Laboratory of Molecular Biology, NIDDK, NIH, 9000 Rockville Pike, Building 5, Room B103, Bethesda, Maryland 20892, USA.
Nature. 2010 Jun 24;465(7301):1044-8. doi: 10.1038/nature09196.
The variant form of the human syndrome xeroderma pigmentosum (XPV) is caused by a deficiency in DNA polymerase eta (Poleta), a DNA polymerase that enables replication through ultraviolet-induced pyrimidine dimers. Here we report high-resolution crystal structures of human Poleta at four consecutive steps during DNA synthesis through cis-syn cyclobutane thymine dimers. Poleta acts like a 'molecular splint' to stabilize damaged DNA in a normal B-form conformation. An enlarged active site accommodates the thymine dimer with excellent stereochemistry for two-metal ion catalysis. Two residues conserved among Poleta orthologues form specific hydrogen bonds with the lesion and the incoming nucleotide to assist translesion synthesis. On the basis of the structures, eight Poleta missense mutations causing XPV can be rationalized as undermining the molecular splint or perturbing the active-site alignment. The structures also provide an insight into the role of Poleta in replicating through D loop and DNA fragile sites.
人类着色性干皮病（XPV）变体是由 DNA 聚合酶 η（Poleta）缺乏引起的，该酶是一种能够通过紫外线诱导的嘧啶二聚体进行复制的 DNA 聚合酶。本文报道了人源 Poleta 在通过顺式-顺式环丁烷胸腺嘧啶二聚体进行 DNA 合成的四个连续步骤中的高分辨率晶体结构。Poleta 充当“分子夹板”，将受损 DNA 稳定在正常 B 型构象中。一个扩大的活性位点容纳胸腺嘧啶二聚体，具有极好的立体化学性质，适合双金属离子催化。在 Poleta 同源物中保守的两个残基与损伤部位和进入的核苷酸形成特定的氢键，以辅助跨损伤合成。基于这些结构，可以将导致 XPV 的八种 Poleta 错义突变合理化，认为它们破坏了分子夹板或扰乱了活性位点的排列。这些结构还提供了对 Poleta 在通过 D 环和 DNA 脆弱位点进行复制中的作用的深入了解。
