Kawamoto Takuo, Araki Kasumi, Sonoda Eiichiro, Yamashita Yukiko M, Harada Kouji, Kikuchi Koji, Masutani Chikahide, Hanaoka Fumio, Nozaki Kazuhiko, Hashimoto Nobuo, Takeda Shunichi
CREST, Japan Science and Technology Agency, Radiation Genetics, Graduate School of Medicine, Kyoto University, Yoshida Konoe, Japan.
Mol Cell. 2005 Dec 9;20(5):793-9. doi: 10.1016/j.molcel.2005.10.016.
Chicken B lymphocyte precursors and DT40 cells diversify their immunoglobulin-variable (IgV) genes through homologous recombination (HR)-mediated Ig gene conversion. To identify DNA polymerases that are involved in Ig gene conversion, we created DT40 clones deficient in DNA polymerase eta (poleta), which, in humans, is defective in the variant form of xeroderma pigmentosum (XP-V). Poleta is an error-prone translesion DNA synthesis polymerase that can bypass UV damage-induced lesions and is involved in IgV hypermutation. Like XP-V cells, poleta-disrupted (poleta) clones exhibited hypersensitivity to UV. Remarkably, poleta cells showed a significant decrease in the frequency of both Ig gene conversion and double-strand break-induced HR when compared to wild-type cells, and these defects were reversed by complementation with human poleta. Our findings identify a DNA polymerase that carries out DNA synthesis for physiological HR and provides evidence that a single DNA polymerase can play multiple cellular roles.
鸡B淋巴细胞前体和DT40细胞通过同源重组（HR）介导的Ig基因转换使其免疫球蛋白可变区（IgV）基因多样化。为了鉴定参与Ig基因转换的DNA聚合酶，我们构建了缺乏DNA聚合酶η（Polη）的DT40克隆，在人类中，该酶在着色性干皮病（XP-V）的变异形式中存在缺陷。Polη是一种易出错的跨损伤DNA合成聚合酶，可绕过紫外线损伤诱导的损伤，并参与IgV高突变。与XP-V细胞一样，Polη缺失（Polη-）克隆对紫外线表现出超敏反应。值得注意的是，与野生型细胞相比，Polη-细胞的Ig基因转换频率和双链断裂诱导的HR均显著降低，并且通过用人Polη互补可逆转这些缺陷。我们的研究结果鉴定了一种为生理性HR进行DNA合成的DNA聚合酶，并提供了单一DNA聚合酶可发挥多种细胞作用的证据。
