Fig. 4.

EGR1 inhibited EPO-R transcription by negatively interacting with HIF1α under hypoxia. a Luciferase reporter activity of the wild-type EPO-R proximal promoters with co-expression of empty vector, constitutive active (ca) EGR1, or zinc-finger mutated (zfm) EGR1 cDNAs alone, or with caHIF1α and SP1, caHIF1α and SP1 and caEGR1, caHIF1α and SP1 and zfmEGR1 in combination. b Luciferase reporter activity of the wild-type EPO-R proximal promoters with co-expression of full-length or truncated HIF1α together with or without wild-type EGR1 cDNA. The empty cDNA and empty promoter vectors were included as controls. The fold change of luciferase 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 and **P < 0.01 versus empty vector