Summary model showing the poised enhancer signature arising specifically during tissue patterning in the Drosophila DV system. Before DV patterning begins in the Drosophila embryo, DV enhancers are primed by the pioneer transcription factor Zld and have low levels of H3K27ac. During DV patterning, DV enhancers may be active in one tissue but repressed by sequence-specific repressors in another tissue and thus remain uninduced. As has been studied extensively, these repressors recruit histone deacetylases, remove H3K27ac, and thus produce the poised enhancer signature. After DV patterning is complete, DV enhancers gradually close, thus enhancers with the poised enhancer signature also close and are not poised for future activation.
