Fig. 8. Full-length CTCF, but not CTCF-ZF, inhibits nucleolar transcription. UR61 cells were transfected with the GFP-CTCF full length (GFP-CTCF; a-c,d-f), the GFP-CTCF-zinc-finger (GFP-ZF; g-i) or the pEGFP vector (GFP; j-l). 24 hours post-transfection cells were pulse-labelled with 5'-fluorouridine (FU) for 5 minutes (b) or 10 minutes (e,h,k). Cells were then fixed and the sites of 5'-FU incorporation revealed with an anti-BrdU antibody and a Texas Red-conjugated secondary antibody. The localization of the GFP-fusion proteins (a,d,g,j; green channel), the 5'-FU incorporation (b,e,h,k; red channel) and the merged images (c,f,i,l) are shown. Confocal images show that GFP-CTCF, but not GFP-ZF or GFP inhibits 5'-FU incorporation into nascent RNA. Bar, 10 µm.