Figure 2.

Abd-B and Ubx promoter insulator activity does not involve tethering. The Abd-B and Ubx stalled promoters were tested for their ability to display promoter competition in a transgenic assay in which the IAB5 enhancer was cloned in between the white reporter and prom/lacZ fusion. As a control, the white/lacZ fusion (A) and white (B) were driven equally well by IAB5 enhancer in a white/lacZ (A,B) transgene. The IAB5-lacZ interaction (C,E) as well as the IAB5–white (D,F) interaction were facilitated in Abd-B/lacZ (C,D) and Ubx/lacZ (E,F) lines, respectively.