Maintaining genome integrity: Avoiding pathological consequences during DNA replication and repair

我们努力延长生命，但与年龄相关的癌症和衰老本身提醒我们，文明已经暴露了细胞衰变的自然过程，而进化从未让我们做好准备。我们细胞内的、生命赖以生存的DNA基因组不断受到威胁其完整性的有毒化学物质和致癌物的攻击，这种攻击是无法避免的，因为这些物质通常是基本细胞代谢的产物。我们之所以能够生存和繁衍，是因为DNA也会对系统进行编码，以消除或至少将其可能遭受的损害降到最低。这些修复系统的失败可能是致命的，或者造成灾难性的后果，比如家族性乳腺癌和结直肠癌。但这样的条件也反映了人类体细胞的一次性特性，这使得在维持基因组方面存在一定程度的缺陷，而这种缺陷是生殖系细胞无法容忍的，因为生殖系细胞会将基因组一代一代地传递给下一代。在人类或我们的动物近亲中，生殖系并不是特别容易获得的，因此，我们依靠对简单的单细胞微生物的研究来了解基因组的完整性是如何保持的，以便传递给下一代。本提案中概述的研究旨在研究蛋白质-DNA和蛋白质-蛋白质相互作用的复杂武库，以应对DNA损伤带来的挑战，并使基因组复制和传播以高效率和高保真度实现。实验计划的目的是剖析我们已经确定的三种蛋白质的活性，这些蛋白质在大肠杆菌的这些相互作用中起着关键作用。研究结果有望揭示染色体复制是如何在DNA受损的情况下进行的，以及那些不必要的和潜在的不稳定事件是如何限制染色体上基因排列的。它们还有望揭示使这些生物如此容易地适应不断变化的环境并因此使致病物种保持毒性的力量。

We strive to prolong life, but the age-related onset of cancer and aging itself provide reminders that civilization has exposed natural processes of cellular decay for which evolution never prepared us. The DNA genome within our cells, and on which life depends, is constantly under attack from toxic chemicals and carcinogens that threaten its integrity, an attack that cannot be avoided as these agents are most commonly the products of essential cellular metabolism. We survive and reproduce because DNA also encodes systems to eliminate or at least minimize any damage it may suffer. Failure of these repair systems can be fatal or have catastrophic consequences, as in familial breast and colorectal cancers. But such conditions also reflect the disposable nature of the human soma, which allows a level of imperfection in maintaining the genome that cannot be tolerated in the reproductive germline cells that transmit the genome from one generation to the next. The germline is not particularly accessible in humans, or in our animal cousins, and therefore we rely on studies with simple, unicellular micro-organisms for much of our understanding of how the integrity of the genome is maintained for transmission to the next generation. The research outlined in this proposal aims to investigate the complex arsenal of protein-DNA and protein-protein interactions deployed to meet the challenges posed by damage to DNA and which enable genome duplication and transmission to be achieved with high efficiency and high fidelity. The experiments planned aim to dissect the activities of three proteins we have identified as having key roles in these interactions in the bacterium Escherichia coli. The results are expected to reveal how chromosome replication is able to proceed in the face of damage to DNA and how unnecessary and potentially destabilising events that reshuffle the arrangement of genes on chromosomes are limited. They are also expected to shed light on the forces that enable these organisms to adapt so readily to changing environments and which thus enable pathogenic species to maintain virulence.