Schurtenberger P, Egelhaaf S U, Hindges R, Maga G, Jónsson Z O, May R P, Glatter O, Hübscher U
Institut für Polymere, ETH Zürich, Switzerland.
J Mol Biol. 1998 Jan 9;275(1):123-32. doi: 10.1006/jmbi.1997.1435.
The function of proliferating cell nuclear antigen (PCNA) in DNA replication and repair is to form a sliding clamp with replication factor C (RF-C) tethering DNA polymerase delta or epsilon to DNA. In addition, PCNA has been found to interact directly with various proteins involved in cell cycle regulation. The crystal structure of yeast PCNA shows that the protein forms a homotrimeric ring lining a hole through which double-stranded DNA can thread, thus forming a moving platform for DNA synthesis. Human and yeast PCNA are highly conserved at a structural and functional level. We determined the solution structure of functionally active human PCNA by small-angle neutron scattering. Our measurements strongly support a trimeric ring-like structure of functionally active PCNA in solution, and the data are in good agreement with model calculations based on the crystal structure from yeast PCNA. The human PCNA used in the small-angle neutron scattering experiments was active before and after the measurements in a RF-C independent and a RF-C dependent assay suggesting that the trimeric structure is the in vivo functional form.
增殖细胞核抗原（PCNA）在DNA复制和修复中的作用是与复制因子C（RF-C）形成一个滑动夹，将DNA聚合酶δ或ε拴系到DNA上。此外，人们发现PCNA能直接与多种参与细胞周期调控的蛋白质相互作用。酵母PCNA的晶体结构表明，该蛋白质形成一个同三聚体环，环内有一个孔，双链DNA可从中穿过，从而形成一个DNA合成的移动平台。人类和酵母的PCNA在结构和功能水平上高度保守。我们通过小角中子散射确定了具有功能活性的人类PCNA的溶液结构。我们的测量结果有力地支持了溶液中具有功能活性的PCNA呈三聚体环状结构，并且这些数据与基于酵母PCNA晶体结构的模型计算结果高度吻合。小角中子散射实验中使用的人类PCNA在测量前后，在独立于RF-C和依赖于RF-C的检测中均具有活性，这表明三聚体结构是其体内功能形式。
