At least seven orphan members of the nuclear receptor superfamily are transcriptionally regulated by the steroid hormone ecdysone and expressed during the onset of Drosophila metamorphosis. A recent paper provides functions for two of these receptors, E75B and DHR3, through trans‐regulation and heterodimerization(1). DHR3 appears to function as a switch that defines the transition from a late larva to a prepupa, and E75B functions as a timer that modulates this transition. This study provides a biological function for orphan receptor interactions (...) during development. (shrink)

Sixteen years ago, Michael Ashburner and his colleagues proposed a hierarchical model for the genetic control of polytene chromosome puffing by the steroid hormone ecdysone. The recent molecular isolation and characterization of three early ecdysone‐inducible genes has confirmed many aspects of this model — these genes are directly induced by ecdysone, repressed by ecdysone‐induced proteins, and appear to encode DNA binding regulatory proteins. The three early genes are also remarkably similar in structure. They are all unusually long and complex, with (...) multiple transcripts that direct the synthesis of several related proteins from each locus. Proteins encoded by two of the early genes bind to both early and late ecdysone‐induced puffs, implying that they are key regulators in the hierarchy. (shrink)

Programmed cell death is a critical part of normal development, removing obsolete tissues or cells and sculpting body parts to assume their appropriate form and function. Most programmed cell death occurs by apoptosis of individual cells or autophagy of groups of cells. Although these pathways have distinct morphological characteristics, they also have a number of features in common, suggesting some overlap in their regulation. A recent paper by Lee and Baehrecke provides further support for this proposal.(1) These authors present, for (...) the first time, a genetic analysis of autophagy, using the steroid‐triggered metamorphosis of Drosophila as a model system. They demonstrate a remarkable degree of overlap between the control of apoptosis and autophagy as well as a key role for the steroid‐inducible gene E93 in directing the autophagic death response. This paper also shows that E93 can direct cell death independently from the known death‐inducer genes, defining a novel death pathway in Drosophila. BioEssays 23:677–682, 2001. © 2001 John Wiley & Sons, Inc. (shrink)