Fig. 1. Reconstitution of active telomerase. (A) The assembly of active telomerase is specific for hTER. TRAP assay for telomerase activity reconstituted with recombinant hTERT expressed in insect cells and in vitro transcribed hTER. An excess of either a telomerase RNA with a mutant template (hTER-mut with the template sequence: 5′-GAUUGGGAUU-3′; lanes 3-5) or unspecific competitor RNA (yeast tRNA; lanes 6-8) was added to the reconstitution mixture. (B) Telomerase was reconstituted with wild-type hTER, one of two different mutant hTER molecules, or without RNA. The telomerase activity of all four samples was measured using either the standard TRAP assay that detects synthesis of TTAGGG repeats (lanes 1, 4, 7, 10) or modified TRAP assays (Feng et al., 1995) that are specific for TTTGGG (lanes 2, 5, 8, 11) and TTGGGG repeats (lanes 3, 6, 9, 12), respectively.