CONTROL OF CNS MIDLINE TRANSCRIPTION BY ASYMMETRIC E-BOX-LIKE ELEMENTS - SIMILARITY TO XENOBIOTIC RESPONSIVE REGULATION

Central nervous system midline cells constitute a discrete group of Dr osophila embryonic cells with numerous functional and developmental ro les. Corresponding to their separate identity, the midline cells displ ay patterns of gene expression distinct from the lateral central nervo us system. A conserved 5 base pair sequence (ACGTG) was identified in central nervous system midline transcriptional enhancers of three gene s. Germ-line transformation experiments indicate that this motif forms the core of an element required for central nervous system midline tr anscription. The central nervous system midline element is related to the mammalian xenobiotic response element, which regulates transcripti on of genes that metabolize aromatic hydrocarbons. These data suggest a model whereby related basic-helix-loop-helix-PAS proteins interact w ith asymmetric E-box-like target sequences to control these disparate processes.