PCNA and Parkinson disease: These results further supported our hypothesis that rotenone-induced apoptosis of SH-SY5Y cell was tightly correlated with the S-nitrosylation of PCNA-Cys81 in response to NO stress induced by rotenone, and offered other evidence that PCNA S-nitrosylation had a direct effect on the caspases-9-initiated apoptosis in the PD model.