Fig. 4. SRC-1 interacts with HIF-1 via CBP. (A) Enhancement of HIF-1 C-TAD-mediated transcription by SRC-1 is dependent on interaction with CBP. Cells were transfected with 500 ng GAL4-driven reporter gene, 10 ng GAL4 (G4) or GAL4-C-TAD expression plasmid (C-TAD) and 200 ng (+) or 400 ng of expression plasmids (++) encoding CBP, CBP/H3P or SRC-1 and carrier DNA, pFLAG-CMV-2 to keep a constant total DNA concentration of 1 µg. No significant difference was observed in the luciferase values obtained with expression of the C-TAD (^*) in the presence or absence of coexpressed CBP/H3P (^*) (P<0.05). (B) CBP/H3P does not potentiate HIF-1-mediated transactivation. Cells were transfected with 500 ng HRE-driven reporter gene, 50 ng Flag (Flag) or mHIF-1 (HIF-1) expression plasmids and 400 ng (+) or 800 ng (++) of expression plasmids encoding CBP, CBP/H3P, or SRC-1. Total DNA concentration was kept at 1.35 µg using pFlag-CMV-2. Data are presented as fold induction over the luciferase activity obtained following transfection of cells using GAL4 expression plasmid (A) or pFlag-CMV-2 (B) and incubation of the cells under normoxic conditions. No significant difference was observed in the luciferase values obtained with expression of HIF-1 (^*) in the presence or absence of coexpressed CBP/H3P (^*) (P<0.05). Values represent the mean ± s.e.m. of three independent experiments performed in duplicate.