cis-Acting elements that confer lung epithelial cell expression of the CC₁₀ gene

To define cis-acting genetic elements responsible for cell-specific transcriptional regulation of the CC₁₀ gene, DNA sequences spanning nucleotides -2338 to +49 of the rat CC₁₀ gene were linked to a reporter gene coding for chloramphenicol acetyltransferase (CAT). In transient expression assays, CC₁₀ sequences were capable of restricting CAT expression to a human lung adenocarcinoma cell line similar to pulmonary Clara cells. Transgenic mice harboring the hybrid RtCC₁₀-CAT construct expressed high levels of CAT activity specifically within protein extracts of lung and trachea. Transcripts for the CAT reporter gene colocalized with those for the endogenous murine CC₁₀ gene within the airways of transgenic mice. Functional analysis of deletion mutants identified stimulatory, inhibitory, and cell type-specific transcriptional regulatory elements. The results of gel retention and DNaseI protection assays suggest that a transcriptional stimulatory region located between -320 and -175, and a cell type-specific regulatory element located between -175 and +49, result from a series of protein-DNA interactions occurring at -220 to -205 and -128 to -86, respectively. Lung epithelial specific transcriptional regulatory elements described herein will be useful for expression of chimeric genes within epithelial cells lining the trachea, bronchi, and bronchioles of mice.