Selective conservation of an E-protein gene promoter during vertebrate evolution

The murine E-protein gene ME1 encodes a non-tissue-specific, helix-loop-helix transcription factor that is associated with morphological development. ME1 gene expression is regulated by a TATA-less promoter that contains multiple Sp1 consensus elements, E-boxes, and a novel transcription initiation site. In this study, we compared DNA homologous to the ME1 promoter from vertebrate species ranging from frog to human. A region of striking sequence similarity was identified in a region corresponding to the ME1 transcription initiation site (ME1 Inr). Within this region, a poly d(A) tract and a 9-bp inverted repeat (5'-GTCCGCCTG) were highly conserved in all species that were examined. Protein complexes that recognized these DNA elements were present among distant vertebrates (frog, chick, monkey and human), and were able to bend the ME1 Inr to a similar extent (approximately 60 degrees) as the previously described murine MBP alpha and MBP beta proteins. Collectively, these results suggest that an ME1 Inr-like element and its associated proteins functioned in an ancestral vertebrate more than 350 million years ago.