ROUGH GENES WITH DEFORMED HOMEOBOX SUBSTITUTIONS EXHIBIT ROUGH REGULATORY SPECIFICITY DURING DROSOPHILA EYE DEVELOPMENT

In certain cases, homeobox genes with different in vivo roles encode p roteins with similar in vitro DNA binding specificities. To test the r ole of the homeobox in the regulatory specificity of such genes, rough homeobox sequences were changed in part or entirely to those of the D eformed gene, and the modified rough genes tested for their ability to rescue the rough mutant phenotype. Surprisingly, the chimaeric genes retained levels of rough regulatory specificity but acquired no novel functions. These results suggest that factors other than the DNA bindi ng specificity of the homeodomain play crucial roles in determining th e target, and thus the regulatory specificity, of such proteins.