Previous work indicated that transcriptional expression of a gene in Drosophila melanogaster, REAPER, is acutely responsive to ionizing radiation. It was also determined that control elements governing this response can be uncoupled from developmental cues which engage this gene. Together, these data implicate a distinct signaling pathway that recruites REAPER in response to genotoxic damage. Since expression of REAPER is sufficient to promote apoptosis, these observations also account for cell killing by a defined external insult in this animal. In recent developments, a discrete 150 bp sequence has been identified in the promoter, referred to as the distal RRE, which alone is sufficient to confer radiation-induced transactivation in the context of a transgenic reporter gene. Through focused studies of this apoptotic target in vivo, the interface between damage signaling and cell death in this genetic model organism will be examined. Specifically: 1) concerted biochemical and molecular approaches to study factors that mediate radiation-induced transactivation of the cell death gene, REAPER, will be done. 2) A genetic approach to identify functions important for radiation-induced trasactivation will be initiated. 3) It will be determined whether signals eliciting alternate forms of "unscheduled" apopotsis recruit REAPER through a pathway that is distinct from radiation-induced responses.
Programmed cell death (apoptosis) is responsible for the deliberate elimination of cells in normal development and is also recruited as an adaptive response to remove cells that are potentially damaged. The broad goal of research proposed here seeks to understand how injured cells engage apoptotic physiology by examining important features of this process in a genetic model, Drosophila. In this animal, a complex genomic interval is required for all programmed cell death during embryonic development. Three genes mapping to this region are well established activators of the apoptotic pathway and one of these genes, REAPER, also contributes important functions during unscheduled deaths provoked either by genotoxic damage (radiation) or by developmental defects. Control elements that mediate radiation-responsive transactivation define an important connection between damage signaling and induction of an apoptosis activator in Drosophila. As such, they offer a unique and attractive vantage point to examine determinants that specify apoptosis in response to genotoxic challenge. The proposed studies should uncover novel insights regarding adaptive apoptotic responses in a sophisticated animal model.
