Mitochondrial transcription factor A promotes DNA strand cleavage at abasic sites
Mitochondrial transcription factor A promotes DNA strand cleavage at abasic sites
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DOI：
10.1073/pnas.1911252116
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发表时间：
2019-09-03
影响因子：
11.1
通讯作者：
Zhao, Linlin
中科院分区：
文献类型：
--
作者：
Xu, Wenyan;Boyd, Riley M.;Zhao, Linlin
在高等真核细胞中，线粒体是能量产生、细胞信号传导和生物分子生物合成所必需的亚细胞器。线粒体DNA（mtDNA）基因组是线粒体功能不可或缺的，因为它编码电子传递链的蛋白质亚基和一整套转移和核糖体RNA。线粒体DNA降解已成为维持线粒体DNA和科普由内源性和环境因素引起的线粒体DNA损伤的重要质量控制措施。在已知的所有类型的DNA损伤中，来源于碱基切除修复和自发碱基丢失的脱碱基（AP）位点是细胞中最丰富的内源性DNA损伤。在线粒体中，AP位点触发快速DNA丢失;然而，参与该过程的机制和分子因素仍然难以捉摸。在此，我们证明，AP网站的稳定性显着降低后，结合到一个主要的线粒体DNA包装蛋白，线粒体转录因子A（TFAM）。TFAM-DNA复合物中AP病变的半衰期比游离DNA中的半衰期短2至3个数量级，这取决于它们的位置。TFAM催化的AP-DNA不稳定发生在非特异性DNA或线粒体轻链启动子序列，产生DNA单链断裂和DNA-TFAM交联。在用人细胞的线粒体提取物处理AP-DNA时，也观察到链断裂前的TFAM-DNA交联中间体。原位捕获的反应中间体（DNA-TFAM交联）表明，反应进行通过希夫碱化学促进赖氨酸残基。总的来说，我们的数据表明TFAM在促进脱碱基DNA的周转方面具有新的作用。
In higher eukaryotic cells, mitochondria are essential subcellular organelles for energy production, cell signaling, and the biosynthesis of biomolecules. The mitochondrial DNA (mtDNA) genome is indispensable for mitochondrial function because it encodes protein subunits of the electron transport chain and a full set of transfer and ribosomal RNAs. MtDNA degradation has emerged as an essential quality control measure to maintain mtDNA and to cope with mtDNA damage resulting from endogenous and environmental factors. Among all types of DNA damage known, abasic (AP) sites, sourced from base excision repair and spontaneous base loss, are the most abundant endogenous DNA lesions in cells. In mitochondria, AP sites trigger rapid DNA loss; however, the mechanism and molecular factors involved in the process remain elusive. Herein, we demonstrate that the stability of AP sites is reduced dramatically upon binding to a major mtDNA packaging protein, mitochondrial transcription factor A (TFAM). The half-life of AP lesions within TFAM-DNA complexes is 2 to 3 orders of magnitude shorter than that in free DNA, depending on their position. The TFAM-catalyzed AP-DNA destabilization occurs with nonspecific DNA or mitochondrial light-strand promoter sequence, yielding DNA single-strand breaks and DNA-TFAM cross-links. TFAM-DNA cross-link intermediates prior to the strand scission were also observed upon treating AP-DNA with mitochondrial extracts of human cells. In situ trapping of the reaction intermediates (DNA-TFAM cross-links) revealed that the reaction proceeds via Schiff base chemistry facilitated by lysine residues. Collectively, our data suggest a novel role of TFAM in facilitating the turnover of abasic DNA.