Pass-through transcription is responsible for suppression of the eye enhancer. (A) (UAS)EyeRYW transgenic lines; the eye enhancer is inserted in the opposite orientation. (B) (UASR)EyeYW transgenic lines; the UAS promoter drives transcription in the direction from the enhancers. (C) (UAS)Ey(e)∆YtsW transgenic lines with deletion of the yellow gene promoter (indicated by the absence of an upstream arrow and by parentheses in front of the gene on the scheme); “ts” is the core 222-bp SV40 terminator. (D) Quantification of (UAS)Ey(e)∆YtsW transcripts by RT-qPCR. Positions of primer pairs (1-2, 3-4, 5-6, 9-10) are indicated. RT-qPCR was conducted on mRNAs isolated from transgenic lines at the mid-late pupae stage. Error bars indicate standard deviations. For other designations, see Figure 1.