Boal Amie K, Genereux Joseph C, Sontz Pamela A, Gralnick Jeffrey A, Newman Dianne K, Barton Jacqueline K
Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
Proc Natl Acad Sci U S A. 2009 Sep 8;106(36):15237-42. doi: 10.1073/pnas.0908059106. Epub 2009 Aug 31.
Base excision repair (BER) enzymes maintain the integrity of the genome, and in humans, BER mutations are associated with cancer. Given the remarkable sensitivity of DNA-mediated charge transport (CT) to mismatched and damaged base pairs, we have proposed that DNA repair glycosylases (EndoIII and MutY) containing a redox-active [4Fe4S] cluster could use DNA CT in signaling one another to search cooperatively for damage in the genome. Here, we examine this model, where we estimate that electron transfers over a few hundred base pairs are sufficient for rapid interrogation of the full genome. Using atomic force microscopy, we found a redistribution of repair proteins onto DNA strands containing a single base mismatch, consistent with our model for CT scanning. We also demonstrated in Escherichia coli a cooperativity between EndoIII and MutY that is predicted by the CT scanning model. This relationship does not require the enzymatic activity of the glycosylase. Y82A EndoIII, a mutation that renders the protein deficient in DNA-mediated CT, however, inhibits cooperativity between MutY and EndoIII. These results illustrate how repair proteins might efficiently locate DNA lesions and point to a biological role for DNA-mediated CT within the cell.
碱基切除修复（BER）酶维持基因组的完整性，在人类中，BER突变与癌症相关。鉴于DNA介导的电荷传输（CT）对错配和受损碱基对具有显著敏感性，我们提出，含有氧化还原活性[4Fe4S]簇的DNA修复糖基化酶（EndoIII和MutY）可以利用DNA CT相互发出信号，协同搜索基因组中的损伤。在此，我们检验了该模型，据估计在该模型中几百个碱基对的电子转移足以快速检测整个基因组。使用原子力显微镜，我们发现修复蛋白重新分布到含有单个碱基错配的DNA链上，这与我们的CT扫描模型一致。我们还在大肠杆菌中证明了EndoIII和MutY之间的协同作用，这是CT扫描模型所预测的。这种关系并不需要糖基化酶的酶活性。然而，Y82A EndoIII是一种使蛋白质缺乏DNA介导的CT功能的突变体，它会抑制MutY和EndoIII之间的协同作用。这些结果说明了修复蛋白如何高效定位DNA损伤，并指出了DNA介导的CT在细胞内的生物学作用。
