CELL-SPECIFIC EXPRESSION OF A TRANSFECTED HUMAN ALPHA-1-ANTITRYPSIN GENE

The human .alpha.1-antitrypsin (.alpha.1-AT) gene was cloned and the promoter and the transcription initiation point identified. The cloned gene, following transfection, is expressed in a cell-specific manner, being transcribed in a human hepatoma cell line(Hep3B) but not in HeLa cells. The 5'' flanking region of the .alpha.1-AT gene contains DNA sequences sufficient for efficient transcription in Hep3B but not in HeLa cells. This DNA sequence also activates, in a cell-specific manner, heterologous promoters such as that of SV40; however, the effect is only obtained in one orientation, suggesting that this cis-acting cell-specific element does not share all the features generally associated with enhancers. Cotransfection-competition experiments also show the existence of a limiting trans-acting factor, essential for the expression of the .alpha.1-AT gene in Hep3B cells.