DJ-1, first identified by Nagakubo et al. [27] as a mitogen-dependent oncogene product, is ubiquitously expressed in almost all human tissues as homodimers and participates in many physiological and pathological processes including tumorigenesis [31–33], fertilization [34, 35], regulation of the androgen receptor [36–40], posttranslational modification of protein SUMO-1, a ubiquitin-like modifier [41], oxidative stress [42–44], and the development of Parkinson's disease [45–49]. The gene discussed is SUMO1; the disease is Parkinson disease.