Sequence of rat surfactant protein A gene and functional mapping of its upstream region.

Surfactant protein A (SP-A) is the major pulmonary surfactant protein. We have isolated a rat SP-A genomic clone and determined the sequence from 2.9 kilobases upstream of the transcriptional start through the termination of translation. The exon-intron structure of the rat gene has been determined and compared with the mouse, rabbit, and human genes. We have localized the major transcriptional start site in adult rat lung to nucleotide 30 downstream from the start of the TATA box. Functional mapping indicates that a DNA fragment containing 163 nucleotides upstream of the transcriptional start (-163) can function as a promoter of transcription of a reporter gene in both lung and nonlung derived cell lines. However, the function of this element is weaker in cells of nonlung origin. DNA elements located between -2902 and -163 silence the promoter activity in both lung and nonlung cells. Because the SP-A gene promoter region exhibits limited tissue specificity, the results suggest the existence of other DNA elements which overcome the silencer and confer further lung specificity.