Defining relevant targets of the DNA dependent protein kinase

描述(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)连接了所有细胞类型和细胞周期所有阶段的大多数DSB。毫不奇怪，完整的c-nhej对人类生命是必不可少的。C-NHEJ在体细胞中的破坏导致基因组不稳定，并与肿瘤的发生密切相关。矛盾的是，破坏c-NHEJ的策略可能有几个潜在的重要治疗应用。因此，对这一途径的深入了解对人类健康非常重要。虽然c-NHEJ已经被研究了几十年，但更多的基础研究是有必要的，因为我们对c-NHEJ的了解不仅不完整，而且可能不准确。目前的研究主要集中在三个方面。第一个将确定由DNA依赖蛋白激酶(DNA-PK)介导的磷酸化如何调节DNA修复的机制细节。DNA-PK是一种启动DNA修复的大型蛋白激酶复合体。它以所有c-NHEJ因子为靶点(通过蛋白质磷酸化)，包括它自己。这种自动磷酸化是修复所必需的，而且功能复杂。第二个研究领域将集中在新出现的数据上，展示DNA-PK如何影响其他DNA修复途径。C-NHEJ不应加入某些类型的DNA损伤；c-NHEJ最好避免的损伤的一个例子是当复制叉坍塌时在DNA复制过程中导致的损伤。第二个目标将确定DNA-PK是否以牺牲基因组完整性为代价在复制应激期间促进细胞存活。第三个目标延续了最近的新发现，这些发现表明XRCC4和XLF[这两个因素以前被归因于c-NHEJ的连接复合体，从而在c-NHEJ后期发挥作用的因素]如何在体外形成连接DNA的丝状结构，并可能在活细胞中发挥作用，在修复之前稳定DNA末端。这表明XRCC4/XLF细丝在c-NHEJ中具有额外的早期作用。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.