FIG. 6.

Knirps CtBP-dependent and CtBP-independent repression domains exhibit similar ranges of action. Gal4-Knirps proteins bound to UAS sites located at −130 bp were assayed for their ability to repress a lacZ reporter containing Dorsal and Twist activators at variable distances 5′ of the repressors. (A, D, G, and J) Reporter gene expression in unrepressed embryos. (B, E, H, and K) Repression activity of the Knirps minimal CtBP-independent domain 139-330. (C, F, I, and L) Repression activity of the Knirps minimal CtBP-dependent domain 202-358. Similar to the case with Gal4-CtBP, strong repression was noted only with activators located adjacent to or 55 bp from repressors but not at 110 or 165 bp, as expected for short-range activity. Brackets indicate the region of expression of the Gal4-Knirps proteins; arrowheads indicate the stripes of expression observed in the central regions for repression of 110- and 165-bp spacing constructs.