Fig. 8.

Reporter gene activities for luciferase (pGL4.23) under control of the COX4-2 promoter and hypoxia responsive elements from candidate vertebrate species. A: PC3 cells were transfected with constructs containing 4 tandem repeats of HRE1 and 2 and the ORE from human (Hu), anole (An), and Xenopus (Xe), and were exposed to normoxia, 2% O₂ (hypoxia), or anoxia for 24 h. B: HepG2 cells were transfected with constructs containing ∼2 kb of promoter sequence directly upstream of the COX4-2 5′-UTR from rat, goldfish, and zebrafish and were treated in the same way as the PC3 cells for A. Also included in both experiments were constructs containing four tandem repeats of a known hypoxia-responsive element from the human iNOS gene and the baseline activities for the empty pGL4.23 vector (EV). *Significant difference from the control treatment as determined by a Mann-Whitney U-test. Results were normalized to cotransfected Renilla reporter activity levels and are presented relative to normoxic activities (+SE).