In vitro transcription of the Drosophila engrailed gene.

An enzyme system that accurately initiates transcription of the engrailed gene has been prepared from Drosophila embryos. The system has been separated chromatographically into two fractions, both of which are required for specific engrailed transcription. DNase footprint and competition analysis detected at least two sequence-specific DNA-binding proteins in one of these two fractions. Together, these proteins bind to eight regions within 400 bp of the transcription initiation sites. Most of the regions containing these binding sites are required for manimal engrailed transcription in vitro. In addition, a region downstream from the initiation sites and within the first 40 residues of the transcription unit is essential for transcription. Transient in vivo expression assays indicated that these same upstream and downstream sequences are required for transcription in Drosophila tissue culture cells.