ABSTRACT
Objective To clone the human mucin (MUC)5AC gene promoter and construct its luciferase reporter vector for human MUC5AC gene and analyze its transcriptional activity. Methods The 1 348 bp DNA sequence at the human MUC5AC gene 5 end was analyzed by the Vector NTI software.After the target sequence from human A549 cells genomic DNA was amplified by PCR method, and the product of PCR was sequenced.By promoter deletion analysis, 3 promoter segments with diferent lengths were amplified by PCR, then the products were identified by DNA sequencing, and 4 promotor segments were inserted into pGL3- enhancer vectors.Site-specific mutagenesis technique was used to establish mutants of specificity protein (SP)-l and nuclear factor-kappa B (NF-кB) site in MUC5AC gene promoter. The relative luciferase activities were detected in the transfected A549 cells. Results Sequence analysis indicated that there were many cis-acting elements in the regions of 1 348 bp DNA sequence at the human MUC5AC gene 5 end.The 4 reporter gene vectors with promoter segments with different lengths were constructed successfully.Dual-luciferase assay revealed the 372 bp fragment including activity with the minimal fragment. Neutrophil elastase (NE) could increase the expression of luciferase reporter gene plasmid containing mutated NF-кB version (P＜0.05 vs. contro1) of MUC5AC promoter in the transfected A549 cells. The induction by NE decreased markedly when the SP-l element in MUC5AC promoter were mutated. Conclusion This research may provide an important basis for the further study of human MUC5AC gene promoter activity and regulation of gene expression.There is an up-regulative element of gene transcription in the region of -324 to -64 bp in MUC5AC gene upstream. SP-l site of the promotor mediates NE-induced MUC5AC expression in human A549 cells.
ABSTRACT
BACKGROUND: Hypersecretion of mucin due to goblet cell hyperplasia is frequently encountered in many chronic airway diseases, such as chronic bronchitis, bronchiectasis, bronchial asthma and cystic fibrosis. Even in normal individuals, viral infection or bacterial pneumonia frequently provoke huge amounts of bronchial secretions which may cause airway obstruction. The production of mucin was regulated by epidermal growth factor (EGF) in vitro. To know whether this EGF system regulates mucin secretion in vivo and Pseudomonas also stimulates the mucin secretion by the same pathway, we studied these relationships in the cultured rat tracheal epithelial cells. METHODS: Rat tracheal epithelial cells were obtained by pronase dissociation from the male Fisher 344 rats. When cells became confluent, they were divided into 6 groups and stimulated with either EGF for 24 hours or Pseudomonas extracts for 12 hours with or without selective EGF-R tyrosine kinase inhibitor tyrphostin AG1478. RESULTS: We found that both EGF and Pseudomonas extracts phosphorylated the tyrosine residue in the EGF receptor from the rat tracheal epithelial cells and this tyrosine phosphorylation was nearly completely blocked by selective EGF-R tyrosine kinase inhibitor tyrphostin AG1478. The mucin secretion was also stimulated by either EGF or Pseudomonas extracts but more strong secretion of mucin and MUC5AC gene expression in the rat tracheal epithelial cell was done by Pseudomonas extracts. CONCLUSION: These data suggest that Pseudomonas secretes the mucin by way of the EGF receptor and MUC5AC gene expression and the inhibitors of EGF receptor tyrosine phosphorylation would be useful to prevent the huge production of mucin due to Pseudomonas aeruginosa lung infection.