Figure 3.
CBP is necessary and sufficient for diap1 down-regulation in response to ecdysone during the mid-third instar transition. (A–F) DIAP1 antibody stains of larval salivary glands dissected from animals that span the mid-L3 transition (larva staged relative to the L2–L3 molt). (A and B) DIAP1 levels drop between 20–24 and 34–38 h in control glands (w) but not in CBPG0350 mutant salivary glands (C and D). (E) Ectopic expression of CBP (w; hs-CBP) in 12-h L3 animals is sufficient to down-regulate DIAP1 expression at 20–24 h, whereas removal of EcR by RNAi blocks DIAP1 down-regulation (F). (G) Northern blots of RNA isolated from wild-type salivary glands from before (20–24 h) or after (34–38 h) the mid-L3 transition, probed to detect CBP, diap1, ng-1, and Sgs-4 mRNA, with rp49 as a control. (H) Organs dissected from L3 were cultured in the presence of 20-hydroxyecdysone (20E), cycloheximide (cyc), or 20E and cycloheximide for 2 or 6 h, and total RNA was extracted for Northern blot hybridization to detect CBP and rp49 mRNA.