Different DNA polymerases are involved in the short- and long-patch base excision repair in mammalian cells
Different DNA polymerases are involved in the short- and long-patch base excision repair in mammalian cells
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DOI：
10.1021/bi972999h
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发表时间：
1998-03-17
期刊：
影响因子：
2.9
通讯作者：
Dogliotti, E
中科院分区：
文献类型：
--
作者：
Fortini, P;Pascucci, B;Dogliotti, E
哺乳动物细胞具有两种不同的完成碱基切除修复（BER）的途径：DNA聚合酶β（Pol beta）依赖性的短补丁途径（替换一个核苷酸），这是主要途径，以及长补丁途径（2-6个核苷酸的重新合成），这是PCNA依赖性的。为了解决这两种途径如何在 BER 中共同发挥作用的问题，在标准体外修复反应中测试了 Pol beta 缺陷型哺乳动物细胞提取物修复环状双链体质粒分子中构建的单个脱碱基位点的能力。 Pol beta 缺陷提取物能够执行两种 BER 途径。然而，在短补丁 BER 的情况下，修复动力学明显慢于 Pol beta 丰富的提取物，而长补丁合成的效率不受 Pol beta 损失的影响。修复合成完全依赖于PCNA来替换长补丁。这些数据首次证明，在细胞提取物中，除 Pol beta 之外的 DNA 聚合酶专门参与长补丁 BER。这些 DNA 聚合酶也能够在没有 PCNA 的情况下执行短补丁 BER，但效率低于 Pol beta。这些发现引出了一种新模型，其中两条 BER 通路的特征在于不同的蛋白质需求，并且 DNA 聚合酶水平的功能冗余为细胞提供了备用系统。
Mammalian cells possess two distinct pathways for completion of base excision repair (BER): the DNA polymerase beta (Pol beta)-dependent short-patch pathway (replacement of one nucleotide), which is the main route, and the long-patch pathway (resynthesis of 2-6 nucleotides), which is PCNA-dependent. To address the issue of how these two pathways share their role in BER the ability of Pol beta-defective mammalian cell extracts to repair a single abasic site constructed in a circular duplex plasmid molecule was tested in a standard in vitro repair reaction. Pol beta-deficient extracts were able to perform both BER pathways. However, in the case of the short-patch BER, the repair kinetics was significantly slower than with Pol beta-proficient extracts, while the efficiency of the long-patch synthesis was unaffected by the loss of Pol beta. The repair synthesis was fully dependent on PCNA for the replacement of long patches. These data give the first evidence that in cell extracts DNA polymerases other than Pol beta are specifically involved in the long-patch BER. These DNA polymerases are also able to perform short patch BER in the absence of PCNA, although less efficiently than Pol beta. These findings lead to a novel model whereby the two BER pathways are characterized by different protein requirements, and a functional redundancy at the level of DNA polymerases provides cells with backup systems.