Figure 6ρ0206_A and ρ0206_B cells were stained with mitoSOX and analyzed by confocal microscopy. DIC, Differential Interference Contrast. Scale bar, 25 µm. Quantification of the MitoSOX fluorescence intensity described in (A). Data are presented as mean ± SD (n = 3 independent experiments, 20 cells per experiment), statistical significance was assessed by student's t-test, **p < 0.01. Mitochondria carrying the 3243A>G mutation in the tRNA Leu(UUR) gene from the same MELAS myoblasts were transferred into ρ0 206 cell line to generate ρ0206_A (100% wild-type mtDNA) and ρ0206_B (~90% m.3243A>G mtDNA) cell lines. ρ0206_A and ρ0206_B cell lysates were analyzed by Western blotting with anti-ATAD3 or anti-Tubulin antibodies. Relative protein levels of proteins were further evaluated by densitometry analysis using ImageJ software. Quantification of the relative protein level of ATAD3B to Tubulin was shown at right panels. Data are presented as mean ± SD (n =3 independent experiments), statistical significance was assessed by student's t-test, ***p < 0.001. Normal or MELAS patient fibroblasts cell lysates were analyzed by Western blotting with anti-ATAD3 or anti-Tubulin antibodies. Relative protein levels of proteins were further evaluated by densitometry analysis using ImageJ software. Quantification of the relative protein level of ATAD3B to Tubulin was shown at right panels. Data are presented as mean ± SD (n =3 independent experiments), statistical significance was assessed by student's t-test, ***p < 0.001. ρ0206_A, ρ0206_B, and ρ0206-B cells pretreated with ddC (50µM) plus EB (0.5µg/ml) for 10 days, and then harvested and lysed. Cell lysates were analyzed by Western blotting with anti-ATAD3 or anti-GAPDH antibodies. ρ0206_B cells were infected with control, ATAD3B-Flag or ATAD3B (mLIR)-Flag. After two weeks, total DNA from cells was isolated and used to calculate the mutation rate of 3243A>G by quantitative real-time PCR using the TaqMan Probe. Data are presented as mean ± SD (n =3 independent experiments), statistical significance was assessed by a one-way ANOVA, N.S., not significant, *p < 0.05. ρ0206_B cells were infected with control, ATAD3A-Flag, ATAD3B-Flag, or ATAD3B (mLIR)-Flag. After two weeks, the cellular ATP levels were measured. Data are presented as mean ± SD (n =3 independent experiments), statistical significance was assessed by a one-way ANOVA, N.S., not significant, *p < 0.05. MELAS patient fibroblasts were infected with control, ATAD3A-Flag, ATAD3B-Flag or ATAD3B(mLIR)-Flag. After two weeks, total DNA was isolated from fibroblasts and used to calculate the mutation rate of 3243A>G by quantitative real-time PCR using the TaqMan Probe. Data are presented as mean ± SD (n =3 independent experiments), statistical significance was assessed by a one-way ANOVA, N.S., not significant, **p < 0.01. The mode of ATAD3B localization. Under normal conditions (a), ATAD3B-ATAD3A hetero-oligomers are formed (cysteine-cysteine interaction may contribute to the formation of ATAD3B-ATAD3A hetero-oligomers), and ATAD3B C-terminus goes across the mitochondrial inner membrane and locates at mitochondrial intermembrane space with the support of ATAD3A; upon oxidative stress (b), ATAD3B-ATAD3A hetero-oligomers are impaired, and ATAD3B C- terminus locates at mitochondrial outer membrane for recruiting LC3. OMM (outer mitochondrial membrane), IMM (inner mitochondrial membrane).