Telomerase reverse transcriptase (TERT, or hTERT in human) is a catalytic subunit of the enzyme telomerase, Ectopic expression of telomerase in telomerase-silent cells is sufficient to overcome senescence and to extend cellular lifespan, and has been used for cell immortalization. This lentivirus coexpresses hTERT and GFP under the control of EF1a promoter with puromycin as a selection marker.