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TAp73 enhances the pentose phosphate pathway and supports cell proliferation.

Du W, Jiang P, Mancuso A, Stonestrom A, Brewer MD, Minn AJ, Mak TW, Wu M, Yang X - Nat. Cell Biol. (2013)

Bottom Line: By stimulating G6PD, TAp73 increases PPP flux and directs glucose to the production of NADPH and ribose, for the synthesis of macromolecules and detoxification of reactive oxygen species (ROS).The growth defect of TAp73-deficient cells can be rescued by either enforced G6PD expression or the presence of nucleosides plus an ROS scavenger.These findings establish a critical role for TAp73 in regulating metabolism, and connect TAp73 and the PPP to oncogenic cell growth.

View Article: PubMed Central - PubMed

Affiliation: Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, 230027, China.

ABSTRACT
TAp73 is a structural homologue of the pre-eminent tumour suppressor p53. However, unlike p53, TAp73 is rarely mutated, and instead is frequently overexpressed in human tumours. It remains unclear whether TAp73 affords an advantage to tumour cells and if so, what the underlying mechanism is. Here we show that TAp73 supports the proliferation of human and mouse tumour cells. TAp73 activates the expression of glucose-6-phosphate dehydrogenase (G6PD), the rate-limiting enzyme of the pentose phosphate pathway (PPP). By stimulating G6PD, TAp73 increases PPP flux and directs glucose to the production of NADPH and ribose, for the synthesis of macromolecules and detoxification of reactive oxygen species (ROS). The growth defect of TAp73-deficient cells can be rescued by either enforced G6PD expression or the presence of nucleosides plus an ROS scavenger. These findings establish a critical role for TAp73 in regulating metabolism, and connect TAp73 and the PPP to oncogenic cell growth.

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p73 regulates DNA synthesis(a) TAp73+/+ and TAp73−/− MEF cells were treated with or without DHEA. DNA synthesis was measured by BrdU incorporation. Percentages of BrdU-positive cells are shown as mean ± SD (n = 3 independent experiments).(b, c) U2OS cells (b) and p53+/+ HCT116 cells (c) were transfected with control siRNA (−), p73 siRNA, and G6PD siRNA as indicated. Cells were assayed for BrdU incorporation. Protein expression is shown below. Data are means ± SD (n = 3 independent experiments). Western blots represent three independent experiments.(d) Cell-cycle profile of p53+/+ HCT116 cells transfected with p73 siRNA, G6PD siRNA, and control siRNA as indicated. Western blots represent three independent experiments.(e) U2OS cells were transfected with control siRNA, p73 siRNA, and Flag-G6PD as indicated. BrdU incorporation (top) and protein expression (bottom) are shown. Data are means ± SD (n = 3 independent experiments). Western blots represent three independent experiments.(f) Percentage of SA-β-gal positive cells in IMR90 cells stably overexpressing G6PD or vector control in the presence or absence of p73 siRNA. Data are means ± SD (n = 3 independent experiments). Western blots represent three independent experiments.
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Figure 6: p73 regulates DNA synthesis(a) TAp73+/+ and TAp73−/− MEF cells were treated with or without DHEA. DNA synthesis was measured by BrdU incorporation. Percentages of BrdU-positive cells are shown as mean ± SD (n = 3 independent experiments).(b, c) U2OS cells (b) and p53+/+ HCT116 cells (c) were transfected with control siRNA (−), p73 siRNA, and G6PD siRNA as indicated. Cells were assayed for BrdU incorporation. Protein expression is shown below. Data are means ± SD (n = 3 independent experiments). Western blots represent three independent experiments.(d) Cell-cycle profile of p53+/+ HCT116 cells transfected with p73 siRNA, G6PD siRNA, and control siRNA as indicated. Western blots represent three independent experiments.(e) U2OS cells were transfected with control siRNA, p73 siRNA, and Flag-G6PD as indicated. BrdU incorporation (top) and protein expression (bottom) are shown. Data are means ± SD (n = 3 independent experiments). Western blots represent three independent experiments.(f) Percentage of SA-β-gal positive cells in IMR90 cells stably overexpressing G6PD or vector control in the presence or absence of p73 siRNA. Data are means ± SD (n = 3 independent experiments). Western blots represent three independent experiments.

Mentions: The PPP provides NADPH and ribose, both of which are important synthetic precursors for nucleic acids. We compared DNA synthesis in TAp73+/+ and TAp73−/− MEFs using 5-bromo-2′-deoxyuridine (BrdU) incorporation assays. DNA synthesis was sharply reduced in TAp73−/−MEFs compared to TAp73+/+ MEFs (Fig. 6a). Likewise, DNA synthesis slowed down when p73 was silenced in U2OS and various HCT116 cells (Fig. 6b,c and Supplementary Fig. S5a,b). In each cell type, treatment with DHEA or G6PD siRNA inhibited DNA synthesis in TAp73-depleted cells and especially in control cells, diminishing the difference between them (Fig. 6a-c and Supplementary Fig. S5a,b).


