Cooperativity of Stress-Responsive Transcription Factors in Core Hypoxia-Inducible Factor Binding Regions
Figure 4
Effect of stress-responsive transcription factor binding sites in the proximity of hypoxia-response elements on hypoxic induction of HIF-responsive promoters.
HeLa cells were transfected with reporter plasmids containing promoter regions of mouse LDHA (A), human GYS1 (B) and human CA9 (C) in their wild-type form or harbouring the indicated mutations. Diagrams to the left of each graph indicate the location of the different mutations in the employed promoter constructs (grey blocks, highlighted with red border). Effects on reporter induction by hypoxia and the hypoxia mimetic DMOG are summarized in the central columns: -, no hypoxic/DMOG induction; +, ++, +++: increasing strength of hypoxic/DMOG induction. Graphs represent the fold induction over normoxia of the wild-type promoter (WT) upon hypoxia or DMOG treatment, compared to that of promoter versions harbouring mutations in the hypoxia response element (HRE), in CREB (A), CEBPB (B), or AP1 (C) binding sites proximal to the HRE, or in control genomic regions (CONTROL). Bars represent average values in four to six independent experiments, and error bars the standard deviation. Statistical significance of observed activity compared to the wild-type promoters are indicated: n.s.: not significant, *: p<0.05, **: p<0.01 (repeated measures ANOVA with Dunnet post-hoc correction).