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Dexamethasone responsive element in the rat Na, K-ATPase beta1 gene coding region
Hong Hao1, Richard Rhodes, David H Ingbar
1Pulmonary and Critical Care Division, Department of Medicine, MMC 276, University of Minnesota, Minneapolis 55455, USA.
Biochimica Et Biophysica Acta
|December 5, 2003
Summary
Glucocorticoids regulate lung fluid balance by affecting the Na, K-ATPase beta(1) gene. Researchers identified a specific DNA sequence (GRE) in exon IV that mediates this response to glucocorticoids in lung epithelial cells.
Area of Science:
- Molecular Biology
- Cell Biology
- Physiology
Background:
- The Na, K-ATPase is crucial for alveolar epithelial fluid resorption.
- Glucocorticoids (GC) enhance Na, K-ATPase activity and gene expression in lung epithelial cells.
Purpose of the Study:
- To identify and characterize glucocorticoid responsive elements (GREs) in the rat Na, K-ATPase beta(1) gene.
- To understand the mechanism of GC-mediated transcriptional regulation of Na, K-ATPase beta(1) in lung epithelial cells.
Main Methods:
- Transient transfection assays using reporter constructs of the beta(1) subunit gene.
- Site-directed mutagenesis to identify functional GREs.
- Electrophoretic mobility shift assays (EMSA) to assess protein-DNA interactions.
Main Results:
- A novel GRE was identified at +434 in exon IV of the rat Na, K-ATPase beta(1) gene.
- This GRE conferred dexamethasone responsiveness to gene transcription in a heterologous promoter system.
- Mutating the +434 GRE abolished dexamethasone-induced transcriptional upregulation.
- EMSA confirmed specific binding of nuclear proteins, including the GC receptor, to the +434 GRE.
Conclusions:
- A functional GRE located within exon IV of the rat Na, K-ATPase beta(1) gene mediates glucocorticoid-induced transcriptional regulation.
- This finding provides a molecular basis for how glucocorticoids influence lung epithelial function and fluid balance.