Structural biology of protein-protein interactions involved in DNA replication under DNA damage

DNA钳参与了DNA的复制、修复和复制等多种细胞事件，并在这些事件中起支架蛋白的作用。DNA钳形成环状三聚体，环绕DNA双螺旋并沿DNA轴自由滑动。PCNA和RAD9/HUS1/RAD1（9-1-1）是真核生物的DNA夹钳。PCNA是同型三聚体，而9-1-1是异型三聚体。9-1-1的每个亚基都由类似pcna的结构域组成。然而，RAD9在c端有一个分子量为13kd的附加结构域。PCNA样结构域的9-1-1三聚体结构与PCNA三聚体相似。在这项研究中，我们制备了RAD9CTD的c端结构域，并通过小角x射线散射（SAXS）进行了结构分析。有些古菌具有异三聚体DNA夹（PCNA1-PCNA2-PCNA3）。通过SAXS分析发现，石竹中的PCNA2-PCNA3在溶液中形成四聚环结构。

DNA clamp is involved in various cellular events on DNA including DNA replication, repair and replication, and functions as a scaffold protein in those events. DNA clamp forms a ring-shaped trimer that encircles the DNA double helix and slides freely along the DNA axis. PCNA and RAD9/HUS1/RAD1(9-1-1) are DNA clamp in eukaryote. PCNA is a homo-trimer, whereas 9-1-1 is a hetero-trimer. Each subunit of 9-1-1 is composed of PCNA-like domain. However, RAD9 has an additional domain with a molecular weight of 13 kD in the C-terminus. Structure of 9-1-1 trimer of PCNA-like domains is similar to that of PCNA trimer. In this study, we prepared the C-terminal domain of RAD9CTD and performed structural analysis by small angle X-ray scattering(SAXS). Some archaea have heterotrimeric DNA clamp(PCNA1-PCNA2-PCNA3). We reveals that PCNA2-PCNA3 from Sulfolobus tokodaii forms tetrameric ring structure in solution by SAXS.