Fig 4. Inserting a flanking P-element promoter induces non-coding transcription, and if it causes read-through, repression of expression from the eve promoter.

eve-lacZ and non-coding RNA expression in stage 5 embryos from eve pseudo-loci flanked by a 5’ P-element promoter (P-pro), inserted in the orientation diagrammed, at a MiMIC site (cytological location 24B1). The 3 loci (map above each one) differ only in the presence (A, Pwt) or absence (B, PΔ and C, PinvΔ) of homie (red box near P-pro), and in the orientation of P-pro (pointing to the left in A and B, and to the right in C). Positions and orientations of the RNA probes are shown as black and red arrows in the map in A (and in B and C for the probe closest to P-pro). Embryos were stained with the probes listed above in A, using either black lettering corresponding to black arrows in the map (detecting transcription from right to left), or red lettering corresponding to red arrows (detecting transcription from left to right).