hairy stripe 7 element mediates activation and repression in response to different domains and levels of Kruppel in the Drosophila embryo

The Drosophila gap gene Kruppel (Kr) encodes a zinc finger-type transcripti on factor required for controlling the spatial expression of other segmenta tion genes during early blastoderm stage. Here we show that two independent and transferable repressor domains of Kruppel act to control expression of the pair-rule gene hairy, and that the minimal cis-acting element of hairy stripe7 (h7) mediates either Kruppel-dependent activation or repression in different regions of the blastoderm embryo. The C-terminal region of Krupp el which encompasses the predominant repressor domain is not essential for activation, but is required to fully suppress h7-mediated transcription in response to high levels of Kruppel activity. This domain contains an intera ction motif for dCtBP, a homologue of the human co-repressor CtBP. dCtBP ac tivity is, however, dispensable for Kruppel-mediated repression in the embr yo since Kruppel-mediated repression functions in the absence of dCtBP. Pos sible modes of h7-mediated gene regulation in response to the different dom ains and levels of Kruppel are discussed. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.