demonstrated direct ER interaction with the multiple half-ERE sites and the importance of the one proximal half-ERE and the multiple upstream half-EREs for eliciting the robust transcription activation of the NHE-RF gene by the estrogen-ER complex. Our findings highlight a paradigm for gene regulation via numerous half-ERE sites that expands the range of modes by which DNA recognition sites mediate the actions of this nuclear receptor.