Molecular determinants of Ku function in non-homologous end-joining and DNA damage signaling pathways

Ku是一种丰富的普遍存在的因子，在整个进化过程中被显著保守，因为它在从细菌到人类的所有有机体中都被发现。Ku是一种由两种蛋白质组成的复合体，在双链DNA断裂的修复中起着至关重要的作用。双链DNA断裂是一种DNA损伤形式，双螺旋断裂的两条链都会导致染色体重排，最终导致基因组不稳定。虽然人们知道Ku对于DNA的正确修复是必不可少的，但它的作用模式仍然不清楚。众所周知，Ku与许多在DNA修复中起作用的其他因素相互作用，然而，这些相互作用的细节和结果尚不清楚。利用最近获得的Ku的晶体结构，我们可以预测蛋白质中可以接触其他蛋白质的区域。因此，我们在这些可接近的区域中进行了几个突变，以测试它们改变了Ku DNA修复功能。我们已经确定了两个Ku突变，它们改变了它对DNA损伤的功能。我们发现，这些突变导致了不同的缺陷，这表明突变区域涉及不同的功能。我们建议确定与这些Ku基序相互作用的蛋白质，并阐明它们如何在DNA修复中共同发挥作用。从长远来看，这些分析将增强我们对Ku在处理双链DNA断裂的机制中的功能的理解。

Ku is an abundant, ubiquitous factor that has been remarkably conserved throughout evolution as it has beenidentified in all organisms from bacteria to man. Ku is a complex of two proteins that plays an essential role inthe repair of double-strand DNA breaks, a form of DNA damage in which both strands of the double helixbreak, leading to chromosome rearrangements and, ultimately, genomic instability.While it is understood that Ku is essential for the proper repair of DNA, its mode of action is still unclear. It isknown that Ku interacts with a number of other factors that play roles in the repair of DNA, however, thedetails and the outcome of these interactions are poorly understood.Using the crystal structure of Ku that was recently made available, we can predict regions of the protein that areaccessible to contact other proteins. Thus we have made mutations in several of these accessible regions to testif they alter Ku DNA repair functions. We have identified two Ku mutations that alter its ability to function inresponse to DNA damage. We found that these mutations result in different defects suggesting that the mutatedregions are involved in distinct functions. We propose to identify the proteins that interact with these Ku motifsand elucidate how they function together in the repair of DNA.In the long-term, these analyses will enhance our understanding of the functions of Ku in the mechanisms thatare set in place to deal with double-stranded DNA breaks.