Figure 3. tribbles is a downstream target of Gbb signaling.

(A) In Drosophila S2 cells, gbb transfection induced expression of trb, not PTP61F and dPten. (B) Expression levels of trb increased in the fat bodies of pS106^GS > gbb + RU flies relative to those in −RU controls, but decreased in pS106^GS > gbb RNAi + RU, pS106^GS > punt DN + RU, and pS106^GS > dMad RNAi + RU. (C) In Drosophila S2 cells, dMad was associated with the trb promoter region, which contains putative dMad-binding sites, but not with the trb coding region (ORF). (D) gbb transfection enriched dMad binding at the trb promoter region, but had no effect on binding by nonspecific IgG (negative control). (E) Schematic representations of the pGL3 luciferase reporter vector (LUC) and trb upstream genomic DNA fragments containing the putative Mad binding site (red box) (left) and the luciferase activities by gbb overexpression (right). The significantly increased luciferases activity with pGL3-trb1.4kb was not observed with pGL3-trb1.1kb and pGL3-trb1.4kbΔMbs. Data are presented as means ± s.e.m. from at least three independent experiments. *P < 0.05.