Figure 5.

ERVH48-1 promoter activity in low and high oxygen conditions. (a) Comparison of ERVH48-1 promoter activity under low and high oxygen conditions (2% or 20%). Luciferase activity of ERVH48-1 promoter sequences in BeWo, JEG3, HTR8, Ishikawa, and HeLa cells when cultured at 20% O₂ (left column) or 2% O₂ (right column). (Bars from left to right: pGL3-basic, -LTR, -5Enh-LTR, -LTR-EIE, and -5Enh-LTR-EIE.) Luciferase activities for each construct were normalized to pGL3-basic and compared to values for each reporter construct cultured under 20% O₂ results to assess statistical differences. (Mann–Whitney U test: * p < 0.05; ** p < 0.01.) Experiments were performed in duplicate, and the means ± SDs were calculated from three independent experiments. (b) The effects of transient expression of hypoxia-inducible proteins (HIF1α, HIF2α, and ARNT) on the transcriptional activity of each ERVH48-1 promoter construct in BeWo cells and (c) in HTR8 cells. pGL3-basic was included as a reference. Statistical analysis was performed, comparing the luciferase activities in cells exposed to the vector-only transfected control with those in which each gene or genes were transiently transfected (Mann–Whitney U test: ** p < 0.01). Experiments were performed in duplicate, and the means ± SDs were calculated from three independent experiments.