AKI is usually accompanied by the presence of DNA damage response (DDR), which leads to ataxia telangiectasia mutation (ATM) and/or ataxia telangiectasia and activation of Rad3-related (ATR) proteins; both these proteins are members of the phosphatidylinositol 3-kinase family that phosphorylates several downstream targets, including p53 and checkpoint kinase 2 (CHK2), and subsequently, produce p21Waf1/Cip1. The gene discussed is CDKN1A; the disease is acute kidney injury.