APC-M2 pAb recognizes endogenous and exogenous APC protein by immunofluorescence microscopy. (A) U2OS cells double-labeled with APC-M2 pAb (red) and commercial anti-APC (ali12-28) mAb (green). (b) Magnified image of a region indicated in (a) shows considerable overlap of red and green signals. Scale bars, 5 μm. (B) Colocalization of APC1417 fused-GFP (green, upper panel) or NLS (nuclear localization signal from SV40) fused-GFP tag (green, lower panel) with APC-M2 pAb (red) signal. Short exposure revealed APC-M2 pAb signal overlapping that of GFP-APC1417. Longer (normal) exposure led to saturated signal in GFP-APC1417-expressing cells but allowed visualization of endogenous APC staining with APC-M2 pAb in adjacent non-transfected HCT116βw cells. Note that there is no overlap of APC-M2 pAb labeling with NLS fused GFP signal. Scale bar, 5 μm.