The presence of rNTPs decreases the speed of mitochondrial DNA replication
The presence of rNTPs decreases the speed of mitochondrial DNA replication
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DOI：
10.1371/journal.pgen.1007315
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发表时间：
2018-03-01
期刊：
影响因子：
4.5
通讯作者：
Wanrooij, Sjoerd
中科院分区：
文献类型：
--
作者：
Forslund, Josefin M. E.;Pfeiffer, Annika;Wanrooij, Sjoerd
核糖核苷酸（rNMP）在DNA聚合酶的复制或修复过程中经常被掺入，并且不能去除它们会导致核DNA（nDNA）的不稳定性。相反，rNMP似乎在线粒体DNA（mtDNA）中耐受性相对良好，尽管耐受性背后的机制仍不清楚。我们在这里表明，人类线粒体DNA聚合酶γ（Pol γ）绕过单一的rNMP具有前所未有的高保真度和效率。此外，Pol γ表现出惊人的低频率的rNMP掺入，一个属性，我们发现这是独立于其核酸外切酶活性。然而，游离rNTPs的生理水平部分抑制DNA合成的Pol γ，使聚合酶更敏感的不平衡的dNTP池。本文报道的Pol γ的特征可能对与不平衡的细胞dNTP池相关的rntDNA耗竭综合征（MDS）的形式有影响。我们的研究结果表明，在rNTPidNIP的比例，预计在这种疾病状态下，Pol γ进入一个聚合酶外切核酸酶闲置模式，导致mtDNA复制停滞。这可能最终导致mtDNA耗竭，并因此导致线粒体疾病表型，如在MDS中观察到的那些。
Ribonucleotides (rNMPs) are frequently incorporated during replication or repair by DNA polymerases and failure to remove them leads to instability of nuclear DNA (nDNA). Conversely, rNMPs appear to be relatively well-tolerated in mitochondnal DNA (mtDNA), although the mechanisms behind the tolerance remain unclear. We here show that the human mitochondrial DNA polymerase gamma (Pol gamma) bypasses single rNMPs with an unprecedentedly high fidelity and efficiency. In addition, Pol gamma exhibits a strikingly low frequency of rNMP incorporation, a property, which we find is independent of its exonuclease activity. However, the physiological levels of free rNTPs partially inhibit DNA synthesis by Pol gamma and render the polymerase more sensitive to imbalanced dNTP pools. The characteristics of Pol gamma reported here could have implications for forms of rntDNA depletion syndrome (MDS) that are associated with imbalanced cellular dNTP pools. Our results show that at the rNTPidNIP ratios that are expected to prevail in such disease states, Pol gamma enters a polymerasetexonuclease idling mode that leads to mtDNA replication stalling. This could ultimately lead to mtDNA depletion and, consequently, to mitochondrial disease phenotypes such as those observed in MDS.