| Abstrakt: |
In the accompanying paper (Friedman et al., Mol. Cell. Biol. 6:3791-3797, 1986), hepatoma-specific expression of the rat albumin promoter within the adenovirus genome was demonstrated. However, the rate of transcription was very low compared with that of the endogenous chromosomal albumin gene. Here we show that in hepatoma cells the adenovirus E1A enhancer, especially in the presence of E1A protein, greatly stimulates transcription from the albumin promoter but not the mouse beta-globin promoter. This enhancer-dependent stimulation did not occur in myeloma cells in which a virus containing a immunoglobulin promoter and enhancer did function. These experiments suggest a limited distribution in cultured differentiated cells of cell-specific transcription factors. However, either the regulation of such cell-specific factors breaks down in other cultured cells, or strictly cell-specific factors are not at play in controlling cell-specific transcription, because HeLa cells could transcribe the albumin promoter from the same start site about 10% as well as hepatomas could and 293 cells could transcribe both albumin and globin promoters. |
