Hoch, M., Gerwin, N., Taubert, H., Jäckle, H. (1992). Competition for overlapping sites in the regulatory region of the Drosophila gene Kruppel.  Science 256(5053): 94--97.

FBrf0057642

Research paper

A 730-base pair element regulates expression of the Drosophila gap gene Krüppel (Kr) in response to the fly anterior morphogen bicoid (bcd). Two hormone receptor-like proteins, encoded by the genes knirps (kni) and tailless (tll), bind specifically to the element. In vitro, kni protein competes with the homeodomain-containing bcd protein in binding to a 16-base pair target sequence. In vivo experiments suggest that both kni and tll act as competitive repressors of bcd-mediated activation of Kr. These results suggest a mechanism by which developmental genes can be regulated in response to an activating morphogen gradient antagonized by repressors.