THE DROSOPHILA TISSUE-SPECIFIC FACTOR GRAINYHEAD CONTAINS NOVEL DNA-BINDING AND DIMERIZATION DOMAINS WHICH ARE CONSERVED IN THE HUMAN PROTEIN CP2

We have mapped the regions in the Drosophila melanogaster tissue-speci fic transcription factor Grainyhead that are required for DNA binding and dimerization. These functional domains correspond to regions conse rved between Grainyhead and the vertebrate transcription factor CP2, w hich we show has similar activities. The identified DNA-binding domain is large (263 amino acids) but contains a smaller core that is able t o interact with DNA at approximately 400-fold lower affinity. The majo r dimerization domain is located in a separate region of the protein a nd is required to stabilize the interactions with DNA. Our data also s uggest that Grainyhead activity can be modulated by an N-terminal inhi bitory domain.