Transcriptional activation by the Antennapedia and fushi tarazu proteins in cultured Drosophila cells.

Drosophila homeodomain proteins bind to specific DNA sequences in vitro and are hypothesized to regulate the transcription of other genes during development. Using a cotransfection assay, we have shown that homeodomain proteins encoded by the homeotic gene Antennapedia (Antp) and the segmentation gene fushi tarazu, as well as a hybrid homeodomain protein, are activators of transcription from specific promoters in cultured Drosophila cells. Sequences downstream of the Antp P1 and Ultrabithorax transcription start sites mediate the observed activation. A TAA-rich DNA sequence to which the Antp protein binds in vitro is sufficient to confer regulation on a heterologous promoter. The results demonstrate that homeodomain proteins are transcriptional regulators in vivo and that in cultured cells, different homeodomain-containing proteins can act upon a common sequence to modulate gene transcription.