Effect of serial 5'-deletions of the rat HL upstream region on transcriptional activity in HepG2 cells. HepG2 cells were transiently transfected with the indicated promoter-reporter constructs. At 48 h post-transfection, cells were lysed and expression of CAT and β-galactosidase protein was determined. Data are expressed as the ratio of CAT over β-galactosidase expression. Data are means ± SD from 4–7 independent experiments, each performed in triplicate. *: P < 0.05; **: P < 0.01; n.s.: not significant.