Defining relevant targets of the DNA dependent protein kinase

描述（申请人提供）：DNA双链断裂（DSBs）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的所有阶段的大多数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，并与肿瘤发生密切相关。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，深入了解这一途径对人类健康至关重要。尽管对c-NHEJ的研究已经进行了几十年，但由于我们对c-NHEJ的认识不仅不完整，而且可能不准确，因此需要进行更多的基础研究。目前的研究主要集中在三个方面。首先将确定由DNA依赖性蛋白激酶（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（通过蛋白质磷酸化）靶向所有的c-NHEJ因子，包括它自己。这种自磷酸化对修复至关重要，功能复杂。第二个研究领域将集中于展示DNA- pk如何影响其他DNA修复途径的新兴数据。c-NHEJ不应该加入某些类型的DNA损伤；c-NHEJ应该尽量避免的损伤的一个例子是在DNA复制过程中，当复制叉崩溃时造成的损伤。第二个目标将确定DNA-PK是否以牺牲基因组完整性为代价促进复制应激期间的细胞存活。第三个目标是跟进最近的新发现，显示XRCC4和XLF[两个先前归因于c-NHEJ结联复合物的因子，因此在c-NHEJ中起作用的因子]如何在体外形成桥接DNA的丝状结构，并可能在活细胞中起作用，在修复之前稳定DNA末端。这表明XRCC4/XLF细丝在早期（在c-NHEJ中）有额外的作用。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.