Covalent Modification of p53 by (<i>E</i>)-1-(4-Methylpiperazin-1-yl)-3-(5-nitrofuran-2-yl)prop-2-en-1-one

<i>TP53</i> is commonly mutated in cancer, giving rise to loss of wild-type tumor suppressor function and increases in gain-of-function oncogenic roles. Thus, inhibition of mutant p53 and reactivation of wild-type function represents a potential means to target diverse tumor types. (<i>E</i>)-1-(4-Methylpiperazin-1-yl)-3-(5-nitrofuran-2-yl)prop-2-en-1-one (NSC59984), first identified from a high-throughput screen, induces wild-type p53 signaling and antiproliferative effects while inhibiting mutant p53 gain-of-function activities. Here, we investigate the specific mechanism of action of NSC59984 against p53. We found that NSC59984 reacts with thiols via an unusual Michael addition at the α-carbon. Covalent modification of p53 Cys124 and Cys229 was observed both following <i>in vitro</i> reaction and upon treatment of cells. Finally, we used a biotinylated form of NSC59984 and, separately, thermal proteome profiling to examine off-target effects, identifying several metabolic proteins involved in cellular metabolism as potential targets. These results demonstrate that covalent modification of p53 by NSC59984 leads to increased wild-type activity and suggest that potential reaction with metabolic enzymes may contribute to antiproliferative function.