IDENTIFICATION AND CHARACTERIZATION OF A GENE ACTIVATED BY THE DEFORMED HOMEOPROTEIN

In Drosophila, the homeotic genes encode transcription factors which c ontrol segment identity during embryogenesis by specifying the appropr iate set of 'target' genes necessary to produce the individual segment al characteristics. Though we know much about the homeotic genes and t he proteins they encode, we know little of their targets. Here we iden tify and characterize one such target gene, a gene activated by the pr oduct of the homeotic gene Deformed. DNA binding assays and expression of reporter gene constructs indicate that activation of this gene req uires a direct interaction between the Deformed protein and an upstrea m enhancer element at this target gene. However, although Deformed is required to activate this gene in cells of the maxillary segment, ecto pically expressed Deformed does not activate the gene in other regions of the embryo. We conclude from this and other observations that addi tional factors may be required to activate the target gene, and, there fore, Deformed may participate in either a combinatorial or hierarchic al activation signal in the maxillary cells. This newly identified gen e encodes a novel protein of unknown function, though proteins with si milar amino acid composition have been found. The pattern of transcrip t accumulation during embryogenesis indicates that this gene may be re gulated by other homeoproteins in addition to Deformed.