An expression profile of active genes in human lung

An expression profile of genes active in the human lung was obtained by collecting 797 partial sequences from a 3'-directed cDNA library. Three genes were found to produce mRNA each of which comprised more than 1% of total mRNA. These three have been identified as genes for pulmonary surfactant apoprotein (PSP-A), Clara cells 10-kDa secretory protein, and HLA-E heavy chain. In the remaining 745 clones, 221 were composed of 89 species that occurred recurrently, and 524 clones appeared only once. Because the 3'-directed cDNA library faithfully represents the mRNA population in the source tissue, these numbers represent the relative activities of the gene expression. Altogether 437 gene species were novel, and 179 gene species were identified in GenBank. A significant portion of these genes encode proteins found in secretory proteins, cell surface proteins, and components in the protein synthesis machinery, representing the function of the lung.