TAF(II)40 protein is encoded by the e(y)1 gene: Biological consequences ofmutations

The enhancer of yellow 1 gene, e(y)1, of Drosophila melanogaster has been c loned and demonstrated to encode the TAF(II)40 protein. The e(y)1 gene is e xpressed in females much more strongly than in males due to the accumulatio n of e(y)1 mRNA in the ovaries. Two different e(y)1 mutations have been obt ained. The e(y)1(ul) mutation, induced by the insertion of Stalker into the coding region, leads to the replacement of 25 carboxyterminal amino acids by 17 amino acids encoded by the Stalker sequences and to a decrease of the e(y)1 transcription level. The latter is the main cause of dramatic underd evelopment of the ovaries and sterility of females bearing the e(y)1 mutati on. This follows from the restoration of female fertility upon transformati on of e(y)1(u1) flies with a construction synthesizing the mutant protein. The e(y)1(P1) mutation induced by P element insertion into the transcribed nontranslated region of the gene has almost no influence on the phenotype o f flies. However, in combination with the ph(P1) mutation, which leads to a strong P element-mediated suppression of e(y)1 transcription, this mutatio n is lethal. Genetic studies of the e(y)1(u1) mutation revealed a sensitivi ty of the yellow and white expression to the TAF(II)40/e(y)1 level. The su( Hw)-binding region, Drosophila insulator, stabilizes the expression of the white gene and makes it independent of the e(y)1(u1) mutation.