IN-VITRO ANALYSIS OF RAT SURFACTANT PROTEIN-A GENE-EXPRESSION

Previous findings suggest that the rat proximal promoter segment (rPPS ) ofthe SP-A gene is important in the regulation of the lung-specific expression of the gene. In this report, two regions within the rPPS co ntaining thyroid transcription factor-1 (TTF-1) binding sites are iden tified that form strong lung- and thyroid-specific DNA-protein complex es. These regions bind nuclear polypeptides with similar apparent mole cular mass to TTF-1, suggesting that TTF-1 binds to these regions. Two regions within the rPPS that form weaker lung-specific DNA-protein co mplexes are also identified. The transcription start site is mapped, a nd a functional analysis shows that the sequences of the 5' flanking r egion are sufficient to support in vitro transcription but are not suf ficient to reproduce tissue-specific expression. Together, these resul ts show that lung- and thyroid-specific, as well as lung-specific, DNA -protein interactions occur within the rPPS but are not sufficient for the lung-specific expression of the rat SP-A gene to be duplicated in vitro.