Protein-Protein Interactions in DNA Repair Pathways

描述(申请人提供)：DNA的化学结构在反应的细胞环境中不断变化。受损的DNA通常会在基因组中引入突变，这些突变可能会产生细胞毒性或功能障碍的影响。因此，生物体已经开发出修复途径来纠正各种类型的DNA损伤。基因突变会导致疾病和癌症，这一事实突显了理解这些修复途径的重要性。 碱基切除修复(BER)是纠正氧化和烷基化试剂造成的DNA损伤的主要手段。BER途径涉及一系列酶，这些酶切除受损的DNA碱基，结合正确的DNA碱基，并将DNA结构恢复到其自然形式。这一途径中的酶以协调的方式发挥作用，将脆弱的DNA中间体从一个步骤传递到下一个步骤。这项研究集中在BER的最后几个步骤：聚合酶填补缺口和连接缺口DNA链。其具体目的是1)确定含有和不含有DNA中间体的人连接酶I(Lig1)或Lig1的催化活性片段的晶体结构；2)鉴定和结晶稳定的Lig1和聚合酶A(Pola)复合体，证明它们之间的生物相互作用，并解决该复合体的晶体结构。

DESCRIPTION (provided by applicant): The chemical structure of DNA is continuously altered in the reactive cellular environment. Damaged DNA often introduces mutations in the genome that have potentially cytotoxic or dysfunctional effects. Therefore, organisms have developed repair pathways to correct various types of DNA damage. The importance in understanding these repair pathways is underscored by the fact that genetic mutations give rise to disease and cancer. Base excision repair (BER) is the primary means for correcting DNA damage done by oxidizing and alkylating agents. The BER pathway involves a series of enzymes that excises damaged DNA bases, incorporates correct DNA bases, and returns the DNA structure to its natural form. The enzymes in this pathway act in a concerted manner, passing fragile DNA intermediates from one step to the next. This study focuses on the last steps of BER: polymerase gap-filling and ligation of nicked DNA strands. The specific aims are to 1) determine crystal structures of human ligase I (Lig1), or catalytically active fragments of Lig1, with and without DNA intermediates and 2) identify and crystallize a stable complex of Lig1 and polymerase a (Pola) that demonstrates their biological interaction and solve the crystal structure of the complex.