Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, 9000 Rockville Pike, Building 5, Room B1-03, Bethesda, MD 20892, USA.
Cell. 2009 Dec 24;139(7):1279-89. doi: 10.1016/j.cell.2009.11.043.
E. coli DNA Pol II and eukaryotic Rev3 are B-family polymerases that can extend primers past a damaged or mismatched site when the high-fidelity replicative polymerases in the same family are ineffective. We report here the biochemical and structural properties of DNA Pol II that facilitate this translesion synthesis. DNA Pol II can extend primers past lesions either directly or by template skipping, in which small protein cavities outside of the active site accommodate looped-out template nucleotides 1 or 2 bp upstream. Because of multiple looping-out alternatives, mutation spectra of bypass synthesis are complicated. Moreover, translesion synthesis is enhanced by altered partitioning of DNA substrate between the polymerase active site and the proofreading exonuclease site. Compared to the replicative B family polymerases, DNA Pol II has subtle amino acid changes remote from the active site that allow it to replicate normal DNA with high efficiency yet conduct translesion synthesis when needed.
大肠杆菌 DNA 聚合酶 II 和真核 Rev3 是 B 族聚合酶，当同一家族中的高保真复制聚合酶无效时，它们可以在受损或错配的部位延伸引物。我们在这里报告了促进这种跨损伤合成的 DNA 聚合酶 II 的生化和结构特性。DNA 聚合酶 II 可以直接或通过模板跳跃来延伸引物，其中活性位点之外的小蛋白腔容纳上游 1 或 2 个碱基的环出模板核苷酸。由于存在多种环出替代方案，旁路合成的突变谱很复杂。此外，DNA 底物在聚合酶活性位点和校对外切酶位点之间的分配改变增强了跨损伤合成。与复制 B 族聚合酶相比，DNA 聚合酶 II 具有远离活性位点的微妙氨基酸变化，使其能够高效复制正常 DNA，但在需要时进行跨损伤合成。
