Department of Biochemistry and Tulane Cancer Center, Tulane University School of Medicine, 1430 Tulane Ave., New Orleans, LA 70112, USA.
Nucleic Acids Res. 2011 Mar;39(5):1763-73. doi: 10.1093/nar/gkq1034. Epub 2010 Oct 29.
Bulk replicative DNA synthesis in eukaryotes is highly accurate and efficient, primarily because of two DNA polymerases (Pols): Pols δ and ε. The high fidelity of these enzymes is due to their intrinsic base selectivity and proofreading exonuclease activity which, when coupled with post-replication mismatch repair, helps to maintain human mutation rates at less than one mutation per genome duplication. Conditions that reduce polymerase fidelity result in increased mutagenesis and can lead to cancer in mice. Whereas yeast Pol ε has been well characterized, human Pol ε remains poorly understood. Here, we present the first report on the fidelity of human Pol ε. We find that human Pol ε carries out DNA synthesis with high fidelity, even in the absence of its 3'→5' exonucleolytic proofreading and is significantly more accurate than yeast Pol ε. Though its spectrum of errors is similar to that of yeast Pol ε, there are several notable exceptions. These include a preference of the human enzyme for T→A over A→T transversions. As compared with other replicative DNA polymerases, human Pol ε is particularly accurate when copying homonucleotide runs of 4-5 bases. The base pair substitution specificity and high fidelity for frameshift errors observed for human Pol ε are distinct from the errors made by human Pol δ.
真核生物的大量复制 DNA 合成具有高度的准确性和效率，主要是因为有两种 DNA 聚合酶（Pols）：Pol δ 和 Pol ε。这些酶的高保真度归因于它们内在的碱基选择性和校对外切核酸酶活性，当与复制后错配修复结合时，有助于将人类的突变率保持在每个基因组复制不到一个突变的水平。降低聚合酶保真度的条件会导致突变增加，并可能导致小鼠癌症。虽然酵母 Pol ε 已经得到了很好的描述，但人类 Pol ε 仍然知之甚少。在这里，我们首次报道了人类 Pol ε 的保真度。我们发现，即使在缺乏其 3'→5'外切核酸酶校对的情况下，人类 Pol ε 也能进行高度准确的 DNA 合成，其准确性明显高于酵母 Pol ε。尽管其错误谱与酵母 Pol ε 相似，但也有几个值得注意的例外。其中包括人类酶对 T→A 颠换的偏好，而不是 A→T 颠换。与其他复制 DNA 聚合酶相比，人类 Pol ε 在复制 4-5 个碱基的同核核苷酸序列时特别准确。与人类 Pol δ 相比，人类 Pol ε 观察到的移码错误的碱基对取代特异性和高保真度是不同的。
