| Nuclear receptors belong to the family of eukaryotic transcription factors. Members of this family act as ligand-activated molecular switches that regulate gene activity. The elucidation of putative ligands may provide relevant information about the biological roles of nuclear receptors. Here, characterization of a Drosophila nuclear receptor, E75, is presented. This ecdysone-induced protein possesses a heme prosthetic group that enables it to bind nitric oxide (NO). E75 functions as a transcriptional repressor. However, in the presence of its ligand, NO, E75 activity is affected, resulting in de-repression. As an NO-sensing nuclear receptor, E75 presents a novel mechanism of regulation for Drosophila nuclear receptors. In the past decade, NO has gained tremendous attention as an important second messenger involved in many signaling pathways. Implications of E75 in Drosophila development and regulation of circadian clock is discussed. Further studies will provide additional insights into the biological roles of E75. |
