Human replicative DNA polymerase δ can bypass T-T (6-4) ultraviolet photoproducts on template strands
Human replicative DNA polymerase δ can bypass T-T (6-4) ultraviolet photoproducts on template strands
复制标题
DOI：
10.1111/j.1365-2443.2010.01457.x
复制
发表时间：
2010-12-01
期刊：
影响因子：
2.1
通讯作者：
Hirota, Kouji
中科院分区：
文献类型：
--
作者：
Narita, Takeo;Tsurimoto, Toshiki;Hirota, Kouji
DNA聚合酶δ（Pol δ）以极高的准确性进行DNA复制。这种高度的保真度主要取决于从聚合酶结构域的活性位点有效排除不正确的碱基对。此外，Pol delta的3 '-5'核酸外切酶活性通过消除错误掺入的核苷酸进一步增强其准确性。据信，这些酶性质还抑制Pol δ相对于受损模板插入核苷酸。为了测试这个被广泛接受的想法，我们检查了体外DNA合成的人Pol δ酶熟练和缺乏核酸外切酶活性。我们选择紫外线诱导的损伤环丁基嘧啶二聚体（CPD）和6-4嘧啶酮光产物（6-4 PP）作为受损模板。6-4 PP代表了对DNA复制的最可怕的挑战，并且没有单个真核DNA聚合酶显示出在体外绕过6-4 PP。出乎意料的是，我们发现Pol delta可以在6-4 PP和CPD中进行DNA合成，即使是在生理浓度的脱氧核糖核苷酸三磷酸（dNTPs）的情况下。跨越6-4 PP的DNA合成通常伴随核苷酸缺失，并且具有高度致突变性。Pol δ在绕过UV光产物中的这种意想不到的酶性质挑战了Pol δ的准确性防止绕过受损模板的公认概念。
DNA polymerase delta (Pol delta) carries out DNA replication with extremely high accuracy. This great fidelity primarily depends on the efficient exclusion of incorrect base pairs from the active site of the polymerase domain. In addition, the 3'-5' exonuclease activity of Pol delta further enhances its accuracy by eliminating misincorporated nucleotides. It is believed that these enzymatic properties also inhibit Pol delta from inserting nucleotides opposite damaged templates. To test this widely accepted idea, we examined in vitro DNA synthesis by human Pol delta enzymes proficient and deficient in the exonuclease activity. We chose the UV-induced lesions cyclobutyl pyrimidine dimer (CPD) and 6-4 pyrimidone photoproduct (6-4 PP) as damaged templates. 6-4 PP represents the most formidable challenge to DNA replication, and no single eukaryotic DNA polymerase has been shown to bypass 6-4 PP in vitro. Unexpectedly, we found that Pol delta can perform DNA synthesis across both 6-4 PP and CPD even with a physiological concentration of deoxyribonucleotide triphosphates (dNTPs). DNA synthesis across 6-4 PP was often accompanied by a nucleotide deletion and was highly mutagenic. This unexpected enzymatic property of Pol delta in the bypass of UV photoproducts challenges the received notion that the accuracy of Pol delta prevents bypassing damaged templates.