Identification of mutations in three genes that interact with zeste in the control of white gene expression in Drosophila melanogaster.

Three previously described genes, enhancer of yellow, 1, 2 and 3, are shown to cooperate with the zeste gene in the control of white gene expression. The mutations e(y)1u1, e(y)3u1, and to a lesser extent e(y)2u1, enhance the effect of the zeste null allele zv77h. Different combinations of e(y)1u1, e(y)2u1 and e(y)3u1 mutations with several other z alleles also enhance the white mutant phenotype, but only to levels characteristic of white alleles containing a deletion of the upstream eye enhancer. Loss of zeste protein binding sites from the white locus does not eliminate the effect of e(y)1u1 and e(y)3u1 mutations, suggesting that the products of these genes interact with some other nucleotide sequences. Combinations of either e(y)1u1 or e(y)2u1 mutations with e(y)3u1 are lethal. The products of these three genes may represent, together with zeste, a group of proteins involved in the organization of long-distance interactions between DNA sequences.