A common cancer-associated DNA polymerase ε mutation causes an exceptionally strong mutator phenotype, indicating fidelity defects distinct from loss of proofreading.
A common cancer-associated DNA polymerase ε mutation causes an exceptionally strong mutator phenotype, indicating fidelity defects distinct from loss of proofreading.
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常见的与癌症相关的DNA聚合酶ε突变会导致异常强的突变器表型，表明富达缺陷与校对丧失不同。
DOI：
10.1158/0008-5472.can-13-2892
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发表时间：
2014-04-01
期刊：
影响因子：
11.2
通讯作者：
Shcherbakova PV
中科院分区：
文献类型：
--
作者：
Kane DP;Shcherbakova PV
核酸外切校正和DNA错配修复（MMR）串联起作用，以维持高保真DNA复制并避免诱变。MMR缺陷提高了总体突变率，并与癌症发病率增加有关。最近报道了具有功能性MMR的高变结直肠和子宫内膜肿瘤在DNA聚合酶ε的核酸外切酶结构域（Polε）中携带氨基酸取代。这就产生了一个概念，即Polε的校对活性的丧失是一些散发性人类癌症的起始原因。在这项研究中，我们确定了一个体细胞P286 R取代的保守ExoI基序的Polε在收集的52散发性结直肠肿瘤标本。在以前的研究中，尽管有许多可能的方法来校正Polε，但在结直肠和子宫内膜肿瘤中反复观察到这种变化。为了了解P286 R变异体反复出现的原因，我们使用酵母模型系统表征了其功能后果。在酵母Polε中的类似替换产生了异常强的增变子表型，超过校正缺陷突变体两个数量级。这表明P286R突变在某种程度上起作用，而不是外切核酸酶的丢失，从而增加癌症风险。变异等位基因的杂合性引起了与完全MMR缺陷相当的强烈增变效应，这为为什么Polε突变型人类肿瘤的发展不需要杂合性缺失提供了解释。
Exonucleolytic proofreading and DNA mismatch repair (MMR) act in series to maintain high-fidelity DNA replication and avoid mutagenesis. MMR defects elevate the overall mutation rate and are associated with increased cancer incidence. Hypermutable colorectal and endometrial tumors with functional MMR were recently reported to carry amino acid substitutions in the exonuclease domain of DNA polymerase ε (Polε). This created a notion that loss of the proofreading activity of Polε is an initiating cause of some sporadic human cancers. In this study, we identified a somatic P286R substitution in the conserved ExoI motif of Polε in a collection of 52 sporadic colorectal tumor specimens. This change has been repeatedly observed in colorectal and endometrial tumors in previous studies despite many possible ways to inactivate Polε proofreading. To understand the reasons for the recurrent appearance of the P286R variant, we characterized its functional consequences using the yeast model system. An analogous substitution in the yeast Polε produced an unusually strong mutator phenotype exceeding that of proofreading-deficient mutants by two orders of magnitude. This argues that the P286R mutation acts at some level other than loss of exonuclease to elevate cancer risk. Heterozygosity for the variant allele caused a strong mutator effect comparable to that of complete MMR deficiency, providing an explanation for why loss of heterozygosity is not required for the development of Polε-mutant human tumors.