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Upregulation of the tracheobronchial mucin gene involves cyclic AMP response elements
M Verma1, C Blass, E A Davidson
1Department of Biochemistry and Molecular Biology, Georgetown University Medical Center, Washington, DC 20007, USA. mverma01@gumedlib.dml.georgetown.edu
Indian Journal of Biochemistry & Biophysics
|February 1, 1997
Summary
Cyclic AMP (cAMP) activates the tracheobronchial mucin (TBM) gene transcription through specific response elements. This finding aids understanding of mucin gene regulation in diseases like cystic fibrosis and asthma.
Area of Science:
- Molecular Biology
- Cell Biology
- Genetics
Background:
- The cAMP response element (CRE)-binding transcription factor CREB regulates gene transcription in response to cAMP.
- The 5'-flanking region of the tracheobronchial mucin (TBM) gene contains CREs with an octamer-like motif.
- Mucin gene overexpression is observed in diseases such as cystic fibrosis (CF) and asthma.
Purpose of the Study:
- To investigate the cAMP responsiveness of TBM CREs in human tracheal epithelial cells (HBE1).
- To understand the mechanisms of TBM gene transcriptional regulation in disease states.
Main Methods:
- Electrophoretic mobility shift assay (EMSA) to identify nuclear protein binding sites.
- Transient transfection analysis using a chloramphenicol acetyl transferase (CAT) reporter gene.
- Nuclear run-on analysis to assess transcriptional activity.
Main Results:
- EMSA confirmed CREs as binding sites for nuclear proteins.
- cAMP was found to induce TBM gene transcription.
- Extracellular 8Br-cAMP dose-dependently modulated TBM CRE transcriptional activity, showing a 6-fold increase at 2 µM compared to 1 nM.
Conclusions:
- The TBM CREs are responsive to cAMP.
- These findings provide insights into the transcriptional regulation of mucin gene expression.
- Understanding these mechanisms is crucial for studying diseases with mucin overexpression.