IDENTIFICATION OF A NOVEL SONIC HEDGEHOG RESPONSE ELEMENT IN THE CHICKEN OVALBUMIN UPSTREAM PROMOTER-TRANSCRIPTION FACTOR-II PROMOTER

Sonic hedgehog (Shh) is a secreted morphogen that regulates dorso-vent ral patterning within the neural tube during embryonic development. it is well established that Shh can induce motor-neuron differentiation that coincides with the appearance of specific motor-neuron markers in cluding chicken ovalbumin upstream promoter-transcription factor II (C OUP-TFII) and IsIl. However, the mechanism of Shh-induced signaling pa thway in vertebrates is not clearly defined. In this report we have id entified COUP-TFII as a target gene for Shh. In addition we have used a 1.6-kb region of the COUP-TFII promoter to identify a target element that mediates the Shh-induced activity. Extensive deletions introduce d within this region have further enabled us to identify a novel sonic hedgehog response element (ShhRE) in the COUP-TFII promoter. Point mu tations introduced within the ShhRE reveal some key nucleotides that a re essential for protein(s)-binding activity, Finally, the ShhRE is ca pable of functioning as a true enhancer element and can mediate Shh-in duced transactivation of reporter gene via a heterologous promoter.