P53 represses the expression of SLC7A11, a component of System Xc, and also prevents the binding and activation of the NADPH oxidase NOX1 by binding to dipeptidyl peptidase-4 (DPP4), leading to ferroptosis (Jiang et al., 2015), which is associated with PD. The gene discussed is DPP4; the disease is Parkinson disease.