Fusaric Acid Induces DNA Damage and Post‐Translational Modifications of p53 in Human Hepatocellular Carcinoma (HepG 2 ) Cells

Fusaric acid (FA), a common fungal contaminant of maize, is known to mediate toxicity in plants and animals; however, its mechanism of action is unclear. p53 is a tumor suppressor protein that is activated in response to cellular stress. The function of p53 is regulated by post‐translational modifications—ubiquitination, phosphorylation, and acetylation. This study investigated a possible mechanism of FA induced toxicity in the human hepatocellular carcinoma (HepG 2 ) cell line. The effect of FA on DNA integrity and post‐translational modifications of p53 were investigated. Methods included: (a) culture and treatment of HepG 2 cells with FA (IC 50 : 580.32 μM, 24 h); (b) comet assay (DNA damage); (c) Western blots (protein expression of p53, MDM2, p‐Ser‐15‐p53, a‐K382‐p53, a‐CBP (K1535)/p300 (K1499), HDAC1 and p‐Ser‐47‐Sirt1); and (d) Hoechst 33342 assay (apoptosis analysis). FA caused DNA damage in HepG 2 cells relative to the control ( P  < 0.0001). FA decreased the protein expression of p53 (0.24‐fold, P  = 0.0004) and increased the expression of p‐Ser‐15‐p53 (12.74‐fold, P  = 0.0126) and a‐K382‐p53 (2.24‐fold, P  = 0.0096). This occurred despite the significant decrease in the histone acetyltransferase, a‐CBP (K1535)/p300 (K1499) (0.42‐fold, P  = 0.0023) and increase in the histone deacetylase, p‐Ser‐47‐Sirt1 (1.22‐fold, P  = 0.0020). The expression of MDM2, a negative regulator of p53, was elevated in the FA treatment compared to the control (1.83‐fold, P  < 0.0001). FA also inhibited cell proliferation and induced apoptosis in HepG 2 cells as evidenced by the Hoechst assay. Together, these results indicate that FA is genotoxic and post‐translationally modified p53 leading to HepG 2 cell death. J. Cell. Biochem. 118: 3866–3874, 2017. © 2017 Wiley Periodicals, Inc.