DEC2 is required for HIF-1α transactivation activity in U2OS. Cells were transfected with either control (NC) or DEC2 siRNAs and exposed to either 21% or 1% oxygen for 8 h. A. Confirmation of DEC2 knockdown by qRT-PCR. B-F. Analyses of the expression levels of HIF-1α downstream target genes ANGPTL4 (B), VEGFA (C), HK2 (D), PGK1 (E) in U2OS cells and PGK1 (F) in MNNG cells by qRT-PCR.