Fig. 3

EGR1 regulated SIRT1 transcription under hypoxic conditions. a Schematic model indicating the construction of truncated SIRT1 promoter segments. The SIRT1 promoter sequence was truncated randomly from distal to proximal and fused with firefly and Renilla luciferase gene sequences. b The results of dual-luciferase reporter system demonstrated that the transcriptional activities of the different truncated segments were all inhibited by hypoxia. Each group was analyzed in triplicate, and each experiment was performed three times. c Western blot analysis of EGR1 and USF2 expression levels in HCT116 and SW480 cells exposed to hypoxia. d Western blot analysis of EGR1 and USF2 expression levels after cobalt chloride treatment (0, 100, 200, and 400 μM) for 24 h. e Dual-luciferase reporter system analysis of the transcriptional activities of USF2, Sp1 and EGR1 for the − 100 ~ + 66 bp segment of the SIRT1 promoter region. Each group was analyzed in triplicate, and each experiment was performed three times. **p < 0.01; ***p < 0.001