Competition for overlapping sites in the regulatory region of the Drosophila gene Kruppel

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Science  03 Apr 1992:
Vol. 256, Issue 5053, pp. 94-97
DOI: 10.1126/science.1348871


A 730-base pair element regulates expression of the Drosophila gap gene Kruppel (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.