HEDGEHOG SIGNALING REGULATES TRANSCRIPTION THROUGH GLI CI BINDING-SITES IN THE WINGLESS ENHANCER/

The segment polarity gene cubitus interuptus (ci) encodes a transcript ional effector of Hedgehog (Hh) signaling in Drosophila. The Ci gene p roduct is a zinc finger protein belonging to the Gli family of sequenc e-specific DNA binding proteins. After gastrulation, segmental express ion of the segment polarity gene wingless (wg) is maintained by Hh sig naling in a pathway requiring Ci activity. In the absence of Hh or Ci activity, wg expression is initiated normally and then fades in the ec toderm after stage 10. We have previously identified a wingless enhanc er region whose Ci binding sites mediate Ci-dependent transcriptional activation in transiently transfected cells. Here we demonstrate that Hh and Patched (Ptc) act through those Ci binding sites to modulate th e level of Ci-dependent transcriptional activation in S2 cells. We dem onstrate that this same wg enhancer region is Hh responsive in vivo an d that its Ci binding sites are necessary for its activity. This provi des strong evidence that Hh affects wg transcription through post-tran slational activation of Ci. (C) 1997 Elsevier Science ireland Ltd.