Functional analysis of human MUC7 mucin gene 5'-flanking region in lung epithelial cells.
The human MUC7 gene encodes a low-molecular-mass mucin glycoprotein that functions in modulation of microbial flora in the oral cavity and respiratory tracts. MUC7 gene expression is tissue- and cell-specific, with dominant expression in salivary gland acinar cells. To begin to understand the molecular mechanisms responsible for controlling MUC7 gene expression, we analyzed the promoter activity of MUC7 5'-flanking region in a human lung epithelial cell line A549. We demonstrated that MUC7 gene is expressed constitutively in this cell line and is upregulated by TNF-alpha stimulation. The promoter activities of a 2,762-bp fragment of the human genomic DNA (-2,732/+30 bp) and its deletion series, subcloned into a luciferase reporter vector, were characterized at the basal level and under stimulation by TNF-alpha. The results indicated that the minimal functional MUC7 promoter is in the region of -138/+30 bp. This region also revealed the greatest increase in the promoter activity upon TNF-alpha stimulation. Two putative AP1-binding elements and one NF-kappaB-binding element were identified within the proximal promoter. Further analyses demonstrated that mutations of these elements dramatically reduced specific DNA-protein binding ability and reporter gene expression. AP1 elements played an essential role in the constitutive expression, while the NF-kappaB element was crucially important in the response to TNF-alpha stimulation, demonstrating that TNF-alpha activates MUC7 transcription via NF-kappaB signaling pathway.
Li
Shimin
S
Department of Oral Biology, University at Buffalo, The State University of New York, 109 Foster Hall, 3435 Main Street, Buffalo, NY 14214, USA.
Bobek
Libuse A
LA
D024506:5' Flanking Region; D001665:Binding Sites; D002460:Cell Line; D004847:Epithelial Cells / Q000166:cytology / Q000502:physiology*; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D006801:Humans; D008168:Lung / Q000166:cytology*; D009077:Mucins / Q000235:genetics* / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D016328:NF-kappa B / Q000378:metabolism; D011401:Promoter Regions, Genetic; D012471:Salivary Proteins and Peptides; D015398:Signal Transduction / Q000502:physiology; D014157:Transcription Factors / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
C083238:MUC7 protein, human; D009077:Mucins; D016328:NF-kappa B; D012471:Salivary Proteins and Peptides; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha