Effect of omHIF-1α overexpression on omTERT promoter activity. CHO Ka13 cells were transiently transfected with 600 ng of a luciferase reporter vector containing 3.5 kb of omTERT 5'-flanking sequence (pTERT-luc; panel B) or 600 ng of empty reporter vector (pGL3-basic; panel A) along with 100 ng of pCMV-omHIF-1α (solid bar) or 100 ng of the empty pCMVTNT vector (open bar) and 100 ng of the pTracer-EF/Bsd/lacZ (β-galactosidase) expression vector. Relative luciferase activity (RLU) is the ratio of luciferase over β-galactosidase activity. Data are the mean ± SD of three independent experiments. Asterisk (*) indicates significant effect (p < 0.001) of omHIF-1α overexpression on induction of pTERT-luc activity.