Reversible Covalent Crosslinking of DNA to Befuddle Its Repair

化学系的生命过程化学项目资助约翰霍普金斯大学的Steven Rokita进行研究，旨在加深我们对细胞对环境中毒素的反应方式的理解。特别是，研究人员正在研究细胞如何修复这些毒素可能造成的损伤。损伤发生的一种方式是通过一种被称为DNA烷基化的过程，在这个过程中，小的化学基团被添加到构成基因的分子中。食品防腐剂、天然香料甚至药物都能诱导DNA烷基化。目前的项目旨在评估毒素与DNA可逆相互作用的生化后果。这些分子和DNA之间有害相互作用的可逆性使毒素的影响有可能被放大，并可能压倒细胞的修复能力。为了详细研究这一过程并确定可逆性的最显著影响，正在制备一系列模型化合物并对DNA修复机制的每一步进行测试。这项工作正在对科学家在物质投放市场之前评估其毒理学的能力产生更广泛的影响。它对培养下一代的科学家（包括本科生和研究生）产生了进一步的影响，鼓励他们认识和追求超越有机化学和生物化学之间传统障碍的问题，这些问题对人类健康很重要。在这个项目中，共价交联在双工DNA内有效扩散所需的结构决定因素正在被确定。这是通过合成和评价甲基醌中间体来完成的，这些中间体表达了一系列反应动力学和DNA亲和性。从第一个活动中收集的原理将用于挑战具有可逆和动态交联的DNA修复酶。在交联修复的每个步骤中形成的实体将通过使用电泳和色谱的诊断碎片和分离来绘制。最初的注意力将指向分离的DNA，然后进展到核小体，最后拥抱粗细胞提取物的复杂性。

The Chemistry of Life Processes Program in the Division of Chemistry is funding Steven Rokita of Johns Hopkins University for research aimed at increasing our understanding of the way in which our cells react to toxins in the environment. In particular, the investigators are looking at how cells repair damage those toxins might inflict. One way the damage occurs is through a process known as DNA alkylation, in which small chemical groups are added to the molecules that make up genes. Food preservatives, natural flavorings and even drugs can induce DNA alkylation. The current project is designed to assess the biochemical consequences of toxins that interact reversibly with DNA. The reversibility of the deleterious interactions between these molecules and DNA creates the possibility that the effects of the toxins are amplified and may overwhelm the repair capacity of cells. To study the process in detail and identify the most dramatic effects of the reversibility, a series of model compounds is being prepared and tested for each step of the DNA repair mechanism. This work is having a broader impact on scientist's ability to evaluate the toxicology of substances prior to their market release. It is having a further impact on the training of the next generation of scientists, both undergraduate and graduate students, by encouraging them to recognize and pursue problems that transcend the traditional barriers between organic chemistry and biochemistry and are important for the human health.In this project, the structural determinants required for efficient diffusion of covalent cross-linking within duplex DNA are being identified. This is being accomplished through the synthesis and evaluation of quinone methide intermediates that express a range of reaction kinetics and DNA affinities. The principles gleaned from this first activity will be used for challenging enzymes responsible for DNA repair with reversible and dynamic cross-links. The entities formed during each step of cross-link repair will be mapped by diagnostic fragmentation and separation using electrophoresis and chromatography. Initial attention will be directed to isolated DNA and then progress to nucleosomes and finally embrace the complexity of crude cell extracts.