Figure 1. Schematic representation of HIF-HBR reporter construct.

3, 6 or 12 tandem units of HIF binding repeats (3U, 6U or 12U-HBR) and a TK minimal promoter together regulate the eYFP expression. b–c) Optimization of the number of HIF binding repeats. b) 6U-HBR HeLa cells turn eYFP on in 2% but not in 20% oxygen. Equal amount of cells (5×10⁴) were plated in both culture dishes and microscopy and FACS analysis were performed after 2 days; c) the signal-to-background ratio is represented by FACS analysis. HeLa cells were transduced with HIF-HBR reporter lentiviral particles for 24 hrs and then grown under normoxia (20% O2) or hypoxia (2% O2) for 48 hours before FACS analysis. Ratios are of geometric means of eYFP intensity in 2% to 20% oxygen.