DNA 聚合酶 β與其交互作用蛋白之結構機制探討

Abstract

DNA polymerase beta (Pol beta) is a key enzyme involved in base excision repair and other DNA metabolism pathway involving gap-filling DNA synthesis. Recently, numerous of biochemical studies illustrated that Pol beta interacts with various proteins and the properties of the enzyme changed during the interaction event. However, there is no any structural and mechanism study about Pol beta with interacting partners has been solved and published until now. In the first part of the present study, we aim to understand the binding mechanism of Pol beta with proliferating cell nuclear antigen (PCNA) by determining the crystal structures of Pol beta/PCNA complex and the Pol beta/PCNA/DNA ternary complex. We have succeeded to obtain the of Pol beta/PCNA complex crystals and the Pol beta/PCNA/DNA ternary complex crystals and both of the complexes only diffracted to 4.5 Å resolution. The diffraction analysis indicated that Pol beta/PCNA complex belonged to space group P222, with unit-cell parameters a = 63, b = 155, c = 185 Å and the Pol beta/PCNA/DNA ternary complex belonged to space group P1, with unit-cell parameters a = 74, b = 111, c = 113 Å. We will further to optimize the crystallization conditions as well as the cryo-protection conditions to facilitate structural determination.

The second part of this study, we focus on the binding mechanism of Pol beta with protein arginine methyltransferase 6 (PRMT6) by determining the crystal structure. Our result showed that Pol beta binds to PRMT6 tightly with a Kd value of 16.8 ± 2.7 μM. However, we failed to crystallize the Pol beta/PRMT6 complex and we only crystallized PRMT6 alone at the crystallization experiments. We will also continue to screen for the optimized conditions and also the additive that can stabilize and crystalize the Pol beta/ PRMT6 complex for the structure determination.