Drosophila tissue-specific transcription factor NTF-1 contains a novel isoleucine-rich activation motif

The Drosophila tissue-specific transcription factor NTF-1 provides a useful model system for studying the mechanisms by which promoter-selective factors control the development of a multicellular organism. A number of promoters that may be targets of NTF-1 regulation have been identified. For example, NTF-1 plays a critical role in the tissue-specific expression of the Drosophila Dopa decarboxylase gene. Additionally, by using in vitro assays, it has been possible to characterize the mechanism of NTF-1 activation, revealing its dependence on specific coactivators, or TAFs. Here, we report the use of both in vivo and in vitro assays to identify the functional domains of NTF-1. These consist of an unusually large, unique DNA-binding and dimerization domain, as well as a novel, isoleucine-rich activation domain. This 56-amino-acid activation region fails to interact with the putative Sp1 coactivator, dTAFII110, and thus appears to use a mechanism distinct from the glutamine-rich activation domain of Sp1. Additionally, NTF-1 appears to activate transcription in a species-specific manner, utilizing distinct domains in Drosophila and yeast.