Fig. 3

Synergistic interaction between HIF1α and SP1 promoted EPO-R transcription under hypoxia. a Luciferase reporter activity of the EPO-R proximal promoters of wild-type or site-direct mutated SP1 site with co-expression of HIF1α and SP1 cDNA alone or HIF1α and SP1 cDNA in combination. b Luciferase reporter activity of the wild-type EPO-R proximal promoters with co-expression of full-length or truncated HIF1α alone or in combination with SP1 cDNA. The empty cDNA and empty promoter vectors were included as negative controls (EV). The fold activity was calculated first by normalizing to cDNA EV and then to promoter EV. Data are from three independent repeats and are represented as Mean ± SD; * P < 0.05, ** P < 0.01 versus empty vector