DNA polymerase zeta (Polζ) is a heterotetramer composed of the catalytic subunit Rev3l, Rev7 and two subunits of Polδ (PolD2/Pol31 and PolD3/Pol32), and this polymerase exerts translesion DNA synthesis (TLS) in yeast. Because Rev3l knockout results in embryonic lethality in mice, the functions of Polζ need further investigation in vivo. Then, we noted the two facts that substitution of leucine 979 of yeast Rev3l with methionine reduces Polζ replication fidelity and that reporter gene transgenic rodents are able to provide the detailed mutation status. Here, we established gpt delta mouse knocked in the constructed gene encoding methionine instead of leucine at residue 2610 of Rev3l (Rev3l L2610M gpt delta mice), to clarify the role of Polζ in TLS of chemical-induced bulky DNA adducts in vivo. Eight-week-old gpt delta mice and Rev3l L2610M gpt delta mice were treated with benzo[a]pyrene (BaP) at 0, 40, 80, or 160 mg/kg via single intraperitoneal injection. At necropsy 31 days after treatment, lungs were collected for reporter gene mutation assays. Although the gpt mutant frequency was significantly increased by BaP in both mouse genotypes, it was three times higher in Rev3l L2610M gpt delta than gpt delta mice after treatment with 160 mg/kg BaP. The frequencies of G:C base substitutions and characteristic complex mutations were significantly increased in Rev3l L2610M gpt delta mice compared with gpt delta mice. The BaP dose–response relationship suggested that Polζ plays a central role in TLS when protective mechanisms against BaP mutagenesis, such as error-free TLS, are saturated. Overall, Polζ may incorporate incorrect nucleotides at the sites opposite to BaP-modified guanines and extend short DNA sequences from the resultant terminal mismatches only when DNA is heavily damaged.

中文翻译：

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DNA聚合酶ζ在苯并[a]芘诱导的小鼠肺诱变中的作用

DNA 聚合酶 zeta (Polζ) 是由催化亚基 Rev3l、Rev7 和 Polδ 的两个亚基 (PolD2/Pol31 和 PolD3/Pol32) 组成的异四聚体，该聚合酶在酵母中发挥转损伤 DNA 合成 (TLS)。由于 Rev3l 敲除导致小鼠胚胎致死，Polζ 的功能需要在体内进一步研究。然后，我们注意到用蛋氨酸替代酵母 Rev3l 的亮氨酸 979 会降低 Polζ 复制保真度和报告基因转基因啮齿动物能够提供详细的突变状态的两个事实。在这里，我们建立了 gpt delta 小鼠，在 Rev3l 的残基 2610 处敲入了编码蛋氨酸而不是亮氨酸的构建基因（Rev3l L2610M gpt delta 小鼠），以阐明 Polζ 在体内化学诱导的大体积 DNA 加合物的 TLS 中的作用。8 周大的 gpt delta 小鼠和 Rev3l L2610M gpt delta 小鼠通过单次腹膜内注射以 0、40、80 或 160 mg/kg 的苯并[a]芘 (BaP) 治疗。在治疗后 31 天进行尸检时，收集肺用于报告基因突变测定。尽管在两种小鼠基因型中，BaP 显着增加了 gpt 突变频率，但在用 160 mg/kg BaP 处理后，Rev3l L2610M gpt delta 小鼠的 gpt 突变频率是 gpt delta 小鼠的三倍。与 gpt delta 小鼠相比，Rev3l L2610M gpt delta 小鼠的 G:C 碱基替换和特征性复合突变的频率显着增加。BaP 剂量-反应关系表明，当针对 BaP 诱变的保护机制（例如无错误 TLS）饱和时，Polζ 在 TLS 中发挥核心作用。全面的，