TAp73 enhances the pentose phosphate pathway and supports cell proliferation.

Du W, Jiang P, Mancuso A, Stonestrom A, Brewer MD, Minn AJ, Mak TW, Wu M, Yang X - Nat. Cell Biol. (2013)

p73 regulates DNA synthesis(a) TAp73+/+ and TAp73−/− MEF cells were treated with or without DHEA. DNA synthesis was measured by BrdU incorporation. Percentages of BrdU-positive cells are shown as mean ± SD (n = 3 independent experiments).(b, c) U2OS cells (b) and p53+/+ HCT116 cells (c) were transfected with control siRNA (−), p73 siRNA, and G6PD siRNA as indicated. Cells were assayed for BrdU incorporation. Protein expression is shown below. Data are means ± SD (n = 3 independent experiments). Western blots represent three independent experiments.(d) Cell-cycle profile of p53+/+ HCT116 cells transfected with p73 siRNA, G6PD siRNA, and control siRNA as indicated. Western blots represent three independent experiments.(e) U2OS cells were transfected with control siRNA, p73 siRNA, and Flag-G6PD as indicated. BrdU incorporation (top) and protein expression (bottom) are shown. Data are means ± SD (n = 3 independent experiments). Western blots represent three independent experiments.(f) Percentage of SA-β-gal positive cells in IMR90 cells stably overexpressing G6PD or vector control in the presence or absence of p73 siRNA. Data are means ± SD (n = 3 independent experiments). Western blots represent three independent experiments.
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Figure 6: p73 regulates DNA synthesis(a) TAp73+/+ and TAp73−/− MEF cells were treated with or without DHEA. DNA synthesis was measured by BrdU incorporation. Percentages of BrdU-positive cells are shown as mean ± SD (n = 3 independent experiments).(b, c) U2OS cells (b) and p53+/+ HCT116 cells (c) were transfected with control siRNA (−), p73 siRNA, and G6PD siRNA as indicated. Cells were assayed for BrdU incorporation. Protein expression is shown below. Data are means ± SD (n = 3 independent experiments). Western blots represent three independent experiments.(d) Cell-cycle profile of p53+/+ HCT116 cells transfected with p73 siRNA, G6PD siRNA, and control siRNA as indicated. Western blots represent three independent experiments.(e) U2OS cells were transfected with control siRNA, p73 siRNA, and Flag-G6PD as indicated. BrdU incorporation (top) and protein expression (bottom) are shown. Data are means ± SD (n = 3 independent experiments). Western blots represent three independent experiments.(f) Percentage of SA-β-gal positive cells in IMR90 cells stably overexpressing G6PD or vector control in the presence or absence of p73 siRNA. Data are means ± SD (n = 3 independent experiments). Western blots represent three independent experiments.
Mentions: The PPP provides NADPH and ribose, both of which are important synthetic precursors for nucleic acids. We compared DNA synthesis in TAp73+/+ and TAp73−/− MEFs using 5-bromo-2′-deoxyuridine (BrdU) incorporation assays. DNA synthesis was sharply reduced in TAp73−/−MEFs compared to TAp73+/+ MEFs (Fig. 6a). Likewise, DNA synthesis slowed down when p73 was silenced in U2OS and various HCT116 cells (Fig. 6b,c and Supplementary Fig. S5a,b). In each cell type, treatment with DHEA or G6PD siRNA inhibited DNA synthesis in TAp73-depleted cells and especially in control cells, diminishing the difference between them (Fig. 6a-c and Supplementary Fig. S5a,b).

Bottom Line: By stimulating G6PD, TAp73 increases PPP flux and directs glucose to the production of NADPH and ribose, for the synthesis of macromolecules and detoxification of reactive oxygen species (ROS).The growth defect of TAp73-deficient cells can be rescued by either enforced G6PD expression or the presence of nucleosides plus an ROS scavenger.These findings establish a critical role for TAp73 in regulating metabolism, and connect TAp73 and the PPP to oncogenic cell growth.

View Article: PubMed Central - PubMed

Affiliation: Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, 230027, China.

ABSTRACT
TAp73 is a structural homologue of the pre-eminent tumour suppressor p53. However, unlike p53, TAp73 is rarely mutated, and instead is frequently overexpressed in human tumours. It remains unclear whether TAp73 affords an advantage to tumour cells and if so, what the underlying mechanism is. Here we show that TAp73 supports the proliferation of human and mouse tumour cells. TAp73 activates the expression of glucose-6-phosphate dehydrogenase (G6PD), the rate-limiting enzyme of the pentose phosphate pathway (PPP). By stimulating G6PD, TAp73 increases PPP flux and directs glucose to the production of NADPH and ribose, for the synthesis of macromolecules and detoxification of reactive oxygen species (ROS). The growth defect of TAp73-deficient cells can be rescued by either enforced G6PD expression or the presence of nucleosides plus an ROS scavenger. These findings establish a critical role for TAp73 in regulating metabolism, and connect TAp73 and the PPP to oncogenic cell growth.

Show MeSH
Related in: MedlinePlus