Fig. 1.

Plasmid structures: plasmid pQTERT (a) and the control plasmid pQeGFP (b). Plasmids contained an ampicillin resistance gene (AMP) for bacterial selection and a neomycin resistance gene (Neo) for the selection of transduced eukaryotic cells. The expression of either hTERT (a) or eGFP (b) sequences is regulated by the internal cytomegalovirus (CMV) promoter. Both sequences are inserted into the multiple cloning site. Moreover, both plasmids have an IRES that induces a co-translation of neomycin resistance and the target genes hTERT or eGFP. Segments in black (5′LTR, 3′LTR, etc.) control virus translation and packaging of the plasmid-containing viruses. GFP and hTERT transfection: Control of retroviral transfection by the eGFP control plasmid as revealed by eGFP fluorescence (c). Telomerase activity of transfected cells (d). Results of the TRAP-assay are normalized to the positive control. Naïve cells (HUVEC) did not have any detectable telomerase activity. HUVEC-hTERT displayed strong telomerase activity comparable to that of the positive control. There was almost no activity after heat inactivation. *P < 0.05 with respect to positive control, scale bar 100 μm