The Novel Transcription Factor e(y)2 Interacts with TAF II 40 and Potentiates Transcription Activation on Chromatin Templates
Résumé
Weak hypomorph mutations in the enhancer of yellow genes, e(y)1 and e(y)2, of Drosophila melanogaster were discovered during the search for genes involved in the organization of interaction between enhancers and promoters. Previously, the e(y)1 gene was cloned and found to encode TAF(II)40 protein. Here we cloned the e(y)2 gene and demonstrated that it encoded a new ubiquitous evolutionarily conserved transcription factor. The e(y)2 gene is located at 10C3 (36.67) region and is expressed at all stages of Drosophila development. It encodes a 101-amino-acid protein, e(y)2. Vertebrates, insects, protozoa, and plants have proteins which demonstrate a high degree of homology to e(y)2. The e(y)2 protein is localized exclusively to the nuclei and is associated with numerous sites along the entire length of the salivary gland polytene chromosomes. Both genetic and biochemical experiments demonstrate an interaction between e(y)2 and TAF(II)40, while immunoprecipitation studies demonstrate that the major complex, including both proteins, appears to be distinct from TFIID. Furthermore, we provide genetic evidence suggesting that the carboxy terminus of dTAF(II)40 is important for mediating this interaction. Finally, using an in vitro transcription system, we demonstrate that recombinant e(y)2 is able to enhance transactivation by GAL4-VP16 on chromatin but not on naked DNA templates, suggesting that this novel protein is involved in the regulation of transcription.