Kuchino Y, Mori F, Kasai H, Inoue H, Iwai S, Miura K, Ohtsuka E, Nishimura S
Nature. 1987;327(6117):77-9. doi: 10.1038/327077a0.
It has been shown previously that deoxyguanosine residues in DNA are hydroxylated at the C-8 position both in vitro and in vivo to produce 8-hydroxydeoxyguanosine (8-OH-dG) by various agents that produce oxygen radicals such as reducing reagents-O2, metal ions-O2, polyphenol-H2O2-Fe3+, asbestos-H2O2 or ionizing radiation. These agents are mostly either mutagenic or carcinogenic; therefore, the formation of 8-OH-dG can also be considered a likely cause of mutation or carcinogenesis by oxygen radicals. It is of interest to know whether the 8-OH-dG residue in DNA is misread during DNA replication. To answer this question, we have examined the effect of the 8-OH-dG residue in DNA on the fidelity of DNA replication using a DNA synthesis system in vitro with Escherichia coli DNA polymerase I (Klenow fragment). The synthetic oligodeoxynucleotides, with or without an 8-OH-dG residue in a specified position, were chemically synthesized and used as templates for DNA synthesis under the conditions of the dideoxy chain termination sequencing method. Surprisingly, in addition to misreading of the 8-OH-dG residue itself, pyrimidines next to the 8-OH-dG residue (G has not yet been tested) were also misread.
先前已经表明，DNA中的脱氧鸟苷残基在体外和体内均会在C-8位被羟基化，通过各种产生氧自由基的试剂，如还原试剂-O₂、金属离子-O₂、多酚-H₂O₂-Fe³⁺、石棉-H₂O₂或电离辐射，生成8-羟基脱氧鸟苷（8-OH-dG）。这些试剂大多具有致突变性或致癌性；因此，8-OH-dG的形成也可被视为氧自由基导致突变或致癌的一个可能原因。了解DNA复制过程中DNA中的8-OH-dG残基是否会被误读很有意义。为了回答这个问题，我们使用含有大肠杆菌DNA聚合酶I（克列诺片段）的体外DNA合成系统，研究了DNA中8-OH-dG残基对DNA复制保真度的影响。在双脱氧链终止测序法的条件下，化学合成了在特定位置含有或不含有8-OH-dG残基的合成寡脱氧核苷酸，并将其用作DNA合成的模板。令人惊讶的是，除了8-OH-dG残基本身被误读外，8-OH-dG残基旁边的嘧啶（G尚未测试）也被误读了。
