Figure 3.

 AE1 can coactivate linked reporter genes. Transgenic embryos carry fusion genes containing the 430-bp AE1 enhancer placed between divergently transcribed reporter genes that can be independently assayed. Embryos are undergoing the rapid phase of germ-band elongation. (A,B) Transgenic embryos carry a fusion gene with linked CAT and lacZ reporter genes. The arrows indicate the location and orientation of the transcription start sites. The leftward CAT gene was linked to the eve promoter, whereas the rightward lacZ reporter gene was attached to the ftz promoter. A was hybridized with a CAT antisense RNA probe; B was hybridized with a lacZ probe. Both reporter genes are expressed in a series of seven stripes, indicating that AE1 activates both the ftz and eve promoters. The diagrams indicate that the promoters contain TATA sequences, but lack optimal Inr (INIT) and Dpe (DPE) sequences. (C,D) Transgenic embryos carry a fusion gene with linked white and lacZ reporter genes. The white gene contains a mini-white promoter sequence, whereas lacZ was placed under the control of the core promoter sequence from the transposase gene (Tp) located within the P-element vector. C was hybridized with a white antisense RNA probe; D was hybridized with a lacZ probe. Both reporter genes are activated by AE1 and expressed in a series of stripes. The diagrams indicate that the promoters lack TATA sequences, but contain INIT and DPE elements.