Poulton J, Morten K, Freeman-Emmerson C, Potter C, Sewry C, Dubowitz V, Kidd H, Stephenson J, Whitehouse W, Hansen F J
Department of Paediatrics, University of Oxford, John Radcliffe Hospital, Headington, UK.
Hum Mol Genet. 1994 Oct;3(10):1763-9. doi: 10.1093/hmg/3.10.1763.
Recent studies show that patients presenting with cytochrome oxidase (COX) deficiency in infancy may have reduced mitochondrial DNA (mtDNA) in muscle. The human mitochondrial transcription factor A (h-mtTFA) may be an important regulator of both transcription and replication of mtDNA. h-mtTFA levels were investigated in cell lines which were either free of mtDNA (rho 0) or temporarily depleted by treatment with dideoxycytidine (ddC), and in tissue from three patients with mtDNA depletion and cytochrome oxidase deficiency. h-mtTFA was compared with other mitochondrial proteins such as pyruvate dehydrogenase and porin by Western blotting. The ratio of mtDNA and h-mtTFA mRNA to reference nuclear probes was measured by dual labelling of dot blots. The ratio of mtDNA to nuclear DNA in skeletal muscle was low in muscle in the three patients and in other tissues in one. h-mtTFA was low in cells depleted either permanently or transiently of mtDNA, and this reduction in h-mtTFA roughly paralleled mtDNA levels. Similarly, treatment of rho 0 cell lines with ddC induced a reduction in mtDNA as well as h-mtTFA protein. The relationship between h-mtTFA and mtDNA levels suggests that they may be causally linked. MtDNA depletion was accompanied by an increase in the level of h-mtTFA RNA in the cell lines but low levels in the patient. This suggests that either h-mtTFA regulates mtDNA levels, or that h-mtTFA expression may be regulated by a feedback mechanism initiated by MtDNA Depletion.
近期研究表明，婴儿期出现细胞色素氧化酶（COX）缺乏的患者，其肌肉中的线粒体DNA（mtDNA）可能减少。人类线粒体转录因子A（h-mtTFA）可能是mtDNA转录和复制的重要调节因子。在不含mtDNA的细胞系（ρ0）或经双脱氧胞苷（ddC）处理而暂时耗尽mtDNA的细胞系中，以及在三名患有mtDNA耗竭和细胞色素氧化酶缺乏症患者的组织中，对h-mtTFA水平进行了研究。通过蛋白质印迹法将h-mtTFA与其他线粒体蛋白如丙酮酸脱氢酶和孔蛋白进行比较。通过斑点印迹的双重标记来测量mtDNA和h-mtTFA mRNA与参考核探针的比率。三名患者的肌肉以及其中一名患者其他组织中的骨骼肌中，mtDNA与核DNA的比率较低。在mtDNA永久或暂时耗尽的细胞中，h-mtTFA水平较低，并且h-mtTFA的这种降低大致与mtDNA水平平行。同样，用ddC处理ρ0细胞系会导致mtDNA以及h-mtTFA蛋白减少。h-mtTFA与mtDNA水平之间的关系表明它们可能存在因果联系。mtDNA耗竭伴随着细胞系中h-mtTFA RNA水平的升高，但患者体内水平较低。这表明要么h-mtTFA调节mtDNA水平，要么h-mtTFA的表达可能受mtDNA耗竭引发的反馈机制调节。
