The Drosophila steroid hormone ecdysone mediates cell death during metamorphosis by regulating the transcription of a number of cell death genes. The apical caspase DRONC is known to be transcriptionally regulated by ecdysone during development. Here we demonstrate that ecdysone also regulates the transcription of DRICE, a major effector caspase and a downstream target for DRONC in the fly. Using RNA interference in an ecdysone-responsive Drosophila cell line, we show that drice up-regulation is essential for apoptosis induced by ecdysone. We also show that drice expression is specifically controlled by the ecdysone-regulated transcription factor BR-C. Combined with previous observations, our results indicate that transcriptional regulation of the components of the core apoptotic machinery plays a key role in hormone-regulated programmed cell death during Drosophila development.Programmed cell death is necessary to delete superfluous cells in metazoans and to maintain homeostasis (reviewed in Refs. 1 and 2). The core cell death machinery, consisting of the BH3-only proteins, BCL-2 family, caspase adaptors, and caspases, is highly conserved and is present in all metazoan cells (reviewed in Refs. 3-6). As most components of the cell death machinery are present constitutively within a cell, it is widely believed that execution of apoptosis is primarily regulated post-transcriptionally, that is apoptotic signals somehow feed into and activate preexisting caspase machinery. However, recent data suggest that many components of the core apoptosis machinery, including some caspases, are transcriptionally regulated during cell death and that the levels of the prosurvival and proapoptotic factors in the cell may be crucial to activate the apoptotic program (reviewed in Ref. 4). Consistent with this, there is evidence that various signals such as cytotoxic insults, hormones, and growth factors regulate the activation of the death program by controlling the balance between prosurvival and proapoptotic proteins of the core cell death machinery (4). To understand cell death regulation, it is thus essential to understand the transcriptional control of apoptosis execution.Steroid hormones are known to regulate cell survival and cell death in many tissues. Drosophila melanogaster is an ideal model system to study steroid hormone-regulated apoptosis as a single steroid hormone, 20-hydroxyecdysone, regulates cell death during development (reviewed in Refs. 5 and 7-9). Ecdysone binds to its heterodimeric EcR/Usp receptor and transcriptionally regulates a number of primary response genes. Waves of ecdysone, produced at various times during fly development, regulate molting, cell proliferation, differentiation, and death in a highly controlled manner (5, 7-9). During the transition of larva into pupa, an ecdysone pulse toward the end of the third larval instar stage signals puparium formation, followed by a second pulse ϳ12 h later, which initiates head eversion. During this process obsolete larval tissues, such as salivary glands an...