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Summary A naturally occurring p53 isoform that lacks 39 residues at the N-terminus (denoted ΔNp53), when expressed with wild-type p53 (WTp53), forms mixed ΔNp53:WTp53 tetramers and causes accelerated aging in mice. Cellular alterations specific to ΔNp53:WTp53 have been difficult to assess because ΔNp53 and WTp53 co-expression results in tetramer heterogeneity, including formation of contaminating WTp53 tetramers. Based upon the p53 tetramer structure, we expressed ΔNp53 and WTp53 as a single transcript that maintained tetramer architecture, ensuring a 2:2 ΔNp53:WTp53 stoichiometry. As expected, ΔNp53:WTp53 tetramers were stable and transcriptionally active in vitro and in cells, largely mimicking the function of WTp53 tetramers. Microarray analyses, however, revealed about 80 genes whose expression was altered 2-fold or more in ΔNp53:WTp53 cells. Moreover, global metabolomic profiling quantitated hundreds of biochemicals across different experiments (WTp53, ΔNp53:WTp53, plus controls). When evaluated collectively, these data suggested altered mTOR signaling and mitochondrial function—each canonical regulators of longevity—in cells expressing ΔNp53:WTp53 vs. WTp53. Increased levels of free amino acids, increased expression of IRS-1, and decreased expression of INPP5D/SHIP-1 suggested activated mTOR signaling in ΔNp53:WTp53 cells; this was confirmed upon comparative analyses of several mTOR pathway intermediates. We also observed changes in mitochondrial function in ΔNp53:WTp53 cells, which correlated with increased MARS2 expression and elevated levels of carnitine, acetyl CoA, ATP, and Krebs cycle intermediates. Finally, elevated levels of succinate and 2-hydroxyglutarate indicate potential epigenetic means to propagate ΔNp53:WTp53-induced gene expression changes to cell progeny. This may be especially important for aging, as biological effects manifest over time.

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