Defining relevant targets of the DNA dependent protein kinase

描述（由申请人提供）：DNA双链断裂（DSB）被认为是威胁基因组完整性的最危险的DNA损伤。在脊椎动物中，经典的非同源末端连接途径（c-NHEJ）在所有细胞类型和细胞周期的所有阶段连接大多数DSB。毫不奇怪，完整的c-NHEJ对人类生命至关重要。体细胞中c-NHEJ的破坏导致基因组不稳定性，并与肿瘤发生密切相关。特别地，用于破坏c-NHEJ的策略可能具有几种潜在的重要治疗应用。因此，深入了解这一途径对人类健康至关重要。虽然c-NHEJ已经研究了几十年，但更多的基础研究是必要的，因为我们对c-NHEJ的了解不仅不完整，而且可能是不准确的。目前的研究集中在三个方面。第一个将确定如何磷酸化介导的DNA依赖性蛋白激酶（DNA-PK）调节DNA修复的机制细节。DNA-PK是启动DNA修复的大蛋白激酶复合物。它靶向（通过蛋白磷酸化）所有的c-NHEJ因子，包括它自己。这种自磷酸化对于修复是必不可少的，并且功能复杂。研究的第二个领域将集中在新出现的数据，证明DNA-PK如何影响其他DNA修复途径。c-NHEJ不应该加入某些类型的DNA损伤; c-NHEJ应该优选避免的损伤的一个例子是当复制叉崩溃时在DNA复制期间导致的损伤。第二个目标将确定DNA-PK是否以基因组完整性为代价在复制应激期间促进细胞存活。第三个目的是跟进最近的新发现，显示XRCC 4和XLF [先前归因于c-NHEJ的连接复合物的两个因子，因此在c-NHEJ中后期起作用的因子]如何形成在体外桥接DNA的丝状结构，并且可能在活细胞中起作用以在修复之前稳定DNA末端。这表明XRCC 4/XLF细丝的额外的早期（在c-NHEJ中）作用。这将是对当前教条的重大转变。

DESCRIPTION (provided by applicant): DNA double stranded-breaks (DSBs) are thought to be the most dangerous DNA lesions that threaten genomic integrity. In vertebrates, the classical non-homologous end joining pathway (c-NHEJ) joins most DSBs in all cell types and at all stages of the cell cycle. Not surprisingly, intact c-NHEJ is essential for human life. Disruption o c-NHEJ in somatic cells results in genomic instability and is strongly associated with tumorigenesis. Paradoxically, strategies for disrupting c-NHEJ, may have several potentially important therapeutic applications. Thus, a solid understanding of this pathway is important to human health. Although c-NHEJ has been studied for decades, more basic research is warranted because our knowledge of c-NHEJ is not only incomplete, but may also be inaccurate. The current research focuses on three areas. The first will ascertain mechanistic details of how phosphorylations mediated by the DNA dependent protein kinase (DNA-PK) regulate DNA repair. DNA-PK is a large protein kinase complex that initiates DNA repair. It targets (by protein phosphorylation) all of the c-NHEJ factors including itself. This autophosphorylation is essential for repair and is functionally complex. The second area of research will focus on emerging data demonstrating how DNA-PK affects other DNA repair pathways. c-NHEJ should not join certain types of DNA damage; one example of damage that c-NHEJ should preferably avoid is the damage that results during DNA replication when a replication fork collapses. The second aim will determine whether DNA-PK promotes cell survival during replication stress at the expense of genome integrity. The third aim follows up on recent novel findings showing how XRCC4 and XLF [two factors previously ascribed to c-NHEJ's ligation complex, and thus factors that function late in c-NHEJ] form filamentous structures that bridge DNA in vitro, and that may function in living cells to stabilize DNA ends prior to repair. This suggests an additional, early (in c-NHEJ) role for XRCC4/XLF filaments. This would be a significant shift from current dogma.