Efficient and accurate replication in the presence of 7,8-dihydro-8-oxoguanine by DNA polymerase η
Efficient and accurate replication in the presence of 7,8-dihydro-8-oxoguanine by DNA polymerase η
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DOI：
10.1038/78169
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发表时间：
2000-08-01
期刊：
影响因子：
30.8
通讯作者：
Prakash, S
中科院分区：
文献类型：
--
作者：
Haracska, L;Yu, SL;Prakash, S
DNA的氧化损伤被认为在癌症和衰老中起作用（1）。在正常有氧细胞代谢过程中形成的氧自由基攻击DNA中的碱基，7，8-二氢-8-氧代鸟嘌呤（8-oxoG）是形成的加合物之一（2，3）。真核复制型DNA聚合酶通过在病变的对面插入腺嘌呤来复制含有8-oxoG的DNA（4）;因此。8-oxoG具有高度致突变性，可导致G：C至T：A颠换（5）。在酵母中的遗传学研究已经表明错配修复在最小化这些突变的发生率中的作用。在酿酒酵母中，缺失OGG 1（编码DNA糖基化酶，当与C配对时，其功能是去除8-oxoG）会导致G：C至TA颠换率增加（6）。与ogg 1 Delta或msh 2 Delta单突变体相比，ogg 1 Delta msh 2 Delta双突变体显示出更高的CAN 1（S）至can 1（r）正向突变率，这种增强的诱变主要是由于C：C至T：A的颠换（7）。将S.酿酒酵母编码DNA聚合酶Pol eta，其通过在二聚体的对面插入两个腺嘌呤而有效地复制含有顺式-顺式胸腺嘧啶-胸腺嘧啶（T-T）二聚体的DNA。在人类中，酵母RAD 30对应物POLH的突变导致着色性干皮病（9，10）（XP-V）的变异形式，并且XP-V个体患有日光诱导的皮肤癌的高发病率。在这里，我们表明，酵母和人类POL eta复制DNA含有8-oxoG有效和准确地插入一个胞嘧啶从病变和熟练地从这个碱基对延伸。与这些生物化学研究一致，自发突变率的协同增加发生在酵母ogg 1 Delta突变体中没有POL eta的情况下。我们的研究结果表明，Pol eta在预防人类内部癌症方面具有额外的作用，否则会导致DNA中8-oxoG的诱变复制。
Oxidative damage to DNA has been proposed to have a role in cancer and ageing(1). Oxygen-free radicals formed during normal aerobic cellular metabolism attack bases in DNA, and 7,8-dihydro-8-oxoguanine (8-oxoG) is one of the adducts formed(2,3). Eukaryotic replicative DNA polymerases replicate DNA containing 8-oxoG by inserting an adenine opposite the lesion(4); consequently. 8-oxoG is highly mutagenic and causes G:C to T:A transversions(5). Genetic studies in yeast have indicated a role for mismatch repair in minimizing the incidence of these mutations. In Saccharomyces cerevisiae, deletion of OGG1, encoding a DNA glycosylase that functions in the removal of 8-oxoG when paired with C, causes an increase in the rate of G:C to TA transversions(6). The ogg1 Delta msh2 Delta double mutant displays a higher rate of CAN1(S) to can1(r) forward mutations than the ogg1 Delta or msh2 Delta single mutants, and this enhanced mutagenesis is primarily due to C:C to T:A transversions(7). The gene RAD30 of S. cerevisiae encodes a DNA polymerase, Pol eta, that efficiently replicates DNA containing a cis-syn thymine-thymine (T-T) dimer by inserting two adenines across from the dimers. In humans, mutations in the yeast RAD30 counterpart, POLH, cause the variant form of xeroderma pigmentosum(9,10) (XP-V), and XP-V individuals suffer from a high incidence of sunlight-induced skin cancers. Here we show that yeast and human POL eta replicate DNA containing 8-oxoG efficiently and accurately by inserting a cytosine across from the lesion and by proficiently extending from this base pair. Consistent with these biochemical studies, a synergistic increase in the rate of spontaneous mutations occurs in the absence of POL eta in the yeast ogg1 Delta mutant. Our results suggest an additional role for Pol eta in the prevention of internal cancers in humans that would otherwise result from the mutagenic replication of 8-oxoG in DNA.