FIGURE 2.

IPAS is responsible for suppression of the hypoxic response. A, TH and IPAS gene expression in CoCl₂-treated PC12 cells cultured in different media. mRNA expression levels were determined by RT-PCR. PCR products were analyzed on 2% agarose gels (left panel) and quantified by densitometry. The data were normalized to 18 S rRNA, and the value of cells cultured in DMEM without CoCl₂ was set to 1. B, repression of HRE-dependent luciferase activity by coexpression of IPAS. mIPAS indicates the mouse IPAS expression plasmid. PC12 cells in 6-well plates were transfected with mIPAS (0.45 μg or 0.9 μg). C, inducible expression of TH mRNA recovered by treatment with IPAS/HIF-3α siRNA in RPMI-cultured PC12 cells. mRNA expression levels were determined by RT-PCR. D, inducible expression of reporter activity recovered by the treatment with IPAS/HIF3α siRNA. Green fluorescent protein siRNA was used for control. *, p < 0.05 for indicated comparison. **, p < 0.01 for indicated comparison. The data shown in the bar graphs are the averages ± S.D. of four independent experiments.