Cellular responses to many xenobiotic compounds, including various toxins and pharmacological agents, are controlled by mammalian Nrf2 and Keap1, and by the homologous Drosophila
CncC and dKeap1 proteins 
. The Nrf2-Keap1 complex has multiple effects on carcinogenesis. Nrf2-deficient mice have increased susceptibility to chemical carcinogens, potentially because of defective activation of cytoprotective genes in response to carcinogen exposure 
. Mutations in Nrf2 and Keap1 that are predicted to disrupt their interactions are found in many human cancers, suggesting that Nrf2 interactions with Keap1 counteract cancer progression 
. Conversely, the deletion of Nrf2 suppresses pancreatic and lung tumorigenesis in a mouse model with constitutively active K-RasG12D
. The mechanisms whereby Nrf2 promotes tumorigenesis in conjunction with K-RasG12D
are not known. Nrf2 and Keap1 are investigated as potential targets for therapeutic interventions in cancer, neurodegenerative diseases and developmental disorders 
Nrf2 (NF-E2-Related Factor 2) is a bZIP family transcription factor that can bind to genes whose transcription is induced by xenobiotic compounds 
. Keap1 (Kelch-like ECH-Associated Protein 1) is a Kelch family protein that can interact with the N-terminal region of Nrf2, and inhibits the activation of many genes activated by Nrf2 
. Studies in cultured mammalian cells indicate that Keap1 is predominantly localized to the cytoplasm 
, where it promotes Nrf2 degradation and inhibits its accumulation in the nucleus 
Studies of the Drosophila
homologues of Nrf2 and Keap1 have provided insights into the functions of these protein families in adult flies. The Drosophila cap‘n’collar
locus encodes CncC, which contains a bZIP domain homologous to that of Nrf2 and N-terminal DLG and ETGE motifs homologous to those that mediate Nrf2 interaction with Keap1 
dKeap1 contains Kelch repeats homologous to those that mediate Keap1 interaction with Nrf2 as well as a sequence motif that is required for mammalian Keap1 export from the nucleus 
. Overexpression of CncC and depletion of dKeap1 in adult flies activates the transcription of many genes that protect cells from xenobiotic compounds, whereas dKeap1 overexpression represses their transcription, indicating that the functions of these protein families in the xenobiotic response are conserved between mammals and Drosophila
CncC and dKeap1 subcellular localization and polytene chromosome occupancy.
Several lines of evidence suggest that CncC and dKeap1 also affect cell proliferation and development. CncC overexpression and dKeap1 depletion inhibit intestinal stem cell proliferation, and counteract the proliferative effects of environmental stress in these cells 
. Loss of function mutations in cncC
cause larval lethality 
. The genes regulated by CncC and dKeap1 during larval development had not been established. Elucidation of the relationship between CncC and dKeap1 functions in xenobiotic responses and in development is important to define how the transcription regulatory functions of CncC and dKeap1 are regulated in response to intrinsic and extrinsic stimuli.
and in other holometabolous insects, the onset of metamorphosis is triggered by an increase in the level of the endocrine hormone ecdysone 
. Ecdysone is synthesized in the prothoracic gland (PG) by a series of cytochrome P450 enzymes 
. The expression of these ecdysone-biosynthetic genes and the timing of pupation are regulated by Ras signaling in response to prothoracicotropic hormone (PTTH) binding to the Torso receptor 
. Ecdysone facilitates the onset of metamorphosis by regulating transcription in many tissues, including the salivary glands where ecdysone-regulated transcription is manifest by puffs at specific polytene chromosome loci 
. The transcription factors that bind to the ecdysone biosynthetic gene promoters and activate their transcription have remained unknown.
In the work presented here, we found that CncC and dKeap1 occupied the classical ecdysone-regulated puffs on polytene chromosomes. Depletion of CncC or of dKeap1 in salivary glands reduced ecdysone-regulated gene transcription. Depletion of CncC or of dKeap1 in the PG as well as cncC and dKeap1 loss of function mutations reduced ecdysone biosynthetic gene transcription in larvae and in embryos, respectively. The reduced ecdysteroid levels caused by CncC and by dKeap1 depletion in the PG delayed pupation and suppressed the premature pupation caused by constitutive Ras signaling. These observations establish roles for CncC and dKeap1 in transcriptional programs in different tissues that coordinate metamorphosis.