Institute of Molecular Medicine, College of Medicine, National Taiwan University, Taipei, Taiwan.
Center of Precision Medicine, College of Medicine, National Taiwan University, Taipei, Taiwan.
Autophagy. 2021 Nov;17(11):3444-3460. doi: 10.1080/15548627.2021.1874209. Epub 2021 Jan 19.
Genotoxic insult causes nuclear and mitochondrial DNA damages with macroautophagy/autophagy induction. The role of mitochondrial DNA (mtDNA) damage in the requirement of autophagy for nuclear DNA (nDNA) stability is unclear. Using site-specific DNA damage approaches, we show that specific nDNA damage alone does not require autophagy for repair unless in the presence of mtDNA damage. We provide evidence that after IR exposure-induced mtDNA and nDNA damages, autophagy suppression causes non-apoptotic mitochondrial permeability, by which mitochondrial ENDOG (endonuclease G) is released and translocated to nuclei to sustain nDNA damage in a TET (tet methylcytosine dioxygenase)-dependent manner. Furthermore, blocking lysosome function is sufficient to increase the amount of mtDNA leakage to the cytosol, accompanied by ENDOG-free mitochondrial puncta formation with concurrent ENDOG nuclear accumulation. We proposed that autophagy eliminates the mitochondria specified by mtDNA damage-driven mitochondrial permeability to prevent ENDOG-mediated genome instability. Finally, we showed that HBx, a hepatitis B viral protein capable of suppressing autophagy, also causes mitochondrial permeability-dependent ENDOG mis-localization in nuclei and is linked to hepatitis B virus (HBV)-mediated hepatocellular carcinoma development. 3-MA: 3-methyladenine; 5-hmC: 5-hydroxymethylcytosine; ACTB: actin beta; ATG5: autophagy related 5; ATM: ATM serine/threonine kinase; DFFB/CAD: DNA fragmentation factor subunit beta; cmtDNA: cytosolic mitochondrial DNA; ConA: concanamycin A; CQ: chloroquine; CsA: cyclosporin A; Dox: doxycycline; DSB: double-strand break; ENDOG: endonuclease G; GFP: green fluorescent protein; Gy: gray; H2AX: H2A.X variant histone; HBV: hepatitis B virus; HBx: hepatitis B virus X protein; HCC: hepatocellular carcinoma; I-PpoI: intron-encoded endonuclease; IR: ionizing radiation; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MOMP: mitochondrial outer membrane permeability; mPTP: mitochondrial permeability transition pore; mtDNA: mitochondrial DNA; nDNA: nuclear DNA; 4-OHT: 4-hydroxytamoxifen; rDNA: ribosomal DNA; ROS: reactive oxygen species; SQSTM1/p62: sequestosome 1; TET: tet methylcytosine dioxygenase; TFAM: transcription factor A, mitochondrial; TOMM20: translocase of outer mitochondrial membrane 20; VDAC: voltage dependent anion channel.
遗传毒性损伤会导致核和线粒体 DNA 损伤，并诱导巨自噬/自噬。线粒体 DNA（mtDNA）损伤在自噬对核 DNA（nDNA）稳定性的要求中的作用尚不清楚。使用特异性 DNA 损伤方法，我们表明，仅特定的 nDNA 损伤本身不需要自噬修复，除非存在 mtDNA 损伤。我们提供的证据表明，在 IR 暴露诱导的 mtDNA 和 nDNA 损伤后，自噬抑制会导致非凋亡性的线粒体通透性，通过这种通透性，线粒体内切核酸酶 G（endonuclease G）被释放并易位到核中，以依赖于 TET（tet 甲基胞嘧啶双加氧酶）的方式维持 nDNA 损伤。此外，阻断溶酶体功能足以增加胞质中线粒体 DNA 泄漏的量，同时形成无内切核酸酶 G 的线粒体点状结构，并伴有核内内切核酸酶 G 的积累。我们提出，自噬消除了由 mtDNA 损伤驱动的线粒体通透性所指定的线粒体，以防止内切核酸酶 G 介导的基因组不稳定性。最后，我们表明，乙型肝炎病毒蛋白 HBx 能够抑制自噬，也会导致线粒体通透性依赖性内切核酸酶 G 的核定位错误，并与乙型肝炎病毒（HBV）介导的肝细胞癌发展有关。3-MA：3-甲基腺嘌呤；5-hmC：5-羟甲基胞嘧啶；ACTB：肌动蛋白 β；ATG5：自噬相关 5；ATM：ATM 丝氨酸/苏氨酸激酶；DFFB/CAD：DNA 片段因子亚基β；cmtDNA：胞质线粒体 DNA；ConA：康纳霉素 A；CQ：氯喹；CsA：环孢素 A；Dox：多西环素；DSB：双链断裂；ENDOG：内切核酸酶 G；GFP：绿色荧光蛋白；Gy：戈瑞；H2AX：H2A.X 变体组蛋白；HBV：乙型肝炎病毒；HBx：乙型肝炎病毒 X 蛋白；HCC：肝细胞癌；I-PpoI：内含子编码内切核酸酶；IR：电离辐射；MAP1LC3/LC3：微管相关蛋白 1 轻链 3；MOMP：线粒体外膜通透性；mPTP：线粒体通透性转换孔；mtDNA：线粒体 DNA；nDNA：核 DNA；4-OHT：4-羟基他莫昔芬；rDNA：核糖体 DNA；ROS：活性氧；SQSTM1/p62：自噬相关蛋白 1；TET：tet 甲基胞嘧啶双加氧酶；TFAM：线粒体转录因子 A；TOMM20：外线粒体膜转运蛋白 20；VDAC：电压依赖性阴离子通道。
