THE DROSOPHILA TANGO GENE ENCODES A BHLH-PAS PROTEIN THAT IS ORTHOLOGOUS TO MAMMALIAN ARNT AND CONTROLS CNS MIDLINE AND TRACHEAL DEVELOPMENT

The Drosophila single-minded and trachealess bHLH-PAS genes control tr anscription and development of the CNS midline cell lineage and trache al tubules, respectively. We show that Single-minded and Trachealess a ctivate transcription by forming dimers with the Drosophila Tango prot ein that is an orthologue of the mammalian Arnt protein, Both cell cul ture and in vivo studies show that a DNA enhancer element acts as a bi nding site for both Single-minded::Tango and Trachealess::Tango hetero dimers and functions in controlling CNS midline and tracheal transcrip tion. Isolation and analysis of tango mutants reveal CNS midline and t racheal defects, and gene dosage studies demonstrate in vivo interacti ons between single-minded::tango and trachealess::tango. These experim ents support the existence of an evolutionarily conserved, functionall y diverse bHLH-PAS protein regulatory system.