Fig. 1.

p53 transcriptionally down-regulates expression of the gluconeogenic genes G6PC and PCK1. (A) Pyruvate tolerance tests in normal C57BL/6J mice and p53 knockout mice. Twelve mice were separated into two groups, with six mice per group. Blood glucose concentration of mice was measured at 22 h after fasting. (B) Ectopic p53-induced G6PC and PCK1 expression in HCT116^(−/−) cells. Cells were transfected with either an empty plasmid as control (hereafter all transfected empty plasmids serve as controls) or a p53WT-expressing plasmid, and mRNA was analyzed by qPCR at 12 h, 24 h, or 36 h after transfection. mRNA levels of the control sample were set as 1, and relative mRNA levels of the other samples were normalized to this control. (C) Ectopic mutant p53-induced G6PC and PCK1 expression in HCT116^(−/−) cells. Cells were transfected with an empty plasmid or with plasmids expressing p53WT, p53(175RH), or p53(ΔTA). Relative mRNA expression levels were measured by qPCR at 36 h. (D) Ectopic p53-induced binding of FoxO1 to G6PC and PCK1 promoters in HCT116^(−/−) cells. A qChIP analysis was performed at 36 h after transfection with empty plasmid or plasmid expressing p53WT. The relative recovery of protein binding to the promoters in cells with empty plasmid was set as 1, and the relative recoveries of the other samples were normalized to this control. All experiments were repeated at least three times. The data are shown as the mean ± SD, with *P < 0.05, **P < 0.01, and ***P < 0.001.