GENE-REGULATION IN THE DROSOPHILA EMBRYO

Pattern formation in Drosophila depends on hierarchical interactions b etween the maternal and zygotic gene activities which subdivide the em bryo into increasingly smaller metameric units along the anterior-post erior axis. Here we describe those genes that encode the transcription factors which control precisely the expression of subordinate transcr iption factors in time and space. This regulation operates through the protein-protein interactions between transcription factors bound to t he cis-acting enhancers, which eventually determine the frequency of t ranscription initiation by polymerase II. Our data show that taking in to account the multiple transcriptional activators and repressors that bind to a typical enhancer element, it is likely that the regulation of gene expression in a given cell is defined by their concentration-d ependent interplay which directs target gene expression in a position- dependent fashion.