Abl requires Su(dx) to internalize Notch into late endosomes and attenuate signaling. (A–D″) Single confocal sections of representative S2 cells showing Notch (indirect immunofluorescence) and Rab7-EYFP. “n” marks the cell nucleus. Transfections shown: (A) Notch + Su(dx) dsRNA, (B) Notch + Abl dsRNA + Su(dx) dsRNA, (C) Notch + Abl + Su(dx) dsRNA, and (D) Notch + Su(dx) + Abl dsRNA. Scale bars = 5 µm. (E and G) Plot showing profiles of Notch levels across LE diameters in the indicated manipulations. Sample size (# of LEs evaluated): Notch (WT, N = 38), Notch + Abl dsRNA (N = 32), Notch + Su(dx) dsRNA (N = 68), Notch + Abl dsRNA + Su(dx) dsRNA (N = 53), Notch + Abl (N = 27), and Notch + Abl + Su(dx) dsRNA (N = 27). (F and H) Relative Notch activity in the indicated manipulations. A t-student means comparison test was performed, and P values <0.05 (*), <0.01 (**), and <0.001(***) are indicated.