Mammalian mitochondrial DNA (mtDNA) is replicated by DNA polymerase γ (POLγ), a heterotrimeric complex consisting of a catalytic POLγA subunit and two accessory POLγB subunits¹. More than 300 mutations in POLG, the gene encoding the catalytic subunit, have been linked to severe, progressive conditions with high rates of morbidity and mortality, for which no treatment exists². Here we report on the discovery and characterization of PZL-A, a first-in-class small-molecule activator of mtDNA synthesis that is capable of restoring function to the most common mutant variants of POLγ. PZL-A binds to an allosteric site at the interface between the catalytic POLγA subunit and the proximal POLγB subunit, a region that is unaffected by nearly all disease-causing mutations. The compound restores wild-type-like activity to mutant forms of POLγ in vitro and activates mtDNA synthesis in cells from paediatric patients with lethal POLG disease, thereby enhancing biogenesis of the oxidative phosphorylation machinery and cellular respiration. Our work demonstrates that a small molecule can restore function to mutant DNA polymerases, offering a promising avenue for treating POLG disorders and other severe conditions linked to depletion of mtDNA.

哺乳动物线粒体 DNA （mtDNA） 由 DNA 聚合酶 γ （POLγ） 复制，POLγ 是一种异源三聚体复合物，由一个催化性 POLγA 亚基和两个辅助 POLγB 亚基¹ 组成。POLG（编码催化亚基的基因）中的 300 多种突变与发病率和死亡率高的严重进行性疾病有关，目前尚无治疗方法²。本文报道了 PZL-A 的发现和表征，PZL-A 是一流的 mtDNA 合成小分子激活剂，能够恢复 POLγ 最常见的突变变体的功能。PZL-A 与催化 POLγA 亚基和近端 POLγB 亚基之间界面处的变构位点结合，该区域几乎不受所有致病突变的影响。该化合物在体外恢复 POLγ 突变形式的野生型样活性，并激活致命性 POLG 病儿科患者细胞中的 mtDNA 合成，从而增强氧化磷酸化机制和细胞呼吸的生物发生。我们的工作表明，小分子可以恢复突变 DNA 聚合酶的功能，为治疗 POLG 疾病和其他与 mtDNA 耗竭相关的严重疾病提供了一条有前途的途径。