(A) U2OS cells were transiently transfected with constructs encoding F-TERT and either hTRmin, hTR, or empty vector (mock). TERT was immunopurified on anti-FLAG agarose from cell extract 48 hr post-transfection. An aliquot of the bound samples were treated with TRIzol to purify RNA, which was analyzed by Northern blot. In parallel, bound samples were tested for telomerase activity by primer extension using 32P dGTP for radiolabeling. Products were precipitated and resolved by denaturing gel electrophoresis. A radioactive oligonucleotide recovery control (RC) was added prior to precipitation. For the hTR cell extract, different amounts of extract were assayed relative to the hTRmin sample set at 100%. All lanes are from the same gel. (B) HCT116 hTR KO#2 cells were transiently transfected to express hTR, CAB-box-mutant hTR (G414C), LhTRmin, or hTRmin. FISH was performed to detect the RNAs (green). Nuclei were counterstained with DAPI (blue).