Drosophila dorsoventral (DV) patterning and mammalian hematopoiesis are regulated by related signaling pathways (Toll, interleukin-1) and transcription factors (dorsal, nuclear factor-kappaB). These factors interact with related enhancers, such as the rhomboid NEE and kappa light chain enhancer, that contain similar arrangements of activator and repressor binding sites. It is shown that the kappa enhancer can generate lateral stripes of gene expression in transgenic Drosophila embryos in a pattern similar to that directed by the rhomboid NEE. Drosophila DV determinants direct these stripes through the corresponding mammalian cis regulatory elements in the kappa enhancer, including the kappaB site and kappaE boxes. These results suggest that enhancers can couple conserved signaling pathways to divergent gene functions.