Assessment of mtDNA damage by quantitative PCR. HEK293 cells infected with control (empty vector) or shATG5 for 5 days. Cells were then incubated with DMSO or 4 mM 3-NPA for 2 h and either immediately harvested or washed with fresh medium and incubated for another 1 h. Cells with or without washout were used for the extraction of total DNA. All DNA samples were used for amplification of 8.9 kb mtDNA fragment using quantitative PCR and were normalized to amplification of a 221 bp mtDNA fragment. PCR products were quantitated by PicoGreen staining using Micro Plate Reader. Data are presented as mean ± SD (n = 3 independent experiments), statistical significance was assessed by two-tailed student's t-test, N.S., not significant, *p < 0.05, **p < 0.01. The data in (A) were further calculated for the frequency of mtDNA damage. The equation was seen in "Materials and Methods". Data are presented as mean ± SD (n = 3 independent experiments), statistical significance was assessed by a two-tailed student's t-test, N.S., not significant, **p < 0.01. 