FIG. 2.
CtBP, unlike Knirps, fails to effectively repress from a promoter-proximal context. Knirps effectively represses transcription from a basal promoter when located −55 bp from the transcription start site (A). In the same context, Gal4-CtBPL shows no activity (B). Rarely, some embryos exhibited weak repression (C). Increasing the number of Gal4 binding sites in the promoter to 4xUAS or 6xUAS does not significantly enhance repression (D and E). Brackets indicate the positions where endogenous Knirps (A) and Gal4-CtBPL (B to D) are expressed in the embryos.