Parkin reduces DNA damage induced by UV irradiation. Stably SH-SY5Y cell lines expressing wild-type parkin, the Del3–4 parkin mutant, or the pcDNA control vector were UV-irradiated (100 J/M2) and then assessed for DNA damage by immunocytochemical staining for cyclopyrimidine dimers (CPD) (red). Nuclei were stained with Hoechst dye. All three cell lines show similar robust CPD staining 1 hr after UV irradiation. Decreased DNA damage in SH-SY5Y cells expressing parkin, but not the pcDNA control and Del3–4 parkin mutant was detected. Quantitation of CPD positive cells in three cell lines after UV irradiation is shown, and represents the mean ± S.D., n = 5. *P < 0.05, **P > 0.05 relative to control by ANOVA with post-hoc Student Neumann-Kiels tests.