Department of Structural and Chemical Biology, Mount Sinai School of Medicine, Box 1677, 1425 Madison Avenue, New York, New York 10029, USA.
Nature. 2010 Jun 24;465(7301):1039-43. doi: 10.1038/nature09104.
DNA polymerase eta (Poleta) is unique among eukaryotic polymerases in its proficient ability for error-free replication through ultraviolet-induced cyclobutane pyrimidine dimers, and inactivation of Poleta (also known as POLH) in humans causes the variant form of xeroderma pigmentosum (XPV). We present the crystal structures of Saccharomyces cerevisiae Poleta (also known as RAD30) in ternary complex with a cis-syn thymine-thymine (T-T) dimer and with undamaged DNA. The structures reveal that the ability of Poleta to replicate efficiently through the ultraviolet-induced lesion derives from a simple and yet elegant mechanism, wherein the two Ts of the T-T dimer are accommodated in an active site cleft that is much more open than in other polymerases. We also show by structural, biochemical and genetic analysis that the two Ts are maintained in a stable configuration in the active site via interactions with Gln 55, Arg 73 and Met 74. Together, these features define the basis for Poleta's action on ultraviolet-damaged DNA that is crucial in suppressing the mutagenic and carcinogenic consequences of sun exposure, thereby reducing the incidence of skin cancers in humans.
DNA 聚合酶 eta（Poleta）在其通过紫外线诱导的环丁烷嘧啶二聚体进行无差错复制的能力方面在真核聚合酶中是独一无二的，并且人类中 Poleta（也称为 POLH）的失活会导致异色性干皮病（XPV）的变体形式。我们展示了酿酒酵母 Poleta（也称为 RAD30）与顺式-顺式胸腺嘧啶-胸腺嘧啶（T-T）二聚体和未损伤 DNA 的三元复合物的晶体结构。这些结构表明，Poleta 能够通过紫外线诱导的损伤有效地复制，这源于一种简单而优雅的机制，其中 T-T 二聚体的两个 Ts 被容纳在一个活性位点裂缝中，该裂缝比其他聚合酶中的活性位点裂缝要宽得多。我们还通过结构、生化和遗传分析表明，两个 Ts 通过与 Gln55、Arg73 和 Met74 的相互作用在活性位点中保持稳定的构象。这些特征共同定义了 Poleta 对紫外线损伤 DNA 的作用基础，这对于抑制阳光照射的诱变和致癌后果至关重要，从而降低了人类皮肤癌的发病率。
