THE DECAPENTAPLEGIC CORE PROMOTER REGION PLAYS AN INTEGRAL ROLE IN THE SPATIAL CONTROL OF TRANSCRIPTION

The Drosophila melanogaster decapentaplegic (dpp) gene encodes a trans forming growth factor beta-related cell signaling molecule that plays a critical role in dorsal/ventral pattern formation. The dpp expressio n pattern in the Drosophila embryo is dynamic, consisting of three pha ses, Phase I, in which dpp is expressed in a broad dorsal domain, depe nds on elements in the dpp second intron that interact with the Dorsal transcription factor to repress transcription ventrally. In contrast, phases II and III, in which dpp is expressed first in broad longitudi nal stripes (phase II) and subsequently in narrow longitudinal stripes (phase III), depend on multiple independent elements in the dpp 5'-fl anking region. Several aspects of the normal dpp expression pattern ap pear to depend on the unique properties of the dpp core promoter. For example, this core promoter (extending from -22 to +6) is able to dire ct a phase II expression pattern in the absence of additional upstream or downstream regulatory elements, In addition, a ventral-specific en hancer in the dpp 5'-flanking region that binds the Dorsal factor acti vates the heterologous hsp70 core promoter but not the dpp core promot er. Thus, the dpp core promoter region may contribute to spatially reg ulated transcription both by interacting directly with spatially restr icted activators and by modifying the activity of proteins bound to en hancer elements.