Mitochondrial translesion DNA synthesis

摘要 线粒体DNA(MtDNA)的完整性对于新陈代谢和细胞能量供应以及人类 健康长寿。由于缺乏修复机制和特异性跨损伤合成(TLS)聚合酶， 线粒体DNA含有较高的紫外线损伤含量。高保真的线粒体DNA聚合酶(POLG)将 线粒体DNA复制过程中不可避免地会遇到紫外线损伤。与其他高保真DNA聚合酶不同 在缺乏TLS活性的情况下，我们发现Pol g具有金属调节的TLS活性。在镁存在的情况下 然而，在生理浓度的锰离子存在下，Pol g没有表现出TLS活性 单独或镁锰混合物均可合成交叉紫外环丁烷二聚体，其合成效率接近紫外环丁烷。 没有损坏的DNA。我们还发现，Pol g有一个广泛的病变识别网络，可以感知 在有Mg2+存在的情况下，上游有多达10个碱基对的损伤，但完全忽略了有Mn2+的损伤。 我们假设，锰离子可以改变POLG的弹性，从而能够适应巨大的病变 跨病变合成。我们将通过完成Pol g的具体目标1)机制来检验假设 集成的病变旁路、延伸和复制活动，2)Pol g远程病变的调查 传感和3)金属导电式热释光的生物物理基础。拟议的研究将说明如何 线粒体复制酶利用必需的金属离子在紫外线辐射下保持基因组的完整性。

ABSTRACT Mitochondrial DNA (mtDNA) integrity is critical for metabolism and cellular energy supply and human health and longevity. Due to lack of repair mechanism and specified translesion synthesis (TLS) polymerase, mtDNA contains higher contents of UV lesions. The high-fidelity mitochondrial DNA polymerase (Pol g) will unavoidably encounter the UV lesions during mtDNA replication. Unlike other high-fidelity DNA polymerases that lack TLS activity, we found Pol g possesses a metal regulated TLS activity. In the presence of magnesium ion, Pol g exhibits no TLS activity, however, in the presence of physiological concentrations of manganese ion alone or Mg/Mn mixture, Pol g can synthesize cross UV lesion cyclobutane dimer with efficiency near that on the non-damaged DNA. We also discovered that Pol g has an extensive lesion recognition network that can sense an upstream lesion as far as 10 base pairs in the presence of Mg2+, but completely ignores the lesion with Mn2+. We hypothesize that Manganese ion can alter the elasticity of Pol g to be able to accommodate bulky lesions for translesion synthesis. we will test the hypothesis by completing the Specific Aims 1) Mechanism of Pol g integrated lesion bypassing, extension, and replication activities, 2) Investigation of Pol g long-range lesion sensing and 3) Biophysical basis for metal-directed Pol g TLS. The proposed studies will illustrate how mitochondrial replicase utilizing the essential metal ions to maintain genome integrity under UV radiation.